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xfs_aops.c

/*
 * 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_dir2.h"
#include "xfs_trans.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_dir2_sf.h"
#include "xfs_attr_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_alloc.h"
#include "xfs_btree.h"
#include "xfs_error.h"
#include "xfs_rw.h"
#include "xfs_iomap.h"
#include "xfs_vnodeops.h"
#include <linux/mpage.h>
#include <linux/pagevec.h>
#include <linux/writeback.h>

STATIC void
xfs_count_page_state(
      struct page       *page,
      int               *delalloc,
      int               *unmapped,
      int               *unwritten)
{
      struct buffer_head      *bh, *head;

      *delalloc = *unmapped = *unwritten = 0;

      bh = head = page_buffers(page);
      do {
            if (buffer_uptodate(bh) && !buffer_mapped(bh))
                  (*unmapped) = 1;
            else if (buffer_unwritten(bh))
                  (*unwritten) = 1;
            else if (buffer_delay(bh))
                  (*delalloc) = 1;
      } while ((bh = bh->b_this_page) != head);
}

#if defined(XFS_RW_TRACE)
void
xfs_page_trace(
      int         tag,
      struct inode      *inode,
      struct page *page,
      unsigned long     pgoff)
{
      xfs_inode_t *ip;
      bhv_vnode_t *vp = vn_from_inode(inode);
      loff_t            isize = i_size_read(inode);
      loff_t            offset = page_offset(page);
      int         delalloc = -1, unmapped = -1, unwritten = -1;

      if (page_has_buffers(page))
            xfs_count_page_state(page, &delalloc, &unmapped, &unwritten);

      ip = xfs_vtoi(vp);
      if (!ip->i_rwtrace)
            return;

      ktrace_enter(ip->i_rwtrace,
            (void *)((unsigned long)tag),
            (void *)ip,
            (void *)inode,
            (void *)page,
            (void *)pgoff,
            (void *)((unsigned long)((ip->i_d.di_size >> 32) & 0xffffffff)),
            (void *)((unsigned long)(ip->i_d.di_size & 0xffffffff)),
            (void *)((unsigned long)((isize >> 32) & 0xffffffff)),
            (void *)((unsigned long)(isize & 0xffffffff)),
            (void *)((unsigned long)((offset >> 32) & 0xffffffff)),
            (void *)((unsigned long)(offset & 0xffffffff)),
            (void *)((unsigned long)delalloc),
            (void *)((unsigned long)unmapped),
            (void *)((unsigned long)unwritten),
            (void *)((unsigned long)current_pid()),
            (void *)NULL);
}
#else
#define xfs_page_trace(tag, inode, page, pgoff)
#endif

/*
 * Schedule IO completion handling on a xfsdatad if this was
 * the final hold on this ioend. If we are asked to wait,
 * flush the workqueue.
 */
STATIC void
xfs_finish_ioend(
      xfs_ioend_t *ioend,
      int         wait)
{
      if (atomic_dec_and_test(&ioend->io_remaining)) {
            queue_work(xfsdatad_workqueue, &ioend->io_work);
            if (wait)
                  flush_workqueue(xfsdatad_workqueue);
      }
}

/*
 * 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 (unlikely(ioend->io_error)) {
            vn_ioerror(XFS_I(ioend->io_inode), ioend->io_error,
                        __FILE__,__LINE__);
      }
      vn_iowake(XFS_I(ioend->io_inode));
      mempool_free(ioend, xfs_ioend_pool);
}

/*
 * 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 io_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.
 */
STATIC void
xfs_setfilesize(
      xfs_ioend_t       *ioend)
{
      xfs_inode_t       *ip = XFS_I(ioend->io_inode);
      xfs_fsize_t       isize;
      xfs_fsize_t       bsize;

