/*
   * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
   * Written by Alex Tomas <alex@clusterfs.com>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public Licens
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-
   */
  
  
  /*
   * mballoc.c contains the multiblocks allocation routines
   */

  #include "mballoc.h"

  #include <linux/debugfs.h>

  #include <linux/slab.h>

  #include <trace/events/ext4.h>

  /*
   * MUSTDO:
   *   - test ext4_ext_search_left() and ext4_ext_search_right()
   *   - search for metadata in few groups
   *
   * TODO v4:
   *   - normalization should take into account whether file is still open
   *   - discard preallocations if no free space left (policy?)
   *   - don't normalize tails
   *   - quota
   *   - reservation for superuser
   *
   * TODO v3:
   *   - bitmap read-ahead (proposed by Oleg Drokin aka green)
   *   - track min/max extents in each group for better group selection
   *   - mb_mark_used() may allocate chunk right after splitting buddy
   *   - tree of groups sorted by number of free blocks
   *   - error handling
   */
  
  /*
   * The allocation request involve request for multiple number of blocks
   * near to the goal(block) value specified.
   *

   * During initialization phase of the allocator we decide to use the
   * group preallocation or inode preallocation depending on the size of
   * the file. The size of the file could be the resulting file size we
   * would have after allocation, or the current file size, which ever
   * is larger. If the size is less than sbi->s_mb_stream_request we
   * select to use the group preallocation. The default value of
   * s_mb_stream_request is 16 blocks. This can also be tuned via
   * /sys/fs/ext4/<partition>/mb_stream_req. The value is represented in
   * terms of number of blocks.

   *
   * The main motivation for having small file use group preallocation is to

   * ensure that we have small files closer together on the disk.

   *

   * First stage the allocator looks at the inode prealloc list,
   * ext4_inode_info->i_prealloc_list, which contains list of prealloc
   * spaces for this particular inode. The inode prealloc space is
   * represented as:

   *
   * pa_lstart -> the logical start block for this prealloc space
   * pa_pstart -> the physical start block for this prealloc space

   * pa_len    -> length for this prealloc space

   * pa_free   ->  free space available in this prealloc space
   *
   * The inode preallocation space is used looking at the _logical_ start
   * block. If only the logical file block falls within the range of prealloc
   * space we will consume the particular prealloc space. This make sure that
   * that the we have contiguous physical blocks representing the file blocks
   *
   * The important thing to be noted in case of inode prealloc space is that
   * we don't modify the values associated to inode prealloc space except
   * pa_free.
   *
   * If we are not able to find blocks in the inode prealloc space and if we
   * have the group allocation flag set then we look at the locality group
   * prealloc space. These are per CPU prealloc list repreasented as
   *
   * ext4_sb_info.s_locality_groups[smp_processor_id()]
   *
   * The reason for having a per cpu locality group is to reduce the contention
   * between CPUs. It is possible to get scheduled at this point.
   *
   * The locality group prealloc space is used looking at whether we have
   * enough free space (pa_free) withing the prealloc space.
   *
   * If we can't allocate blocks via inode prealloc or/and locality group
   * prealloc then we look at the buddy cache. The buddy cache is represented
   * by ext4_sb_info.s_buddy_cache (struct inode) whose file offset gets
   * mapped to the buddy and bitmap information regarding different
   * groups. The buddy information is attached to buddy cache inode so that
   * we can access them through the page cache. The information regarding
   * each group is loaded via ext4_mb_load_buddy.  The information involve
   * block bitmap and buddy information. The information are stored in the
   * inode as:
   *
   *  {                        page                        }

   *  [ group 0 bitmap][ group 0 buddy] [group 1][ group 1]...

   *
   *
   * one block each for bitmap and buddy information.  So for each group we
   * take up 2 blocks. A page can contain blocks_per_page (PAGE_CACHE_SIZE /
   * blocksize) blocks.  So it can have information regarding groups_per_page
   * which is blocks_per_page/2
   *
   * The buddy cache inode is not stored on disk. The inode is thrown
   * away when the filesystem is unmounted.
   *
   * We look for count number of blocks in the buddy cache. If we were able
   * to locate that many free blocks we return with additional information
   * regarding rest of the contiguous physical block available
   *
   * Before allocating blocks via buddy cache we normalize the request
   * blocks. This ensure we ask for more blocks that we needed. The extra
   * blocks that we get after allocation is added to the respective prealloc
   * list. In case of inode preallocation we follow a list of heuristics
   * based on file size. This can be found in ext4_mb_normalize_request. If
   * we are doing a group prealloc we try to normalize the request to

   * sbi->s_mb_group_prealloc. Default value of s_mb_group_prealloc is

   * 512 blocks. This can be tuned via

   * /sys/fs/ext4/<partition/mb_group_prealloc. The value is represented in

   * terms of number of blocks. If we have mounted the file system with -O
   * stripe=<value> option the group prealloc request is normalized to the
   * stripe value (sbi->s_stripe)
   *

   * The regular allocator(using the buddy cache) supports few tunables.

   *

   * /sys/fs/ext4/<partition>/mb_min_to_scan
   * /sys/fs/ext4/<partition>/mb_max_to_scan
   * /sys/fs/ext4/<partition>/mb_order2_req

   *

   * The regular allocator uses buddy scan only if the request len is power of

   * 2 blocks and the order of allocation is >= sbi->s_mb_order2_reqs. The
   * value of s_mb_order2_reqs can be tuned via

   * /sys/fs/ext4/<partition>/mb_order2_req.  If the request len is equal to

   * stripe size (sbi->s_stripe), we try to search for contiguous block in

   * stripe size. This should result in better allocation on RAID setups. If
   * not, we search in the specific group using bitmap for best extents. The
   * tunable min_to_scan and max_to_scan control the behaviour here.

   * min_to_scan indicate how long the mballoc __must__ look for a best

   * extent and max_to_scan indicates how long the mballoc __can__ look for a

   * best extent in the found extents. Searching for the blocks starts with
   * the group specified as the goal value in allocation context via
   * ac_g_ex. Each group is first checked based on the criteria whether it
   * can used for allocation. ext4_mb_good_group explains how the groups are
   * checked.
   *
   * Both the prealloc space are getting populated as above. So for the first
   * request we will hit the buddy cache which will result in this prealloc
   * space getting filled. The prealloc space is then later used for the
   * subsequent request.
   */
  
  /*
   * mballoc operates on the following data:
   *  - on-disk bitmap
   *  - in-core buddy (actually includes buddy and bitmap)
   *  - preallocation descriptors (PAs)
   *
   * there are two types of preallocations:
   *  - inode
   *    assiged to specific inode and can be used for this inode only.
   *    it describes part of inode's space preallocated to specific
   *    physical blocks. any block from that preallocated can be used
   *    independent. the descriptor just tracks number of blocks left
   *    unused. so, before taking some block from descriptor, one must
   *    make sure corresponded logical block isn't allocated yet. this
   *    also means that freeing any block within descriptor's range
   *    must discard all preallocated blocks.
   *  - locality group
   *    assigned to specific locality group which does not translate to
   *    permanent set of inodes: inode can join and leave group. space
   *    from this type of preallocation can be used for any inode. thus
   *    it's consumed from the beginning to the end.
   *
   * relation between them can be expressed as:
   *    in-core buddy = on-disk bitmap + preallocation descriptors
   *
   * this mean blocks mballoc considers used are:
   *  - allocated blocks (persistent)
   *  - preallocated blocks (non-persistent)
   *
   * consistency in mballoc world means that at any time a block is either
   * free or used in ALL structures. notice: "any time" should not be read
   * literally -- time is discrete and delimited by locks.
   *
   *  to keep it simple, we don't use block numbers, instead we count number of
   *  blocks: how many blocks marked used/free in on-disk bitmap, buddy and PA.
   *
   * all operations can be expressed as:
   *  - init buddy:			buddy = on-disk + PAs
   *  - new PA:				buddy += N; PA = N
   *  - use inode PA:			on-disk += N; PA -= N
   *  - discard inode PA			buddy -= on-disk - PA; PA = 0
   *  - use locality group PA		on-disk += N; PA -= N
   *  - discard locality group PA		buddy -= PA; PA = 0
   *  note: 'buddy -= on-disk - PA' is used to show that on-disk bitmap
   *        is used in real operation because we can't know actual used
   *        bits from PA, only from on-disk bitmap
   *
   * if we follow this strict logic, then all operations above should be atomic.
   * given some of them can block, we'd have to use something like semaphores
   * killing performance on high-end SMP hardware. let's try to relax it using
   * the following knowledge:
   *  1) if buddy is referenced, it's already initialized
   *  2) while block is used in buddy and the buddy is referenced,
   *     nobody can re-allocate that block
   *  3) we work on bitmaps and '+' actually means 'set bits'. if on-disk has
   *     bit set and PA claims same block, it's OK. IOW, one can set bit in
   *     on-disk bitmap if buddy has same bit set or/and PA covers corresponded
   *     block
   *
   * so, now we're building a concurrency table:
   *  - init buddy vs.
   *    - new PA
   *      blocks for PA are allocated in the buddy, buddy must be referenced
   *      until PA is linked to allocation group to avoid concurrent buddy init
   *    - use inode PA
   *      we need to make sure that either on-disk bitmap or PA has uptodate data
   *      given (3) we care that PA-=N operation doesn't interfere with init
   *    - discard inode PA
   *      the simplest way would be to have buddy initialized by the discard
   *    - use locality group PA
   *      again PA-=N must be serialized with init
   *    - discard locality group PA
   *      the simplest way would be to have buddy initialized by the discard
   *  - new PA vs.
   *    - use inode PA
   *      i_data_sem serializes them
   *    - discard inode PA
   *      discard process must wait until PA isn't used by another process
   *    - use locality group PA
   *      some mutex should serialize them
   *    - discard locality group PA
   *      discard process must wait until PA isn't used by another process
   *  - use inode PA
   *    - use inode PA
   *      i_data_sem or another mutex should serializes them
   *    - discard inode PA
   *      discard process must wait until PA isn't used by another process
   *    - use locality group PA
   *      nothing wrong here -- they're different PAs covering different blocks
   *    - discard locality group PA
   *      discard process must wait until PA isn't used by another process
   *
   * now we're ready to make few consequences:
   *  - PA is referenced and while it is no discard is possible
   *  - PA is referenced until block isn't marked in on-disk bitmap
   *  - PA changes only after on-disk bitmap
   *  - discard must not compete with init. either init is done before
   *    any discard or they're serialized somehow
   *  - buddy init as sum of on-disk bitmap and PAs is done atomically
   *
   * a special case when we've used PA to emptiness. no need to modify buddy
   * in this case, but we should care about concurrent init
   *
   */
  
   /*
   * Logic in few words:
   *
   *  - allocation:
   *    load group
   *    find blocks
   *    mark bits in on-disk bitmap
   *    release group
   *
   *  - use preallocation:
   *    find proper PA (per-inode or group)
   *    load group
   *    mark bits in on-disk bitmap
   *    release group
   *    release PA
   *
   *  - free:
   *    load group
   *    mark bits in on-disk bitmap
   *    release group
   *
   *  - discard preallocations in group:
   *    mark PAs deleted
   *    move them onto local list
   *    load on-disk bitmap
   *    load group
   *    remove PA from object (inode or locality group)
   *    mark free blocks in-core
   *
   *  - discard inode's preallocations:
   */
  
  /*
   * Locking rules
   *
   * Locks:
   *  - bitlock on a group	(group)
   *  - object (inode/locality)	(object)
   *  - per-pa lock		(pa)
   *
   * Paths:
   *  - new pa
   *    object
   *    group
   *
   *  - find and use pa:
   *    pa
   *
   *  - release consumed pa:
   *    pa
   *    group
   *    object
   *
   *  - generate in-core bitmap:
   *    group
   *        pa
   *
   *  - discard all for given object (inode, locality group):
   *    object
   *        pa
   *    group
   *
   *  - discard all for given group:
   *    group
   *        pa
   *    group
   *        object
   *
   */

  static struct kmem_cache *ext4_pspace_cachep;
  static struct kmem_cache *ext4_ac_cachep;
  static struct kmem_cache *ext4_free_ext_cachep;
  static void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,
  					ext4_group_t group);

  static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
  						ext4_group_t group);

  static void release_blocks_on_commit(journal_t *journal, transaction_t *txn);

  static inline void *mb_correct_addr_and_bit(int *bit, void *addr)
  {

  #if BITS_PER_LONG == 64

  	*bit += ((unsigned long) addr & 7UL) << 3;
  	addr = (void *) ((unsigned long) addr & ~7UL);

  #elif BITS_PER_LONG == 32

  	*bit += ((unsigned long) addr & 3UL) << 3;
  	addr = (void *) ((unsigned long) addr & ~3UL);

  #else
  #error "how many bits you are?!"
  #endif

  	return addr;
  }

  
  static inline int mb_test_bit(int bit, void *addr)
  {
  	/*
  	 * ext4_test_bit on architecture like powerpc
  	 * needs unsigned long aligned address
  	 */

  	addr = mb_correct_addr_and_bit(&bit, addr);

  	return ext4_test_bit(bit, addr);
  }
  
  static inline void mb_set_bit(int bit, void *addr)
  {

  	addr = mb_correct_addr_and_bit(&bit, addr);

  	ext4_set_bit(bit, addr);
  }

  static inline void mb_clear_bit(int bit, void *addr)
  {

  	addr = mb_correct_addr_and_bit(&bit, addr);

  	ext4_clear_bit(bit, addr);
  }

  static inline int mb_find_next_zero_bit(void *addr, int max, int start)
  {

  	int fix = 0, ret, tmpmax;

  	addr = mb_correct_addr_and_bit(&fix, addr);

  	tmpmax = max + fix;

  	start += fix;

  	ret = ext4_find_next_zero_bit(addr, tmpmax, start) - fix;
  	if (ret > max)
  		return max;
  	return ret;

  }
  
  static inline int mb_find_next_bit(void *addr, int max, int start)
  {

  	int fix = 0, ret, tmpmax;

  	addr = mb_correct_addr_and_bit(&fix, addr);

  	tmpmax = max + fix;

  	start += fix;

  	ret = ext4_find_next_bit(addr, tmpmax, start) - fix;
  	if (ret > max)
  		return max;
  	return ret;

  }

  static void *mb_find_buddy(struct ext4_buddy *e4b, int order, int *max)
  {
  	char *bb;

  	BUG_ON(EXT4_MB_BITMAP(e4b) == EXT4_MB_BUDDY(e4b));
  	BUG_ON(max == NULL);
  
  	if (order > e4b->bd_blkbits + 1) {
  		*max = 0;
  		return NULL;
  	}
  
  	/* at order 0 we see each particular block */
  	*max = 1 << (e4b->bd_blkbits + 3);
  	if (order == 0)
  		return EXT4_MB_BITMAP(e4b);
  
  	bb = EXT4_MB_BUDDY(e4b) + EXT4_SB(e4b->bd_sb)->s_mb_offsets[order];
  	*max = EXT4_SB(e4b->bd_sb)->s_mb_maxs[order];
  
  	return bb;
  }
  
  #ifdef DOUBLE_CHECK
  static void mb_free_blocks_double(struct inode *inode, struct ext4_buddy *e4b,
  			   int first, int count)
  {
  	int i;
  	struct super_block *sb = e4b->bd_sb;
  
  	if (unlikely(e4b->bd_info->bb_bitmap == NULL))
  		return;

  	assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group));

  	for (i = 0; i < count; i++) {
  		if (!mb_test_bit(first + i, e4b->bd_info->bb_bitmap)) {
  			ext4_fsblk_t blocknr;

  
  			blocknr = ext4_group_first_block_no(sb, e4b->bd_group);

  			blocknr += first + i;

  			ext4_grp_locked_error(sb, e4b->bd_group,

  					      inode ? inode->i_ino : 0,
  					      blocknr,
  					      "freeing block already freed "
  					      "(bit %u)",
  					      first + i);

