/*

   * Copyright (c) 2000-2005 Silicon Graphics, Inc.
   * All Rights Reserved.

   *

   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as

   * published by the Free Software Foundation.
   *

   * This program is distributed in the hope that it would 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 License
   * along with this program; if not, write the Free Software Foundation,
   * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

   */

  #include "xfs.h"

  #include "xfs_bit.h"

  #include "xfs_log.h"

  #include "xfs_inum.h"

  #include "xfs_sb.h"

  #include "xfs_ag.h"

  #include "xfs_trans.h"

  #include "xfs_mount.h"
  #include "xfs_bmap_btree.h"

  #include "xfs_dinode.h"
  #include "xfs_inode.h"

  #include "xfs_alloc.h"

  #include "xfs_error.h"
  #include "xfs_rw.h"
  #include "xfs_iomap.h"

  #include "xfs_vnodeops.h"

  #include "xfs_trace.h"

  #include "xfs_bmap.h"

  #include <linux/gfp.h>

  #include <linux/mpage.h>

  #include <linux/pagevec.h>

  #include <linux/writeback.h>

  void

  xfs_count_page_state(
  	struct page		*page,
  	int			*delalloc,

  	int			*unwritten)
  {
  	struct buffer_head	*bh, *head;

  	*delalloc = *unwritten = 0;

  
  	bh = head = page_buffers(page);
  	do {

  		if (buffer_unwritten(bh))

  			(*unwritten) = 1;
  		else if (buffer_delay(bh))
  			(*delalloc) = 1;
  	} while ((bh = bh->b_this_page) != head);
  }

  STATIC struct block_device *
  xfs_find_bdev_for_inode(

  	struct inode		*inode)

  {

  	struct xfs_inode	*ip = XFS_I(inode);

  	struct xfs_mount	*mp = ip->i_mount;

  	if (XFS_IS_REALTIME_INODE(ip))

  		return mp->m_rtdev_targp->bt_bdev;
  	else
  		return mp->m_ddev_targp->bt_bdev;
  }

  /*

   * We're now finished for good with this ioend structure.
   * Update the page state via the associated buffer_heads,
   * release holds on the inode and bio, and finally free
   * up memory.  Do not use the ioend after this.
   */

  STATIC void
  xfs_destroy_ioend(
  	xfs_ioend_t		*ioend)
  {

  	struct buffer_head	*bh, *next;
  
  	for (bh = ioend->io_buffer_head; bh; bh = next) {
  		next = bh->b_private;

  		bh->b_end_io(bh, !ioend->io_error);

  	}

  	if (ioend->io_iocb) {

  		if (ioend->io_isasync) {
  			aio_complete(ioend->io_iocb, ioend->io_error ?
  					ioend->io_error : ioend->io_result, 0);
  		}

  		inode_dio_done(ioend->io_inode);
  	}

  	mempool_free(ioend, xfs_ioend_pool);
  }
  
  /*

   * If the end of the current ioend is beyond the current EOF,
   * return the new EOF value, otherwise zero.
   */
  STATIC xfs_fsize_t
  xfs_ioend_new_eof(
  	xfs_ioend_t		*ioend)
  {
  	xfs_inode_t		*ip = XFS_I(ioend->io_inode);
  	xfs_fsize_t		isize;
  	xfs_fsize_t		bsize;
  
  	bsize = ioend->io_offset + ioend->io_size;
  	isize = MAX(ip->i_size, ip->i_new_size);
  	isize = MIN(isize, bsize);
  	return isize > ip->i_d.di_size ? isize : 0;
  }
  
  /*

   * Fast and loose check if this write could update the on-disk inode size.
   */
  static inline bool xfs_ioend_is_append(struct xfs_ioend *ioend)
  {
  	return ioend->io_offset + ioend->io_size >
  		XFS_I(ioend->io_inode)->i_d.di_size;
  }
  
  /*

   * Update on-disk file size now that data has been written to disk.  The
   * current in-memory file size is i_size.  If a write is beyond eof i_new_size
   * will be the intended file size until i_size is updated.  If this write does
   * not extend all the way to the valid file size then restrict this update to
   * the end of the write.
   *
   * This function does not block as blocking on the inode lock in IO completion
   * can lead to IO completion order dependency deadlocks.. If it can't get the
   * inode ilock it will return EAGAIN. Callers must handle this.

   */

  STATIC int

  xfs_setfilesize(
  	xfs_ioend_t		*ioend)
  {

  	xfs_inode_t		*ip = XFS_I(ioend->io_inode);

  	xfs_fsize_t		isize;

  	if (!xfs_ilock_nowait(ip, XFS_ILOCK_EXCL))
  		return EAGAIN;

  	isize = xfs_ioend_new_eof(ioend);
  	if (isize) {

  		trace_xfs_setfilesize(ip, ioend->io_offset, ioend->io_size);

  		ip->i_d.di_size = isize;

  		xfs_mark_inode_dirty(ip);

  	}
  
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);

  	return 0;
  }
  
  /*

   * Schedule IO completion handling on the final put of an ioend.

   *
   * If there is no work to do we might as well call it a day and free the
   * ioend right now.

   */
  STATIC void
  xfs_finish_ioend(

  	struct xfs_ioend	*ioend)

  {
  	if (atomic_dec_and_test(&ioend->io_remaining)) {

  		if (ioend->io_type == IO_UNWRITTEN)
  			queue_work(xfsconvertd_workqueue, &ioend->io_work);

  		else if (xfs_ioend_is_append(ioend))

  			queue_work(xfsdatad_workqueue, &ioend->io_work);

  		else
  			xfs_destroy_ioend(ioend);

  	}

  }
  
  /*

   * IO write completion.

