/*
   * linux/fs/ext4/page-io.c
   *
   * This contains the new page_io functions for ext4
   *
   * Written by Theodore Ts'o, 2010.
   */

  #include <linux/fs.h>
  #include <linux/time.h>
  #include <linux/jbd2.h>
  #include <linux/highuid.h>
  #include <linux/pagemap.h>
  #include <linux/quotaops.h>
  #include <linux/string.h>
  #include <linux/buffer_head.h>
  #include <linux/writeback.h>
  #include <linux/pagevec.h>
  #include <linux/mpage.h>
  #include <linux/namei.h>

  #include <linux/aio.h>

  #include <linux/uio.h>
  #include <linux/bio.h>
  #include <linux/workqueue.h>
  #include <linux/kernel.h>
  #include <linux/slab.h>

  #include <linux/mm.h>

  #include <linux/ratelimit.h>

  
  #include "ext4_jbd2.h"
  #include "xattr.h"
  #include "acl.h"

  static struct kmem_cache *io_end_cachep;

  int __init ext4_init_pageio(void)

  {

  	io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);

  	if (io_end_cachep == NULL)

  		return -ENOMEM;

  	return 0;
  }

  void ext4_exit_pageio(void)

  {
  	kmem_cache_destroy(io_end_cachep);

  }

  /*

   * Print an buffer I/O error compatible with the fs/buffer.c.  This
   * provides compatibility with dmesg scrapers that look for a specific
   * buffer I/O error message.  We really need a unified error reporting
   * structure to userspace ala Digital Unix's uerf system, but it's
   * probably not going to happen in my lifetime, due to LKML politics...
   */
  static void buffer_io_error(struct buffer_head *bh)
  {
  	char b[BDEVNAME_SIZE];

  	printk_ratelimited(KERN_ERR "Buffer I/O error on device %s, logical block %llu
  ",

  			bdevname(bh->b_bdev, b),
  			(unsigned long long)bh->b_blocknr);
  }
  
  static void ext4_finish_bio(struct bio *bio)
  {
  	int i;
  	int error = !test_bit(BIO_UPTODATE, &bio->bi_flags);

  	struct bio_vec *bvec;

  	bio_for_each_segment_all(bvec, bio, i) {

  		struct page *page = bvec->bv_page;
  		struct buffer_head *bh, *head;
  		unsigned bio_start = bvec->bv_offset;
  		unsigned bio_end = bio_start + bvec->bv_len;
  		unsigned under_io = 0;
  		unsigned long flags;
  
  		if (!page)
  			continue;
  
  		if (error) {
  			SetPageError(page);
  			set_bit(AS_EIO, &page->mapping->flags);
  		}
  		bh = head = page_buffers(page);
  		/*
  		 * We check all buffers in the page under BH_Uptodate_Lock
  		 * to avoid races with other end io clearing async_write flags
  		 */
  		local_irq_save(flags);
  		bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
  		do {
  			if (bh_offset(bh) < bio_start ||
  			    bh_offset(bh) + bh->b_size > bio_end) {
  				if (buffer_async_write(bh))
  					under_io++;
  				continue;
  			}
  			clear_buffer_async_write(bh);
  			if (error)
  				buffer_io_error(bh);
  		} while ((bh = bh->b_this_page) != head);
  		bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
  		local_irq_restore(flags);
  		if (!under_io)
  			end_page_writeback(page);
  	}
  }

  static void ext4_release_io_end(ext4_io_end_t *io_end)

  {

  	struct bio *bio, *next_bio;

  	BUG_ON(!list_empty(&io_end->list));
  	BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);

  	WARN_ON(io_end->handle);

  
  	if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
  		wake_up_all(ext4_ioend_wq(io_end->inode));

  
  	for (bio = io_end->bio; bio; bio = next_bio) {
  		next_bio = bio->bi_private;
  		ext4_finish_bio(bio);
  		bio_put(bio);
  	}

  	kmem_cache_free(io_end_cachep, io_end);
  }
  
  static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
  {
  	struct inode *inode = io_end->inode;

  	io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
  	/* Wake up anyone waiting on unwritten extent conversion */
  	if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
  		wake_up_all(ext4_ioend_wq(inode));

