[PATCH 19/75] ext4: fix error handling in ext4_ext_truncate()

[Kamal Mostafa]

3.8.13.6 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso at mit.edu>

commit 8acd5e9b1217e58a57124d9e225afa12efeae20d upstream.

Previously ext4_ext_truncate() was ignoring potential error returns
from ext4_es_remove_extent() and ext4_ext_remove_space().  This can
lead to the on-diks extent tree and the extent status tree cache
getting out of sync, which is particuarlly bad, and can lead to file
system corruption and potential data loss.

Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
[ kamal: backport to 3.8 (context) ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ext4/extents.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index a5ce6ce..728c8f6 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4326,9 +4326,20 @@ void ext4_ext_truncate(struct inode *inode)
 
 	last_block = (inode->i_size + sb->s_blocksize - 1)
 			>> EXT4_BLOCK_SIZE_BITS(sb);
+retry:
 	err = ext4_es_remove_extent(inode, last_block,
 				    EXT_MAX_BLOCKS - last_block);
+	if (err == ENOMEM) {
+		cond_resched();
+		congestion_wait(BLK_RW_ASYNC, HZ/50);
+		goto retry;
+	}
+	if (err) {
+		ext4_std_error(inode->i_sb, err);
+		return;
+	}
 	err = ext4_ext_remove_space(inode, last_block, EXT_MAX_BLOCKS - 1);
+	ext4_std_error(inode->i_sb, err);
 
 	/* In a multi-transaction truncate, we only make the final
 	 * transaction synchronous.
-- 
1.8.1.2