/*
   * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.

   * Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.

   *
   * This copyrighted material is made available to anyone wishing to use,
   * modify, copy, or redistribute it subject to the terms and conditions

   * of the GNU General Public License version 2.

   */
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/completion.h>
  #include <linux/buffer_head.h>

  #include <linux/gfs2_ondisk.h>

  #include <linux/crc32.h>

  #include <linux/delay.h>

  #include <linux/kthread.h>
  #include <linux/freezer.h>

  #include <linux/bio.h>

  #include <linux/writeback.h>

  
  #include "gfs2.h"

  #include "incore.h"

  #include "bmap.h"
  #include "glock.h"
  #include "log.h"
  #include "lops.h"
  #include "meta_io.h"

  #include "util.h"

  #include "dir.h"

  #include "trace_gfs2.h"

  
  #define PULL 1

  /**
   * gfs2_struct2blk - compute stuff
   * @sdp: the filesystem
   * @nstruct: the number of structures
   * @ssize: the size of the structures
   *
   * Compute the number of log descriptor blocks needed to hold a certain number
   * of structures of a certain size.
   *
   * Returns: the number of blocks needed (minimum is always 1)
   */
  
  unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct,
  			     unsigned int ssize)
  {
  	unsigned int blks;
  	unsigned int first, second;
  
  	blks = 1;

  	first = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / ssize;

  
  	if (nstruct > first) {

  		second = (sdp->sd_sb.sb_bsize -
  			  sizeof(struct gfs2_meta_header)) / ssize;

  		blks += DIV_ROUND_UP(nstruct - first, second);

  	}
  
  	return blks;
  }

  /**

   * gfs2_remove_from_ail - Remove an entry from the ail lists, updating counters
   * @mapping: The associated mapping (maybe NULL)
   * @bd: The gfs2_bufdata to remove
   *

   * The ail lock _must_ be held when calling this function

   *
   */

  void gfs2_remove_from_ail(struct gfs2_bufdata *bd)

  {
  	bd->bd_ail = NULL;

  	list_del_init(&bd->bd_ail_st_list);
  	list_del_init(&bd->bd_ail_gl_list);

  	atomic_dec(&bd->bd_gl->gl_ail_count);

  	brelse(bd->bd_bh);
  }
  
  /**

   * gfs2_ail1_start_one - Start I/O on a part of the AIL
   * @sdp: the filesystem

   * @wbc: The writeback control structure
   * @ai: The ail structure

   *
   */

  static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
  			       struct writeback_control *wbc,
  			       struct gfs2_ail *ai)

  __releases(&sdp->sd_ail_lock)
  __acquires(&sdp->sd_ail_lock)

  {

  	struct gfs2_glock *gl = NULL;

  	struct address_space *mapping;

  	struct gfs2_bufdata *bd, *s;
  	struct buffer_head *bh;

  	list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list, bd_ail_st_list) {
  		bh = bd->bd_bh;

  		gfs2_assert(sdp, bd->bd_ail == ai);

  		if (!buffer_busy(bh)) {
  			if (!buffer_uptodate(bh))
  				gfs2_io_error_bh(sdp, bh);
  			list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
  			continue;
  		}
  
  		if (!buffer_dirty(bh))
  			continue;
  		if (gl == bd->bd_gl)
  			continue;
  		gl = bd->bd_gl;
  		list_move(&bd->bd_ail_st_list, &ai->ai_ail1_list);
  		mapping = bh->b_page->mapping;

  		if (!mapping)
  			continue;

  		spin_unlock(&sdp->sd_ail_lock);
  		generic_writepages(mapping, wbc);
  		spin_lock(&sdp->sd_ail_lock);
  		if (wbc->nr_to_write <= 0)
  			break;

  		return 1;

  	}

  
  	return 0;

  }

  /**
   * gfs2_ail1_flush - start writeback of some ail1 entries 
   * @sdp: The super block
   * @wbc: The writeback control structure
   *
   * Writes back some ail1 entries, according to the limits in the
   * writeback control structure
   */

  void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
  {
  	struct list_head *head = &sdp->sd_ail1_list;
  	struct gfs2_ail *ai;

  	trace_gfs2_ail_flush(sdp, wbc, 1);

  	spin_lock(&sdp->sd_ail_lock);

  restart:

  	list_for_each_entry_reverse(ai, head, ai_list) {
  		if (wbc->nr_to_write <= 0)

  			break;

  		if (gfs2_ail1_start_one(sdp, wbc, ai))
  			goto restart;