  }

  /*
   * Check a range of space and convert unwritten extents to written. Note that
   * we are protected from truncate touching same part of extent tree by the
   * fact that truncate code waits for all DIO to finish (thus exclusion from
   * direct IO is achieved) and also waits for PageWriteback bits. Thus we
   * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
   * completed (happens from ext4_free_ioend()).
   */

  static int ext4_end_io(ext4_io_end_t *io)

  {
  	struct inode *inode = io->inode;
  	loff_t offset = io->offset;
  	ssize_t size = io->size;

  	handle_t *handle = io->handle;

  	int ret = 0;
  
  	ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
  		   "list->prev 0x%p
  ",
  		   io, inode->i_ino, io->list.next, io->list.prev);

  	io->handle = NULL;	/* Following call will use up the handle */
  	ret = ext4_convert_unwritten_extents(handle, inode, offset, size);

  	if (ret < 0) {

  		ext4_msg(inode->i_sb, KERN_EMERG,
  			 "failed to convert unwritten extents to written "
  			 "extents -- potential data loss!  "
  			 "(inode %lu, offset %llu, size %zd, error %d)",
  			 inode->i_ino, offset, size, ret);

  	}

  	ext4_clear_io_unwritten_flag(io);
  	ext4_release_io_end(io);

  	return ret;
  }

  static void dump_completed_IO(struct inode *inode, struct list_head *head)

  {
  #ifdef	EXT4FS_DEBUG
  	struct list_head *cur, *before, *after;
  	ext4_io_end_t *io, *io0, *io1;

  	if (list_empty(head))

  		return;

  	ext4_debug("Dump inode %lu completed io list
  ", inode->i_ino);
  	list_for_each_entry(io, head, list) {

  		cur = &io->list;
  		before = cur->prev;
  		io0 = container_of(before, ext4_io_end_t, list);
  		after = cur->next;
  		io1 = container_of(after, ext4_io_end_t, list);
  
  		ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p
  ",
  			    io, inode->i_ino, io0, io1);
  	}
  #endif
  }
  
  /* Add the io_end to per-inode completed end_io list. */

  static void ext4_add_complete_io(ext4_io_end_t *io_end)

  {

  	struct ext4_inode_info *ei = EXT4_I(io_end->inode);

  	struct ext4_sb_info *sbi = EXT4_SB(io_end->inode->i_sb);

  	struct workqueue_struct *wq;
  	unsigned long flags;

  	/* Only reserved conversions from writeback should enter here */
  	WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));

  	WARN_ON(!io_end->handle && sbi->s_journal);

  	spin_lock_irqsave(&ei->i_completed_io_lock, flags);

  	wq = sbi->rsv_conversion_wq;

  	if (list_empty(&ei->i_rsv_conversion_list))
  		queue_work(wq, &ei->i_rsv_conversion_work);
  	list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);

  	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
  }

  static int ext4_do_flush_completed_IO(struct inode *inode,
  				      struct list_head *head)

  {
  	ext4_io_end_t *io;

  	struct list_head unwritten;

  	unsigned long flags;
  	struct ext4_inode_info *ei = EXT4_I(inode);
  	int err, ret = 0;

  	spin_lock_irqsave(&ei->i_completed_io_lock, flags);

  	dump_completed_IO(inode, head);
  	list_replace_init(head, &unwritten);

  	spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
  
  	while (!list_empty(&unwritten)) {
  		io = list_entry(unwritten.next, ext4_io_end_t, list);
  		BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
  		list_del_init(&io->list);
  
  		err = ext4_end_io(io);
  		if (unlikely(!ret && err))
  			ret = err;