   */
  STATIC void

  xfs_end_io(

  	struct work_struct *work)

  {

  	xfs_ioend_t	*ioend = container_of(work, xfs_ioend_t, io_work);
  	struct xfs_inode *ip = XFS_I(ioend->io_inode);

  	int		error = 0;

  	if (XFS_FORCED_SHUTDOWN(ip->i_mount)) {

  		ioend->io_error = -EIO;

  		goto done;
  	}
  	if (ioend->io_error)
  		goto done;

  	/*
  	 * For unwritten extents we need to issue transactions to convert a
  	 * range to normal written extens after the data I/O has finished.
  	 */

  	if (ioend->io_type == IO_UNWRITTEN) {

  		error = xfs_iomap_write_unwritten(ip, ioend->io_offset,
  						 ioend->io_size);

  		if (error) {
  			ioend->io_error = -error;
  			goto done;
  		}

  	}

  	/*
  	 * We might have to update the on-disk file size after extending
  	 * writes.
  	 */

  	error = xfs_setfilesize(ioend);
  	ASSERT(!error || error == EAGAIN);

  done:

  	/*
  	 * If we didn't complete processing of the ioend, requeue it to the
  	 * tail of the workqueue for another attempt later. Otherwise destroy
  	 * it.
  	 */
  	if (error == EAGAIN) {
  		atomic_inc(&ioend->io_remaining);

  		xfs_finish_ioend(ioend);

  		/* ensure we don't spin on blocked ioends */
  		delay(1);

  	} else {

  		xfs_destroy_ioend(ioend);

  	}

  }
  
  /*

   * Call IO completion handling in caller context on the final put of an ioend.
   */
  STATIC void
  xfs_finish_ioend_sync(
  	struct xfs_ioend	*ioend)
  {
  	if (atomic_dec_and_test(&ioend->io_remaining))
  		xfs_end_io(&ioend->io_work);
  }
  
  /*

   * Allocate and initialise an IO completion structure.
   * We need to track unwritten extent write completion here initially.
   * We'll need to extend this for updating the ondisk inode size later
   * (vs. incore size).
   */
  STATIC xfs_ioend_t *
  xfs_alloc_ioend(

  	struct inode		*inode,
  	unsigned int		type)

  {
  	xfs_ioend_t		*ioend;
  
  	ioend = mempool_alloc(xfs_ioend_pool, GFP_NOFS);
  
  	/*
  	 * Set the count to 1 initially, which will prevent an I/O
  	 * completion callback from happening before we have started
  	 * all the I/O from calling the completion routine too early.
  	 */
  	atomic_set(&ioend->io_remaining, 1);

  	ioend->io_isasync = 0;

  	ioend->io_error = 0;

  	ioend->io_list = NULL;
  	ioend->io_type = type;

  	ioend->io_inode = inode;

  	ioend->io_buffer_head = NULL;

  	ioend->io_buffer_tail = NULL;

  	ioend->io_offset = 0;
  	ioend->io_size = 0;

  	ioend->io_iocb = NULL;
  	ioend->io_result = 0;

  	INIT_WORK(&ioend->io_work, xfs_end_io);

  	return ioend;
  }

  STATIC int
  xfs_map_blocks(
  	struct inode		*inode,
  	loff_t			offset,

  	struct xfs_bmbt_irec	*imap,

  	int			type,
  	int			nonblocking)

  {

  	struct xfs_inode	*ip = XFS_I(inode);
  	struct xfs_mount	*mp = ip->i_mount;

  	ssize_t			count = 1 << inode->i_blkbits;

  	xfs_fileoff_t		offset_fsb, end_fsb;
  	int			error = 0;

  	int			bmapi_flags = XFS_BMAPI_ENTIRE;
  	int			nimaps = 1;
  
  	if (XFS_FORCED_SHUTDOWN(mp))
  		return -XFS_ERROR(EIO);

  	if (type == IO_UNWRITTEN)

  		bmapi_flags |= XFS_BMAPI_IGSTATE;

  
  	if (!xfs_ilock_nowait(ip, XFS_ILOCK_SHARED)) {
  		if (nonblocking)
  			return -XFS_ERROR(EAGAIN);
  		xfs_ilock(ip, XFS_ILOCK_SHARED);

  	}

  	ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE ||
  	       (ip->i_df.if_flags & XFS_IFEXTENTS));

  	ASSERT(offset <= mp->m_maxioffset);

  	if (offset + count > mp->m_maxioffset)
  		count = mp->m_maxioffset - offset;
  	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count);
  	offset_fsb = XFS_B_TO_FSBT(mp, offset);

  	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
  				imap, &nimaps, bmapi_flags);

  	xfs_iunlock(ip, XFS_ILOCK_SHARED);

  	if (error)
  		return -XFS_ERROR(error);

  	if (type == IO_DELALLOC &&
  	    (!nimaps || isnullstartblock(imap->br_startblock))) {

  		error = xfs_iomap_write_allocate(ip, offset, count, imap);
  		if (!error)
  			trace_xfs_map_blocks_alloc(ip, offset, count, type, imap);

  		return -XFS_ERROR(error);

  	}

  #ifdef DEBUG
  	if (type == IO_UNWRITTEN) {
  		ASSERT(nimaps);
  		ASSERT(imap->br_startblock != HOLESTARTBLOCK);
  		ASSERT(imap->br_startblock != DELAYSTARTBLOCK);
  	}
  #endif
  	if (nimaps)
  		trace_xfs_map_blocks_found(ip, offset, count, type, imap);
  	return 0;

  }

  STATIC int

  xfs_imap_valid(

  	struct inode		*inode,

  	struct xfs_bmbt_irec	*imap,

  	xfs_off_t		offset)

  {

  	offset >>= inode->i_blkbits;

  	return offset >= imap->br_startoff &&
  		offset < imap->br_startoff + imap->br_blockcount;

  }

  /*
   * BIO completion handler for buffered IO.
   */

  STATIC void

  xfs_end_bio(
  	struct bio		*bio,

  	int			error)
  {
  	xfs_ioend_t		*ioend = bio->bi_private;

  	ASSERT(atomic_read(&bio->bi_cnt) >= 1);

  	ioend->io_error = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : error;