  	}
  	spin_unlock(&sdp->sd_ail_lock);

  	trace_gfs2_ail_flush(sdp, wbc, 0);

  }
  
  /**
   * gfs2_ail1_start - start writeback of all ail1 entries
   * @sdp: The superblock
   */
  
  static void gfs2_ail1_start(struct gfs2_sbd *sdp)
  {
  	struct writeback_control wbc = {
  		.sync_mode = WB_SYNC_NONE,
  		.nr_to_write = LONG_MAX,
  		.range_start = 0,
  		.range_end = LLONG_MAX,
  	};
  
  	return gfs2_ail1_flush(sdp, &wbc);

  }
  
  /**
   * gfs2_ail1_empty_one - Check whether or not a trans in the AIL has been synced
   * @sdp: the filesystem
   * @ai: the AIL entry
   *
   */

  static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)

  {
  	struct gfs2_bufdata *bd, *s;
  	struct buffer_head *bh;
  
  	list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list,
  					 bd_ail_st_list) {
  		bh = bd->bd_bh;

  		gfs2_assert(sdp, bd->bd_ail == ai);

  		if (buffer_busy(bh))
  			continue;

  		if (!buffer_uptodate(bh))
  			gfs2_io_error_bh(sdp, bh);

  		list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
  	}

  }

  /**
   * gfs2_ail1_empty - Try to empty the ail1 lists
   * @sdp: The superblock
   *
   * Tries to empty the ail1 lists, starting with the oldest first
   */

  static int gfs2_ail1_empty(struct gfs2_sbd *sdp)

  {
  	struct gfs2_ail *ai, *s;
  	int ret;

  	spin_lock(&sdp->sd_ail_lock);

  	list_for_each_entry_safe_reverse(ai, s, &sdp->sd_ail1_list, ai_list) {

  		gfs2_ail1_empty_one(sdp, ai);
  		if (list_empty(&ai->ai_ail1_list))

  			list_move(&ai->ai_list, &sdp->sd_ail2_list);

  		else

  			break;
  	}

  	ret = list_empty(&sdp->sd_ail1_list);

  	spin_unlock(&sdp->sd_ail_lock);

  
  	return ret;
  }

  static void gfs2_ail1_wait(struct gfs2_sbd *sdp)
  {
  	struct gfs2_ail *ai;
  	struct gfs2_bufdata *bd;
  	struct buffer_head *bh;
  
  	spin_lock(&sdp->sd_ail_lock);
  	list_for_each_entry_reverse(ai, &sdp->sd_ail1_list, ai_list) {
  		list_for_each_entry(bd, &ai->ai_ail1_list, bd_ail_st_list) {
  			bh = bd->bd_bh;
  			if (!buffer_locked(bh))
  				continue;
  			get_bh(bh);
  			spin_unlock(&sdp->sd_ail_lock);
  			wait_on_buffer(bh);
  			brelse(bh);
  			return;
  		}
  	}
  	spin_unlock(&sdp->sd_ail_lock);
  }

  
  /**
   * gfs2_ail2_empty_one - Check whether or not a trans in the AIL has been synced
   * @sdp: the filesystem
   * @ai: the AIL entry
   *
   */
  
  static void gfs2_ail2_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
  {
  	struct list_head *head = &ai->ai_ail2_list;
  	struct gfs2_bufdata *bd;
  
  	while (!list_empty(head)) {
  		bd = list_entry(head->prev, struct gfs2_bufdata,
  				bd_ail_st_list);
  		gfs2_assert(sdp, bd->bd_ail == ai);

  		gfs2_remove_from_ail(bd);

  	}
  }

  static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
  {
  	struct gfs2_ail *ai, *safe;
  	unsigned int old_tail = sdp->sd_log_tail;
  	int wrap = (new_tail < old_tail);
  	int a, b, rm;

  	spin_lock(&sdp->sd_ail_lock);

  
  	list_for_each_entry_safe(ai, safe, &sdp->sd_ail2_list, ai_list) {
  		a = (old_tail <= ai->ai_first);
  		b = (ai->ai_first < new_tail);
  		rm = (wrap) ? (a || b) : (a && b);
  		if (!rm)
  			continue;
  
  		gfs2_ail2_empty_one(sdp, ai);
  		list_del(&ai->ai_list);
  		gfs2_assert_warn(sdp, list_empty(&ai->ai_ail1_list));
  		gfs2_assert_warn(sdp, list_empty(&ai->ai_ail2_list));
  		kfree(ai);
  	}

  	spin_unlock(&sdp->sd_ail_lock);