  		}
  		mb_clear_bit(first + i, e4b->bd_info->bb_bitmap);
  	}
  }
  
  static void mb_mark_used_double(struct ext4_buddy *e4b, int first, int count)
  {
  	int i;
  
  	if (unlikely(e4b->bd_info->bb_bitmap == NULL))
  		return;

  	assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));

  	for (i = 0; i < count; i++) {
  		BUG_ON(mb_test_bit(first + i, e4b->bd_info->bb_bitmap));
  		mb_set_bit(first + i, e4b->bd_info->bb_bitmap);
  	}
  }
  
  static void mb_cmp_bitmaps(struct ext4_buddy *e4b, void *bitmap)
  {
  	if (memcmp(e4b->bd_info->bb_bitmap, bitmap, e4b->bd_sb->s_blocksize)) {
  		unsigned char *b1, *b2;
  		int i;
  		b1 = (unsigned char *) e4b->bd_info->bb_bitmap;
  		b2 = (unsigned char *) bitmap;
  		for (i = 0; i < e4b->bd_sb->s_blocksize; i++) {
  			if (b1[i] != b2[i]) {

  				printk(KERN_ERR "corruption in group %u "

  				       "at byte %u(%u): %x in copy != %x "
  				       "on disk/prealloc
  ",
  				       e4b->bd_group, i, i * 8, b1[i], b2[i]);

  				BUG();
  			}
  		}
  	}
  }
  
  #else
  static inline void mb_free_blocks_double(struct inode *inode,
  				struct ext4_buddy *e4b, int first, int count)
  {
  	return;
  }
  static inline void mb_mark_used_double(struct ext4_buddy *e4b,
  						int first, int count)
  {
  	return;
  }
  static inline void mb_cmp_bitmaps(struct ext4_buddy *e4b, void *bitmap)
  {
  	return;
  }
  #endif
  
  #ifdef AGGRESSIVE_CHECK
  
  #define MB_CHECK_ASSERT(assert)						\
  do {									\
  	if (!(assert)) {						\
  		printk(KERN_EMERG					\
  			"Assertion failure in %s() at %s:%d: \"%s\"
  ",	\
  			function, file, line, # assert);		\
  		BUG();							\
  	}								\
  } while (0)
  
  static int __mb_check_buddy(struct ext4_buddy *e4b, char *file,
  				const char *function, int line)
  {
  	struct super_block *sb = e4b->bd_sb;
  	int order = e4b->bd_blkbits + 1;
  	int max;
  	int max2;
  	int i;
  	int j;
  	int k;
  	int count;
  	struct ext4_group_info *grp;
  	int fragments = 0;
  	int fstart;
  	struct list_head *cur;
  	void *buddy;
  	void *buddy2;

  	{
  		static int mb_check_counter;
  		if (mb_check_counter++ % 100 != 0)
  			return 0;
  	}
  
  	while (order > 1) {
  		buddy = mb_find_buddy(e4b, order, &max);
  		MB_CHECK_ASSERT(buddy);
  		buddy2 = mb_find_buddy(e4b, order - 1, &max2);
  		MB_CHECK_ASSERT(buddy2);
  		MB_CHECK_ASSERT(buddy != buddy2);
  		MB_CHECK_ASSERT(max * 2 == max2);
  
  		count = 0;
  		for (i = 0; i < max; i++) {
  
  			if (mb_test_bit(i, buddy)) {
  				/* only single bit in buddy2 may be 1 */
  				if (!mb_test_bit(i << 1, buddy2)) {
  					MB_CHECK_ASSERT(
  						mb_test_bit((i<<1)+1, buddy2));
  				} else if (!mb_test_bit((i << 1) + 1, buddy2)) {
  					MB_CHECK_ASSERT(
  						mb_test_bit(i << 1, buddy2));
  				}
  				continue;
  			}
  
  			/* both bits in buddy2 must be 0 */
  			MB_CHECK_ASSERT(mb_test_bit(i << 1, buddy2));
  			MB_CHECK_ASSERT(mb_test_bit((i << 1) + 1, buddy2));
  
  			for (j = 0; j < (1 << order); j++) {
  				k = (i * (1 << order)) + j;
  				MB_CHECK_ASSERT(
  					!mb_test_bit(k, EXT4_MB_BITMAP(e4b)));
  			}
  			count++;
  		}
  		MB_CHECK_ASSERT(e4b->bd_info->bb_counters[order] == count);
  		order--;
  	}
  
  	fstart = -1;
  	buddy = mb_find_buddy(e4b, 0, &max);
  	for (i = 0; i < max; i++) {
  		if (!mb_test_bit(i, buddy)) {
  			MB_CHECK_ASSERT(i >= e4b->bd_info->bb_first_free);
  			if (fstart == -1) {
  				fragments++;
  				fstart = i;
  			}
  			continue;
  		}
  		fstart = -1;
  		/* check used bits only */
  		for (j = 0; j < e4b->bd_blkbits + 1; j++) {
  			buddy2 = mb_find_buddy(e4b, j, &max2);
  			k = i >> j;
  			MB_CHECK_ASSERT(k < max2);
  			MB_CHECK_ASSERT(mb_test_bit(k, buddy2));
  		}
  	}
  	MB_CHECK_ASSERT(!EXT4_MB_GRP_NEED_INIT(e4b->bd_info));
  	MB_CHECK_ASSERT(e4b->bd_info->bb_fragments == fragments);
  
  	grp = ext4_get_group_info(sb, e4b->bd_group);
  	buddy = mb_find_buddy(e4b, 0, &max);
  	list_for_each(cur, &grp->bb_prealloc_list) {
  		ext4_group_t groupnr;
  		struct ext4_prealloc_space *pa;

  		pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
  		ext4_get_group_no_and_offset(sb, pa->pa_pstart, &groupnr, &k);

  		MB_CHECK_ASSERT(groupnr == e4b->bd_group);

  		for (i = 0; i < pa->pa_len; i++)

  			MB_CHECK_ASSERT(mb_test_bit(k + i, buddy));
  	}
  	return 0;
  }
  #undef MB_CHECK_ASSERT
  #define mb_check_buddy(e4b) __mb_check_buddy(e4b,	\

  					__FILE__, __func__, __LINE__)

  #else
  #define mb_check_buddy(e4b)
  #endif
  
  /* FIXME!! need more doc */
  static void ext4_mb_mark_free_simple(struct super_block *sb,

  				void *buddy, ext4_grpblk_t first, ext4_grpblk_t len,

  					struct ext4_group_info *grp)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	ext4_grpblk_t min;
  	ext4_grpblk_t max;
  	ext4_grpblk_t chunk;

  	unsigned short border;

  	BUG_ON(len > EXT4_BLOCKS_PER_GROUP(sb));

  
  	border = 2 << sb->s_blocksize_bits;
  
  	while (len > 0) {
  		/* find how many blocks can be covered since this position */
  		max = ffs(first | border) - 1;
  
  		/* find how many blocks of power 2 we need to mark */
  		min = fls(len) - 1;
  
  		if (max < min)
  			min = max;
  		chunk = 1 << min;
  
  		/* mark multiblock chunks only */
  		grp->bb_counters[min]++;
  		if (min > 0)
  			mb_clear_bit(first >> min,
  				     buddy + sbi->s_mb_offsets[min]);
  
  		len -= chunk;
  		first += chunk;
  	}
  }

  /*
   * Cache the order of the largest free extent we have available in this block
   * group.
   */
  static void
  mb_set_largest_free_order(struct super_block *sb, struct ext4_group_info *grp)
  {
  	int i;
  	int bits;
  
  	grp->bb_largest_free_order = -1; /* uninit */
  
  	bits = sb->s_blocksize_bits + 1;
  	for (i = bits; i >= 0; i--) {
  		if (grp->bb_counters[i] > 0) {
  			grp->bb_largest_free_order = i;
  			break;
  		}
  	}
  }

  static noinline_for_stack
  void ext4_mb_generate_buddy(struct super_block *sb,

  				void *buddy, void *bitmap, ext4_group_t group)
  {
  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);

  	ext4_grpblk_t max = EXT4_BLOCKS_PER_GROUP(sb);
  	ext4_grpblk_t i = 0;
  	ext4_grpblk_t first;
  	ext4_grpblk_t len;

  	unsigned free = 0;
  	unsigned fragments = 0;
  	unsigned long long period = get_cycles();
  
  	/* initialize buddy from bitmap which is aggregation
  	 * of on-disk bitmap and preallocations */

  	i = mb_find_next_zero_bit(bitmap, max, 0);

  	grp->bb_first_free = i;
  	while (i < max) {
  		fragments++;
  		first = i;

  		i = mb_find_next_bit(bitmap, max, i);

  		len = i - first;
  		free += len;
  		if (len > 1)
  			ext4_mb_mark_free_simple(sb, buddy, first, len, grp);
  		else
  			grp->bb_counters[0]++;
  		if (i < max)

  			i = mb_find_next_zero_bit(bitmap, max, i);

  	}
  	grp->bb_fragments = fragments;
  
  	if (free != grp->bb_free) {

  		ext4_grp_locked_error(sb, group, 0, 0,
  				      "%u blocks in bitmap, %u in gd",
  				      free, grp->bb_free);

  		/*
  		 * If we intent to continue, we consider group descritor
  		 * corrupt and update bb_free using bitmap value
  		 */

  		grp->bb_free = free;
  	}

  	mb_set_largest_free_order(sb, grp);

  
  	clear_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
  
  	period = get_cycles() - period;
  	spin_lock(&EXT4_SB(sb)->s_bal_lock);
  	EXT4_SB(sb)->s_mb_buddies_generated++;
  	EXT4_SB(sb)->s_mb_generation_time += period;
  	spin_unlock(&EXT4_SB(sb)->s_bal_lock);
  }
  
  /* The buddy information is attached the buddy cache inode
   * for convenience. The information regarding each group
   * is loaded via ext4_mb_load_buddy. The information involve
   * block bitmap and buddy information. The information are
   * stored in the inode as
   *
   * {                        page                        }

   * [ group 0 bitmap][ group 0 buddy] [group 1][ group 1]...

   *
   *
   * one block each for bitmap and buddy information.
   * So for each group we take up 2 blocks. A page can
   * contain blocks_per_page (PAGE_CACHE_SIZE / blocksize)  blocks.
   * So it can have information regarding groups_per_page which
   * is blocks_per_page/2

   *
   * Locking note:  This routine takes the block group lock of all groups
   * for this page; do not hold this lock when calling this routine!

   */
  
  static int ext4_mb_init_cache(struct page *page, char *incore)
  {

  	ext4_group_t ngroups;

  	int blocksize;
  	int blocks_per_page;
  	int groups_per_page;
  	int err = 0;
  	int i;
  	ext4_group_t first_group;
  	int first_block;
  	struct super_block *sb;
  	struct buffer_head *bhs;
  	struct buffer_head **bh;
  	struct inode *inode;
  	char *data;
  	char *bitmap;

  	mb_debug(1, "init page %lu
  ", page->index);

  
  	inode = page->mapping->host;
  	sb = inode->i_sb;

  	ngroups = ext4_get_groups_count(sb);

  	blocksize = 1 << inode->i_blkbits;
  	blocks_per_page = PAGE_CACHE_SIZE / blocksize;
  
  	groups_per_page = blocks_per_page >> 1;
  	if (groups_per_page == 0)
  		groups_per_page = 1;
  
  	/* allocate buffer_heads to read bitmaps */
  	if (groups_per_page > 1) {
  		err = -ENOMEM;
  		i = sizeof(struct buffer_head *) * groups_per_page;
  		bh = kzalloc(i, GFP_NOFS);
  		if (bh == NULL)
  			goto out;
  	} else
  		bh = &bhs;
  
  	first_group = page->index * blocks_per_page / 2;
  
  	/* read all groups the page covers into the cache */
  	for (i = 0; i < groups_per_page; i++) {
  		struct ext4_group_desc *desc;

  		if (first_group + i >= ngroups)

  			break;
  
  		err = -EIO;
  		desc = ext4_get_group_desc(sb, first_group + i, NULL);
  		if (desc == NULL)
  			goto out;
  
  		err = -ENOMEM;
  		bh[i] = sb_getblk(sb, ext4_block_bitmap(sb, desc));
  		if (bh[i] == NULL)
  			goto out;

  		if (bitmap_uptodate(bh[i]))

  			continue;

  		lock_buffer(bh[i]);

  		if (bitmap_uptodate(bh[i])) {
  			unlock_buffer(bh[i]);
  			continue;
  		}

  		ext4_lock_group(sb, first_group + i);

  		if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
  			ext4_init_block_bitmap(sb, bh[i],
  						first_group + i, desc);

  			set_bitmap_uptodate(bh[i]);

  			set_buffer_uptodate(bh[i]);

  			ext4_unlock_group(sb, first_group + i);

  			unlock_buffer(bh[i]);

  			continue;
  		}

  		ext4_unlock_group(sb, first_group + i);

  		if (buffer_uptodate(bh[i])) {
  			/*
  			 * if not uninit if bh is uptodate,
  			 * bitmap is also uptodate
  			 */
  			set_bitmap_uptodate(bh[i]);
  			unlock_buffer(bh[i]);
  			continue;
  		}

  		get_bh(bh[i]);

  		/*
  		 * submit the buffer_head for read. We can
  		 * safely mark the bitmap as uptodate now.
  		 * We do it here so the bitmap uptodate bit
  		 * get set with buffer lock held.
  		 */
  		set_bitmap_uptodate(bh[i]);

  		bh[i]->b_end_io = end_buffer_read_sync;
  		submit_bh(READ, bh[i]);

  		mb_debug(1, "read bitmap for group %u
  ", first_group + i);

  	}
  
  	/* wait for I/O completion */
  	for (i = 0; i < groups_per_page && bh[i]; i++)
  		wait_on_buffer(bh[i]);
  
  	err = -EIO;
  	for (i = 0; i < groups_per_page && bh[i]; i++)
  		if (!buffer_uptodate(bh[i]))
  			goto out;

  	err = 0;

  	first_block = page->index * blocks_per_page;

  	/* init the page  */
  	memset(page_address(page), 0xff, PAGE_CACHE_SIZE);

  	for (i = 0; i < blocks_per_page; i++) {
  		int group;
  		struct ext4_group_info *grinfo;
  
  		group = (first_block + i) >> 1;

  		if (group >= ngroups)

  			break;
  
  		/*
  		 * data carry information regarding this
  		 * particular group in the format specified
  		 * above
  		 *
  		 */
  		data = page_address(page) + (i * blocksize);
  		bitmap = bh[group - first_group]->b_data;
  
  		/*
  		 * We place the buddy block and bitmap block
  		 * close together
  		 */
  		if ((first_block + i) & 1) {
  			/* this is block of buddy */
  			BUG_ON(incore == NULL);

  			mb_debug(1, "put buddy for group %u in page %lu/%x
  ",

  				group, page->index, i * blocksize);

  			trace_ext4_mb_buddy_bitmap_load(sb, group);

  			grinfo = ext4_get_group_info(sb, group);
  			grinfo->bb_fragments = 0;
  			memset(grinfo->bb_counters, 0,

  			       sizeof(*grinfo->bb_counters) *
  				(sb->s_blocksize_bits+2));

  			/*
  			 * incore got set to the group block bitmap below
  			 */

  			ext4_lock_group(sb, group);

  			ext4_mb_generate_buddy(sb, data, incore, group);

  			ext4_unlock_group(sb, group);

  			incore = NULL;
  		} else {
  			/* this is block of bitmap */
  			BUG_ON(incore != NULL);

  			mb_debug(1, "put bitmap for group %u in page %lu/%x
  ",

  				group, page->index, i * blocksize);

  			trace_ext4_mb_bitmap_load(sb, group);

  
  			/* see comments in ext4_mb_put_pa() */
  			ext4_lock_group(sb, group);
  			memcpy(data, bitmap, blocksize);
  
  			/* mark all preallocated blks used in in-core bitmap */
  			ext4_mb_generate_from_pa(sb, data, group);

  			ext4_mb_generate_from_freelist(sb, data, group);

  			ext4_unlock_group(sb, group);
  
  			/* set incore so that the buddy information can be
  			 * generated using this
  			 */
  			incore = data;
  		}
  	}
  	SetPageUptodate(page);
  
  out:
  	if (bh) {
  		for (i = 0; i < groups_per_page && bh[i]; i++)
  			brelse(bh[i]);
  		if (bh != &bhs)
  			kfree(bh);
  	}
  	return err;
  }

  /*
   * Locking note:  This routine calls ext4_mb_init_cache(), which takes the
   * block group lock of all groups for this page; do not hold the BG lock when
   * calling this routine!
   */

  static noinline_for_stack
  int ext4_mb_init_group(struct super_block *sb, ext4_group_t group)
  {
  
  	int ret = 0;
  	void *bitmap;
  	int blocks_per_page;
  	int block, pnum, poff;
  	int num_grp_locked = 0;
  	struct ext4_group_info *this_grp;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct inode *inode = sbi->s_buddy_cache;
  	struct page *page = NULL, *bitmap_page = NULL;
  
  	mb_debug(1, "init group %u
  ", group);
  	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
  	this_grp = ext4_get_group_info(sb, group);
  	/*

  	 * This ensures that we don't reinit the buddy cache
  	 * page which map to the group from which we are already
  	 * allocating. If we are looking at the buddy cache we would
  	 * have taken a reference using ext4_mb_load_buddy and that
  	 * would have taken the alloc_sem lock.