      ASSERT((ip->i_d.di_mode & S_IFMT) == S_IFREG);
      ASSERT(ioend->io_type != IOMAP_READ);

      if (unlikely(ioend->io_error))
            return;

      bsize = ioend->io_offset + ioend->io_size;

      xfs_ilock(ip, XFS_ILOCK_EXCL);

      isize = MAX(ip->i_size, ip->i_iocore.io_new_size);
      isize = MIN(isize, bsize);

      if (ip->i_d.di_size < isize) {
            ip->i_d.di_size = isize;
            ip->i_update_core = 1;
            ip->i_update_size = 1;
            mark_inode_dirty_sync(ioend->io_inode);
      }

      xfs_iunlock(ip, XFS_ILOCK_EXCL);
}

/*
 * Buffered IO write completion for delayed allocate extents.
 */
STATIC void
xfs_end_bio_delalloc(
      struct work_struct      *work)
{
      xfs_ioend_t       *ioend =
            container_of(work, xfs_ioend_t, io_work);

      xfs_setfilesize(ioend);
      xfs_destroy_ioend(ioend);
}

/*
 * Buffered IO write completion for regular, written extents.
 */
STATIC void
xfs_end_bio_written(
      struct work_struct      *work)
{
      xfs_ioend_t       *ioend =
            container_of(work, xfs_ioend_t, io_work);

      xfs_setfilesize(ioend);
      xfs_destroy_ioend(ioend);
}

/*
 * IO write completion for unwritten extents.
 *
 * Issue transactions to convert a buffer range from unwritten
 * to written extents.
 */
STATIC void
xfs_end_bio_unwritten(
      struct work_struct      *work)
{
      xfs_ioend_t       *ioend =
            container_of(work, xfs_ioend_t, io_work);
      xfs_off_t         offset = ioend->io_offset;
      size_t                  size = ioend->io_size;

      if (likely(!ioend->io_error)) {
            xfs_bmap(XFS_I(ioend->io_inode), offset, size,
                        BMAPI_UNWRITTEN, NULL, NULL);
            xfs_setfilesize(ioend);
      }
      xfs_destroy_ioend(ioend);
}

/*
 * IO read completion for regular, written extents.
 */
STATIC void
xfs_end_bio_read(
      struct work_struct      *work)
{
      xfs_ioend_t       *ioend =
            container_of(work, xfs_ioend_t, io_work);

      xfs_destroy_ioend(ioend);
}

/*
 * 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_error = 0;
      ioend->io_list = NULL;
      ioend->io_type = type;
      ioend->io_inode = inode;
      ioend->io_buffer_head = NULL;
      ioend->io_buffer_tail = NULL;
      atomic_inc(&XFS_I(ioend->io_inode)->i_iocount);
      ioend->io_offset = 0;
      ioend->io_size = 0;

      if (type == IOMAP_UNWRITTEN)
            INIT_WORK(&ioend->io_work, xfs_end_bio_unwritten);
      else if (type == IOMAP_DELAY)
            INIT_WORK(&ioend->io_work, xfs_end_bio_delalloc);
      else if (type == IOMAP_READ)
            INIT_WORK(&ioend->io_work, xfs_end_bio_read);
      else
            INIT_WORK(&ioend->io_work, xfs_end_bio_written);

      return ioend;
}

STATIC int
xfs_map_blocks(
      struct inode            *inode,
      loff_t                  offset,
      ssize_t                 count,
      xfs_iomap_t       *mapp,
      int               flags)
{
      xfs_inode_t       *ip = XFS_I(inode);
      int               error, nmaps = 1;

      error = xfs_bmap(ip, offset, count,
                        flags, mapp, &nmaps);
      if (!error && (flags & (BMAPI_WRITE|BMAPI_ALLOCATE)))
            xfs_iflags_set(ip, XFS_IMODIFIED);
      return -error;
}

STATIC_INLINE int
xfs_iomap_valid(
      xfs_iomap_t       *iomapp,
      loff_t                  offset)
{
      return offset >= iomapp->iomap_offset &&
            offset < iomapp->iomap_offset + iomapp->iomap_bsize;
}

/*
 * 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, 0);
}

STATIC void
xfs_submit_ioend_bio(
      xfs_ioend_t *ioend,
      struct bio  *bio)
{
      atomic_inc(&ioend->io_remaining);

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

      submit_bio(WRITE, bio);
      ASSERT(!bio_flagged(bio, BIO_EOPNOTSUPP));
      bio_put(bio);
}