  }
  
  /**
   * gfs2_log_reserve - Make a log reservation
   * @sdp: The GFS2 superblock
   * @blks: The number of blocks to reserve
   *

   * Note that we never give out the last few blocks of the journal. Thats

   * due to the fact that there is a small number of header blocks

   * associated with each log flush. The exact number can't be known until
   * flush time, so we ensure that we have just enough free blocks at all
   * times to avoid running out during a log flush.
   *

   * We no longer flush the log here, instead we wake up logd to do that
   * for us. To avoid the thundering herd and to ensure that we deal fairly
   * with queued waiters, we use an exclusive wait. This means that when we
   * get woken with enough journal space to get our reservation, we need to
   * wake the next waiter on the list.
   *

   * Returns: errno
   */
  
  int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
  {

  	unsigned reserved_blks = 6 * (4096 / sdp->sd_vfs->s_blocksize);

  	unsigned wanted = blks + reserved_blks;
  	DEFINE_WAIT(wait);
  	int did_wait = 0;
  	unsigned int free_blocks;

  
  	if (gfs2_assert_warn(sdp, blks) ||
  	    gfs2_assert_warn(sdp, blks <= sdp->sd_jdesc->jd_blocks))
  		return -EINVAL;

  retry:
  	free_blocks = atomic_read(&sdp->sd_log_blks_free);
  	if (unlikely(free_blocks <= wanted)) {
  		do {
  			prepare_to_wait_exclusive(&sdp->sd_log_waitq, &wait,
  					TASK_UNINTERRUPTIBLE);
  			wake_up(&sdp->sd_logd_waitq);
  			did_wait = 1;
  			if (atomic_read(&sdp->sd_log_blks_free) <= wanted)
  				io_schedule();
  			free_blocks = atomic_read(&sdp->sd_log_blks_free);
  		} while(free_blocks <= wanted);
  		finish_wait(&sdp->sd_log_waitq, &wait);

  	}

  	if (atomic_cmpxchg(&sdp->sd_log_blks_free, free_blocks,
  				free_blocks - blks) != free_blocks)
  		goto retry;

  	trace_gfs2_log_blocks(sdp, -blks);

  
  	/*
  	 * If we waited, then so might others, wake them up _after_ we get
  	 * our share of the log.
  	 */
  	if (unlikely(did_wait))
  		wake_up(&sdp->sd_log_waitq);

  
  	down_read(&sdp->sd_log_flush_lock);

  
  	return 0;
  }

  static u64 log_bmap(struct gfs2_sbd *sdp, unsigned int lbn)

  {

  	struct gfs2_journal_extent *je;
  
  	list_for_each_entry(je, &sdp->sd_jdesc->extent_list, extent_list) {
  		if (lbn >= je->lblock && lbn < je->lblock + je->blocks)

  			return je->dblock + lbn - je->lblock;

  	}
  
  	return -1;

  }
  
  /**
   * log_distance - Compute distance between two journal blocks
   * @sdp: The GFS2 superblock
   * @newer: The most recent journal block of the pair
   * @older: The older journal block of the pair
   *
   *   Compute the distance (in the journal direction) between two
   *   blocks in the journal
   *
   * Returns: the distance in blocks
   */

  static inline unsigned int log_distance(struct gfs2_sbd *sdp, unsigned int newer,

  					unsigned int older)
  {
  	int dist;
  
  	dist = newer - older;
  	if (dist < 0)
  		dist += sdp->sd_jdesc->jd_blocks;
  