  	 */
  	num_grp_locked =  ext4_mb_get_buddy_cache_lock(sb, group);
  	if (!EXT4_MB_GRP_NEED_INIT(this_grp)) {
  		/*
  		 * somebody initialized the group
  		 * return without doing anything
  		 */
  		ret = 0;
  		goto err;
  	}
  	/*
  	 * the buddy cache inode stores the block bitmap
  	 * and buddy information in consecutive blocks.
  	 * So for each group we need two blocks.
  	 */
  	block = group * 2;
  	pnum = block / blocks_per_page;
  	poff = block % blocks_per_page;
  	page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
  	if (page) {
  		BUG_ON(page->mapping != inode->i_mapping);
  		ret = ext4_mb_init_cache(page, NULL);
  		if (ret) {
  			unlock_page(page);
  			goto err;
  		}
  		unlock_page(page);
  	}
  	if (page == NULL || !PageUptodate(page)) {
  		ret = -EIO;
  		goto err;
  	}
  	mark_page_accessed(page);
  	bitmap_page = page;
  	bitmap = page_address(page) + (poff * sb->s_blocksize);
  
  	/* init buddy cache */
  	block++;
  	pnum = block / blocks_per_page;
  	poff = block % blocks_per_page;
  	page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
  	if (page == bitmap_page) {
  		/*
  		 * If both the bitmap and buddy are in
  		 * the same page we don't need to force
  		 * init the buddy
  		 */
  		unlock_page(page);
  	} else if (page) {
  		BUG_ON(page->mapping != inode->i_mapping);
  		ret = ext4_mb_init_cache(page, bitmap);
  		if (ret) {
  			unlock_page(page);
  			goto err;
  		}
  		unlock_page(page);
  	}
  	if (page == NULL || !PageUptodate(page)) {
  		ret = -EIO;
  		goto err;
  	}
  	mark_page_accessed(page);
  err:
  	ext4_mb_put_buddy_cache_lock(sb, group, num_grp_locked);
  	if (bitmap_page)
  		page_cache_release(bitmap_page);
  	if (page)
  		page_cache_release(page);
  	return ret;
  }

  /*
   * Locking note:  This routine calls ext4_mb_init_cache(), which takes the
   * block group lock of all groups for this page; do not hold the BG lock when
   * calling this routine!
   */

  static noinline_for_stack int
  ext4_mb_load_buddy(struct super_block *sb, ext4_group_t group,
  					struct ext4_buddy *e4b)

  {

  	int blocks_per_page;
  	int block;
  	int pnum;
  	int poff;
  	struct page *page;

  	int ret;

  	struct ext4_group_info *grp;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct inode *inode = sbi->s_buddy_cache;

  	mb_debug(1, "load group %u
  ", group);

  
  	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;

  	grp = ext4_get_group_info(sb, group);

  
  	e4b->bd_blkbits = sb->s_blocksize_bits;
  	e4b->bd_info = ext4_get_group_info(sb, group);
  	e4b->bd_sb = sb;
  	e4b->bd_group = group;
  	e4b->bd_buddy_page = NULL;
  	e4b->bd_bitmap_page = NULL;

  	e4b->alloc_semp = &grp->alloc_sem;
  
  	/* Take the read lock on the group alloc
  	 * sem. This would make sure a parallel
  	 * ext4_mb_init_group happening on other
  	 * groups mapped by the page is blocked
  	 * till we are done with allocation
  	 */

  repeat_load_buddy:

  	down_read(e4b->alloc_semp);

  	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
  		/* we need to check for group need init flag
  		 * with alloc_semp held so that we can be sure
  		 * that new blocks didn't get added to the group
  		 * when we are loading the buddy cache
  		 */
  		up_read(e4b->alloc_semp);
  		/*
  		 * we need full data about the group
  		 * to make a good selection
  		 */
  		ret = ext4_mb_init_group(sb, group);
  		if (ret)
  			return ret;
  		goto repeat_load_buddy;
  	}

  	/*
  	 * the buddy cache inode stores the block bitmap
  	 * and buddy information in consecutive blocks.
  	 * So for each group we need two blocks.
  	 */
  	block = group * 2;
  	pnum = block / blocks_per_page;
  	poff = block % blocks_per_page;
  
  	/* we could use find_or_create_page(), but it locks page
  	 * what we'd like to avoid in fast path ... */
  	page = find_get_page(inode->i_mapping, pnum);
  	if (page == NULL || !PageUptodate(page)) {
  		if (page)

  			/*
  			 * drop the page reference and try
  			 * to get the page with lock. If we
  			 * are not uptodate that implies
  			 * somebody just created the page but
  			 * is yet to initialize the same. So
  			 * wait for it to initialize.
  			 */

  			page_cache_release(page);
  		page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
  		if (page) {
  			BUG_ON(page->mapping != inode->i_mapping);
  			if (!PageUptodate(page)) {

  				ret = ext4_mb_init_cache(page, NULL);
  				if (ret) {
  					unlock_page(page);
  					goto err;
  				}

  				mb_cmp_bitmaps(e4b, page_address(page) +
  					       (poff * sb->s_blocksize));
  			}
  			unlock_page(page);
  		}
  	}

  	if (page == NULL || !PageUptodate(page)) {
  		ret = -EIO;

  		goto err;

  	}

  	e4b->bd_bitmap_page = page;
  	e4b->bd_bitmap = page_address(page) + (poff * sb->s_blocksize);
  	mark_page_accessed(page);
  
  	block++;
  	pnum = block / blocks_per_page;
  	poff = block % blocks_per_page;
  
  	page = find_get_page(inode->i_mapping, pnum);
  	if (page == NULL || !PageUptodate(page)) {
  		if (page)
  			page_cache_release(page);
  		page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
  		if (page) {
  			BUG_ON(page->mapping != inode->i_mapping);

  			if (!PageUptodate(page)) {
  				ret = ext4_mb_init_cache(page, e4b->bd_bitmap);
  				if (ret) {
  					unlock_page(page);
  					goto err;
  				}
  			}

  			unlock_page(page);
  		}
  	}

  	if (page == NULL || !PageUptodate(page)) {
  		ret = -EIO;

  		goto err;

  	}

  	e4b->bd_buddy_page = page;
  	e4b->bd_buddy = page_address(page) + (poff * sb->s_blocksize);
  	mark_page_accessed(page);
  
  	BUG_ON(e4b->bd_bitmap_page == NULL);
  	BUG_ON(e4b->bd_buddy_page == NULL);
  
  	return 0;
  
  err:
  	if (e4b->bd_bitmap_page)
  		page_cache_release(e4b->bd_bitmap_page);
  	if (e4b->bd_buddy_page)
  		page_cache_release(e4b->bd_buddy_page);
  	e4b->bd_buddy = NULL;
  	e4b->bd_bitmap = NULL;

  
  	/* Done with the buddy cache */
  	up_read(e4b->alloc_semp);

  	return ret;

  }

  static void ext4_mb_unload_buddy(struct ext4_buddy *e4b)

  {
  	if (e4b->bd_bitmap_page)
  		page_cache_release(e4b->bd_bitmap_page);
  	if (e4b->bd_buddy_page)
  		page_cache_release(e4b->bd_buddy_page);

  	/* Done with the buddy cache */

  	if (e4b->alloc_semp)
  		up_read(e4b->alloc_semp);

  }
  
  
  static int mb_find_order_for_block(struct ext4_buddy *e4b, int block)
  {
  	int order = 1;
  	void *bb;
  
  	BUG_ON(EXT4_MB_BITMAP(e4b) == EXT4_MB_BUDDY(e4b));
  	BUG_ON(block >= (1 << (e4b->bd_blkbits + 3)));
  
  	bb = EXT4_MB_BUDDY(e4b);
  	while (order <= e4b->bd_blkbits + 1) {
  		block = block >> 1;
  		if (!mb_test_bit(block, bb)) {
  			/* this block is part of buddy of order 'order' */
  			return order;
  		}
  		bb += 1 << (e4b->bd_blkbits - order);
  		order++;
  	}
  	return 0;
  }

  static void mb_clear_bits(void *bm, int cur, int len)

  {
  	__u32 *addr;
  
  	len = cur + len;
  	while (cur < len) {
  		if ((cur & 31) == 0 && (len - cur) >= 32) {
  			/* fast path: clear whole word at once */
  			addr = bm + (cur >> 3);
  			*addr = 0;
  			cur += 32;
  			continue;
  		}

  		mb_clear_bit(cur, bm);

  		cur++;
  	}
  }

  static void mb_set_bits(void *bm, int cur, int len)

  {
  	__u32 *addr;
  
  	len = cur + len;
  	while (cur < len) {
  		if ((cur & 31) == 0 && (len - cur) >= 32) {
  			/* fast path: set whole word at once */
  			addr = bm + (cur >> 3);
  			*addr = 0xffffffff;
  			cur += 32;
  			continue;
  		}

  		mb_set_bit(cur, bm);

  		cur++;
  	}
  }

  static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b,

  			  int first, int count)
  {
  	int block = 0;
  	int max = 0;
  	int order;
  	void *buddy;
  	void *buddy2;
  	struct super_block *sb = e4b->bd_sb;
  
  	BUG_ON(first + count > (sb->s_blocksize << 3));

  	assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group));

  	mb_check_buddy(e4b);
  	mb_free_blocks_double(inode, e4b, first, count);
  
  	e4b->bd_info->bb_free += count;
  	if (first < e4b->bd_info->bb_first_free)
  		e4b->bd_info->bb_first_free = first;
  
  	/* let's maintain fragments counter */
  	if (first != 0)
  		block = !mb_test_bit(first - 1, EXT4_MB_BITMAP(e4b));
  	if (first + count < EXT4_SB(sb)->s_mb_maxs[0])
  		max = !mb_test_bit(first + count, EXT4_MB_BITMAP(e4b));
  	if (block && max)
  		e4b->bd_info->bb_fragments--;
  	else if (!block && !max)
  		e4b->bd_info->bb_fragments++;
  
  	/* let's maintain buddy itself */
  	while (count-- > 0) {
  		block = first++;
  		order = 0;
  
  		if (!mb_test_bit(block, EXT4_MB_BITMAP(e4b))) {
  			ext4_fsblk_t blocknr;

  
  			blocknr = ext4_group_first_block_no(sb, e4b->bd_group);

  			blocknr += block;

  			ext4_grp_locked_error(sb, e4b->bd_group,

  					      inode ? inode->i_ino : 0,
  					      blocknr,
  					      "freeing already freed block "
  					      "(bit %u)", block);

  		}
  		mb_clear_bit(block, EXT4_MB_BITMAP(e4b));
  		e4b->bd_info->bb_counters[order]++;
  
  		/* start of the buddy */
  		buddy = mb_find_buddy(e4b, order, &max);
  
  		do {
  			block &= ~1UL;
  			if (mb_test_bit(block, buddy) ||
  					mb_test_bit(block + 1, buddy))
  				break;
  
  			/* both the buddies are free, try to coalesce them */
  			buddy2 = mb_find_buddy(e4b, order + 1, &max);
  
  			if (!buddy2)
  				break;
  
  			if (order > 0) {
  				/* for special purposes, we don't set
  				 * free bits in bitmap */
  				mb_set_bit(block, buddy);
  				mb_set_bit(block + 1, buddy);
  			}
  			e4b->bd_info->bb_counters[order]--;
  			e4b->bd_info->bb_counters[order]--;
  
  			block = block >> 1;
  			order++;
  			e4b->bd_info->bb_counters[order]++;
  
  			mb_clear_bit(block, buddy2);
  			buddy = buddy2;
  		} while (1);
  	}

  	mb_set_largest_free_order(sb, e4b->bd_info);

  	mb_check_buddy(e4b);

  }
  
  static int mb_find_extent(struct ext4_buddy *e4b, int order, int block,
  				int needed, struct ext4_free_extent *ex)
  {
  	int next = block;
  	int max;
  	int ord;
  	void *buddy;

  	assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));

  	BUG_ON(ex == NULL);
  
  	buddy = mb_find_buddy(e4b, order, &max);
  	BUG_ON(buddy == NULL);
  	BUG_ON(block >= max);
  	if (mb_test_bit(block, buddy)) {
  		ex->fe_len = 0;
  		ex->fe_start = 0;
  		ex->fe_group = 0;
  		return 0;
  	}
  
  	/* FIXME dorp order completely ? */
  	if (likely(order == 0)) {
  		/* find actual order */
  		order = mb_find_order_for_block(e4b, block);
  		block = block >> order;
  	}
  
  	ex->fe_len = 1 << order;
  	ex->fe_start = block << order;
  	ex->fe_group = e4b->bd_group;
  
  	/* calc difference from given start */
  	next = next - ex->fe_start;
  	ex->fe_len -= next;
  	ex->fe_start += next;
  
  	while (needed > ex->fe_len &&
  	       (buddy = mb_find_buddy(e4b, order, &max))) {
  
  		if (block + 1 >= max)
  			break;
  
  		next = (block + 1) * (1 << order);
  		if (mb_test_bit(next, EXT4_MB_BITMAP(e4b)))
  			break;
  
  		ord = mb_find_order_for_block(e4b, next);
  
  		order = ord;
  		block = next >> order;
  		ex->fe_len += 1 << order;
  	}
  
  	BUG_ON(ex->fe_start + ex->fe_len > (1 << (e4b->bd_blkbits + 3)));
  	return ex->fe_len;
  }
  
  static int mb_mark_used(struct ext4_buddy *e4b, struct ext4_free_extent *ex)
  {
  	int ord;
  	int mlen = 0;
  	int max = 0;
  	int cur;
  	int start = ex->fe_start;
  	int len = ex->fe_len;
  	unsigned ret = 0;
  	int len0 = len;
  	void *buddy;
  