STATIC struct bio *
xfs_alloc_ioend_bio(
      struct buffer_head      *bh)
{
      struct bio        *bio;
      int               nvecs = bio_get_nr_vecs(bh->b_bdev);

      do {
            bio = bio_alloc(GFP_NOIO, nvecs);
            nvecs >>= 1;
      } while (!bio);

      ASSERT(bio->bi_private == NULL);
      bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
      bio->bi_bdev = bh->b_bdev;
      bio_get(bio);
      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,
      struct writeback_control *wbc,
      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(
      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(ioend, bio);
                        goto retry;
                  }

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

                  lastblock = bh->b_blocknr;
            }
            if (bio)
                  xfs_submit_ioend_bio(ioend, bio);
            xfs_finish_ioend(ioend, 0);
      } 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);

            vn_iowake(XFS_I(ioend->io_inode));
            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 buffer_head      *bh,
      xfs_iomap_t       *mp,
      xfs_off_t         offset,
      uint              block_bits)
{
      sector_t          bn;

      ASSERT(mp->iomap_bn != IOMAP_DADDR_NULL);

      bn = (mp->iomap_bn >> (block_bits - BBSHIFT)) +
            ((offset - mp->iomap_offset) >> block_bits);

      ASSERT(bn || (mp->iomap_flags & IOMAP_REALTIME));

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

STATIC void
xfs_map_at_offset(
      struct buffer_head      *bh,
      loff_t                  offset,
      int               block_bits,
      xfs_iomap_t       *iomapp)
{
      ASSERT(!(iomapp->iomap_flags & IOMAP_HOLE));
      ASSERT(!(iomapp->iomap_flags & IOMAP_DELAY));

      lock_buffer(bh);
      xfs_map_buffer(bh, iomapp, offset, block_bits);
      bh->b_bdev = iomapp->iomap_target->bt_bdev;
      set_buffer_mapped(bh);
      clear_buffer_delay(bh);
      clear_buffer_unwritten(bh);
}

/*
 * Look for a page at index that is suitable for clustering.
 */
STATIC unsigned int
xfs_probe_page(
      struct page       *page,
      unsigned int            pg_offset,
      int               mapped)
{
      int               ret = 0;

      if (PageWriteback(page))
            return 0;

      if (page->mapping && PageDirty(page)) {
            if (page_has_buffers(page)) {
                  struct buffer_head      *bh, *head;

                  bh = head = page_buffers(page);
                  do {
                        if (!buffer_uptodate(bh))
                              break;
                        if (mapped != buffer_mapped(bh))
                              break;
                        ret += bh->b_size;
                        if (ret >= pg_offset)
                              break;
                  } while ((bh = bh->b_this_page) != head);
            } else
                  ret = mapped ? 0 : PAGE_CACHE_SIZE;
      }

      return ret;
}

STATIC size_t
xfs_probe_cluster(
      struct inode            *inode,
      struct page       *startpage,
      struct buffer_head      *bh,
      struct buffer_head      *head,
      int               mapped)
{
      struct pagevec          pvec;
      pgoff_t                 tindex, tlast, tloff;
      size_t                  total = 0;
      int               done = 0, i;

      /* First sum forwards in this page */
      do {
            if (!buffer_uptodate(bh) || (mapped != buffer_mapped(bh)))
                  return total;
            total += bh->b_size;
      } while ((bh = bh->b_this_page) != head);

      /* if we reached the end of the page, sum forwards in following pages */
      tlast = i_size_read(inode) >> PAGE_CACHE_SHIFT;
      tindex = startpage->index + 1;

      /* Prune this back to avoid pathological behavior */
      tloff = min(tlast, startpage->index + 64);

      pagevec_init(&pvec, 0);
      while (!done && tindex <= tloff) {
            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++) {
                  struct page *page = pvec.pages[i];
                  size_t pg_offset, pg_len = 0;

                  if (tindex == tlast) {
                        pg_offset =
                            i_size_read(inode) & (PAGE_CACHE_SIZE - 1);
                        if (!pg_offset) {
                              done = 1;
                              break;
                        }
                  } else
                        pg_offset = PAGE_CACHE_SIZE;

                  if (page->index == tindex && !TestSetPageLocked(page)) {
                        pg_len = xfs_probe_page(page, pg_offset, mapped);
                        unlock_page(page);
                  }