  	return dist;
  }

  /**
   * calc_reserved - Calculate the number of blocks to reserve when
   *                 refunding a transaction's unused buffers.
   * @sdp: The GFS2 superblock
   *
   * This is complex.  We need to reserve room for all our currently used
   * metadata buffers (e.g. normal file I/O rewriting file time stamps) and 
   * all our journaled data buffers for journaled files (e.g. files in the 
   * meta_fs like rindex, or files for which chattr +j was done.)
   * If we don't reserve enough space, gfs2_log_refund and gfs2_log_flush
   * will count it as free space (sd_log_blks_free) and corruption will follow.
   *
   * We can have metadata bufs and jdata bufs in the same journal.  So each
   * type gets its own log header, for which we need to reserve a block.
   * In fact, each type has the potential for needing more than one header 
   * in cases where we have more buffers than will fit on a journal page.
   * Metadata journal entries take up half the space of journaled buffer entries.
   * Thus, metadata entries have buf_limit (502) and journaled buffers have
   * databuf_limit (251) before they cause a wrap around.
   *
   * Also, we need to reserve blocks for revoke journal entries and one for an
   * overall header for the lot.
   *
   * Returns: the number of blocks reserved
   */
  static unsigned int calc_reserved(struct gfs2_sbd *sdp)
  {
  	unsigned int reserved = 0;
  	unsigned int mbuf_limit, metabufhdrs_needed;
  	unsigned int dbuf_limit, databufhdrs_needed;
  	unsigned int revokes = 0;
  
  	mbuf_limit = buf_limit(sdp);
  	metabufhdrs_needed = (sdp->sd_log_commited_buf +
  			      (mbuf_limit - 1)) / mbuf_limit;
  	dbuf_limit = databuf_limit(sdp);
  	databufhdrs_needed = (sdp->sd_log_commited_databuf +
  			      (dbuf_limit - 1)) / dbuf_limit;

  	if (sdp->sd_log_commited_revoke > 0)

  		revokes = gfs2_struct2blk(sdp, sdp->sd_log_commited_revoke,
  					  sizeof(u64));
  
  	reserved = sdp->sd_log_commited_buf + metabufhdrs_needed +
  		sdp->sd_log_commited_databuf + databufhdrs_needed +
  		revokes;
  	/* One for the overall header */
  	if (reserved)
  		reserved++;
  	return reserved;
  }

  static unsigned int current_tail(struct gfs2_sbd *sdp)
  {
  	struct gfs2_ail *ai;
  	unsigned int tail;

  	spin_lock(&sdp->sd_ail_lock);

  	if (list_empty(&sdp->sd_ail1_list)) {

  		tail = sdp->sd_log_head;

  	} else {
  		ai = list_entry(sdp->sd_ail1_list.prev, struct gfs2_ail, ai_list);

  		tail = ai->ai_first;
  	}

  	spin_unlock(&sdp->sd_ail_lock);

  
  	return tail;
  }

  void gfs2_log_incr_head(struct gfs2_sbd *sdp)

  {
  	if (sdp->sd_log_flush_head == sdp->sd_log_tail)

  		BUG_ON(sdp->sd_log_flush_head != sdp->sd_log_head);

  
  	if (++sdp->sd_log_flush_head == sdp->sd_jdesc->jd_blocks) {
  		sdp->sd_log_flush_head = 0;
  		sdp->sd_log_flush_wrapped = 1;
  	}
  }
  
  /**

   * gfs2_log_write_endio - End of I/O for a log buffer
   * @bh: The buffer head
   * @uptodate: I/O Status
   *
   */
  
  static void gfs2_log_write_endio(struct buffer_head *bh, int uptodate)
  {
  	struct gfs2_sbd *sdp = bh->b_private;
  	bh->b_private = NULL;
  
  	end_buffer_write_sync(bh, uptodate);
  	if (atomic_dec_and_test(&sdp->sd_log_in_flight))
  		wake_up(&sdp->sd_log_flush_wait);
  }
  
  /**

   * gfs2_log_get_buf - Get and initialize a buffer to use for log control data
   * @sdp: The GFS2 superblock
   *
   * Returns: the buffer_head
   */
  
  struct buffer_head *gfs2_log_get_buf(struct gfs2_sbd *sdp)
  {

  	u64 blkno = log_bmap(sdp, sdp->sd_log_flush_head);

  	struct buffer_head *bh;

  	bh = sb_getblk(sdp->sd_vfs, blkno);

  	lock_buffer(bh);
  	memset(bh->b_data, 0, bh->b_size);
  	set_buffer_uptodate(bh);
  	clear_buffer_dirty(bh);

  	gfs2_log_incr_head(sdp);
  	atomic_inc(&sdp->sd_log_in_flight);
  	bh->b_private = sdp;
  	bh->b_end_io = gfs2_log_write_endio;