  
  	/* Toss bio and pass work off to an xfsdatad thread */

  	bio->bi_private = NULL;
  	bio->bi_end_io = NULL;

  	bio_put(bio);

  	xfs_finish_ioend(ioend);

  }
  
  STATIC void
  xfs_submit_ioend_bio(

  	struct writeback_control *wbc,
  	xfs_ioend_t		*ioend,
  	struct bio		*bio)

  {
  	atomic_inc(&ioend->io_remaining);

  	bio->bi_private = ioend;
  	bio->bi_end_io = xfs_end_bio;

  	/*
  	 * If the I/O is beyond EOF we mark the inode dirty immediately
  	 * but don't update the inode size until I/O completion.
  	 */
  	if (xfs_ioend_new_eof(ioend))

  		xfs_mark_inode_dirty(XFS_I(ioend->io_inode));

  	submit_bio(wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE, bio);

  }
  
  STATIC struct bio *
  xfs_alloc_ioend_bio(
  	struct buffer_head	*bh)
  {

  	int			nvecs = bio_get_nr_vecs(bh->b_bdev);

  	struct bio		*bio = bio_alloc(GFP_NOIO, nvecs);

  
  	ASSERT(bio->bi_private == NULL);
  	bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
  	bio->bi_bdev = bh->b_bdev;

  	return bio;
  }
  
  STATIC void
  xfs_start_buffer_writeback(
  	struct buffer_head	*bh)
  {
  	ASSERT(buffer_mapped(bh));
  	ASSERT(buffer_locked(bh));
  	ASSERT(!buffer_delay(bh));
  	ASSERT(!buffer_unwritten(bh));
  
  	mark_buffer_async_write(bh);
  	set_buffer_uptodate(bh);
  	clear_buffer_dirty(bh);
  }
  
  STATIC void
  xfs_start_page_writeback(
  	struct page		*page,

  	int			clear_dirty,
  	int			buffers)
  {
  	ASSERT(PageLocked(page));
  	ASSERT(!PageWriteback(page));

  	if (clear_dirty)

  		clear_page_dirty_for_io(page);
  	set_page_writeback(page);

  	unlock_page(page);

  	/* If no buffers on the page are to be written, finish it here */
  	if (!buffers)

  		end_page_writeback(page);

  }
  
  static inline int bio_add_buffer(struct bio *bio, struct buffer_head *bh)
  {
  	return bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
  }
  
  /*

   * Submit all of the bios for all of the ioends we have saved up, covering the
   * initial writepage page and also any probed pages.
   *
   * Because we may have multiple ioends spanning a page, we need to start
   * writeback on all the buffers before we submit them for I/O. If we mark the
   * buffers as we got, then we can end up with a page that only has buffers
   * marked async write and I/O complete on can occur before we mark the other
   * buffers async write.
   *
   * The end result of this is that we trip a bug in end_page_writeback() because
   * we call it twice for the one page as the code in end_buffer_async_write()
   * assumes that all buffers on the page are started at the same time.
   *
   * The fix is two passes across the ioend list - one to start writeback on the

   * buffer_heads, and then submit them for I/O on the second pass.

   */
  STATIC void
  xfs_submit_ioend(

  	struct writeback_control *wbc,

  	xfs_ioend_t		*ioend)
  {

  	xfs_ioend_t		*head = ioend;

  	xfs_ioend_t		*next;
  	struct buffer_head	*bh;
  	struct bio		*bio;
  	sector_t		lastblock = 0;

  	/* Pass 1 - start writeback */
  	do {
  		next = ioend->io_list;

  		for (bh = ioend->io_buffer_head; bh; bh = bh->b_private)

  			xfs_start_buffer_writeback(bh);

  	} while ((ioend = next) != NULL);
  
  	/* Pass 2 - submit I/O */
  	ioend = head;

  	do {
  		next = ioend->io_list;
  		bio = NULL;
  
  		for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {

  
  			if (!bio) {
   retry:
  				bio = xfs_alloc_ioend_bio(bh);
  			} else if (bh->b_blocknr != lastblock + 1) {

  				xfs_submit_ioend_bio(wbc, ioend, bio);

  				goto retry;
  			}
  
  			if (bio_add_buffer(bio, bh) != bh->b_size) {

  				xfs_submit_ioend_bio(wbc, ioend, bio);

  				goto retry;
  			}
  
  			lastblock = bh->b_blocknr;
  		}
  		if (bio)

  			xfs_submit_ioend_bio(wbc, ioend, bio);

  		xfs_finish_ioend(ioend);

  	} while ((ioend = next) != NULL);
  }
  
  /*
   * Cancel submission of all buffer_heads so far in this endio.
   * Toss the endio too.  Only ever called for the initial page
   * in a writepage request, so only ever one page.
   */
  STATIC void
  xfs_cancel_ioend(
  	xfs_ioend_t		*ioend)
  {
  	xfs_ioend_t		*next;
  	struct buffer_head	*bh, *next_bh;
  
  	do {
  		next = ioend->io_list;
  		bh = ioend->io_buffer_head;
  		do {
  			next_bh = bh->b_private;
  			clear_buffer_async_write(bh);
  			unlock_buffer(bh);
  		} while ((bh = next_bh) != NULL);

  		mempool_free(ioend, xfs_ioend_pool);
  	} while ((ioend = next) != NULL);
  }
  
  /*
   * Test to see if we've been building up a completion structure for
   * earlier buffers -- if so, we try to append to this ioend if we
   * can, otherwise we finish off any current ioend and start another.
   * Return true if we've finished the given ioend.
   */
  STATIC void
  xfs_add_to_ioend(
  	struct inode		*inode,
  	struct buffer_head	*bh,

  	xfs_off_t		offset,

  	unsigned int		type,
  	xfs_ioend_t		**result,
  	int			need_ioend)
  {
  	xfs_ioend_t		*ioend = *result;
  
  	if (!ioend || need_ioend || type != ioend->io_type) {
  		xfs_ioend_t	*previous = *result;

  		ioend = xfs_alloc_ioend(inode, type);
  		ioend->io_offset = offset;
  		ioend->io_buffer_head = bh;
  		ioend->io_buffer_tail = bh;
  		if (previous)
  			previous->io_list = ioend;
  		*result = ioend;
  	} else {
  		ioend->io_buffer_tail->b_private = bh;
  		ioend->io_buffer_tail = bh;
  	}
  
  	bh->b_private = NULL;
  	ioend->io_size += bh->b_size;
  }

  STATIC void

  xfs_map_buffer(

  	struct inode		*inode,

  	struct buffer_head	*bh,

  	struct xfs_bmbt_irec	*imap,

  	xfs_off_t		offset)

