struct xfs_inode        *ip = XFS_I(inode);
        struct buffer_head      *bh, *head;
        loff_t                  offset = page_offset(page);
-       ssize_t                 len = 1 << inode->i_blkbits;
 
        if (!xfs_is_delayed_page(page, IO_DELAY))
                goto out_invalidate;
        xfs_ilock(ip, XFS_ILOCK_EXCL);
        bh = head = page_buffers(page);
        do {
-               int             done;
-               xfs_fileoff_t   offset_fsb;
-               xfs_bmbt_irec_t imap;
-               int             nimaps = 1;
                int             error;
-               xfs_fsblock_t   firstblock;
-               xfs_bmap_free_t flist;
+               xfs_fileoff_t   start_fsb;
 
                if (!buffer_delay(bh))
                        goto next_buffer;
 
-               offset_fsb = XFS_B_TO_FSBT(ip->i_mount, offset);
-
-               /*
-                * Map the range first and check that it is a delalloc extent
-                * before trying to unmap the range. Otherwise we will be
-                * trying to remove a real extent (which requires a
-                * transaction) or a hole, which is probably a bad idea...
-                */
-               error = xfs_bmapi(NULL, ip, offset_fsb, 1,
-                               XFS_BMAPI_ENTIRE,  NULL, 0, &imap,
-                               &nimaps, NULL);
-
-               if (error) {
-                       /* something screwed, just bail */
-                       if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
-                               xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
-                               "page discard failed delalloc mapping lookup.");
-                       }
-                       break;
-               }
-               if (!nimaps) {
-                       /* nothing there */
-                       goto next_buffer;
-               }
-               if (imap.br_startblock != DELAYSTARTBLOCK) {
-                       /* been converted, ignore */
-                       goto next_buffer;
-               }
-               WARN_ON(imap.br_blockcount == 0);
-
-               /*
-                * Note: while we initialise the firstblock/flist pair, they
-                * should never be used because blocks should never be
-                * allocated or freed for a delalloc extent and hence we need
-                * don't cancel or finish them after the xfs_bunmapi() call.
-                */
-               xfs_bmap_init(&flist, &firstblock);
-               error = xfs_bunmapi(NULL, ip, offset_fsb, 1, 0, 1, &firstblock,
-                                       &flist, &done);
-
-               ASSERT(!flist.xbf_count && !flist.xbf_first);
+               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)) {
                        break;
                }
 next_buffer:
-               offset += len;
+               offset += 1 << inode->i_blkbits;
 
        } while ((bh = bh->b_this_page) != head);
 
        struct inode            *inode = mapping->host;
 
        if (to > inode->i_size) {
-               struct iattr    ia = {
-                       .ia_valid       = ATTR_SIZE | ATTR_FORCE,
-                       .ia_size        = inode->i_size,
-               };
-               xfs_setattr(XFS_I(inode), &ia, XFS_ATTR_NOLOCK);
+               /*
+                * 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_fs_cmn_err(CE_ALERT, ip->i_mount,
+                       "xfs_vm_write_failed: unable to clean up ino %lld",
+                                               ip->i_ino);
+                       }
+               }
+               xfs_iunlock(ip, XFS_ILOCK_EXCL);
        }
 }
 
 
                *count += xfs_bmbt_disk_get_blockcount(frp);
        }
 }
+
+/*
+ * dead simple method of punching delalyed allocation blocks from a range in
+ * the inode. Walks a block at a time so will be slow, but is only executed in
+ * rare error cases so the overhead is not critical. This will alays punch out
+ * both the start and end blocks, even if the ranges only partially overlap
+ * them, so it is up to the caller to ensure that partial blocks are not
+ * passed in.
+ */
+int
+xfs_bmap_punch_delalloc_range(
+       struct xfs_inode        *ip,
+       xfs_fileoff_t           start_fsb,
+       xfs_fileoff_t           length)
+{
+       xfs_fileoff_t           remaining = length;
+       int                     error = 0;
+
+       ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
+
+       do {
+               int             done;
+               xfs_bmbt_irec_t imap;
+               int             nimaps = 1;
+               xfs_fsblock_t   firstblock;
+               xfs_bmap_free_t flist;
+
+               /*
+                * Map the range first and check that it is a delalloc extent
+                * before trying to unmap the range. Otherwise we will be
+                * trying to remove a real extent (which requires a
+                * transaction) or a hole, which is probably a bad idea...
+                */
+               error = xfs_bmapi(NULL, ip, start_fsb, 1,
+                               XFS_BMAPI_ENTIRE,  NULL, 0, &imap,
+                               &nimaps, NULL);
+
+               if (error) {
+                       /* something screwed, just bail */
+                       if (!XFS_FORCED_SHUTDOWN(ip->i_mount)) {
+                               xfs_fs_cmn_err(CE_ALERT, ip->i_mount,
+                       "Failed delalloc mapping lookup ino %lld fsb %lld.",
+                                               ip->i_ino, start_fsb);
+                       }
+                       break;
+               }
+               if (!nimaps) {
+                       /* nothing there */
+                       goto next_block;
+               }
+               if (imap.br_startblock != DELAYSTARTBLOCK) {
+                       /* been converted, ignore */
+                       goto next_block;
+               }
+               WARN_ON(imap.br_blockcount == 0);
+
+               /*
+                * Note: while we initialise the firstblock/flist pair, they
+                * should never be used because blocks should never be
+                * allocated or freed for a delalloc extent and hence we need
+                * don't cancel or finish them after the xfs_bunmapi() call.
+                */
+               xfs_bmap_init(&flist, &firstblock);
+               error = xfs_bunmapi(NULL, ip, start_fsb, 1, 0, 1, &firstblock,
+                                       &flist, &done);
+               if (error)
+                       break;
+
+               ASSERT(!flist.xbf_count && !flist.xbf_first);
+next_block:
+               start_fsb++;
+               remaining--;
+       } while(remaining > 0);
+
+       return error;
+}