  
  	return bh;
  }
  
  /**

   * gfs2_fake_write_endio - 
   * @bh: The buffer head
   * @uptodate: The I/O Status
   *
   */
  
  static void gfs2_fake_write_endio(struct buffer_head *bh, int uptodate)
  {
  	struct buffer_head *real_bh = bh->b_private;

  	struct gfs2_bufdata *bd = real_bh->b_private;
  	struct gfs2_sbd *sdp = bd->bd_gl->gl_sbd;

  
  	end_buffer_write_sync(bh, uptodate);
  	free_buffer_head(bh);
  	unlock_buffer(real_bh);
  	brelse(real_bh);
  	if (atomic_dec_and_test(&sdp->sd_log_in_flight))
  		wake_up(&sdp->sd_log_flush_wait);
  }
  
  /**

   * gfs2_log_fake_buf - Build a fake buffer head to write metadata buffer to log
   * @sdp: the filesystem
   * @data: the data the buffer_head should point to
   *
   * Returns: the log buffer descriptor
   */
  
  struct buffer_head *gfs2_log_fake_buf(struct gfs2_sbd *sdp,
  				      struct buffer_head *real)
  {

  	u64 blkno = log_bmap(sdp, sdp->sd_log_flush_head);

  	struct buffer_head *bh;

  	bh = alloc_buffer_head(GFP_NOFS | __GFP_NOFAIL);

  	atomic_set(&bh->b_count, 1);

  	bh->b_state = (1 << BH_Mapped) | (1 << BH_Uptodate) | (1 << BH_Lock);

  	set_bh_page(bh, real->b_page, bh_offset(real));

  	bh->b_blocknr = blkno;
  	bh->b_size = sdp->sd_sb.sb_bsize;
  	bh->b_bdev = sdp->sd_vfs->s_bdev;

  	bh->b_private = real;
  	bh->b_end_io = gfs2_fake_write_endio;

  	gfs2_log_incr_head(sdp);
  	atomic_inc(&sdp->sd_log_in_flight);

  
  	return bh;
  }

  static void log_pull_tail(struct gfs2_sbd *sdp, unsigned int new_tail)

  {
  	unsigned int dist = log_distance(sdp, new_tail, sdp->sd_log_tail);
  
  	ail2_empty(sdp, new_tail);

  	atomic_add(dist, &sdp->sd_log_blks_free);

  	trace_gfs2_log_blocks(sdp, dist);

  	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
  			     sdp->sd_jdesc->jd_blocks);

  
  	sdp->sd_log_tail = new_tail;
  }
  
  /**
   * log_write_header - Get and initialize a journal header buffer
   * @sdp: The GFS2 superblock
   *
   * Returns: the initialized log buffer descriptor
   */

  static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)

  {

  	u64 blkno = log_bmap(sdp, sdp->sd_log_flush_head);

  	struct buffer_head *bh;
  	struct gfs2_log_header *lh;
  	unsigned int tail;

  	u32 hash;

  	bh = sb_getblk(sdp->sd_vfs, blkno);
  	lock_buffer(bh);
  	memset(bh->b_data, 0, bh->b_size);
  	set_buffer_uptodate(bh);
  	clear_buffer_dirty(bh);

  	gfs2_ail1_empty(sdp);

  	tail = current_tail(sdp);
  
  	lh = (struct gfs2_log_header *)bh->b_data;
  	memset(lh, 0, sizeof(struct gfs2_log_header));
  	lh->lh_header.mh_magic = cpu_to_be32(GFS2_MAGIC);

  	lh->lh_header.mh_type = cpu_to_be32(GFS2_METATYPE_LH);

  	lh->lh_header.__pad0 = cpu_to_be64(0);

  	lh->lh_header.mh_format = cpu_to_be32(GFS2_FORMAT_LH);

  	lh->lh_header.mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);

  	lh->lh_sequence = cpu_to_be64(sdp->sd_log_sequence++);
  	lh->lh_flags = cpu_to_be32(flags);
  	lh->lh_tail = cpu_to_be32(tail);
  	lh->lh_blkno = cpu_to_be32(sdp->sd_log_flush_head);

  	hash = gfs2_disk_hash(bh->b_data, sizeof(struct gfs2_log_header));
  	lh->lh_hash = cpu_to_be32(hash);

  	bh->b_end_io = end_buffer_write_sync;

  	get_bh(bh);

  	if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags))

  		submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh);

  	else

  		submit_bh(WRITE_FLUSH_FUA | REQ_META, bh);

  	wait_on_buffer(bh);

  	if (!buffer_uptodate(bh))

  		gfs2_io_error_bh(sdp, bh);
  	brelse(bh);
  
  	if (sdp->sd_log_tail != tail)

  		log_pull_tail(sdp, tail);

  	else
  		gfs2_assert_withdraw(sdp, !pull);
  
  	sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);

  	gfs2_log_incr_head(sdp);