                  if (!pg_len) {
                        done = 1;
                        break;
                  }

                  total += pg_len;
                  tindex++;
            }

            pagevec_release(&pvec);
            cond_resched();
      }

      return total;
}

/*
 * 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 == IOMAP_UNWRITTEN);
                  else if (buffer_delay(bh))
                        acceptable = (type == IOMAP_DELAY);
                  else if (buffer_dirty(bh) && buffer_mapped(bh))
                        acceptable = (type == IOMAP_NEW);
                  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,
      xfs_iomap_t       *mp,
      xfs_ioend_t       **ioendp,
      struct writeback_control *wbc,
      int               startio,
      int               all_bh)
{
      struct buffer_head      *bh, *head;
      xfs_off_t         end_offset;
      unsigned long           p_offset;
      unsigned int            type;
      int               bbits = inode->i_blkbits;
      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 (TestSetPageLocked(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)) {
                  if (buffer_unwritten(bh))
                        type = IOMAP_UNWRITTEN;
                  else
                        type = IOMAP_DELAY;

                  if (!xfs_iomap_valid(mp, offset)) {
                        done = 1;
                        continue;
                  }

                  ASSERT(!(mp->iomap_flags & IOMAP_HOLE));
                  ASSERT(!(mp->iomap_flags & IOMAP_DELAY));

                  xfs_map_at_offset(bh, offset, bbits, mp);
                  if (startio) {
                        xfs_add_to_ioend(inode, bh, offset,
                                    type, ioendp, done);
                  } else {
                        set_buffer_dirty(bh);
                        unlock_buffer(bh);
                        mark_buffer_dirty(bh);
                  }
                  page_dirty--;
                  count++;
            } else {
                  type = IOMAP_NEW;
                  if (buffer_mapped(bh) && all_bh && startio) {
                        lock_buffer(bh);
                        xfs_add_to_ioend(inode, bh, offset,
                                    type, ioendp, done);
                        count++;
                        page_dirty--;
                  } else {
                        done = 1;
                  }
            }
      } while (offset += len, (bh = bh->b_this_page) != head);

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

      if (startio) {
            if (count) {
                  struct backing_dev_info *bdi;

                  bdi = inode->i_mapping->backing_dev_info;
                  wbc->nr_to_write--;
                  if (bdi_write_congested(bdi)) {
                        wbc->encountered_congestion = 1;
                        done = 1;
                  } else if (wbc->nr_to_write <= 0) {
                        done = 1;
                  }
            }
            xfs_start_page_writeback(page, wbc, !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,
      xfs_iomap_t       *iomapp,
      xfs_ioend_t       **ioendp,
      struct writeback_control *wbc,
      int               startio,
      int               all_bh,
      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++,
                              iomapp, ioendp, wbc, startio, all_bh);
                  if (done)
                        break;
            }

            pagevec_release(&pvec);
            cond_resched();
      }
}

/*
 * Calling this without startio set means we are being asked to make a dirty
 * page ready for freeing it's buffers.  When called with startio set then
 * we are coming from writepage.
 *
 * When called with startio set it is important that we write the WHOLE
 * page if possible.
 * The bh->b_state's cannot know if any of the blocks or which block for
 * that matter are dirty due to mmap writes, and therefore bh uptodate is
 * only valid if the page itself isn't completely uptodate.  Some layers
 * may clear the page dirty flag prior to calling write page, under the
 * assumption the entire page will be written out; by not writing out the
 * whole page the page can be reused before all valid dirty data is
 * written out.  Note: in the case of a page that has been dirty'd by
 * mapwrite and but partially setup by block_prepare_write the
 * bh->b_states's will not agree and only ones setup by BPW/BCW will have
 * valid state, thus the whole page must be written out thing.
 */

STATIC int
xfs_page_state_convert(
      struct inode      *inode,
      struct page *page,
      struct writeback_control *wbc,
      int         startio,
      int         unmapped) /* also implies page uptodate */
{
      struct buffer_head      *bh, *head;
      xfs_iomap_t       iomap;
      xfs_ioend_t       *ioend = NULL, *iohead = NULL;
      loff_t                  offset;
      unsigned long           p_offset = 0;
      unsigned int            type;
      __uint64_t              end_offset;
      pgoff_t                 end_index, last_index, tlast;
      ssize_t                 size, len;
      int               flags, err, iomap_valid = 0, uptodate = 1;
      int               page_dirty, count = 0;
      int               trylock = 0;
      int               all_bh = unmapped;

      if (startio) {
            if (wbc->sync_mode == WB_SYNC_NONE && wbc->nonblocking)
                  trylock |= BMAPI_TRYLOCK;
      }