  {
  	sector_t		bn;

  	struct xfs_mount	*m = XFS_I(inode)->i_mount;

  	xfs_off_t		iomap_offset = XFS_FSB_TO_B(m, imap->br_startoff);
  	xfs_daddr_t		iomap_bn = xfs_fsb_to_db(XFS_I(inode), imap->br_startblock);

  	ASSERT(imap->br_startblock != HOLESTARTBLOCK);
  	ASSERT(imap->br_startblock != DELAYSTARTBLOCK);

  	bn = (iomap_bn >> (inode->i_blkbits - BBSHIFT)) +

  	      ((offset - iomap_offset) >> inode->i_blkbits);

  	ASSERT(bn || XFS_IS_REALTIME_INODE(XFS_I(inode)));

  
  	bh->b_blocknr = bn;
  	set_buffer_mapped(bh);
  }
  
  STATIC void

  xfs_map_at_offset(

  	struct inode		*inode,

  	struct buffer_head	*bh,

  	struct xfs_bmbt_irec	*imap,

  	xfs_off_t		offset)

  {

  	ASSERT(imap->br_startblock != HOLESTARTBLOCK);
  	ASSERT(imap->br_startblock != DELAYSTARTBLOCK);

  	xfs_map_buffer(inode, bh, imap, offset);

  	set_buffer_mapped(bh);
  	clear_buffer_delay(bh);

  	clear_buffer_unwritten(bh);

  }
  
  /*

   * Test if a given page is suitable for writing as part of an unwritten
   * or delayed allocate extent.

   */

  STATIC int
  xfs_is_delayed_page(
  	struct page		*page,

  	unsigned int		type)

  {

  	if (PageWriteback(page))

  		return 0;

  
  	if (page->mapping && page_has_buffers(page)) {
  		struct buffer_head	*bh, *head;
  		int			acceptable = 0;
  
  		bh = head = page_buffers(page);
  		do {

  			if (buffer_unwritten(bh))

  				acceptable = (type == IO_UNWRITTEN);

  			else if (buffer_delay(bh))

  				acceptable = (type == IO_DELALLOC);

  			else if (buffer_dirty(bh) && buffer_mapped(bh))

  				acceptable = (type == IO_OVERWRITE);

  			else

  				break;

  		} while ((bh = bh->b_this_page) != head);
  
  		if (acceptable)

  			return 1;

  	}

  	return 0;

  }

  /*
   * Allocate & map buffers for page given the extent map. Write it out.
   * except for the original page of a writepage, this is called on
   * delalloc/unwritten pages only, for the original page it is possible
   * that the page has no mapping at all.
   */

  STATIC int

  xfs_convert_page(
  	struct inode		*inode,
  	struct page		*page,

  	loff_t			tindex,

  	struct xfs_bmbt_irec	*imap,

  	xfs_ioend_t		**ioendp,

  	struct writeback_control *wbc)

  {

  	struct buffer_head	*bh, *head;

  	xfs_off_t		end_offset;
  	unsigned long		p_offset;

  	unsigned int		type;

  	int			len, page_dirty;

  	int			count = 0, done = 0, uptodate = 1;

   	xfs_off_t		offset = page_offset(page);

  	if (page->index != tindex)
  		goto fail;

  	if (!trylock_page(page))

  		goto fail;
  	if (PageWriteback(page))
  		goto fail_unlock_page;
  	if (page->mapping != inode->i_mapping)
  		goto fail_unlock_page;
  	if (!xfs_is_delayed_page(page, (*ioendp)->io_type))
  		goto fail_unlock_page;

  	/*
  	 * page_dirty is initially a count of buffers on the page before

  	 * EOF and is decremented as we move each into a cleanable state.

  	 *
  	 * Derivation:
  	 *
  	 * End offset is the highest offset that this page should represent.
  	 * If we are on the last page, (end_offset & (PAGE_CACHE_SIZE - 1))
  	 * will evaluate non-zero and be less than PAGE_CACHE_SIZE and
  	 * hence give us the correct page_dirty count. On any other page,
  	 * it will be zero and in that case we need page_dirty to be the
  	 * count of buffers on the page.

  	 */

  	end_offset = min_t(unsigned long long,
  			(xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT,
  			i_size_read(inode));

  	len = 1 << inode->i_blkbits;

  	p_offset = min_t(unsigned long, end_offset & (PAGE_CACHE_SIZE - 1),
  					PAGE_CACHE_SIZE);
  	p_offset = p_offset ? roundup(p_offset, len) : PAGE_CACHE_SIZE;
  	page_dirty = p_offset / len;

  	bh = head = page_buffers(page);
  	do {

  		if (offset >= end_offset)

  			break;

  		if (!buffer_uptodate(bh))
  			uptodate = 0;
  		if (!(PageUptodate(page) || buffer_uptodate(bh))) {
  			done = 1;

  			continue;

  		}

  		if (buffer_unwritten(bh) || buffer_delay(bh) ||
  		    buffer_mapped(bh)) {

  			if (buffer_unwritten(bh))

  				type = IO_UNWRITTEN;

  			else if (buffer_delay(bh))

  				type = IO_DELALLOC;

  			else
  				type = IO_OVERWRITE;

  			if (!xfs_imap_valid(inode, imap, offset)) {

  				done = 1;

  				continue;
  			}

  			lock_buffer(bh);
  			if (type != IO_OVERWRITE)

  				xfs_map_at_offset(inode, bh, imap, offset);

  			xfs_add_to_ioend(inode, bh, offset, type,
  					 ioendp, done);

  			page_dirty--;
  			count++;
  		} else {

  			done = 1;