  }
  
  static void log_flush_commit(struct gfs2_sbd *sdp)
  {

  	DEFINE_WAIT(wait);
  
  	if (atomic_read(&sdp->sd_log_in_flight)) {
  		do {
  			prepare_to_wait(&sdp->sd_log_flush_wait, &wait,
  					TASK_UNINTERRUPTIBLE);
  			if (atomic_read(&sdp->sd_log_in_flight))
  				io_schedule();
  		} while(atomic_read(&sdp->sd_log_in_flight));
  		finish_wait(&sdp->sd_log_flush_wait, &wait);

  	}

  	log_write_header(sdp, 0, 0);

  }

  static void gfs2_ordered_write(struct gfs2_sbd *sdp)
  {
  	struct gfs2_bufdata *bd;
  	struct buffer_head *bh;
  	LIST_HEAD(written);
  
  	gfs2_log_lock(sdp);
  	while (!list_empty(&sdp->sd_log_le_ordered)) {
  		bd = list_entry(sdp->sd_log_le_ordered.next, struct gfs2_bufdata, bd_le.le_list);
  		list_move(&bd->bd_le.le_list, &written);
  		bh = bd->bd_bh;
  		if (!buffer_dirty(bh))
  			continue;
  		get_bh(bh);
  		gfs2_log_unlock(sdp);
  		lock_buffer(bh);

  		if (buffer_mapped(bh) && test_clear_buffer_dirty(bh)) {

  			bh->b_end_io = end_buffer_write_sync;

  			submit_bh(WRITE_SYNC, bh);

  		} else {
  			unlock_buffer(bh);
  			brelse(bh);
  		}
  		gfs2_log_lock(sdp);
  	}
  	list_splice(&written, &sdp->sd_log_le_ordered);
  	gfs2_log_unlock(sdp);
  }
  
  static void gfs2_ordered_wait(struct gfs2_sbd *sdp)
  {
  	struct gfs2_bufdata *bd;
  	struct buffer_head *bh;
  
  	gfs2_log_lock(sdp);
  	while (!list_empty(&sdp->sd_log_le_ordered)) {
  		bd = list_entry(sdp->sd_log_le_ordered.prev, struct gfs2_bufdata, bd_le.le_list);
  		bh = bd->bd_bh;
  		if (buffer_locked(bh)) {
  			get_bh(bh);
  			gfs2_log_unlock(sdp);
  			wait_on_buffer(bh);
  			brelse(bh);
  			gfs2_log_lock(sdp);
  			continue;
  		}
  		list_del_init(&bd->bd_le.le_list);
  	}
  	gfs2_log_unlock(sdp);
  }

  /**

   * gfs2_log_flush - flush incore transaction(s)

   * @sdp: the filesystem
   * @gl: The glock structure to flush.  If NULL, flush the whole incore log
   *
   */

  void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl)

  {
  	struct gfs2_ail *ai;

  	down_write(&sdp->sd_log_flush_lock);

  	/* Log might have been flushed while we waited for the flush lock */
  	if (gl && !test_bit(GLF_LFLUSH, &gl->gl_flags)) {
  		up_write(&sdp->sd_log_flush_lock);
  		return;

  	}

  	trace_gfs2_log_flush(sdp, 1);

  	ai = kzalloc(sizeof(struct gfs2_ail), GFP_NOFS | __GFP_NOFAIL);
  	INIT_LIST_HEAD(&ai->ai_ail1_list);
  	INIT_LIST_HEAD(&ai->ai_ail2_list);

  	if (sdp->sd_log_num_buf != sdp->sd_log_commited_buf) {
  		printk(KERN_INFO "GFS2: log buf %u %u
  ", sdp->sd_log_num_buf,
  		       sdp->sd_log_commited_buf);
  		gfs2_assert_withdraw(sdp, 0);
  	}
  	if (sdp->sd_log_num_databuf != sdp->sd_log_commited_databuf) {
  		printk(KERN_INFO "GFS2: log databuf %u %u
  ",
  		       sdp->sd_log_num_databuf, sdp->sd_log_commited_databuf);
  		gfs2_assert_withdraw(sdp, 0);
  	}