  	BUG_ON(start + len > (e4b->bd_sb->s_blocksize << 3));
  	BUG_ON(e4b->bd_group != ex->fe_group);

  	assert_spin_locked(ext4_group_lock_ptr(e4b->bd_sb, e4b->bd_group));

  	mb_check_buddy(e4b);
  	mb_mark_used_double(e4b, start, len);
  
  	e4b->bd_info->bb_free -= len;
  	if (e4b->bd_info->bb_first_free == start)
  		e4b->bd_info->bb_first_free += len;
  
  	/* let's maintain fragments counter */
  	if (start != 0)
  		mlen = !mb_test_bit(start - 1, EXT4_MB_BITMAP(e4b));
  	if (start + len < EXT4_SB(e4b->bd_sb)->s_mb_maxs[0])
  		max = !mb_test_bit(start + len, EXT4_MB_BITMAP(e4b));
  	if (mlen && max)
  		e4b->bd_info->bb_fragments++;
  	else if (!mlen && !max)
  		e4b->bd_info->bb_fragments--;
  
  	/* let's maintain buddy itself */
  	while (len) {
  		ord = mb_find_order_for_block(e4b, start);
  
  		if (((start >> ord) << ord) == start && len >= (1 << ord)) {
  			/* the whole chunk may be allocated at once! */
  			mlen = 1 << ord;
  			buddy = mb_find_buddy(e4b, ord, &max);
  			BUG_ON((start >> ord) >= max);
  			mb_set_bit(start >> ord, buddy);
  			e4b->bd_info->bb_counters[ord]--;
  			start += mlen;
  			len -= mlen;
  			BUG_ON(len < 0);
  			continue;
  		}
  
  		/* store for history */
  		if (ret == 0)
  			ret = len | (ord << 16);
  
  		/* we have to split large buddy */
  		BUG_ON(ord <= 0);
  		buddy = mb_find_buddy(e4b, ord, &max);
  		mb_set_bit(start >> ord, buddy);
  		e4b->bd_info->bb_counters[ord]--;
  
  		ord--;
  		cur = (start >> ord) & ~1U;
  		buddy = mb_find_buddy(e4b, ord, &max);
  		mb_clear_bit(cur, buddy);
  		mb_clear_bit(cur + 1, buddy);
  		e4b->bd_info->bb_counters[ord]++;
  		e4b->bd_info->bb_counters[ord]++;
  	}

  	mb_set_largest_free_order(e4b->bd_sb, e4b->bd_info);

  	mb_set_bits(EXT4_MB_BITMAP(e4b), ex->fe_start, len0);

  	mb_check_buddy(e4b);
  
  	return ret;
  }
  
  /*
   * Must be called under group lock!
   */
  static void ext4_mb_use_best_found(struct ext4_allocation_context *ac,
  					struct ext4_buddy *e4b)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	int ret;
  
  	BUG_ON(ac->ac_b_ex.fe_group != e4b->bd_group);
  	BUG_ON(ac->ac_status == AC_STATUS_FOUND);
  
  	ac->ac_b_ex.fe_len = min(ac->ac_b_ex.fe_len, ac->ac_g_ex.fe_len);
  	ac->ac_b_ex.fe_logical = ac->ac_g_ex.fe_logical;
  	ret = mb_mark_used(e4b, &ac->ac_b_ex);
  
  	/* preallocation can change ac_b_ex, thus we store actually
  	 * allocated blocks for history */
  	ac->ac_f_ex = ac->ac_b_ex;
  
  	ac->ac_status = AC_STATUS_FOUND;
  	ac->ac_tail = ret & 0xffff;
  	ac->ac_buddy = ret >> 16;

  	/*
  	 * take the page reference. We want the page to be pinned
  	 * so that we don't get a ext4_mb_init_cache_call for this
  	 * group until we update the bitmap. That would mean we
  	 * double allocate blocks. The reference is dropped
  	 * in ext4_mb_release_context
  	 */

  	ac->ac_bitmap_page = e4b->bd_bitmap_page;
  	get_page(ac->ac_bitmap_page);
  	ac->ac_buddy_page = e4b->bd_buddy_page;
  	get_page(ac->ac_buddy_page);

  	/* on allocation we use ac to track the held semaphore */
  	ac->alloc_semp =  e4b->alloc_semp;
  	e4b->alloc_semp = NULL;

  	/* store last allocated for subsequent stream allocation */

  	if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {

  		spin_lock(&sbi->s_md_lock);
  		sbi->s_mb_last_group = ac->ac_f_ex.fe_group;
  		sbi->s_mb_last_start = ac->ac_f_ex.fe_start;
  		spin_unlock(&sbi->s_md_lock);
  	}
  }
  
  /*
   * regular allocator, for general purposes allocation
   */
  
  static void ext4_mb_check_limits(struct ext4_allocation_context *ac,
  					struct ext4_buddy *e4b,
  					int finish_group)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  	struct ext4_free_extent *bex = &ac->ac_b_ex;
  	struct ext4_free_extent *gex = &ac->ac_g_ex;
  	struct ext4_free_extent ex;
  	int max;

  	if (ac->ac_status == AC_STATUS_FOUND)
  		return;

  	/*
  	 * We don't want to scan for a whole year
  	 */
  	if (ac->ac_found > sbi->s_mb_max_to_scan &&
  			!(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
  		ac->ac_status = AC_STATUS_BREAK;
  		return;
  	}
  
  	/*
  	 * Haven't found good chunk so far, let's continue
  	 */
  	if (bex->fe_len < gex->fe_len)
  		return;
  
  	if ((finish_group || ac->ac_found > sbi->s_mb_min_to_scan)
  			&& bex->fe_group == e4b->bd_group) {
  		/* recheck chunk's availability - we don't know
  		 * when it was found (within this lock-unlock
  		 * period or not) */
  		max = mb_find_extent(e4b, 0, bex->fe_start, gex->fe_len, &ex);
  		if (max >= gex->fe_len) {
  			ext4_mb_use_best_found(ac, e4b);
  			return;
  		}
  	}
  }
  
  /*
   * The routine checks whether found extent is good enough. If it is,
   * then the extent gets marked used and flag is set to the context
   * to stop scanning. Otherwise, the extent is compared with the
   * previous found extent and if new one is better, then it's stored
   * in the context. Later, the best found extent will be used, if
   * mballoc can't find good enough extent.
   *
   * FIXME: real allocation policy is to be designed yet!
   */
  static void ext4_mb_measure_extent(struct ext4_allocation_context *ac,
  					struct ext4_free_extent *ex,
  					struct ext4_buddy *e4b)
  {
  	struct ext4_free_extent *bex = &ac->ac_b_ex;
  	struct ext4_free_extent *gex = &ac->ac_g_ex;
  
  	BUG_ON(ex->fe_len <= 0);

  	BUG_ON(ex->fe_len > EXT4_BLOCKS_PER_GROUP(ac->ac_sb));

  	BUG_ON(ex->fe_start >= EXT4_BLOCKS_PER_GROUP(ac->ac_sb));
  	BUG_ON(ac->ac_status != AC_STATUS_CONTINUE);
  
  	ac->ac_found++;
  
  	/*
  	 * The special case - take what you catch first
  	 */
  	if (unlikely(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
  		*bex = *ex;
  		ext4_mb_use_best_found(ac, e4b);
  		return;
  	}
  
  	/*
  	 * Let's check whether the chuck is good enough
  	 */
  	if (ex->fe_len == gex->fe_len) {
  		*bex = *ex;
  		ext4_mb_use_best_found(ac, e4b);
  		return;
  	}
  
  	/*
  	 * If this is first found extent, just store it in the context
  	 */
  	if (bex->fe_len == 0) {
  		*bex = *ex;
  		return;
  	}
  
  	/*
  	 * If new found extent is better, store it in the context
  	 */
  	if (bex->fe_len < gex->fe_len) {
  		/* if the request isn't satisfied, any found extent
  		 * larger than previous best one is better */
  		if (ex->fe_len > bex->fe_len)
  			*bex = *ex;
  	} else if (ex->fe_len > gex->fe_len) {
  		/* if the request is satisfied, then we try to find
  		 * an extent that still satisfy the request, but is
  		 * smaller than previous one */
  		if (ex->fe_len < bex->fe_len)
  			*bex = *ex;
  	}
  
  	ext4_mb_check_limits(ac, e4b, 0);
  }

  static noinline_for_stack
  int ext4_mb_try_best_found(struct ext4_allocation_context *ac,

  					struct ext4_buddy *e4b)
  {
  	struct ext4_free_extent ex = ac->ac_b_ex;
  	ext4_group_t group = ex.fe_group;
  	int max;
  	int err;
  
  	BUG_ON(ex.fe_len <= 0);
  	err = ext4_mb_load_buddy(ac->ac_sb, group, e4b);
  	if (err)
  		return err;
  
  	ext4_lock_group(ac->ac_sb, group);
  	max = mb_find_extent(e4b, 0, ex.fe_start, ex.fe_len, &ex);
  
  	if (max > 0) {
  		ac->ac_b_ex = ex;
  		ext4_mb_use_best_found(ac, e4b);
  	}
  
  	ext4_unlock_group(ac->ac_sb, group);

  	ext4_mb_unload_buddy(e4b);

  
  	return 0;
  }

  static noinline_for_stack
  int ext4_mb_find_by_goal(struct ext4_allocation_context *ac,

  				struct ext4_buddy *e4b)
  {
  	ext4_group_t group = ac->ac_g_ex.fe_group;
  	int max;
  	int err;
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);

  	struct ext4_free_extent ex;
  
  	if (!(ac->ac_flags & EXT4_MB_HINT_TRY_GOAL))
  		return 0;
  
  	err = ext4_mb_load_buddy(ac->ac_sb, group, e4b);
  	if (err)
  		return err;
  
  	ext4_lock_group(ac->ac_sb, group);
  	max = mb_find_extent(e4b, 0, ac->ac_g_ex.fe_start,
  			     ac->ac_g_ex.fe_len, &ex);
  
  	if (max >= ac->ac_g_ex.fe_len && ac->ac_g_ex.fe_len == sbi->s_stripe) {
  		ext4_fsblk_t start;

  		start = ext4_group_first_block_no(ac->ac_sb, e4b->bd_group) +
  			ex.fe_start;

  		/* use do_div to get remainder (would be 64-bit modulo) */
  		if (do_div(start, sbi->s_stripe) == 0) {
  			ac->ac_found++;
  			ac->ac_b_ex = ex;
  			ext4_mb_use_best_found(ac, e4b);
  		}
  	} else if (max >= ac->ac_g_ex.fe_len) {
  		BUG_ON(ex.fe_len <= 0);
  		BUG_ON(ex.fe_group != ac->ac_g_ex.fe_group);
  		BUG_ON(ex.fe_start != ac->ac_g_ex.fe_start);
  		ac->ac_found++;
  		ac->ac_b_ex = ex;
  		ext4_mb_use_best_found(ac, e4b);
  	} else if (max > 0 && (ac->ac_flags & EXT4_MB_HINT_MERGE)) {
  		/* Sometimes, caller may want to merge even small
  		 * number of blocks to an existing extent */
  		BUG_ON(ex.fe_len <= 0);
  		BUG_ON(ex.fe_group != ac->ac_g_ex.fe_group);
  		BUG_ON(ex.fe_start != ac->ac_g_ex.fe_start);
  		ac->ac_found++;
  		ac->ac_b_ex = ex;
  		ext4_mb_use_best_found(ac, e4b);
  	}
  	ext4_unlock_group(ac->ac_sb, group);

  	ext4_mb_unload_buddy(e4b);

  
  	return 0;
  }
  
  /*
   * The routine scans buddy structures (not bitmap!) from given order
   * to max order and tries to find big enough chunk to satisfy the req
   */

  static noinline_for_stack
  void ext4_mb_simple_scan_group(struct ext4_allocation_context *ac,

  					struct ext4_buddy *e4b)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_group_info *grp = e4b->bd_info;
  	void *buddy;
  	int i;
  	int k;
  	int max;
  
  	BUG_ON(ac->ac_2order <= 0);
  	for (i = ac->ac_2order; i <= sb->s_blocksize_bits + 1; i++) {
  		if (grp->bb_counters[i] == 0)
  			continue;
  
  		buddy = mb_find_buddy(e4b, i, &max);
  		BUG_ON(buddy == NULL);

  		k = mb_find_next_zero_bit(buddy, max, 0);

  		BUG_ON(k >= max);
  
  		ac->ac_found++;
  
  		ac->ac_b_ex.fe_len = 1 << i;
  		ac->ac_b_ex.fe_start = k << i;
  		ac->ac_b_ex.fe_group = e4b->bd_group;
  
  		ext4_mb_use_best_found(ac, e4b);
  
  		BUG_ON(ac->ac_b_ex.fe_len != ac->ac_g_ex.fe_len);
  
  		if (EXT4_SB(sb)->s_mb_stats)
  			atomic_inc(&EXT4_SB(sb)->s_bal_2orders);
  
  		break;
  	}
  }
  
  /*
   * The routine scans the group and measures all found extents.
   * In order to optimize scanning, caller must pass number of
   * free blocks in the group, so the routine can know upper limit.
   */

  static noinline_for_stack
  void ext4_mb_complex_scan_group(struct ext4_allocation_context *ac,

  					struct ext4_buddy *e4b)
  {
  	struct super_block *sb = ac->ac_sb;
  	void *bitmap = EXT4_MB_BITMAP(e4b);
  	struct ext4_free_extent ex;
  	int i;
  	int free;
  
  	free = e4b->bd_info->bb_free;
  	BUG_ON(free <= 0);
  
  	i = e4b->bd_info->bb_first_free;
  
  	while (free && ac->ac_status == AC_STATUS_CONTINUE) {

  		i = mb_find_next_zero_bit(bitmap,

  						EXT4_BLOCKS_PER_GROUP(sb), i);
  		if (i >= EXT4_BLOCKS_PER_GROUP(sb)) {

  			/*

  			 * IF we have corrupt bitmap, we won't find any

  			 * free blocks even though group info says we
  			 * we have free blocks
  			 */

  			ext4_grp_locked_error(sb, e4b->bd_group, 0, 0,
  					"%d free blocks as per "

  					"group info. But bitmap says 0",

  					free);

  			break;
  		}
  
  		mb_find_extent(e4b, 0, i, ac->ac_g_ex.fe_len, &ex);
  		BUG_ON(ex.fe_len <= 0);

  		if (free < ex.fe_len) {

  			ext4_grp_locked_error(sb, e4b->bd_group, 0, 0,
  					"%d free blocks as per "

  					"group info. But got %d blocks",

  					free, ex.fe_len);

  			/*
  			 * The number of free blocks differs. This mostly
  			 * indicate that the bitmap is corrupt. So exit
  			 * without claiming the space.
  			 */
  			break;

  		}

  
  		ext4_mb_measure_extent(ac, &ex, e4b);
  
  		i += ex.fe_len;
  		free -= ex.fe_len;
  	}
  
  	ext4_mb_check_limits(ac, e4b, 1);
  }
  
  /*
   * This is a special case for storages like raid5

   * we try to find stripe-aligned chunks for stripe-size-multiple requests

   */

  static noinline_for_stack
  void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,

  				 struct ext4_buddy *e4b)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	void *bitmap = EXT4_MB_BITMAP(e4b);
  	struct ext4_free_extent ex;
  	ext4_fsblk_t first_group_block;
  	ext4_fsblk_t a;
  	ext4_grpblk_t i;
  	int max;
  
  	BUG_ON(sbi->s_stripe == 0);
  