  		}

  	} while (offset += len, (bh = bh->b_this_page) != head);

  	if (uptodate && bh == head)
  		SetPageUptodate(page);

  	if (count) {

  		if (--wbc->nr_to_write <= 0 &&
  		    wbc->sync_mode == WB_SYNC_NONE)

  			done = 1;

  	}

  	xfs_start_page_writeback(page, !page_dirty, count);

  
  	return done;

   fail_unlock_page:
  	unlock_page(page);
   fail:
  	return 1;

  }
  
  /*
   * Convert & write out a cluster of pages in the same extent as defined
   * by mp and following the start page.
   */
  STATIC void
  xfs_cluster_write(
  	struct inode		*inode,
  	pgoff_t			tindex,

  	struct xfs_bmbt_irec	*imap,

  	xfs_ioend_t		**ioendp,

  	struct writeback_control *wbc,

  	pgoff_t			tlast)
  {

  	struct pagevec		pvec;
  	int			done = 0, i;

  	pagevec_init(&pvec, 0);
  	while (!done && tindex <= tlast) {
  		unsigned len = min_t(pgoff_t, PAGEVEC_SIZE, tlast - tindex + 1);
  
  		if (!pagevec_lookup(&pvec, inode->i_mapping, tindex, len))

  			break;

  
  		for (i = 0; i < pagevec_count(&pvec); i++) {
  			done = xfs_convert_page(inode, pvec.pages[i], tindex++,

  					imap, ioendp, wbc);

  			if (done)
  				break;
  		}
  
  		pagevec_release(&pvec);
  		cond_resched();

  	}
  }

  STATIC void
  xfs_vm_invalidatepage(
  	struct page		*page,
  	unsigned long		offset)
  {
  	trace_xfs_invalidatepage(page->mapping->host, page, offset);
  	block_invalidatepage(page, offset);
  }
  
  /*
   * If the page has delalloc buffers on it, we need to punch them out before we
   * invalidate the page. If we don't, we leave a stale delalloc mapping on the
   * inode that can trip a BUG() in xfs_get_blocks() later on if a direct IO read
   * is done on that same region - the delalloc extent is returned when none is
   * supposed to be there.
   *
   * We prevent this by truncating away the delalloc regions on the page before
   * invalidating it. Because they are delalloc, we can do this without needing a
   * transaction. Indeed - if we get ENOSPC errors, we have to be able to do this
   * truncation without a transaction as there is no space left for block
   * reservation (typically why we see a ENOSPC in writeback).
   *
   * This is not a performance critical path, so for now just do the punching a
   * buffer head at a time.
   */
  STATIC void
  xfs_aops_discard_page(
  	struct page		*page)
  {
  	struct inode		*inode = page->mapping->host;
  	struct xfs_inode	*ip = XFS_I(inode);
  	struct buffer_head	*bh, *head;
  	loff_t			offset = page_offset(page);

  	if (!xfs_is_delayed_page(page, IO_DELALLOC))

  		goto out_invalidate;

  	if (XFS_FORCED_SHUTDOWN(ip->i_mount))
  		goto out_invalidate;

  	xfs_alert(ip->i_mount,

  		"page discard on page %p, inode 0x%llx, offset %llu.",
  			page, ip->i_ino, offset);
  
  	xfs_ilock(ip, XFS_ILOCK_EXCL);
  	bh = head = page_buffers(page);
  	do {

  		int		error;

  		xfs_fileoff_t	start_fsb;

  
  		if (!buffer_delay(bh))
  			goto next_buffer;

  		start_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
  		error = xfs_bmap_punch_delalloc_range(ip, start_fsb, 1);

  		if (error) {
  			/* something screwed, just bail */

  			if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {

  				xfs_alert(ip->i_mount,

  			"page discard unable to remove delalloc mapping.");

  			}

  			break;
  		}
  next_buffer:

  		offset += 1 << inode->i_blkbits;

  
  	} while ((bh = bh->b_this_page) != head);
  
  	xfs_iunlock(ip, XFS_ILOCK_EXCL);
  out_invalidate:
  	xfs_vm_invalidatepage(page, 0);
  	return;
  }

  /*

   * Write out a dirty page.
   *
   * For delalloc space on the page we need to allocate space and flush it.
   * For unwritten space on the page we need to start the conversion to
   * regular allocated space.

   * For any other dirty buffer heads on the page we should flush them.

   */

  STATIC int

  xfs_vm_writepage(
  	struct page		*page,
  	struct writeback_control *wbc)

  {

  	struct inode		*inode = page->mapping->host;

  	struct buffer_head	*bh, *head;

  	struct xfs_bmbt_irec	imap;

  	xfs_ioend_t		*ioend = NULL, *iohead = NULL;

  	loff_t			offset;

  	unsigned int		type;

  	__uint64_t              end_offset;

  	pgoff_t                 end_index, last_index;

  	ssize_t			len;

  	int			err, imap_valid = 0, uptodate = 1;

  	int			count = 0;

  	int			nonblocking = 0;

  
  	trace_xfs_writepage(inode, page, 0);

  	ASSERT(page_has_buffers(page));

  	/*
  	 * Refuse to write the page out if we are called from reclaim context.
  	 *

  	 * This avoids stack overflows when called from deeply used stacks in
  	 * random callers for direct reclaim or memcg reclaim.  We explicitly
  	 * allow reclaim from kswapd as the stack usage there is relatively low.

  	 *

  	 * This should never happen except in the case of a VM regression so
  	 * warn about it.

  	 */

  	if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
  			PF_MEMALLOC))

  		goto redirty;

  	/*

  	 * Given that we do not allow direct reclaim to call us, we should
  	 * never be called while in a filesystem transaction.