  	gfs2_assert_withdraw(sdp,
  			sdp->sd_log_num_revoke == sdp->sd_log_commited_revoke);

  	sdp->sd_log_flush_head = sdp->sd_log_head;
  	sdp->sd_log_flush_wrapped = 0;
  	ai->ai_first = sdp->sd_log_flush_head;

  	gfs2_ordered_write(sdp);

  	lops_before_commit(sdp);

  	gfs2_ordered_wait(sdp);

  	if (sdp->sd_log_head != sdp->sd_log_flush_head)

  		log_flush_commit(sdp);

  	else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle){
  		gfs2_log_lock(sdp);

  		atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */

  		trace_gfs2_log_blocks(sdp, -1);

  		gfs2_log_unlock(sdp);

  		log_write_header(sdp, 0, PULL);

  	}

  	lops_after_commit(sdp, ai);

  	gfs2_log_lock(sdp);
  	sdp->sd_log_head = sdp->sd_log_flush_head;

  	sdp->sd_log_blks_reserved = 0;
  	sdp->sd_log_commited_buf = 0;

  	sdp->sd_log_commited_databuf = 0;

  	sdp->sd_log_commited_revoke = 0;

  	spin_lock(&sdp->sd_ail_lock);

  	if (!list_empty(&ai->ai_ail1_list)) {
  		list_add(&ai->ai_list, &sdp->sd_ail1_list);
  		ai = NULL;
  	}

  	spin_unlock(&sdp->sd_ail_lock);

  	gfs2_log_unlock(sdp);

  	trace_gfs2_log_flush(sdp, 0);

  	up_write(&sdp->sd_log_flush_lock);

  
  	kfree(ai);
  }
  
  static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
  {

  	unsigned int reserved;

  	unsigned int unused;

  
  	gfs2_log_lock(sdp);
  
  	sdp->sd_log_commited_buf += tr->tr_num_buf_new - tr->tr_num_buf_rm;

  	sdp->sd_log_commited_databuf += tr->tr_num_databuf_new -
  		tr->tr_num_databuf_rm;
  	gfs2_assert_withdraw(sdp, (((int)sdp->sd_log_commited_buf) >= 0) ||
  			     (((int)sdp->sd_log_commited_databuf) >= 0));

  	sdp->sd_log_commited_revoke += tr->tr_num_revoke - tr->tr_num_revoke_rm;

  	reserved = calc_reserved(sdp);

  	gfs2_assert_withdraw(sdp, sdp->sd_log_blks_reserved + tr->tr_reserved >= reserved);

  	unused = sdp->sd_log_blks_reserved - reserved + tr->tr_reserved;

  	atomic_add(unused, &sdp->sd_log_blks_free);

  	trace_gfs2_log_blocks(sdp, unused);

  	gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=

  			     sdp->sd_jdesc->jd_blocks);

  	sdp->sd_log_blks_reserved = reserved;
  
  	gfs2_log_unlock(sdp);
  }

  static void buf_lo_incore_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
  {
  	struct list_head *head = &tr->tr_list_buf;
  	struct gfs2_bufdata *bd;
  
  	gfs2_log_lock(sdp);
  	while (!list_empty(head)) {
  		bd = list_entry(head->next, struct gfs2_bufdata, bd_list_tr);
  		list_del_init(&bd->bd_list_tr);
  		tr->tr_num_buf--;
  	}
  	gfs2_log_unlock(sdp);
  	gfs2_assert_warn(sdp, !tr->tr_num_buf);
  }

  /**
   * gfs2_log_commit - Commit a transaction to the log
   * @sdp: the filesystem
   * @tr: the transaction
   *

   * We wake up gfs2_logd if the number of pinned blocks exceed thresh1
   * or the total number of used blocks (pinned blocks plus AIL blocks)
   * is greater than thresh2.
   *
   * At mount time thresh1 is 1/3rd of journal size, thresh2 is 2/3rd of
   * journal size.
   *