  	}
  	return ret;
  }
  
  /*

   * work on completed IO, to convert unwritten extents to extents

   */

  void ext4_end_io_rsv_work(struct work_struct *work)
  {
  	struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
  						  i_rsv_conversion_work);
  	ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
  }

  ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
  {

  	ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);

  	if (io) {

  		atomic_inc(&EXT4_I(inode)->i_ioend_count);
  		io->inode = inode;

  		INIT_LIST_HEAD(&io->list);

  		atomic_set(&io->count, 1);

  	}
  	return io;
  }

  void ext4_put_io_end_defer(ext4_io_end_t *io_end)
  {
  	if (atomic_dec_and_test(&io_end->count)) {
  		if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
  			ext4_release_io_end(io_end);
  			return;
  		}
  		ext4_add_complete_io(io_end);
  	}
  }
  
  int ext4_put_io_end(ext4_io_end_t *io_end)
  {
  	int err = 0;
  
  	if (atomic_dec_and_test(&io_end->count)) {
  		if (io_end->flag & EXT4_IO_END_UNWRITTEN) {

  			err = ext4_convert_unwritten_extents(io_end->handle,
  						io_end->inode, io_end->offset,
  						io_end->size);
  			io_end->handle = NULL;

  			ext4_clear_io_unwritten_flag(io_end);
  		}
  		ext4_release_io_end(io_end);
  	}
  	return err;
  }
  
  ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
  {
  	atomic_inc(&io_end->count);
  	return io_end;
  }

  /* BIO completion function for page writeback */

  static void ext4_end_bio(struct bio *bio, int error)
  {
  	ext4_io_end_t *io_end = bio->bi_private;

  	sector_t bi_sector = bio->bi_iter.bi_sector;

  
  	BUG_ON(!io_end);

  	bio->bi_end_io = NULL;
  	if (test_bit(BIO_UPTODATE, &bio->bi_flags))
  		error = 0;

  	if (error) {

  		struct inode *inode = io_end->inode;

  		ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "

  			     "(offset %llu size %ld starting block %llu)",

  			     error, inode->i_ino,

  			     (unsigned long long) io_end->offset,
  			     (long) io_end->size,
  			     (unsigned long long)

  			     bi_sector >> (inode->i_blkbits - 9));

  		mapping_set_error(inode->i_mapping, error);

  	}

  
  	if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
  		/*
  		 * Link bio into list hanging from io_end. We have to do it
  		 * atomically as bio completions can be racing against each
  		 * other.
  		 */
  		bio->bi_private = xchg(&io_end->bio, bio);
  		ext4_put_io_end_defer(io_end);
  	} else {
  		/*
  		 * Drop io_end reference early. Inode can get freed once
  		 * we finish the bio.
  		 */
  		ext4_put_io_end_defer(io_end);
  		ext4_finish_bio(bio);
  		bio_put(bio);
  	}

  }
  
  void ext4_io_submit(struct ext4_io_submit *io)
  {
  	struct bio *bio = io->io_bio;
  
  	if (bio) {
  		bio_get(io->io_bio);
  		submit_bio(io->io_op, io->io_bio);
  		BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
  		bio_put(io->io_bio);
  	}

  	io->io_bio = NULL;

  }
  
  void ext4_io_submit_init(struct ext4_io_submit *io,
  			 struct writeback_control *wbc)
  {
  	io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
  	io->io_bio = NULL;

  	io->io_end = NULL;

  }

  static int io_submit_init_bio(struct ext4_io_submit *io,
  			      struct buffer_head *bh)