      /* 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))) {
                  if (startio)
                        unlock_page(page);
                  return 0;
            }
      }

      /*
       * 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, offset);
      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);
      offset = page_offset(page);
      flags = BMAPI_READ;
      type = IOMAP_NEW;

      /* TODO: cleanup count and page_dirty */

      do {
            if (offset >= end_offset)
                  break;
            if (!buffer_uptodate(bh))
                  uptodate = 0;
            if (!(PageUptodate(page) || buffer_uptodate(bh)) && !startio) {
                  /*
                   * the iomap is actually still valid, but the ioend
                   * isn't.  shouldn't happen too often.
                   */
                  iomap_valid = 0;
                  continue;
            }

            if (iomap_valid)
                  iomap_valid = xfs_iomap_valid(&iomap, offset);

            /*
             * First case, map an unwritten extent and prepare for
             * extent state conversion transaction on completion.
             *
             * Second case, allocate space for a delalloc buffer.
             * We can return EAGAIN here in the release page case.
             *
             * Third case, an unmapped buffer was found, and we are
             * in a path where we need to write the whole page out.
             */
            if (buffer_unwritten(bh) || buffer_delay(bh) ||
                ((buffer_uptodate(bh) || PageUptodate(page)) &&
                 !buffer_mapped(bh) && (unmapped || startio))) {
                  int new_ioend = 0;

                  /*
                   * Make sure we don't use a read-only iomap
                   */
                  if (flags == BMAPI_READ)
                        iomap_valid = 0;

                  if (buffer_unwritten(bh)) {
                        type = IOMAP_UNWRITTEN;
                        flags = BMAPI_WRITE | BMAPI_IGNSTATE;
                  } else if (buffer_delay(bh)) {
                        type = IOMAP_DELAY;
                        flags = BMAPI_ALLOCATE | trylock;
                  } else {
                        type = IOMAP_NEW;
                        flags = BMAPI_WRITE | BMAPI_MMAP;
                  }

                  if (!iomap_valid) {
                        /*
                         * if we didn't have a valid mapping then we
                         * need to ensure that we put the new mapping
                         * in a new ioend structure. This needs to be
                         * done to ensure that the ioends correctly
                         * reflect the block mappings at io completion
                         * for unwritten extent conversion.
                         */
                        new_ioend = 1;
                        if (type == IOMAP_NEW) {
                              size = xfs_probe_cluster(inode,
                                          page, bh, head, 0);
                        } else {
                              size = len;
                        }

                        err = xfs_map_blocks(inode, offset, size,
                                    &iomap, flags);
                        if (err)
                              goto error;
                        iomap_valid = xfs_iomap_valid(&iomap, offset);
                  }
                  if (iomap_valid) {
                        xfs_map_at_offset(bh, offset,
                                    inode->i_blkbits, &iomap);
                        if (startio) {
                              xfs_add_to_ioend(inode, bh, offset,
                                          type, &ioend,
                                          new_ioend);
                        } else {
                              set_buffer_dirty(bh);
                              unlock_buffer(bh);
                              mark_buffer_dirty(bh);
                        }
                        page_dirty--;
                        count++;
                  }
            } else if (buffer_uptodate(bh) && startio) {
                  /*
                   * we got here because the buffer is already mapped.
                   * That means it must already have extents allocated
                   * underneath it. Map the extent by reading it.
                   */
                  if (!iomap_valid || flags != BMAPI_READ) {
                        flags = BMAPI_READ;
                        size = xfs_probe_cluster(inode, page, bh,
                                                head, 1);
                        err = xfs_map_blocks(inode, offset, size,
                                    &iomap, flags);
                        if (err)
                              goto error;
                        iomap_valid = xfs_iomap_valid(&iomap, offset);
                  }

