xfs: xfs_vm_write_end truncates too much on failure

Similar to the write_begin problem, xfs-vm_write_end will truncate
back to the old EOF, potentially removing page cache from over the
top of delalloc blocks with valid data in them. Fix this by
truncating back to just the start of the failed write.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Tested-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 5f296934879ff64f696c794d497341fde3c81779..e0a793113ea9b6c1ab5b84aac39032419f2794f6 100644 (file)
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1634,9 +1634,12 @@ xfs_vm_write_begin(
 }
 
 /*
- * On failure, we only need to kill delalloc blocks beyond EOF because they
- * will never be written. For blocks within EOF, generic_write_end() zeros them
- * so they are safe to leave alone and be written with all the other valid data.
+ * On failure, we only need to kill delalloc blocks beyond EOF in the range of
+ * this specific write because they will never be written. Previous writes
+ * beyond EOF where block allocation succeeded do not need to be trashed, so
+ * only new blocks from this write should be trashed. For blocks within
+ * EOF, generic_write_end() zeros them so they are safe to leave alone and be
+ * written with all the other valid data.
  */
 STATIC int
 xfs_vm_write_end(
@@ -1659,8 +1662,11 @@ xfs_vm_write_end(
                loff_t          to = pos + len;
 
                if (to > isize) {
-                       truncate_pagecache(inode, isize);
+                       /* only kill blocks in this write beyond EOF */
+                       if (pos > isize)
+                               isize = pos;
                        xfs_vm_kill_delalloc_range(inode, isize, to);
+                       truncate_pagecache_range(inode, isize, to);
                }
        }
        return ret;