  	/* find first stripe-aligned block in group */

  	first_group_block = ext4_group_first_block_no(sb, e4b->bd_group);

  	a = first_group_block + sbi->s_stripe - 1;
  	do_div(a, sbi->s_stripe);
  	i = (a * sbi->s_stripe) - first_group_block;
  
  	while (i < EXT4_BLOCKS_PER_GROUP(sb)) {
  		if (!mb_test_bit(i, bitmap)) {
  			max = mb_find_extent(e4b, 0, i, sbi->s_stripe, &ex);
  			if (max >= sbi->s_stripe) {
  				ac->ac_found++;
  				ac->ac_b_ex = ex;
  				ext4_mb_use_best_found(ac, e4b);
  				break;
  			}
  		}
  		i += sbi->s_stripe;
  	}
  }

  /* This is now called BEFORE we load the buddy bitmap. */

  static int ext4_mb_good_group(struct ext4_allocation_context *ac,
  				ext4_group_t group, int cr)
  {
  	unsigned free, fragments;

  	int flex_size = ext4_flex_bg_size(EXT4_SB(ac->ac_sb));

  	struct ext4_group_info *grp = ext4_get_group_info(ac->ac_sb, group);
  
  	BUG_ON(cr < 0 || cr >= 4);

  
  	/* We only do this if the grp has never been initialized */
  	if (unlikely(EXT4_MB_GRP_NEED_INIT(grp))) {
  		int ret = ext4_mb_init_group(ac->ac_sb, group);
  		if (ret)
  			return 0;
  	}

  
  	free = grp->bb_free;
  	fragments = grp->bb_fragments;
  	if (free == 0)
  		return 0;
  	if (fragments == 0)
  		return 0;
  
  	switch (cr) {
  	case 0:
  		BUG_ON(ac->ac_2order == 0);

  		if (grp->bb_largest_free_order < ac->ac_2order)
  			return 0;

  		/* Avoid using the first bg of a flexgroup for data files */
  		if ((ac->ac_flags & EXT4_MB_HINT_DATA) &&
  		    (flex_size >= EXT4_FLEX_SIZE_DIR_ALLOC_SCHEME) &&
  		    ((group % flex_size) == 0))
  			return 0;

  		return 1;

  	case 1:
  		if ((free / fragments) >= ac->ac_g_ex.fe_len)
  			return 1;
  		break;
  	case 2:
  		if (free >= ac->ac_g_ex.fe_len)
  			return 1;
  		break;
  	case 3:
  		return 1;
  	default:
  		BUG();
  	}
  
  	return 0;
  }

  /*
   * lock the group_info alloc_sem of all the groups
   * belonging to the same buddy cache page. This
   * make sure other parallel operation on the buddy
   * cache doesn't happen  whild holding the buddy cache
   * lock
   */
  int ext4_mb_get_buddy_cache_lock(struct super_block *sb, ext4_group_t group)
  {
  	int i;
  	int block, pnum;
  	int blocks_per_page;
  	int groups_per_page;

  	ext4_group_t ngroups = ext4_get_groups_count(sb);

  	ext4_group_t first_group;
  	struct ext4_group_info *grp;
  
  	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
  	/*
  	 * the buddy cache inode stores the block bitmap
  	 * and buddy information in consecutive blocks.
  	 * So for each group we need two blocks.
  	 */
  	block = group * 2;
  	pnum = block / blocks_per_page;
  	first_group = pnum * blocks_per_page / 2;
  
  	groups_per_page = blocks_per_page >> 1;
  	if (groups_per_page == 0)
  		groups_per_page = 1;
  	/* read all groups the page covers into the cache */
  	for (i = 0; i < groups_per_page; i++) {

  		if ((first_group + i) >= ngroups)

  			break;
  		grp = ext4_get_group_info(sb, first_group + i);
  		/* take all groups write allocation
  		 * semaphore. This make sure there is
  		 * no block allocation going on in any
  		 * of that groups
  		 */

  		down_write_nested(&grp->alloc_sem, i);

  	}
  	return i;
  }
  
  void ext4_mb_put_buddy_cache_lock(struct super_block *sb,
  					ext4_group_t group, int locked_group)
  {
  	int i;
  	int block, pnum;
  	int blocks_per_page;
  	ext4_group_t first_group;
  	struct ext4_group_info *grp;
  
  	blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
  	/*
  	 * the buddy cache inode stores the block bitmap
  	 * and buddy information in consecutive blocks.
  	 * So for each group we need two blocks.
  	 */
  	block = group * 2;
  	pnum = block / blocks_per_page;
  	first_group = pnum * blocks_per_page / 2;
  	/* release locks on all the groups */
  	for (i = 0; i < locked_group; i++) {
  
  		grp = ext4_get_group_info(sb, first_group + i);
  		/* take all groups write allocation
  		 * semaphore. This make sure there is
  		 * no block allocation going on in any
  		 * of that groups
  		 */
  		up_write(&grp->alloc_sem);
  	}
  
  }

  static noinline_for_stack int
  ext4_mb_regular_allocator(struct ext4_allocation_context *ac)

  {

  	ext4_group_t ngroups, group, i;

  	int cr;
  	int err = 0;

  	struct ext4_sb_info *sbi;
  	struct super_block *sb;
  	struct ext4_buddy e4b;

  
  	sb = ac->ac_sb;
  	sbi = EXT4_SB(sb);

  	ngroups = ext4_get_groups_count(sb);

  	/* non-extent files are limited to low blocks/groups */

  	if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)))

  		ngroups = sbi->s_blockfile_groups;

  	BUG_ON(ac->ac_status == AC_STATUS_FOUND);
  
  	/* first, try the goal */
  	err = ext4_mb_find_by_goal(ac, &e4b);
  	if (err || ac->ac_status == AC_STATUS_FOUND)
  		goto out;
  
  	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
  		goto out;
  
  	/*
  	 * ac->ac2_order is set only if the fe_len is a power of 2
  	 * if ac2_order is set we also set criteria to 0 so that we
  	 * try exact allocation using buddy.
  	 */
  	i = fls(ac->ac_g_ex.fe_len);
  	ac->ac_2order = 0;
  	/*
  	 * We search using buddy data only if the order of the request
  	 * is greater than equal to the sbi_s_mb_order2_reqs

  	 * You can tune it via /sys/fs/ext4/<partition>/mb_order2_req

  	 */
  	if (i >= sbi->s_mb_order2_reqs) {
  		/*
  		 * This should tell if fe_len is exactly power of 2
  		 */
  		if ((ac->ac_g_ex.fe_len & (~(1 << (i - 1)))) == 0)
  			ac->ac_2order = i - 1;
  	}

  	/* if stream allocation is enabled, use global goal */
  	if (ac->ac_flags & EXT4_MB_STREAM_ALLOC) {

  		/* TBD: may be hot point */
  		spin_lock(&sbi->s_md_lock);
  		ac->ac_g_ex.fe_group = sbi->s_mb_last_group;
  		ac->ac_g_ex.fe_start = sbi->s_mb_last_start;
  		spin_unlock(&sbi->s_md_lock);
  	}

  	/* Let's just scan groups to find more-less suitable blocks */
  	cr = ac->ac_2order ? 0 : 1;
  	/*
  	 * cr == 0 try to get exact allocation,
  	 * cr == 3  try to get anything
  	 */
  repeat:
  	for (; cr < 4 && ac->ac_status == AC_STATUS_CONTINUE; cr++) {
  		ac->ac_criteria = cr;

  		/*
  		 * searching for the right group start
  		 * from the goal value specified
  		 */
  		group = ac->ac_g_ex.fe_group;

  		for (i = 0; i < ngroups; group++, i++) {

  			if (group == ngroups)

  				group = 0;

  			/* This now checks without needing the buddy page */
  			if (!ext4_mb_good_group(ac, group, cr))

  				continue;

  			err = ext4_mb_load_buddy(sb, group, &e4b);
  			if (err)
  				goto out;
  
  			ext4_lock_group(sb, group);

  
  			/*
  			 * We need to check again after locking the
  			 * block group
  			 */

  			if (!ext4_mb_good_group(ac, group, cr)) {

  				ext4_unlock_group(sb, group);

  				ext4_mb_unload_buddy(&e4b);

  				continue;
  			}
  
  			ac->ac_groups_scanned++;

  			if (cr == 0)

  				ext4_mb_simple_scan_group(ac, &e4b);

  			else if (cr == 1 && sbi->s_stripe &&
  					!(ac->ac_g_ex.fe_len % sbi->s_stripe))

  				ext4_mb_scan_aligned(ac, &e4b);
  			else
  				ext4_mb_complex_scan_group(ac, &e4b);
  
  			ext4_unlock_group(sb, group);

  			ext4_mb_unload_buddy(&e4b);

  
  			if (ac->ac_status != AC_STATUS_CONTINUE)
  				break;
  		}
  	}
  
  	if (ac->ac_b_ex.fe_len > 0 && ac->ac_status != AC_STATUS_FOUND &&
  	    !(ac->ac_flags & EXT4_MB_HINT_FIRST)) {
  		/*
  		 * We've been searching too long. Let's try to allocate
  		 * the best chunk we've found so far
  		 */
  
  		ext4_mb_try_best_found(ac, &e4b);
  		if (ac->ac_status != AC_STATUS_FOUND) {
  			/*
  			 * Someone more lucky has already allocated it.
  			 * The only thing we can do is just take first
  			 * found block(s)
  			printk(KERN_DEBUG "EXT4-fs: someone won our chunk
  ");
  			 */
  			ac->ac_b_ex.fe_group = 0;
  			ac->ac_b_ex.fe_start = 0;
  			ac->ac_b_ex.fe_len = 0;
  			ac->ac_status = AC_STATUS_CONTINUE;
  			ac->ac_flags |= EXT4_MB_HINT_FIRST;
  			cr = 3;
  			atomic_inc(&sbi->s_mb_lost_chunks);
  			goto repeat;
  		}
  	}
  out:
  	return err;
  }

  static void *ext4_mb_seq_groups_start(struct seq_file *seq, loff_t *pos)
  {
  	struct super_block *sb = seq->private;

  	ext4_group_t group;

  	if (*pos < 0 || *pos >= ext4_get_groups_count(sb))

  		return NULL;

  	group = *pos + 1;

  	return (void *) ((unsigned long) group);

  }
  
  static void *ext4_mb_seq_groups_next(struct seq_file *seq, void *v, loff_t *pos)
  {
  	struct super_block *sb = seq->private;

  	ext4_group_t group;
  
  	++*pos;

  	if (*pos < 0 || *pos >= ext4_get_groups_count(sb))

  		return NULL;
  	group = *pos + 1;

  	return (void *) ((unsigned long) group);

  }
  
  static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
  {
  	struct super_block *sb = seq->private;

  	ext4_group_t group = (ext4_group_t) ((unsigned long) v);

  	int i;
  	int err;
  	struct ext4_buddy e4b;
  	struct sg {
  		struct ext4_group_info info;

  		ext4_grpblk_t counters[16];

  	} sg;
  
  	group--;
  	if (group == 0)
  		seq_printf(seq, "#%-5s: %-5s %-5s %-5s "
  				"[ %-5s %-5s %-5s %-5s %-5s %-5s %-5s "
  				  "%-5s %-5s %-5s %-5s %-5s %-5s %-5s ]
  ",
  			   "group", "free", "frags", "first",
  			   "2^0", "2^1", "2^2", "2^3", "2^4", "2^5", "2^6",
  			   "2^7", "2^8", "2^9", "2^10", "2^11", "2^12", "2^13");
  
  	i = (sb->s_blocksize_bits + 2) * sizeof(sg.info.bb_counters[0]) +
  		sizeof(struct ext4_group_info);
  	err = ext4_mb_load_buddy(sb, group, &e4b);
  	if (err) {

  		seq_printf(seq, "#%-5u: I/O error
  ", group);

  		return 0;
  	}
  	ext4_lock_group(sb, group);
  	memcpy(&sg, ext4_get_group_info(sb, group), i);
  	ext4_unlock_group(sb, group);

  	ext4_mb_unload_buddy(&e4b);

  	seq_printf(seq, "#%-5u: %-5u %-5u %-5u [", group, sg.info.bb_free,

  			sg.info.bb_fragments, sg.info.bb_first_free);
  	for (i = 0; i <= 13; i++)
  		seq_printf(seq, " %-5u", i <= sb->s_blocksize_bits + 1 ?
  				sg.info.bb_counters[i] : 0);
  	seq_printf(seq, " ]
  ");
  
  	return 0;
  }
  
  static void ext4_mb_seq_groups_stop(struct seq_file *seq, void *v)
  {
  }

  static const struct seq_operations ext4_mb_seq_groups_ops = {

  	.start  = ext4_mb_seq_groups_start,
  	.next   = ext4_mb_seq_groups_next,
  	.stop   = ext4_mb_seq_groups_stop,
  	.show   = ext4_mb_seq_groups_show,
  };
  
  static int ext4_mb_seq_groups_open(struct inode *inode, struct file *file)
  {
  	struct super_block *sb = PDE(inode)->data;
  	int rc;
  
  	rc = seq_open(file, &ext4_mb_seq_groups_ops);
  	if (rc == 0) {

  		struct seq_file *m = file->private_data;

  		m->private = sb;
  	}
  	return rc;
  
  }

  static const struct file_operations ext4_mb_seq_groups_fops = {

  	.owner		= THIS_MODULE,
  	.open		= ext4_mb_seq_groups_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  
  /* Create and initialize ext4_group_info data for the given group. */

  int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,

  			  struct ext4_group_desc *desc)
  {
  	int i, len;
  	int metalen = 0;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);
  	struct ext4_group_info **meta_group_info;
  
  	/*
  	 * First check if this group is the first of a reserved block.
  	 * If it's true, we have to allocate a new table of pointers
  	 * to ext4_group_info structures
  	 */
  	if (group % EXT4_DESC_PER_BLOCK(sb) == 0) {
  		metalen = sizeof(*meta_group_info) <<
  			EXT4_DESC_PER_BLOCK_BITS(sb);
  		meta_group_info = kmalloc(metalen, GFP_KERNEL);
  		if (meta_group_info == NULL) {
  			printk(KERN_ERR "EXT4-fs: can't allocate mem for a "
  			       "buddy group
  ");
  			goto exit_meta_group_info;
  		}
  		sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)] =
  			meta_group_info;
  	}
  
  	/*
  	 * calculate needed size. if change bb_counters size,
  	 * don't forget about ext4_mb_generate_buddy()
  	 */
  	len = offsetof(typeof(**meta_group_info),
  		       bb_counters[sb->s_blocksize_bits + 2]);
  
  	meta_group_info =
  		sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)];
  	i = group & (EXT4_DESC_PER_BLOCK(sb) - 1);
  
  	meta_group_info[i] = kzalloc(len, GFP_KERNEL);
  	if (meta_group_info[i] == NULL) {
  		printk(KERN_ERR "EXT4-fs: can't allocate buddy mem
  ");
  		goto exit_group_info;
  	}
  	set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT,
  		&(meta_group_info[i]->bb_state));
  
  	/*
  	 * initialize bb_free to be able to skip
  	 * empty groups without initialization
  	 */
  	if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
  		meta_group_info[i]->bb_free =
  			ext4_free_blocks_after_init(sb, group, desc);
  	} else {
  		meta_group_info[i]->bb_free =

  			ext4_free_blks_count(sb, desc);