  	 */

  	if (WARN_ON(current->flags & PF_FSTRANS))

  		goto redirty;

  	/* Is this page beyond the end of the file? */
  	offset = i_size_read(inode);
  	end_index = offset >> PAGE_CACHE_SHIFT;
  	last_index = (offset - 1) >> PAGE_CACHE_SHIFT;
  	if (page->index >= end_index) {
  		if ((page->index >= end_index + 1) ||
  		    !(i_size_read(inode) & (PAGE_CACHE_SIZE - 1))) {

  			unlock_page(page);

  			return 0;

  		}
  	}

  	end_offset = min_t(unsigned long long,

  			(xfs_off_t)(page->index + 1) << PAGE_CACHE_SHIFT,
  			offset);

  	len = 1 << inode->i_blkbits;

  	bh = head = page_buffers(page);

  	offset = page_offset(page);

  	type = IO_OVERWRITE;

  	if (wbc->sync_mode == WB_SYNC_NONE)

  		nonblocking = 1;

  	do {

  		int new_ioend = 0;

  		if (offset >= end_offset)
  			break;
  		if (!buffer_uptodate(bh))
  			uptodate = 0;

  		/*

  		 * set_page_dirty dirties all buffers in a page, independent
  		 * of their state.  The dirty state however is entirely
  		 * meaningless for holes (!mapped && uptodate), so skip
  		 * buffers covering holes here.

  		 */
  		if (!buffer_mapped(bh) && buffer_uptodate(bh)) {

  			imap_valid = 0;
  			continue;
  		}

  		if (buffer_unwritten(bh)) {
  			if (type != IO_UNWRITTEN) {
  				type = IO_UNWRITTEN;
  				imap_valid = 0;

  			}

  		} else if (buffer_delay(bh)) {
  			if (type != IO_DELALLOC) {
  				type = IO_DELALLOC;
  				imap_valid = 0;

  			}

  		} else if (buffer_uptodate(bh)) {

  			if (type != IO_OVERWRITE) {
  				type = IO_OVERWRITE;

  				imap_valid = 0;
  			}

  		} else {
  			if (PageUptodate(page)) {
  				ASSERT(buffer_mapped(bh));
  				imap_valid = 0;

  			}

  			continue;
  		}

  		if (imap_valid)
  			imap_valid = xfs_imap_valid(inode, &imap, offset);
  		if (!imap_valid) {
  			/*
  			 * If we didn't have a valid mapping then we need to
  			 * put the new mapping into a separate ioend structure.
  			 * This ensures non-contiguous extents always have
  			 * separate ioends, which is particularly important
  			 * for unwritten extent conversion at I/O completion
  			 * time.
  			 */
  			new_ioend = 1;
  			err = xfs_map_blocks(inode, offset, &imap, type,
  					     nonblocking);
  			if (err)
  				goto error;
  			imap_valid = xfs_imap_valid(inode, &imap, offset);
  		}
  		if (imap_valid) {

  			lock_buffer(bh);
  			if (type != IO_OVERWRITE)

  				xfs_map_at_offset(inode, bh, &imap, offset);
  			xfs_add_to_ioend(inode, bh, offset, type, &ioend,
  					 new_ioend);
  			count++;

  		}

  
  		if (!iohead)
  			iohead = ioend;
  
  	} while (offset += len, ((bh = bh->b_this_page) != head));

  
  	if (uptodate && bh == head)
  		SetPageUptodate(page);

  	xfs_start_page_writeback(page, 1, count);

  	if (ioend && imap_valid) {

  		xfs_off_t		end_index;
  
  		end_index = imap.br_startoff + imap.br_blockcount;
  
  		/* to bytes */
  		end_index <<= inode->i_blkbits;
  
  		/* to pages */
  		end_index = (end_index - 1) >> PAGE_CACHE_SHIFT;
  
  		/* check against file size */
  		if (end_index > last_index)
  			end_index = last_index;

  		xfs_cluster_write(inode, page->index + 1, &imap, &ioend,

  				  wbc, end_index);

  	}

  	if (iohead)

  		xfs_submit_ioend(wbc, iohead);

  	return 0;

  
  error:

  	if (iohead)
  		xfs_cancel_ioend(iohead);

  	if (err == -EAGAIN)
  		goto redirty;

  	xfs_aops_discard_page(page);

  	ClearPageUptodate(page);
  	unlock_page(page);

  	return err;

  redirty:

  	redirty_page_for_writepage(wbc, page);
  	unlock_page(page);
  	return 0;

  }

  STATIC int
  xfs_vm_writepages(
  	struct address_space	*mapping,
  	struct writeback_control *wbc)
  {

  	xfs_iflags_clear(XFS_I(mapping->host), XFS_ITRUNCATED);

  	return generic_writepages(mapping, wbc);
  }

  /*
   * Called to move a page into cleanable state - and from there

   * to be released. The page should already be clean. We always

   * have buffer heads in this call.
   *

   * Returns 1 if the page is ok to release, 0 otherwise.

   */
  STATIC int

  xfs_vm_releasepage(

  	struct page		*page,
  	gfp_t			gfp_mask)
  {

  	int			delalloc, unwritten;

  	trace_xfs_releasepage(page->mapping->host, page, 0);

  	xfs_count_page_state(page, &delalloc, &unwritten);

  	if (WARN_ON(delalloc))

  		return 0;

  	if (WARN_ON(unwritten))

  		return 0;

  	return try_to_free_buffers(page);
  }

  STATIC int

  __xfs_get_blocks(

  	struct inode		*inode,
  	sector_t		iblock,

  	struct buffer_head	*bh_result,
  	int			create,

  	int			direct)

  {

  	struct xfs_inode	*ip = XFS_I(inode);
  	struct xfs_mount	*mp = ip->i_mount;
  	xfs_fileoff_t		offset_fsb, end_fsb;
  	int			error = 0;
  	int			lockmode = 0;

  	struct xfs_bmbt_irec	imap;

  	int			nimaps = 1;

  	xfs_off_t		offset;
  	ssize_t			size;

  	int			new = 0;

  
  	if (XFS_FORCED_SHUTDOWN(mp))
  		return -XFS_ERROR(EIO);

  	offset = (xfs_off_t)iblock << inode->i_blkbits;