                  /*
                   * We set the type to IOMAP_NEW in case we are doing a
                   * small write at EOF that is extending the file but
                   * without needing an allocation. We need to update the
                   * file size on I/O completion in this case so it is
                   * the same case as having just allocated a new extent
                   * that we are writing into for the first time.
                   */
                  type = IOMAP_NEW;
                  if (!test_and_set_bit(BH_Lock, &bh->b_state)) {
                        ASSERT(buffer_mapped(bh));
                        if (iomap_valid)
                              all_bh = 1;
                        xfs_add_to_ioend(inode, bh, offset, type,
                                    &ioend, !iomap_valid);
                        page_dirty--;
                        count++;
                  } else {
                        iomap_valid = 0;
                  }
            } else if ((buffer_uptodate(bh) || PageUptodate(page)) &&
                     (unmapped || startio)) {
                  iomap_valid = 0;
            }

            if (!iohead)
                  iohead = ioend;

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

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

      if (startio)
            xfs_start_page_writeback(page, wbc, 1, count);

      if (ioend && iomap_valid) {
            offset = (iomap.iomap_offset + iomap.iomap_bsize - 1) >>
                              PAGE_CACHE_SHIFT;
            tlast = min_t(pgoff_t, offset, last_index);
            xfs_cluster_write(inode, page->index + 1, &iomap, &ioend,
                              wbc, startio, all_bh, tlast);
      }

      if (iohead)
            xfs_submit_ioend(iohead);

      return page_dirty;

error:
      if (iohead)
            xfs_cancel_ioend(iohead);

      /*
       * If it's delalloc and we have nowhere to put it,
       * throw it away, unless the lower layers told
       * us to try again.
       */
      if (err != -EAGAIN) {
            if (!unmapped)
                  block_invalidatepage(page, 0);
            ClearPageUptodate(page);
      }
      return err;
}

/*
 * writepage: Called from one of two places:
 *
 * 1. we are flushing a delalloc buffer head.
 *
 * 2. we are writing out a dirty page. Typically the page dirty
 *    state is cleared before we get here. In this case is it
 *    conceivable we have no buffer heads.
 *
 * For delalloc space on the page we need to allocate space and
 * flush it. For unmapped buffer heads on the page we should
 * allocate space if the page is uptodate. For any other dirty
 * buffer heads on the page we should flush them.
 *
 * If we detect that a transaction would be required to flush
 * the page, we have to check the process flags first, if we
 * are already in a transaction or disk I/O during allocations
 * is off, we need to fail the writepage and redirty the page.
 */

STATIC int
xfs_vm_writepage(
      struct page       *page,
      struct writeback_control *wbc)
{
      int               error;
      int               need_trans;
      int               delalloc, unmapped, unwritten;
      struct inode            *inode = page->mapping->host;

      xfs_page_trace(XFS_WRITEPAGE_ENTER, inode, page, 0);

      /*
       * We need a transaction if:
       *  1. There are delalloc buffers on the page
       *  2. The page is uptodate and we have unmapped buffers
       *  3. The page is uptodate and we have no buffers
       *  4. There are unwritten buffers on the page
       */

      if (!page_has_buffers(page)) {
            unmapped = 1;
            need_trans = 1;
      } else {
            xfs_count_page_state(page, &delalloc, &unmapped, &unwritten);
            if (!PageUptodate(page))
                  unmapped = 0;
            need_trans = delalloc + unmapped + unwritten;
      }

      /*
       * If we need a transaction and the process flags say
       * we are already in a transaction, or no IO is allowed
       * then mark the page dirty again and leave the page
       * as is.
       */
      if (current_test_flags(PF_FSTRANS) && need_trans)
            goto out_fail;

      /*
       * Delay hooking up buffer heads until we have
       * made our go/no-go decision.
       */
      if (!page_has_buffers(page))
            create_empty_buffers(page, 1 << inode->i_blkbits, 0);

      /*
       * Convert delayed allocate, unwritten or unmapped space
       * to real space and flush out to disk.
       */
      error = xfs_page_state_convert(inode, page, wbc, 1, unmapped);
      if (error == -EAGAIN)
            goto out_fail;
      if (unlikely(error < 0))
            goto out_unlock;

      return 0;

out_fail:
      redirty_page_for_writepage(wbc, page);
      unlock_page(page);
      return 0;
out_unlock:
      unlock_page(page);
      return error;
}