  	}
  
  	INIT_LIST_HEAD(&meta_group_info[i]->bb_prealloc_list);

  	init_rwsem(&meta_group_info[i]->alloc_sem);

  	meta_group_info[i]->bb_free_root = RB_ROOT;

  	meta_group_info[i]->bb_largest_free_order = -1;  /* uninit */

  
  #ifdef DOUBLE_CHECK
  	{
  		struct buffer_head *bh;
  		meta_group_info[i]->bb_bitmap =
  			kmalloc(sb->s_blocksize, GFP_KERNEL);
  		BUG_ON(meta_group_info[i]->bb_bitmap == NULL);
  		bh = ext4_read_block_bitmap(sb, group);
  		BUG_ON(bh == NULL);
  		memcpy(meta_group_info[i]->bb_bitmap, bh->b_data,
  			sb->s_blocksize);
  		put_bh(bh);
  	}
  #endif
  
  	return 0;
  
  exit_group_info:
  	/* If a meta_group_info table has been allocated, release it now */
  	if (group % EXT4_DESC_PER_BLOCK(sb) == 0)
  		kfree(sbi->s_group_info[group >> EXT4_DESC_PER_BLOCK_BITS(sb)]);
  exit_meta_group_info:
  	return -ENOMEM;
  } /* ext4_mb_add_groupinfo */

  static int ext4_mb_init_backend(struct super_block *sb)
  {

  	ext4_group_t ngroups = ext4_get_groups_count(sb);

  	ext4_group_t i;

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	struct ext4_super_block *es = sbi->s_es;
  	int num_meta_group_infos;
  	int num_meta_group_infos_max;
  	int array_size;

  	struct ext4_group_desc *desc;
  
  	/* This is the number of blocks used by GDT */

  	num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) -

  				1) >> EXT4_DESC_PER_BLOCK_BITS(sb);
  
  	/*
  	 * This is the total number of blocks used by GDT including
  	 * the number of reserved blocks for GDT.
  	 * The s_group_info array is allocated with this value
  	 * to allow a clean online resize without a complex
  	 * manipulation of pointer.
  	 * The drawback is the unused memory when no resize
  	 * occurs but it's very low in terms of pages
  	 * (see comments below)
  	 * Need to handle this properly when META_BG resizing is allowed
  	 */
  	num_meta_group_infos_max = num_meta_group_infos +
  				le16_to_cpu(es->s_reserved_gdt_blocks);

  	/*
  	 * array_size is the size of s_group_info array. We round it
  	 * to the next power of two because this approximation is done
  	 * internally by kmalloc so we can have some more memory
  	 * for free here (e.g. may be used for META_BG resize).
  	 */
  	array_size = 1;
  	while (array_size < sizeof(*sbi->s_group_info) *
  	       num_meta_group_infos_max)
  		array_size = array_size << 1;

  	/* An 8TB filesystem with 64-bit pointers requires a 4096 byte
  	 * kmalloc. A 128kb malloc should suffice for a 256TB filesystem.
  	 * So a two level scheme suffices for now. */

  	sbi->s_group_info = kmalloc(array_size, GFP_KERNEL);

  	if (sbi->s_group_info == NULL) {
  		printk(KERN_ERR "EXT4-fs: can't allocate buddy meta group
  ");
  		return -ENOMEM;
  	}
  	sbi->s_buddy_cache = new_inode(sb);
  	if (sbi->s_buddy_cache == NULL) {
  		printk(KERN_ERR "EXT4-fs: can't get new inode
  ");
  		goto err_freesgi;
  	}
  	EXT4_I(sbi->s_buddy_cache)->i_disksize = 0;

  	for (i = 0; i < ngroups; i++) {

  		desc = ext4_get_group_desc(sb, i, NULL);
  		if (desc == NULL) {
  			printk(KERN_ERR

  				"EXT4-fs: can't read descriptor %u
  ", i);

  			goto err_freebuddy;
  		}

  		if (ext4_mb_add_groupinfo(sb, i, desc) != 0)
  			goto err_freebuddy;

  	}
  
  	return 0;
  
  err_freebuddy:

  	while (i-- > 0)

  		kfree(ext4_get_group_info(sb, i));

  	i = num_meta_group_infos;

  	while (i-- > 0)

  		kfree(sbi->s_group_info[i]);
  	iput(sbi->s_buddy_cache);
  err_freesgi:
  	kfree(sbi->s_group_info);
  	return -ENOMEM;
  }
  
  int ext4_mb_init(struct super_block *sb, int needs_recovery)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	unsigned i, j;

  	unsigned offset;
  	unsigned max;

  	int ret;

  	i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_offsets);

  
  	sbi->s_mb_offsets = kmalloc(i, GFP_KERNEL);
  	if (sbi->s_mb_offsets == NULL) {

  		return -ENOMEM;
  	}

  	i = (sb->s_blocksize_bits + 2) * sizeof(*sbi->s_mb_maxs);

  	sbi->s_mb_maxs = kmalloc(i, GFP_KERNEL);
  	if (sbi->s_mb_maxs == NULL) {

  		kfree(sbi->s_mb_offsets);

  		return -ENOMEM;
  	}
  
  	/* order 0 is regular bitmap */
  	sbi->s_mb_maxs[0] = sb->s_blocksize << 3;
  	sbi->s_mb_offsets[0] = 0;
  
  	i = 1;
  	offset = 0;
  	max = sb->s_blocksize << 2;
  	do {
  		sbi->s_mb_offsets[i] = offset;
  		sbi->s_mb_maxs[i] = max;
  		offset += 1 << (sb->s_blocksize_bits - i);
  		max = max >> 1;
  		i++;
  	} while (i <= sb->s_blocksize_bits + 1);
  
  	/* init file for buddy data */

  	ret = ext4_mb_init_backend(sb);
  	if (ret != 0) {

  		kfree(sbi->s_mb_offsets);
  		kfree(sbi->s_mb_maxs);

  		return ret;

  	}
  
  	spin_lock_init(&sbi->s_md_lock);

  	spin_lock_init(&sbi->s_bal_lock);
  
  	sbi->s_mb_max_to_scan = MB_DEFAULT_MAX_TO_SCAN;
  	sbi->s_mb_min_to_scan = MB_DEFAULT_MIN_TO_SCAN;
  	sbi->s_mb_stats = MB_DEFAULT_STATS;
  	sbi->s_mb_stream_request = MB_DEFAULT_STREAM_THRESHOLD;
  	sbi->s_mb_order2_reqs = MB_DEFAULT_ORDER2_REQS;

  	sbi->s_mb_group_prealloc = MB_DEFAULT_GROUP_PREALLOC;

  	sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group);

  	if (sbi->s_locality_groups == NULL) {

  		kfree(sbi->s_mb_offsets);
  		kfree(sbi->s_mb_maxs);
  		return -ENOMEM;
  	}

  	for_each_possible_cpu(i) {

  		struct ext4_locality_group *lg;

  		lg = per_cpu_ptr(sbi->s_locality_groups, i);

  		mutex_init(&lg->lg_mutex);

  		for (j = 0; j < PREALLOC_TB_SIZE; j++)
  			INIT_LIST_HEAD(&lg->lg_prealloc_list[j]);

  		spin_lock_init(&lg->lg_prealloc_lock);
  	}

  	if (sbi->s_proc)
  		proc_create_data("mb_groups", S_IRUGO, sbi->s_proc,
  				 &ext4_mb_seq_groups_fops, sb);

  	if (sbi->s_journal)
  		sbi->s_journal->j_commit_callback = release_blocks_on_commit;

  	return 0;
  }

  /* need to called with the ext4 group lock held */

  static void ext4_mb_cleanup_pa(struct ext4_group_info *grp)
  {
  	struct ext4_prealloc_space *pa;
  	struct list_head *cur, *tmp;
  	int count = 0;
  
  	list_for_each_safe(cur, tmp, &grp->bb_prealloc_list) {
  		pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
  		list_del(&pa->pa_group_list);
  		count++;

  		kmem_cache_free(ext4_pspace_cachep, pa);

  	}
  	if (count)

  		mb_debug(1, "mballoc: %u PAs left
  ", count);

  
  }
  
  int ext4_mb_release(struct super_block *sb)
  {

  	ext4_group_t ngroups = ext4_get_groups_count(sb);

  	ext4_group_t i;
  	int num_meta_group_infos;
  	struct ext4_group_info *grinfo;
  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	if (sbi->s_group_info) {

  		for (i = 0; i < ngroups; i++) {

  			grinfo = ext4_get_group_info(sb, i);
  #ifdef DOUBLE_CHECK
  			kfree(grinfo->bb_bitmap);
  #endif
  			ext4_lock_group(sb, i);
  			ext4_mb_cleanup_pa(grinfo);
  			ext4_unlock_group(sb, i);
  			kfree(grinfo);
  		}

  		num_meta_group_infos = (ngroups +

  				EXT4_DESC_PER_BLOCK(sb) - 1) >>
  			EXT4_DESC_PER_BLOCK_BITS(sb);
  		for (i = 0; i < num_meta_group_infos; i++)
  			kfree(sbi->s_group_info[i]);
  		kfree(sbi->s_group_info);
  	}
  	kfree(sbi->s_mb_offsets);
  	kfree(sbi->s_mb_maxs);
  	if (sbi->s_buddy_cache)
  		iput(sbi->s_buddy_cache);
  	if (sbi->s_mb_stats) {
  		printk(KERN_INFO
  		       "EXT4-fs: mballoc: %u blocks %u reqs (%u success)
  ",
  				atomic_read(&sbi->s_bal_allocated),
  				atomic_read(&sbi->s_bal_reqs),
  				atomic_read(&sbi->s_bal_success));
  		printk(KERN_INFO
  		      "EXT4-fs: mballoc: %u extents scanned, %u goal hits, "
  				"%u 2^N hits, %u breaks, %u lost
  ",
  				atomic_read(&sbi->s_bal_ex_scanned),
  				atomic_read(&sbi->s_bal_goals),
  				atomic_read(&sbi->s_bal_2orders),
  				atomic_read(&sbi->s_bal_breaks),
  				atomic_read(&sbi->s_mb_lost_chunks));
  		printk(KERN_INFO
  		       "EXT4-fs: mballoc: %lu generated and it took %Lu
  ",
  				sbi->s_mb_buddies_generated++,
  				sbi->s_mb_generation_time);
  		printk(KERN_INFO
  		       "EXT4-fs: mballoc: %u preallocated, %u discarded
  ",
  				atomic_read(&sbi->s_mb_preallocated),
  				atomic_read(&sbi->s_mb_discarded));
  	}

  	free_percpu(sbi->s_locality_groups);

  	if (sbi->s_proc)
  		remove_proc_entry("mb_groups", sbi->s_proc);

  
  	return 0;
  }

  static inline void ext4_issue_discard(struct super_block *sb,
  		ext4_group_t block_group, ext4_grpblk_t block, int count)
  {
  	int ret;
  	ext4_fsblk_t discard_block;
  
  	discard_block = block + ext4_group_first_block_no(sb, block_group);
  	trace_ext4_discard_blocks(sb,
  			(unsigned long long) discard_block, count);
  	ret = sb_issue_discard(sb, discard_block, count);
  	if (ret == EOPNOTSUPP) {
  		ext4_warning(sb, "discard not supported, disabling");
  		clear_opt(EXT4_SB(sb)->s_mount_opt, DISCARD);
  	}
  }

  /*
   * This function is called by the jbd2 layer once the commit has finished,
   * so we know we can free the blocks that were released with that commit.
   */
  static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)

  {

  	struct super_block *sb = journal->j_private;

  	struct ext4_buddy e4b;

  	struct ext4_group_info *db;

  	int err, count = 0, count2 = 0;
  	struct ext4_free_data *entry;

  	struct list_head *l, *ltmp;

  	list_for_each_safe(l, ltmp, &txn->t_private_list) {
  		entry = list_entry(l, struct ext4_free_data, list);

  		mb_debug(1, "gonna free %u blocks in group %u (0x%p):",

  			 entry->count, entry->group, entry);

  		if (test_opt(sb, DISCARD))
  			ext4_issue_discard(sb, entry->group,
  					entry->start_blk, entry->count);

  		err = ext4_mb_load_buddy(sb, entry->group, &e4b);

  		/* we expect to find existing buddy because it's pinned */
  		BUG_ON(err != 0);

  		db = e4b.bd_info;

  		/* there are blocks to put in buddy to make them really free */

  		count += entry->count;

  		count2++;

  		ext4_lock_group(sb, entry->group);
  		/* Take it out of per group rb tree */
  		rb_erase(&entry->node, &(db->bb_free_root));
  		mb_free_blocks(NULL, &e4b, entry->start_blk, entry->count);
  
  		if (!db->bb_free_root.rb_node) {
  			/* No more items in the per group rb tree
  			 * balance refcounts from ext4_mb_free_metadata()
  			 */
  			page_cache_release(e4b.bd_buddy_page);
  			page_cache_release(e4b.bd_bitmap_page);

  		}

  		ext4_unlock_group(sb, entry->group);

  		kmem_cache_free(ext4_free_ext_cachep, entry);

  		ext4_mb_unload_buddy(&e4b);

  	}

  	mb_debug(1, "freed %u blocks in %u structures
  ", count, count2);

  }

  #ifdef CONFIG_EXT4_DEBUG
  u8 mb_enable_debug __read_mostly;
  
  static struct dentry *debugfs_dir;
  static struct dentry *debugfs_debug;
  
  static void __init ext4_create_debugfs_entry(void)
  {
  	debugfs_dir = debugfs_create_dir("ext4", NULL);
  	if (debugfs_dir)
  		debugfs_debug = debugfs_create_u8("mballoc-debug",
  						  S_IRUGO | S_IWUSR,
  						  debugfs_dir,
  						  &mb_enable_debug);
  }
  
  static void ext4_remove_debugfs_entry(void)
  {
  	debugfs_remove(debugfs_debug);
  	debugfs_remove(debugfs_dir);
  }
  
  #else
  
  static void __init ext4_create_debugfs_entry(void)
  {
  }
  
  static void ext4_remove_debugfs_entry(void)
  {
  }
  
  #endif

  int __init init_ext4_mballoc(void)
  {
  	ext4_pspace_cachep =
  		kmem_cache_create("ext4_prealloc_space",
  				     sizeof(struct ext4_prealloc_space),
  				     0, SLAB_RECLAIM_ACCOUNT, NULL);
  	if (ext4_pspace_cachep == NULL)
  		return -ENOMEM;

  	ext4_ac_cachep =
  		kmem_cache_create("ext4_alloc_context",
  				     sizeof(struct ext4_allocation_context),
  				     0, SLAB_RECLAIM_ACCOUNT, NULL);
  	if (ext4_ac_cachep == NULL) {
  		kmem_cache_destroy(ext4_pspace_cachep);
  		return -ENOMEM;
  	}

  
  	ext4_free_ext_cachep =
  		kmem_cache_create("ext4_free_block_extents",
  				     sizeof(struct ext4_free_data),
  				     0, SLAB_RECLAIM_ACCOUNT, NULL);
  	if (ext4_free_ext_cachep == NULL) {
  		kmem_cache_destroy(ext4_pspace_cachep);
  		kmem_cache_destroy(ext4_ac_cachep);
  		return -ENOMEM;
  	}

  	ext4_create_debugfs_entry();

  	return 0;
  }
  
  void exit_ext4_mballoc(void)
  {

  	/*

  	 * Wait for completion of call_rcu()'s on ext4_pspace_cachep
  	 * before destroying the slab cache.
  	 */
  	rcu_barrier();

  	kmem_cache_destroy(ext4_pspace_cachep);

  	kmem_cache_destroy(ext4_ac_cachep);

  	kmem_cache_destroy(ext4_free_ext_cachep);

  	ext4_remove_debugfs_entry();

  }
  
  
  /*

   * Check quota and mark chosen space (ac->ac_b_ex) non-free in bitmaps

   * Returns 0 if success or error code
   */

  static noinline_for_stack int
  ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,

  				handle_t *handle, unsigned int reserv_blks)