  	ASSERT(bh_result->b_size >= (1 << inode->i_blkbits));
  	size = bh_result->b_size;

  
  	if (!create && direct && offset >= i_size_read(inode))
  		return 0;

  	if (create) {
  		lockmode = XFS_ILOCK_EXCL;
  		xfs_ilock(ip, lockmode);
  	} else {
  		lockmode = xfs_ilock_map_shared(ip);
  	}

  	ASSERT(offset <= mp->m_maxioffset);
  	if (offset + size > mp->m_maxioffset)
  		size = mp->m_maxioffset - offset;
  	end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + size);
  	offset_fsb = XFS_B_TO_FSBT(mp, offset);

  	error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
  				&imap, &nimaps, XFS_BMAPI_ENTIRE);

  	if (error)

  		goto out_unlock;
  
  	if (create &&
  	    (!nimaps ||
  	     (imap.br_startblock == HOLESTARTBLOCK ||
  	      imap.br_startblock == DELAYSTARTBLOCK))) {
  		if (direct) {
  			error = xfs_iomap_write_direct(ip, offset, size,
  						       &imap, nimaps);
  		} else {
  			error = xfs_iomap_write_delay(ip, offset, size, &imap);
  		}
  		if (error)
  			goto out_unlock;
  
  		trace_xfs_get_blocks_alloc(ip, offset, size, 0, &imap);
  	} else if (nimaps) {
  		trace_xfs_get_blocks_found(ip, offset, size, 0, &imap);
  	} else {
  		trace_xfs_get_blocks_notfound(ip, offset, size);
  		goto out_unlock;
  	}
  	xfs_iunlock(ip, lockmode);

  	if (imap.br_startblock != HOLESTARTBLOCK &&
  	    imap.br_startblock != DELAYSTARTBLOCK) {

  		/*
  		 * For unwritten extents do not report a disk address on

  		 * the read case (treat as if we're reading into a hole).
  		 */

  		if (create || !ISUNWRITTEN(&imap))
  			xfs_map_buffer(inode, bh_result, &imap, offset);
  		if (create && ISUNWRITTEN(&imap)) {

  			if (direct)
  				bh_result->b_private = inode;
  			set_buffer_unwritten(bh_result);

  		}
  	}

  	/*
  	 * If this is a realtime file, data may be on a different device.
  	 * to that pointed to from the buffer_head b_bdev currently.
  	 */

  	bh_result->b_bdev = xfs_find_bdev_for_inode(inode);

  	/*

  	 * If we previously allocated a block out beyond eof and we are now
  	 * coming back to use it then we will need to flag it as new even if it
  	 * has a disk address.
  	 *
  	 * With sub-block writes into unwritten extents we also need to mark
  	 * the buffer as new so that the unwritten parts of the buffer gets
  	 * correctly zeroed.

  	 */
  	if (create &&
  	    ((!buffer_mapped(bh_result) && !buffer_uptodate(bh_result)) ||

  	     (offset >= i_size_read(inode)) ||

  	     (new || ISUNWRITTEN(&imap))))

  		set_buffer_new(bh_result);

  	if (imap.br_startblock == DELAYSTARTBLOCK) {

  		BUG_ON(direct);
  		if (create) {
  			set_buffer_uptodate(bh_result);
  			set_buffer_mapped(bh_result);
  			set_buffer_delay(bh_result);
  		}
  	}

  	/*
  	 * If this is O_DIRECT or the mpage code calling tell them how large
  	 * the mapping is, so that we can avoid repeated get_blocks calls.
  	 */

  	if (direct || size > (1 << inode->i_blkbits)) {

  		xfs_off_t		mapping_size;
  
  		mapping_size = imap.br_startoff + imap.br_blockcount - iblock;
  		mapping_size <<= inode->i_blkbits;
  
  		ASSERT(mapping_size > 0);
  		if (mapping_size > size)
  			mapping_size = size;
  		if (mapping_size > LONG_MAX)
  			mapping_size = LONG_MAX;
  
  		bh_result->b_size = mapping_size;

  	}
  
  	return 0;

  
  out_unlock:
  	xfs_iunlock(ip, lockmode);
  	return -error;

  }
  
  int

  xfs_get_blocks(

  	struct inode		*inode,
  	sector_t		iblock,
  	struct buffer_head	*bh_result,
  	int			create)
  {

  	return __xfs_get_blocks(inode, iblock, bh_result, create, 0);

  }
  
  STATIC int

  xfs_get_blocks_direct(

  	struct inode		*inode,
  	sector_t		iblock,

  	struct buffer_head	*bh_result,
  	int			create)
  {

  	return __xfs_get_blocks(inode, iblock, bh_result, create, 1);

  }

  /*
   * Complete a direct I/O write request.
   *
   * If the private argument is non-NULL __xfs_get_blocks signals us that we
   * need to issue a transaction to convert the range from unwritten to written
   * extents.  In case this is regular synchronous I/O we just call xfs_end_io

   * to do this and we are done.  But in case this was a successful AIO

   * request this handler is called from interrupt context, from which we
   * can't start transactions.  In that case offload the I/O completion to
   * the workqueues we also use for buffered I/O completion.
   */

  STATIC void

  xfs_end_io_direct_write(
  	struct kiocb		*iocb,
  	loff_t			offset,
  	ssize_t			size,
  	void			*private,
  	int			ret,
  	bool			is_async)

  {

  	struct xfs_ioend	*ioend = iocb->private;

  
  	/*

  	 * blockdev_direct_IO can return an error even after the I/O
  	 * completion handler was called.  Thus we need to protect
  	 * against double-freeing.

