Btrfs: move btrfs_truncate_page to btrfs_cont_expand instead of btrfs_truncate

This has plagued us forever and I'm so over working around it.  When we truncate
down to a non-page aligned offset we will call btrfs_truncate_page to zero out
the end of the page and write it back to disk, this will keep us from exposing
stale data if we truncate back up from that point.  The problem with this is it
requires data space to do this, and people don't really expect to get ENOSPC
from truncate() for these sort of things.  This also tends to bite the orphan
cleanup stuff too which keeps people from mounting.  To get around this we can
just move this into btrfs_cont_expand() to make sure if we are truncating up
from a non-page size aligned i_size we will zero out the rest of this page so
that we don't expose stale data.  This will give ENOSPC if you try to truncate()
up or if you try to write past the end of isize, which is much more reasonable.
This fixes xfstests generic/083 failing to mount because of the orphan cleanup
failing.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>

1 files changed, 15 insertions, 6 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 185af15ad9e4..5ffde5603686 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2173,12 +2173,6 @@ static long btrfs_fallocate(struct file *file, int mode,
                         goto out_reserve_fail;
         }
 
-        /*
-         * wait for ordered IO before we have any locks.  We'll loop again
-         * below with the locks held.
-         */
-        btrfs_wait_ordered_range(inode, alloc_start, alloc_end - alloc_start);
-
         mutex_lock(&inode->i_mutex);
         ret = inode_newsize_ok(inode, alloc_end);
         if (ret)
@@ -2189,8 +2183,23 @@ static long btrfs_fallocate(struct file *file, int mode,
                                         alloc_start);
                 if (ret)
                         goto out;
+        } else {
+                /*
+                 * If we are fallocating from the end of the file onward we
+                 * need to zero out the end of the page if i_size lands in the
+                 * middle of a page.
+                 */
+                ret = btrfs_truncate_page(inode, inode->i_size, 0, 0);
+                if (ret)
+                        goto out;
         }
 
+        /*
+         * wait for ordered IO before we have any locks.  We'll loop again
+         * below with the locks held.
+         */
+        btrfs_wait_ordered_range(inode, alloc_start, alloc_end - alloc_start);
+
         locked_end = alloc_end - 1;
         while (1) {
                 struct btrfs_ordered_extent *ordered;