   * Returns: errno
   */
  
  void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
  {
  	log_refund(sdp, tr);

  	buf_lo_incore_commit(sdp, tr);

  	up_read(&sdp->sd_log_flush_lock);

  	if (atomic_read(&sdp->sd_log_pinned) > atomic_read(&sdp->sd_log_thresh1) ||
  	    ((sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free)) >
  	    atomic_read(&sdp->sd_log_thresh2)))
  		wake_up(&sdp->sd_logd_waitq);

  }
  
  /**
   * gfs2_log_shutdown - write a shutdown header into a journal
   * @sdp: the filesystem
   *
   */
  
  void gfs2_log_shutdown(struct gfs2_sbd *sdp)
  {

  	down_write(&sdp->sd_log_flush_lock);

  	gfs2_assert_withdraw(sdp, !sdp->sd_log_blks_reserved);

  	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_buf);
  	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
  	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_rg);
  	gfs2_assert_withdraw(sdp, !sdp->sd_log_num_databuf);
  	gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));
  
  	sdp->sd_log_flush_head = sdp->sd_log_head;
  	sdp->sd_log_flush_wrapped = 0;

  	log_write_header(sdp, GFS2_LOG_HEAD_UNMOUNT,
  			 (sdp->sd_log_tail == current_tail(sdp)) ? 0 : PULL);

  	gfs2_assert_warn(sdp, atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks);

  	gfs2_assert_warn(sdp, sdp->sd_log_head == sdp->sd_log_tail);
  	gfs2_assert_warn(sdp, list_empty(&sdp->sd_ail2_list));

  
  	sdp->sd_log_head = sdp->sd_log_flush_head;

  	sdp->sd_log_tail = sdp->sd_log_head;

  	up_write(&sdp->sd_log_flush_lock);

  }

  
  /**
   * gfs2_meta_syncfs - sync all the buffers in a filesystem
   * @sdp: the filesystem
   *
   */
  
  void gfs2_meta_syncfs(struct gfs2_sbd *sdp)
  {
  	gfs2_log_flush(sdp, NULL);
  	for (;;) {

  		gfs2_ail1_start(sdp);

  		gfs2_ail1_wait(sdp);

  		if (gfs2_ail1_empty(sdp))

  			break;

  	}

  	gfs2_log_flush(sdp, NULL);

  }

  static inline int gfs2_jrnl_flush_reqd(struct gfs2_sbd *sdp)
  {
  	return (atomic_read(&sdp->sd_log_pinned) >= atomic_read(&sdp->sd_log_thresh1));
  }
  
  static inline int gfs2_ail_flush_reqd(struct gfs2_sbd *sdp)
  {
  	unsigned int used_blocks = sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free);
  	return used_blocks >= atomic_read(&sdp->sd_log_thresh2);
  }

  
  /**
   * gfs2_logd - Update log tail as Active Items get flushed to in-place blocks
   * @sdp: Pointer to GFS2 superblock
   *
   * Also, periodically check to make sure that we're using the most recent
   * journal index.
   */
  
  int gfs2_logd(void *data)
  {
  	struct gfs2_sbd *sdp = data;

  	unsigned long t = 1;
  	DEFINE_WAIT(wait);
  	unsigned preflush;

  
  	while (!kthread_should_stop()) {

  		preflush = atomic_read(&sdp->sd_log_pinned);
  		if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {

  			gfs2_ail1_empty(sdp);

  			gfs2_log_flush(sdp, NULL);

  		}

  		if (gfs2_ail_flush_reqd(sdp)) {
  			gfs2_ail1_start(sdp);

  			gfs2_ail1_wait(sdp);

  			gfs2_ail1_empty(sdp);

  			gfs2_log_flush(sdp, NULL);

  		}

  		if (!gfs2_ail_flush_reqd(sdp))
  			wake_up(&sdp->sd_log_waitq);

  		t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;

  
  		try_to_freeze();

  
  		do {
  			prepare_to_wait(&sdp->sd_logd_waitq, &wait,

  					TASK_INTERRUPTIBLE);

  			if (!gfs2_ail_flush_reqd(sdp) &&
  			    !gfs2_jrnl_flush_reqd(sdp) &&
  			    !kthread_should_stop())
  				t = schedule_timeout(t);
  		} while(t && !gfs2_ail_flush_reqd(sdp) &&
  			!gfs2_jrnl_flush_reqd(sdp) &&
  			!kthread_should_stop());
  		finish_wait(&sdp->sd_logd_waitq, &wait);

  	}
  
  	return 0;
  }