  {
  	struct buffer_head *bitmap_bh = NULL;

  	struct ext4_group_desc *gdp;
  	struct buffer_head *gdp_bh;
  	struct ext4_sb_info *sbi;
  	struct super_block *sb;
  	ext4_fsblk_t block;

  	int err, len;

  
  	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
  	BUG_ON(ac->ac_b_ex.fe_len <= 0);
  
  	sb = ac->ac_sb;
  	sbi = EXT4_SB(sb);

  
  	err = -EIO;

  	bitmap_bh = ext4_read_block_bitmap(sb, ac->ac_b_ex.fe_group);

  	if (!bitmap_bh)
  		goto out_err;
  
  	err = ext4_journal_get_write_access(handle, bitmap_bh);
  	if (err)
  		goto out_err;
  
  	err = -EIO;
  	gdp = ext4_get_group_desc(sb, ac->ac_b_ex.fe_group, &gdp_bh);
  	if (!gdp)
  		goto out_err;

  	ext4_debug("using block group %u(%d)
  ", ac->ac_b_ex.fe_group,

  			ext4_free_blks_count(sb, gdp));

  	err = ext4_journal_get_write_access(handle, gdp_bh);
  	if (err)
  		goto out_err;

  	block = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);

  	len = ac->ac_b_ex.fe_len;

  	if (!ext4_data_block_valid(sbi, block, len)) {

  		ext4_error(sb, "Allocating blocks %llu-%llu which overlap "

  			   "fs metadata
  ", block, block+len);

  		/* File system mounted not to panic on error
  		 * Fix the bitmap and repeat the block allocation
  		 * We leak some of the blocks here.
  		 */

  		ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  		mb_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,
  			    ac->ac_b_ex.fe_len);
  		ext4_unlock_group(sb, ac->ac_b_ex.fe_group);

  		err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);

  		if (!err)
  			err = -EAGAIN;
  		goto out_err;

  	}

  
  	ext4_lock_group(sb, ac->ac_b_ex.fe_group);

  #ifdef AGGRESSIVE_CHECK
  	{
  		int i;
  		for (i = 0; i < ac->ac_b_ex.fe_len; i++) {
  			BUG_ON(mb_test_bit(ac->ac_b_ex.fe_start + i,
  						bitmap_bh->b_data));
  		}
  	}
  #endif

  	mb_set_bits(bitmap_bh->b_data, ac->ac_b_ex.fe_start,ac->ac_b_ex.fe_len);

  	if (gdp->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
  		gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);

  		ext4_free_blks_set(sb, gdp,
  					ext4_free_blocks_after_init(sb,
  					ac->ac_b_ex.fe_group, gdp));

  	}

  	len = ext4_free_blks_count(sb, gdp) - ac->ac_b_ex.fe_len;
  	ext4_free_blks_set(sb, gdp, len);

  	gdp->bg_checksum = ext4_group_desc_csum(sbi, ac->ac_b_ex.fe_group, gdp);

  
  	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);

  	percpu_counter_sub(&sbi->s_freeblocks_counter, ac->ac_b_ex.fe_len);

  	/*

  	 * Now reduce the dirty block count also. Should not go negative

  	 */

  	if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED))
  		/* release all the reserved blocks if non delalloc */
  		percpu_counter_sub(&sbi->s_dirtyblocks_counter, reserv_blks);

  	if (sbi->s_log_groups_per_flex) {
  		ext4_group_t flex_group = ext4_flex_group(sbi,
  							  ac->ac_b_ex.fe_group);

  		atomic_sub(ac->ac_b_ex.fe_len,
  			   &sbi->s_flex_groups[flex_group].free_blocks);

  	}

  	err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);

  	if (err)
  		goto out_err;

  	err = ext4_handle_dirty_metadata(handle, NULL, gdp_bh);

  
  out_err:

  	ext4_mark_super_dirty(sb);

  	brelse(bitmap_bh);

  	return err;
  }
  
  /*
   * here we normalize request for locality group
   * Group request are normalized to s_strip size if we set the same via mount
   * option. If not we set it to s_mb_group_prealloc which can be configured via

   * /sys/fs/ext4/<partition>/mb_group_prealloc

   *
   * XXX: should we try to preallocate more than the group has now?
   */
  static void ext4_mb_normalize_group_request(struct ext4_allocation_context *ac)
  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_locality_group *lg = ac->ac_lg;
  
  	BUG_ON(lg == NULL);
  	if (EXT4_SB(sb)->s_stripe)
  		ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_stripe;
  	else
  		ac->ac_g_ex.fe_len = EXT4_SB(sb)->s_mb_group_prealloc;

  	mb_debug(1, "#%u: goal %u blocks for locality group
  ",

  		current->pid, ac->ac_g_ex.fe_len);
  }
  
  /*
   * Normalization means making request better in terms of
   * size and alignment
   */

  static noinline_for_stack void
  ext4_mb_normalize_request(struct ext4_allocation_context *ac,

  				struct ext4_allocation_request *ar)
  {
  	int bsbits, max;
  	ext4_lblk_t end;

  	loff_t size, orig_size, start_off;

  	ext4_lblk_t start;

  	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);

  	struct ext4_prealloc_space *pa;

  
  	/* do normalize only data requests, metadata requests
  	   do not need preallocation */
  	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
  		return;
  
  	/* sometime caller may want exact blocks */
  	if (unlikely(ac->ac_flags & EXT4_MB_HINT_GOAL_ONLY))
  		return;
  
  	/* caller may indicate that preallocation isn't
  	 * required (it's a tail, for example) */
  	if (ac->ac_flags & EXT4_MB_HINT_NOPREALLOC)
  		return;
  
  	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC) {
  		ext4_mb_normalize_group_request(ac);
  		return ;
  	}
  
  	bsbits = ac->ac_sb->s_blocksize_bits;
  
  	/* first, let's learn actual file size
  	 * given current request is allocated */
  	size = ac->ac_o_ex.fe_logical + ac->ac_o_ex.fe_len;
  	size = size << bsbits;
  	if (size < i_size_read(ac->ac_inode))
  		size = i_size_read(ac->ac_inode);

  	orig_size = size;

  	/* max size of free chunks */
  	max = 2 << bsbits;

  #define NRL_CHECK_SIZE(req, size, max, chunk_size)	\
  		(req <= (size) || max <= (chunk_size))

  
  	/* first, try to predict filesize */
  	/* XXX: should this table be tunable? */
  	start_off = 0;
  	if (size <= 16 * 1024) {
  		size = 16 * 1024;
  	} else if (size <= 32 * 1024) {
  		size = 32 * 1024;
  	} else if (size <= 64 * 1024) {
  		size = 64 * 1024;
  	} else if (size <= 128 * 1024) {
  		size = 128 * 1024;
  	} else if (size <= 256 * 1024) {
  		size = 256 * 1024;
  	} else if (size <= 512 * 1024) {
  		size = 512 * 1024;
  	} else if (size <= 1024 * 1024) {
  		size = 1024 * 1024;

  	} else if (NRL_CHECK_SIZE(size, 4 * 1024 * 1024, max, 2 * 1024)) {

  		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>

  						(21 - bsbits)) << 21;
  		size = 2 * 1024 * 1024;
  	} else if (NRL_CHECK_SIZE(size, 8 * 1024 * 1024, max, 4 * 1024)) {

  		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
  							(22 - bsbits)) << 22;
  		size = 4 * 1024 * 1024;
  	} else if (NRL_CHECK_SIZE(ac->ac_o_ex.fe_len,

  					(8<<20)>>bsbits, max, 8 * 1024)) {

  		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
  							(23 - bsbits)) << 23;
  		size = 8 * 1024 * 1024;
  	} else {
  		start_off = (loff_t)ac->ac_o_ex.fe_logical << bsbits;
  		size	  = ac->ac_o_ex.fe_len << bsbits;
  	}

  	size = size >> bsbits;
  	start = start_off >> bsbits;

  
  	/* don't cover already allocated blocks in selected range */
  	if (ar->pleft && start <= ar->lleft) {
  		size -= ar->lleft + 1 - start;
  		start = ar->lleft + 1;
  	}
  	if (ar->pright && start + size - 1 >= ar->lright)
  		size -= start + size - ar->lright;
  
  	end = start + size;
  
  	/* check we don't cross already preallocated blocks */
  	rcu_read_lock();

  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {

  		ext4_lblk_t pa_end;

  		if (pa->pa_deleted)
  			continue;
  		spin_lock(&pa->pa_lock);
  		if (pa->pa_deleted) {
  			spin_unlock(&pa->pa_lock);
  			continue;
  		}
  
  		pa_end = pa->pa_lstart + pa->pa_len;
  
  		/* PA must not overlap original request */
  		BUG_ON(!(ac->ac_o_ex.fe_logical >= pa_end ||
  			ac->ac_o_ex.fe_logical < pa->pa_lstart));

  		/* skip PAs this normalized request doesn't overlap with */
  		if (pa->pa_lstart >= end || pa_end <= start) {

  			spin_unlock(&pa->pa_lock);
  			continue;
  		}
  		BUG_ON(pa->pa_lstart <= start && pa_end >= end);

  		/* adjust start or end to be adjacent to this pa */

  		if (pa_end <= ac->ac_o_ex.fe_logical) {
  			BUG_ON(pa_end < start);
  			start = pa_end;

  		} else if (pa->pa_lstart > ac->ac_o_ex.fe_logical) {

  			BUG_ON(pa->pa_lstart > end);
  			end = pa->pa_lstart;
  		}
  		spin_unlock(&pa->pa_lock);
  	}
  	rcu_read_unlock();
  	size = end - start;
  
  	/* XXX: extra loop to check we really don't overlap preallocations */
  	rcu_read_lock();

  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {

  		ext4_lblk_t pa_end;

  		spin_lock(&pa->pa_lock);
  		if (pa->pa_deleted == 0) {
  			pa_end = pa->pa_lstart + pa->pa_len;
  			BUG_ON(!(start >= pa_end || end <= pa->pa_lstart));
  		}
  		spin_unlock(&pa->pa_lock);
  	}
  	rcu_read_unlock();
  
  	if (start + size <= ac->ac_o_ex.fe_logical &&
  			start > ac->ac_o_ex.fe_logical) {
  		printk(KERN_ERR "start %lu, size %lu, fe_logical %lu
  ",
  			(unsigned long) start, (unsigned long) size,
  			(unsigned long) ac->ac_o_ex.fe_logical);
  	}
  	BUG_ON(start + size <= ac->ac_o_ex.fe_logical &&
  			start > ac->ac_o_ex.fe_logical);

  	BUG_ON(size <= 0 || size > EXT4_BLOCKS_PER_GROUP(ac->ac_sb));

  
  	/* now prepare goal request */
  
  	/* XXX: is it better to align blocks WRT to logical
  	 * placement or satisfy big request as is */
  	ac->ac_g_ex.fe_logical = start;
  	ac->ac_g_ex.fe_len = size;
  
  	/* define goal start in order to merge */
  	if (ar->pright && (ar->lright == (start + size))) {
  		/* merge to the right */
  		ext4_get_group_no_and_offset(ac->ac_sb, ar->pright - size,
  						&ac->ac_f_ex.fe_group,
  						&ac->ac_f_ex.fe_start);
  		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
  	}
  	if (ar->pleft && (ar->lleft + 1 == start)) {
  		/* merge to the left */
  		ext4_get_group_no_and_offset(ac->ac_sb, ar->pleft + 1,
  						&ac->ac_f_ex.fe_group,
  						&ac->ac_f_ex.fe_start);
  		ac->ac_flags |= EXT4_MB_HINT_TRY_GOAL;
  	}

  	mb_debug(1, "goal: %u(was %u) blocks at %u
  ", (unsigned) size,

  		(unsigned) orig_size, (unsigned) start);
  }
  
  static void ext4_mb_collect_stats(struct ext4_allocation_context *ac)
  {
  	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
  
  	if (sbi->s_mb_stats && ac->ac_g_ex.fe_len > 1) {
  		atomic_inc(&sbi->s_bal_reqs);
  		atomic_add(ac->ac_b_ex.fe_len, &sbi->s_bal_allocated);

  		if (ac->ac_b_ex.fe_len >= ac->ac_o_ex.fe_len)

  			atomic_inc(&sbi->s_bal_success);
  		atomic_add(ac->ac_found, &sbi->s_bal_ex_scanned);
  		if (ac->ac_g_ex.fe_start == ac->ac_b_ex.fe_start &&
  				ac->ac_g_ex.fe_group == ac->ac_b_ex.fe_group)
  			atomic_inc(&sbi->s_bal_goals);
  		if (ac->ac_found > sbi->s_mb_max_to_scan)
  			atomic_inc(&sbi->s_bal_breaks);
  	}

  	if (ac->ac_op == EXT4_MB_HISTORY_ALLOC)
  		trace_ext4_mballoc_alloc(ac);
  	else
  		trace_ext4_mballoc_prealloc(ac);

  }
  
  /*

   * Called on failure; free up any blocks from the inode PA for this
   * context.  We don't need this for MB_GROUP_PA because we only change
   * pa_free in ext4_mb_release_context(), but on failure, we've already
   * zeroed out ac->ac_b_ex.fe_len, so group_pa->pa_free is not changed.
   */
  static void ext4_discard_allocated_blocks(struct ext4_allocation_context *ac)
  {
  	struct ext4_prealloc_space *pa = ac->ac_pa;
  	int len;
  
  	if (pa && pa->pa_type == MB_INODE_PA) {
  		len = ac->ac_b_ex.fe_len;
  		pa->pa_free += len;
  	}
  
  }
  
  /*

   * use blocks preallocated to inode
   */
  static void ext4_mb_use_inode_pa(struct ext4_allocation_context *ac,
  				struct ext4_prealloc_space *pa)
  {
  	ext4_fsblk_t start;
  	ext4_fsblk_t end;
  	int len;
  
  	/* found preallocated blocks, use them */
  	start = pa->pa_pstart + (ac->ac_o_ex.fe_logical - pa->pa_lstart);
  	end = min(pa->pa_pstart + pa->pa_len, start + ac->ac_o_ex.fe_len);
  	len = end - start;
  	ext4_get_group_no_and_offset(ac->ac_sb, start, &ac->ac_b_ex.fe_group,
  					&ac->ac_b_ex.fe_start);
  	ac->ac_b_ex.fe_len = len;
  	ac->ac_status = AC_STATUS_FOUND;
  	ac->ac_pa = pa;
  
  	BUG_ON(start < pa->pa_pstart);
  	BUG_ON(start + len > pa->pa_pstart + pa->pa_len);
  	BUG_ON(pa->pa_free < len);
  	pa->pa_free -= len;

  	mb_debug(1, "use %llu/%u from inode pa %p
  ", start, len, pa);

  }
  
  /*
   * use blocks preallocated to locality group
   */
  static void ext4_mb_use_group_pa(struct ext4_allocation_context *ac,
  				struct ext4_prealloc_space *pa)
  {

  	unsigned int len = ac->ac_o_ex.fe_len;

  	ext4_get_group_no_and_offset(ac->ac_sb, pa->pa_pstart,
  					&ac->ac_b_ex.fe_group,
  					&ac->ac_b_ex.fe_start);
  	ac->ac_b_ex.fe_len = len;
  	ac->ac_status = AC_STATUS_FOUND;
  	ac->ac_pa = pa;
  
  	/* we don't correct pa_pstart or pa_plen here to avoid

  	 * possible race when the group is being loaded concurrently

  	 * instead we correct pa later, after blocks are marked

  	 * in on-disk bitmap -- see ext4_mb_release_context()
  	 * Other CPUs are prevented from allocating from this pa by lg_mutex