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. Possibly the page is already clean. We always
 * have buffer heads in this call.
 *
 * Returns 0 if the page is ok to release, 1 otherwise.
 *
 * Possible scenarios are:
 *
 * 1. We are being called to release a page which has been written
 *    to via regular I/O. buffer heads will be dirty and possibly
 *    delalloc. If no delalloc buffer heads in this case then we
 *    can just return zero.
 *
 * 2. We are called to release a page which has been written via
 *    mmap, all we need to do is ensure there is no delalloc
 *    state in the buffer heads, if not we can let the caller
 *    free them and we should come back later via writepage.
 */
STATIC int
xfs_vm_releasepage(
      struct page       *page,
      gfp_t             gfp_mask)
{
      struct inode            *inode = page->mapping->host;
      int               dirty, delalloc, unmapped, unwritten;
      struct writeback_control wbc = {
            .sync_mode = WB_SYNC_ALL,
            .nr_to_write = 1,
      };

      xfs_page_trace(XFS_RELEASEPAGE_ENTER, inode, page, 0);

      if (!page_has_buffers(page))
            return 0;

      xfs_count_page_state(page, &delalloc, &unmapped, &unwritten);
      if (!delalloc && !unwritten)
            goto free_buffers;

      if (!(gfp_mask & __GFP_FS))
            return 0;

      /* If we are already inside a transaction or the thread cannot
       * do I/O, we cannot release this page.
       */
      if (current_test_flags(PF_FSTRANS))
            return 0;

      /*
       * Convert delalloc space to real space, do not flush the
       * data out to disk, that will be done by the caller.
       * Never need to allocate space here - we will always
       * come back to writepage in that case.
       */
      dirty = xfs_page_state_convert(inode, page, &wbc, 0, 0);
      if (dirty == 0 && !unwritten)
            goto free_buffers;
      return 0;

free_buffers:
      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,
      bmapi_flags_t           flags)
{
      xfs_iomap_t       iomap;
      xfs_off_t         offset;
      ssize_t                 size;
      int               niomap = 1;
      int               error;

      offset = (xfs_off_t)iblock << inode->i_blkbits;
      ASSERT(bh_result->b_size >= (1 << inode->i_blkbits));
      size = bh_result->b_size;
      error = xfs_bmap(XFS_I(inode), offset, size,
                       create ? flags : BMAPI_READ, &iomap, &niomap);
      if (error)
            return -error;
      if (niomap == 0)
            return 0;

      if (iomap.iomap_bn != IOMAP_DADDR_NULL) {
            /*
             * For unwritten extents do not report a disk address on
             * the read case (treat as if we're reading into a hole).
             */
            if (create || !(iomap.iomap_flags & IOMAP_UNWRITTEN)) {
                  xfs_map_buffer(bh_result, &iomap, offset,
                               inode->i_blkbits);
            }
            if (create && (iomap.iomap_flags & IOMAP_UNWRITTEN)) {
                  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 = iomap.iomap_target->bt_bdev;

      /*
       * 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)) ||
           (iomap.iomap_flags & (IOMAP_NEW|IOMAP_UNWRITTEN))))
            set_buffer_new(bh_result);

      if (iomap.iomap_flags & IOMAP_DELAY) {
            BUG_ON(direct);
            if (create) {
                  set_buffer_uptodate(bh_result);
                  set_buffer_mapped(bh_result);
                  set_buffer_delay(bh_result);
            }
      }

      if (direct || size > (1 << inode->i_blkbits)) {
            ASSERT(iomap.iomap_bsize - iomap.iomap_delta > 0);
            offset = min_t(xfs_off_t,
                        iomap.iomap_bsize - iomap.iomap_delta, size);
            bh_result->b_size = (ssize_t)min_t(xfs_off_t, LONG_MAX, offset);
      }

      return 0;
}

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, BMAPI_WRITE);
}

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, BMAPI_WRITE|BMAPI_DIRECT);
}

STATIC void
xfs_end_io_direct(
      struct kiocb      *iocb,
      loff_t            offset,
      ssize_t           size,
      void        *private)
{
      xfs_ioend_t *ioend = iocb->private;

