Btrfs: take i_mutex before generic_write_checks
btrfs_file_write was incorrectly calling generic_write_checks without
taking i_mutex. This lead to problems with racing around i_size when
doing O_APPEND writes.
The fix here is to move i_mutex higher.
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 1be96ba..f155179 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -920,26 +920,35 @@
start_pos = pos;
vfs_check_frozen(inode->i_sb, SB_FREEZE_WRITE);
- current->backing_dev_info = inode->i_mapping->backing_dev_info;
- err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
- if (err)
- goto out_nolock;
- if (count == 0)
- goto out_nolock;
- err = file_remove_suid(file);
- if (err)
- goto out_nolock;
-
+ /* do the reserve before the mutex lock in case we have to do some
+ * flushing. We wouldn't deadlock, but this is more polite.
+ */
err = btrfs_reserve_metadata_for_delalloc(root, inode, 1);
if (err)
goto out_nolock;
+ mutex_lock(&inode->i_mutex);
+
+ current->backing_dev_info = inode->i_mapping->backing_dev_info;
+ err = generic_write_checks(file, &pos, &count, S_ISBLK(inode->i_mode));
+ if (err)
+ goto out;
+
+ if (count == 0)
+ goto out;
+
+ err = file_remove_suid(file);
+ if (err)
+ goto out;
+
file_update_time(file);
pages = kmalloc(nrptrs * sizeof(struct page *), GFP_KERNEL);
- mutex_lock(&inode->i_mutex);
+ /* generic_write_checks can change our pos */
+ start_pos = pos;
+
BTRFS_I(inode)->sequence++;
first_index = pos >> PAGE_CACHE_SHIFT;
last_index = (pos + count) >> PAGE_CACHE_SHIFT;