  {

  	int nvecs = bio_get_nr_vecs(bh->b_bdev);
  	struct bio *bio;

  	bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));

  	if (!bio)
  		return -ENOMEM;

  	bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);

  	bio->bi_bdev = bh->b_bdev;

  	bio->bi_end_io = ext4_end_bio;

  	bio->bi_private = ext4_get_io_end(io->io_end);

  	io->io_bio = bio;

  	io->io_next_block = bh->b_blocknr;
  	return 0;
  }
  
  static int io_submit_add_bh(struct ext4_io_submit *io,

  			    struct inode *inode,

  			    struct buffer_head *bh)
  {

  	int ret;

  	if (io->io_bio && bh->b_blocknr != io->io_next_block) {
  submit_and_retry:
  		ext4_io_submit(io);
  	}
  	if (io->io_bio == NULL) {

  		ret = io_submit_init_bio(io, bh);

  		if (ret)
  			return ret;
  	}

  	ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
  	if (ret != bh->b_size)
  		goto submit_and_retry;

  	io->io_next_block++;

  	return 0;
  }
  
  int ext4_bio_write_page(struct ext4_io_submit *io,
  			struct page *page,
  			int len,
  			struct writeback_control *wbc)
  {
  	struct inode *inode = page->mapping->host;

  	unsigned block_start, blocksize;

  	struct buffer_head *bh, *head;
  	int ret = 0;

  	int nr_submitted = 0;

  
  	blocksize = 1 << inode->i_blkbits;

  	BUG_ON(!PageLocked(page));

  	BUG_ON(PageWriteback(page));

  	set_page_writeback(page);
  	ClearPageError(page);

  	/*
  	 * In the first loop we prepare and mark buffers to submit. We have to
  	 * mark all buffers in the page before submitting so that
  	 * end_page_writeback() cannot be called from ext4_bio_end_io() when IO
  	 * on the first buffer finishes and we are still working on submitting
  	 * the second buffer.
  	 */
  	bh = head = page_buffers(page);
  	do {
  		block_start = bh_offset(bh);

  		if (block_start >= len) {

  			/*
  			 * Comments copied from block_write_full_page_endio:
  			 *
  			 * The page straddles i_size.  It must be zeroed out on
  			 * each and every writepage invocation because it may
  			 * be mmapped.  "A file is mapped in multiples of the
  			 * page size.  For a file that is not a multiple of
  			 * the  page size, the remaining memory is zeroed when
  			 * mapped, and writes to that region are not written
  			 * out to the file."
  			 */

  			zero_user_segment(page, block_start,
  					  block_start + blocksize);

  			clear_buffer_dirty(bh);
  			set_buffer_uptodate(bh);
  			continue;
  		}

  		if (!buffer_dirty(bh) || buffer_delay(bh) ||
  		    !buffer_mapped(bh) || buffer_unwritten(bh)) {
  			/* A hole? We can safely clear the dirty bit */
  			if (!buffer_mapped(bh))
  				clear_buffer_dirty(bh);
  			if (io->io_bio)
  				ext4_io_submit(io);
  			continue;
  		}

  		if (buffer_new(bh)) {
  			clear_buffer_new(bh);
  			unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
  		}
  		set_buffer_async_write(bh);
  	} while ((bh = bh->b_this_page) != head);
  
  	/* Now submit buffers to write */
  	bh = head = page_buffers(page);
  	do {
  		if (!buffer_async_write(bh))
  			continue;

  		ret = io_submit_add_bh(io, inode, bh);

  		if (ret) {
  			/*
  			 * We only get here on ENOMEM.  Not much else
  			 * we can do but mark the page as dirty, and
  			 * better luck next time.
  			 */

  			redirty_page_for_writepage(wbc, page);

  			break;
  		}

  		nr_submitted++;

  		clear_buffer_dirty(bh);

  	} while ((bh = bh->b_this_page) != head);
  
  	/* Error stopped previous loop? Clean up buffers... */
  	if (ret) {
  		do {
  			clear_buffer_async_write(bh);
  			bh = bh->b_this_page;
  		} while (bh != head);

  	}
  	unlock_page(page);

  	/* Nothing submitted - we have to end page writeback */
  	if (!nr_submitted)
  		end_page_writeback(page);

  	return ret;
  }