      /*
       * Non-NULL private data means we need to issue a transaction to
       * convert a range from unwritten to written extents.  This needs
       * to happen from process context but aio+dio I/O completion
       * happens from irq context so we need to defer it to a workqueue.
       * This is not necessary for synchronous direct I/O, but we do
       * it anyway to keep the code uniform and simpler.
       *
       * Well, if only it were that simple. Because synchronous direct I/O
       * requires extent conversion to occur *before* we return to userspace,
       * we have to wait for extent conversion to complete. Look at the
       * iocb that has been passed to us to determine if this is AIO or
       * not. If it is synchronous, tell xfs_finish_ioend() to kick the
       * workqueue and wait for it to complete.
       *
       * The core direct I/O code might be changed to always call the
       * completion handler in the future, in which case all this can
       * go away.
       */
      ioend->io_offset = offset;
      ioend->io_size = size;
      if (ioend->io_type == IOMAP_READ) {
            xfs_finish_ioend(ioend, 0);
      } else if (private && size > 0) {
            xfs_finish_ioend(ioend, is_sync_kiocb(iocb));
      } else {
            /*
             * A direct I/O write ioend starts it's life in unwritten
             * state in case they map an unwritten extent.  This write
             * didn't map an unwritten extent so switch it's completion
             * handler.
             */
            INIT_WORK(&ioend->io_work, xfs_end_bio_written);
            xfs_finish_ioend(ioend, 0);
      }

      /*
       * 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;
}

STATIC ssize_t
xfs_vm_direct_IO(
      int               rw,
      struct kiocb            *iocb,
      const struct iovec      *iov,
      loff_t                  offset,
      unsigned long           nr_segs)
{
      struct file *file = iocb->ki_filp;
      struct inode      *inode = file->f_mapping->host;
      xfs_iomap_t iomap;
      int         maps = 1;
      int         error;
      ssize_t           ret;

      error = xfs_bmap(XFS_I(inode), offset, 0,
                        BMAPI_DEVICE, &iomap, &maps);
      if (error)
            return -error;

      if (rw == WRITE) {
            iocb->private = xfs_alloc_ioend(inode, IOMAP_UNWRITTEN);
            ret = blockdev_direct_IO_own_locking(rw, iocb, inode,
                  iomap.iomap_target->bt_bdev,
                  iov, offset, nr_segs,
                  xfs_get_blocks_direct,
                  xfs_end_io_direct);
      } else {
            iocb->private = xfs_alloc_ioend(inode, IOMAP_READ);
            ret = blockdev_direct_IO_no_locking(rw, iocb, inode,
                  iomap.iomap_target->bt_bdev,
                  iov, offset, nr_segs,
                  xfs_get_blocks_direct,
                  xfs_end_io_direct);
      }

      if (unlikely(ret != -EIOCBQUEUED && iocb->private))
            xfs_destroy_ioend(iocb->private);
      return ret;
}

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)
{
      *pagep = NULL;
      return block_write_begin(file, mapping, pos, len, flags, pagep, fsdata,
                                                xfs_get_blocks);
}

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);

      vn_trace_entry(XFS_I(inode), __FUNCTION__,
                  (inst_t *)__return_address);
      xfs_rwlock(ip, VRWLOCK_READ);
      xfs_flush_pages(ip, (xfs_off_t)0, -1, 0, FI_REMAPF);
      xfs_rwunlock(ip, VRWLOCK_READ);
      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);
}

STATIC void
xfs_vm_invalidatepage(
      struct page       *page,
      unsigned long           offset)
{
      xfs_page_trace(XFS_INVALIDPAGE_ENTER,
                  page->mapping->host, page, offset);
      block_invalidatepage(page, offset);
}

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,
      .sync_page        = block_sync_page,
      .releasepage            = xfs_vm_releasepage,
      .invalidatepage         = xfs_vm_invalidatepage,
      .write_begin            = xfs_vm_write_begin,
      .write_end        = generic_write_end,
      .bmap             = xfs_vm_bmap,
      .direct_IO        = xfs_vm_direct_IO,
      .migratepage            = buffer_migrate_page,
};

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