  	 */

  	mb_debug(1, "use %u/%u from group pa %p
  ", pa->pa_lstart-len, len, pa);

  }
  
  /*

   * Return the prealloc space that have minimal distance
   * from the goal block. @cpa is the prealloc
   * space that is having currently known minimal distance
   * from the goal block.
   */
  static struct ext4_prealloc_space *
  ext4_mb_check_group_pa(ext4_fsblk_t goal_block,
  			struct ext4_prealloc_space *pa,
  			struct ext4_prealloc_space *cpa)
  {
  	ext4_fsblk_t cur_distance, new_distance;
  
  	if (cpa == NULL) {
  		atomic_inc(&pa->pa_count);
  		return pa;
  	}
  	cur_distance = abs(goal_block - cpa->pa_pstart);
  	new_distance = abs(goal_block - pa->pa_pstart);
  
  	if (cur_distance < new_distance)
  		return cpa;
  
  	/* drop the previous reference */
  	atomic_dec(&cpa->pa_count);
  	atomic_inc(&pa->pa_count);
  	return pa;
  }
  
  /*

   * search goal blocks in preallocated space
   */

  static noinline_for_stack int
  ext4_mb_use_preallocated(struct ext4_allocation_context *ac)

  {

  	int order, i;

  	struct ext4_inode_info *ei = EXT4_I(ac->ac_inode);
  	struct ext4_locality_group *lg;

  	struct ext4_prealloc_space *pa, *cpa = NULL;
  	ext4_fsblk_t goal_block;

  
  	/* only data can be preallocated */
  	if (!(ac->ac_flags & EXT4_MB_HINT_DATA))
  		return 0;
  
  	/* first, try per-file preallocation */
  	rcu_read_lock();

  	list_for_each_entry_rcu(pa, &ei->i_prealloc_list, pa_inode_list) {

  
  		/* all fields in this condition don't change,
  		 * so we can skip locking for them */
  		if (ac->ac_o_ex.fe_logical < pa->pa_lstart ||
  			ac->ac_o_ex.fe_logical >= pa->pa_lstart + pa->pa_len)
  			continue;

  		/* non-extent files can't have physical blocks past 2^32 */

  		if (!(ext4_test_inode_flag(ac->ac_inode, EXT4_INODE_EXTENTS)) &&

  			pa->pa_pstart + pa->pa_len > EXT4_MAX_BLOCK_FILE_PHYS)
  			continue;

  		/* found preallocated blocks, use them */
  		spin_lock(&pa->pa_lock);
  		if (pa->pa_deleted == 0 && pa->pa_free) {
  			atomic_inc(&pa->pa_count);
  			ext4_mb_use_inode_pa(ac, pa);
  			spin_unlock(&pa->pa_lock);
  			ac->ac_criteria = 10;
  			rcu_read_unlock();
  			return 1;
  		}
  		spin_unlock(&pa->pa_lock);
  	}
  	rcu_read_unlock();
  
  	/* can we use group allocation? */
  	if (!(ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC))
  		return 0;
  
  	/* inode may have no locality group for some reason */
  	lg = ac->ac_lg;
  	if (lg == NULL)
  		return 0;

  	order  = fls(ac->ac_o_ex.fe_len) - 1;
  	if (order > PREALLOC_TB_SIZE - 1)
  		/* The max size of hash table is PREALLOC_TB_SIZE */
  		order = PREALLOC_TB_SIZE - 1;

  	goal_block = ext4_grp_offs_to_block(ac->ac_sb, &ac->ac_g_ex);

  	/*
  	 * search for the prealloc space that is having
  	 * minimal distance from the goal block.
  	 */

  	for (i = order; i < PREALLOC_TB_SIZE; i++) {
  		rcu_read_lock();
  		list_for_each_entry_rcu(pa, &lg->lg_prealloc_list[i],
  					pa_inode_list) {
  			spin_lock(&pa->pa_lock);
  			if (pa->pa_deleted == 0 &&
  					pa->pa_free >= ac->ac_o_ex.fe_len) {

  
  				cpa = ext4_mb_check_group_pa(goal_block,
  								pa, cpa);

  			}

  			spin_unlock(&pa->pa_lock);

  		}

  		rcu_read_unlock();

  	}

  	if (cpa) {
  		ext4_mb_use_group_pa(ac, cpa);
  		ac->ac_criteria = 20;
  		return 1;
  	}

  	return 0;
  }
  
  /*

   * the function goes through all block freed in the group
   * but not yet committed and marks them used in in-core bitmap.
   * buddy must be generated from this bitmap

   * Need to be called with the ext4 group lock held

   */
  static void ext4_mb_generate_from_freelist(struct super_block *sb, void *bitmap,
  						ext4_group_t group)
  {
  	struct rb_node *n;
  	struct ext4_group_info *grp;
  	struct ext4_free_data *entry;
  
  	grp = ext4_get_group_info(sb, group);
  	n = rb_first(&(grp->bb_free_root));
  
  	while (n) {
  		entry = rb_entry(n, struct ext4_free_data, node);

  		mb_set_bits(bitmap, entry->start_blk, entry->count);

  		n = rb_next(n);
  	}
  	return;
  }
  
  /*

   * the function goes through all preallocation in this group and marks them
   * used in in-core bitmap. buddy must be generated from this bitmap

   * Need to be called with ext4 group lock held

   */

  static noinline_for_stack
  void ext4_mb_generate_from_pa(struct super_block *sb, void *bitmap,

  					ext4_group_t group)
  {
  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
  	struct ext4_prealloc_space *pa;
  	struct list_head *cur;
  	ext4_group_t groupnr;
  	ext4_grpblk_t start;
  	int preallocated = 0;
  	int count = 0;
  	int len;
  
  	/* all form of preallocation discards first load group,
  	 * so the only competing code is preallocation use.
  	 * we don't need any locking here
  	 * notice we do NOT ignore preallocations with pa_deleted
  	 * otherwise we could leave used blocks available for
  	 * allocation in buddy when concurrent ext4_mb_put_pa()
  	 * is dropping preallocation
  	 */
  	list_for_each(cur, &grp->bb_prealloc_list) {
  		pa = list_entry(cur, struct ext4_prealloc_space, pa_group_list);
  		spin_lock(&pa->pa_lock);
  		ext4_get_group_no_and_offset(sb, pa->pa_pstart,
  					     &groupnr, &start);
  		len = pa->pa_len;
  		spin_unlock(&pa->pa_lock);
  		if (unlikely(len == 0))
  			continue;
  		BUG_ON(groupnr != group);

  		mb_set_bits(bitmap, start, len);

  		preallocated += len;
  		count++;
  	}

  	mb_debug(1, "prellocated %u for group %u
  ", preallocated, group);

  }
  
  static void ext4_mb_pa_callback(struct rcu_head *head)
  {
  	struct ext4_prealloc_space *pa;
  	pa = container_of(head, struct ext4_prealloc_space, u.pa_rcu);
  	kmem_cache_free(ext4_pspace_cachep, pa);
  }
  
  /*
   * drops a reference to preallocated space descriptor
   * if this was the last reference and the space is consumed
   */
  static void ext4_mb_put_pa(struct ext4_allocation_context *ac,
  			struct super_block *sb, struct ext4_prealloc_space *pa)
  {

  	ext4_group_t grp;

  	ext4_fsblk_t grp_blk;

  
  	if (!atomic_dec_and_test(&pa->pa_count) || pa->pa_free != 0)
  		return;
  
  	/* in this short window concurrent discard can set pa_deleted */
  	spin_lock(&pa->pa_lock);
  	if (pa->pa_deleted == 1) {
  		spin_unlock(&pa->pa_lock);
  		return;
  	}
  
  	pa->pa_deleted = 1;
  	spin_unlock(&pa->pa_lock);

  	grp_blk = pa->pa_pstart;

  	/*

  	 * If doing group-based preallocation, pa_pstart may be in the
  	 * next group when pa is used up
  	 */
  	if (pa->pa_type == MB_GROUP_PA)

  		grp_blk--;
  
  	ext4_get_group_no_and_offset(sb, grp_blk, &grp, NULL);

  
  	/*
  	 * possible race:
  	 *
  	 *  P1 (buddy init)			P2 (regular allocation)
  	 *					find block B in PA
  	 *  copy on-disk bitmap to buddy
  	 *  					mark B in on-disk bitmap
  	 *					drop PA from group
  	 *  mark all PAs in buddy
  	 *
  	 * thus, P1 initializes buddy with B available. to prevent this
  	 * we make "copy" and "mark all PAs" atomic and serialize "drop PA"
  	 * against that pair
  	 */
  	ext4_lock_group(sb, grp);
  	list_del(&pa->pa_group_list);
  	ext4_unlock_group(sb, grp);
  
  	spin_lock(pa->pa_obj_lock);
  	list_del_rcu(&pa->pa_inode_list);
  	spin_unlock(pa->pa_obj_lock);
  
  	call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
  }
  
  /*
   * creates new preallocated space for given inode
   */

  static noinline_for_stack int
  ext4_mb_new_inode_pa(struct ext4_allocation_context *ac)

  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_prealloc_space *pa;
  	struct ext4_group_info *grp;
  	struct ext4_inode_info *ei;
  
  	/* preallocate only when found space is larger then requested */
  	BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
  	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
  	BUG_ON(!S_ISREG(ac->ac_inode->i_mode));
  
  	pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
  	if (pa == NULL)
  		return -ENOMEM;
  
  	if (ac->ac_b_ex.fe_len < ac->ac_g_ex.fe_len) {
  		int winl;
  		int wins;
  		int win;
  		int offs;
  
  		/* we can't allocate as much as normalizer wants.
  		 * so, found space must get proper lstart
  		 * to cover original request */
  		BUG_ON(ac->ac_g_ex.fe_logical > ac->ac_o_ex.fe_logical);
  		BUG_ON(ac->ac_g_ex.fe_len < ac->ac_o_ex.fe_len);
  
  		/* we're limited by original request in that
  		 * logical block must be covered any way
  		 * winl is window we can move our chunk within */
  		winl = ac->ac_o_ex.fe_logical - ac->ac_g_ex.fe_logical;
  
  		/* also, we should cover whole original request */
  		wins = ac->ac_b_ex.fe_len - ac->ac_o_ex.fe_len;
  
  		/* the smallest one defines real window */
  		win = min(winl, wins);
  
  		offs = ac->ac_o_ex.fe_logical % ac->ac_b_ex.fe_len;
  		if (offs && offs < win)
  			win = offs;
  
  		ac->ac_b_ex.fe_logical = ac->ac_o_ex.fe_logical - win;
  		BUG_ON(ac->ac_o_ex.fe_logical < ac->ac_b_ex.fe_logical);
  		BUG_ON(ac->ac_o_ex.fe_len > ac->ac_b_ex.fe_len);
  	}
  
  	/* preallocation can change ac_b_ex, thus we store actually
  	 * allocated blocks for history */
  	ac->ac_f_ex = ac->ac_b_ex;
  
  	pa->pa_lstart = ac->ac_b_ex.fe_logical;
  	pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
  	pa->pa_len = ac->ac_b_ex.fe_len;
  	pa->pa_free = pa->pa_len;
  	atomic_set(&pa->pa_count, 1);
  	spin_lock_init(&pa->pa_lock);

  	INIT_LIST_HEAD(&pa->pa_inode_list);
  	INIT_LIST_HEAD(&pa->pa_group_list);

  	pa->pa_deleted = 0;

  	pa->pa_type = MB_INODE_PA;

  	mb_debug(1, "new inode pa %p: %llu/%u for %u
  ", pa,

  			pa->pa_pstart, pa->pa_len, pa->pa_lstart);

  	trace_ext4_mb_new_inode_pa(ac, pa);

  
  	ext4_mb_use_inode_pa(ac, pa);
  	atomic_add(pa->pa_free, &EXT4_SB(sb)->s_mb_preallocated);
  
  	ei = EXT4_I(ac->ac_inode);
  	grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);
  
  	pa->pa_obj_lock = &ei->i_prealloc_lock;
  	pa->pa_inode = ac->ac_inode;
  
  	ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  	list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
  	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
  
  	spin_lock(pa->pa_obj_lock);
  	list_add_rcu(&pa->pa_inode_list, &ei->i_prealloc_list);
  	spin_unlock(pa->pa_obj_lock);
  
  	return 0;
  }
  
  /*
   * creates new preallocated space for locality group inodes belongs to
   */

  static noinline_for_stack int
  ext4_mb_new_group_pa(struct ext4_allocation_context *ac)

  {
  	struct super_block *sb = ac->ac_sb;
  	struct ext4_locality_group *lg;
  	struct ext4_prealloc_space *pa;
  	struct ext4_group_info *grp;
  
  	/* preallocate only when found space is larger then requested */
  	BUG_ON(ac->ac_o_ex.fe_len >= ac->ac_b_ex.fe_len);
  	BUG_ON(ac->ac_status != AC_STATUS_FOUND);
  	BUG_ON(!S_ISREG(ac->ac_inode->i_mode));
  
  	BUG_ON(ext4_pspace_cachep == NULL);
  	pa = kmem_cache_alloc(ext4_pspace_cachep, GFP_NOFS);
  	if (pa == NULL)
  		return -ENOMEM;
  
  	/* preallocation can change ac_b_ex, thus we store actually
  	 * allocated blocks for history */
  	ac->ac_f_ex = ac->ac_b_ex;
  
  	pa->pa_pstart = ext4_grp_offs_to_block(sb, &ac->ac_b_ex);
  	pa->pa_lstart = pa->pa_pstart;
  	pa->pa_len = ac->ac_b_ex.fe_len;
  	pa->pa_free = pa->pa_len;
  	atomic_set(&pa->pa_count, 1);
  	spin_lock_init(&pa->pa_lock);

  	INIT_LIST_HEAD(&pa->pa_inode_list);

  	INIT_LIST_HEAD(&pa->pa_group_list);

  	pa->pa_deleted = 0;

  	pa->pa_type = MB_GROUP_PA;

  	mb_debug(1, "new group pa %p: %llu/%u for %u
  ", pa,

  			pa->pa_pstart, pa->pa_len, pa->pa_lstart);
  	trace_ext4_mb_new_group_pa(ac, pa);

  
  	ext4_mb_use_group_pa(ac, pa);
  	atomic_add(pa->pa_free, &EXT4_SB(sb)->s_mb_preallocated);
  
  	grp = ext4_get_group_info(sb, ac->ac_b_ex.fe_group);
  	lg = ac->ac_lg;
  	BUG_ON(lg == NULL);
  
  	pa->pa_obj_lock = &lg->lg_prealloc_lock;
  	pa->pa_inode = NULL;
  
  	ext4_lock_group(sb, ac->ac_b_ex.fe_group);
  	list_add(&pa->pa_group_list, &grp->bb_prealloc_list);
  	ext4_unlock_group(sb, ac->ac_b_ex.fe_group);

  	/*
  	 * We will later add the new pa to the right bucket
  	 * after updating the pa_free in ext4_mb_release_context
  	 */

  	return 0;
  }
  
  static int ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
  {
  	int err;
  
  	if (ac->ac_flags & EXT4_MB_HINT_GROUP_ALLOC)
  		err = ext4_mb_new_group_pa(ac);
  	else
  		err = ext4_mb_new_inode_pa(ac);
  	return err;
  }
  
  /*
   * finds all unused blocks in on-disk bitmap, frees them in
   * in-core bitmap and buddy.
   * @pa must be unlinked from inode and group lists, so that
   * nobody else can find/use it.
   * the caller MUST hold group/inode locks.
   * TODO: optimize the case when there are no in-core structures yet
   */