  	 */

  	iocb->private = NULL;

  	ioend->io_offset = offset;
  	ioend->io_size = size;

  	ioend->io_iocb = iocb;
  	ioend->io_result = ret;

  	if (private && size > 0)
  		ioend->io_type = IO_UNWRITTEN;
  
  	if (is_async) {

  		ioend->io_isasync = 1;

  		xfs_finish_ioend(ioend);

  	} else {

  		xfs_finish_ioend_sync(ioend);

  	}

  }

  STATIC ssize_t

  xfs_vm_direct_IO(

  	int			rw,
  	struct kiocb		*iocb,
  	const struct iovec	*iov,
  	loff_t			offset,
  	unsigned long		nr_segs)
  {

  	struct inode		*inode = iocb->ki_filp->f_mapping->host;
  	struct block_device	*bdev = xfs_find_bdev_for_inode(inode);
  	ssize_t			ret;
  
  	if (rw & WRITE) {

  		iocb->private = xfs_alloc_ioend(inode, IO_DIRECT);

  		ret = __blockdev_direct_IO(rw, iocb, inode, bdev, iov,
  					    offset, nr_segs,
  					    xfs_get_blocks_direct,
  					    xfs_end_io_direct_write, NULL, 0);

  		if (ret != -EIOCBQUEUED && iocb->private)
  			xfs_destroy_ioend(iocb->private);
  	} else {

  		ret = __blockdev_direct_IO(rw, iocb, inode, bdev, iov,
  					    offset, nr_segs,
  					    xfs_get_blocks_direct,
  					    NULL, NULL, 0);

  	}

  	return ret;

  }

  STATIC void
  xfs_vm_write_failed(
  	struct address_space	*mapping,
  	loff_t			to)
  {
  	struct inode		*inode = mapping->host;
  
  	if (to > inode->i_size) {

  		/*
  		 * punch out the delalloc blocks we have already allocated. We
  		 * don't call xfs_setattr() to do this as we may be in the
  		 * middle of a multi-iovec write and so the vfs inode->i_size
  		 * will not match the xfs ip->i_size and so it will zero too
  		 * much. Hence we jus truncate the page cache to zero what is
  		 * necessary and punch the delalloc blocks directly.
  		 */
  		struct xfs_inode	*ip = XFS_I(inode);
  		xfs_fileoff_t		start_fsb;
  		xfs_fileoff_t		end_fsb;
  		int			error;
  
  		truncate_pagecache(inode, to, inode->i_size);
  
  		/*
  		 * Check if there are any blocks that are outside of i_size
  		 * that need to be trimmed back.
  		 */
  		start_fsb = XFS_B_TO_FSB(ip->i_mount, inode->i_size) + 1;
  		end_fsb = XFS_B_TO_FSB(ip->i_mount, to);
  		if (end_fsb <= start_fsb)
  			return;
  
  		xfs_ilock(ip, XFS_ILOCK_EXCL);
  		error = xfs_bmap_punch_delalloc_range(ip, start_fsb,
  							end_fsb - start_fsb);
  		if (error) {
  			/* something screwed, just bail */
  			if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {

  				xfs_alert(ip->i_mount,

  			"xfs_vm_write_failed: unable to clean up ino %lld",
  						ip->i_ino);
  			}
  		}
  		xfs_iunlock(ip, XFS_ILOCK_EXCL);

  	}
  }

  STATIC int

  xfs_vm_write_begin(

  	struct file		*file,

  	struct address_space	*mapping,
  	loff_t			pos,
  	unsigned		len,
  	unsigned		flags,
  	struct page		**pagep,
  	void			**fsdata)

  {

  	int			ret;
  
  	ret = block_write_begin(mapping, pos, len, flags | AOP_FLAG_NOFS,
  				pagep, xfs_get_blocks);

  	if (unlikely(ret))
  		xfs_vm_write_failed(mapping, pos + len);
  	return ret;
  }
  
  STATIC int
  xfs_vm_write_end(
  	struct file		*file,
  	struct address_space	*mapping,
  	loff_t			pos,
  	unsigned		len,
  	unsigned		copied,
  	struct page		*page,
  	void			*fsdata)
  {
  	int			ret;

  	ret = generic_write_end(file, mapping, pos, len, copied, page, fsdata);
  	if (unlikely(ret < len))
  		xfs_vm_write_failed(mapping, pos + len);

  	return ret;

  }

  
  STATIC sector_t

  xfs_vm_bmap(

  	struct address_space	*mapping,
  	sector_t		block)
  {
  	struct inode		*inode = (struct inode *)mapping->host;

  	struct xfs_inode	*ip = XFS_I(inode);

  	trace_xfs_vm_bmap(XFS_I(inode));

  	xfs_ilock(ip, XFS_IOLOCK_SHARED);

  	xfs_flush_pages(ip, (xfs_off_t)0, -1, 0, FI_REMAPF);

  	xfs_iunlock(ip, XFS_IOLOCK_SHARED);

  	return generic_block_bmap(mapping, block, xfs_get_blocks);

  }
  
  STATIC int

  xfs_vm_readpage(

  	struct file		*unused,
  	struct page		*page)
  {

  	return mpage_readpage(page, xfs_get_blocks);

  }
  
  STATIC int

  xfs_vm_readpages(

  	struct file		*unused,
  	struct address_space	*mapping,
  	struct list_head	*pages,
  	unsigned		nr_pages)
  {

  	return mpage_readpages(mapping, pages, nr_pages, xfs_get_blocks);

  }

  const struct address_space_operations xfs_address_space_operations = {

  	.readpage		= xfs_vm_readpage,
  	.readpages		= xfs_vm_readpages,
  	.writepage		= xfs_vm_writepage,

  	.writepages		= xfs_vm_writepages,

  	.releasepage		= xfs_vm_releasepage,
  	.invalidatepage		= xfs_vm_invalidatepage,

  	.write_begin		= xfs_vm_write_begin,

  	.write_end		= xfs_vm_write_end,

  	.bmap			= xfs_vm_bmap,
  	.direct_IO		= xfs_vm_direct_IO,

  	.migratepage		= buffer_migrate_page,

  	.is_partially_uptodate  = block_is_partially_uptodate,

  	.error_remove_page	= generic_error_remove_page,

  };