[3.8.y.z extended stable] Patch "ext4: call ext4_error_inode() if jbd2_journal_dirty_metadata() fails" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    ext4: call ext4_error_inode() if jbd2_journal_dirty_metadata() fails

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.16.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 0089eedbaf25d66f228d7ce85eed397b47229fa8 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso at mit.edu>
Date: Mon, 2 Dec 2013 09:31:36 -0500
Subject: ext4: call ext4_error_inode() if jbd2_journal_dirty_metadata() fails

commit ae1495b12df1897d4f42842a7aa7276d920f6290 upstream.

While it's true that errors can only happen if there is a bug in
jbd2_journal_dirty_metadata(), if a bug does happen, we need to halt
the kernel or remount the file system read-only in order to avoid
further data loss.  The ext4_journal_abort_handle() function doesn't
do any of this, and while it's likely that this call (since it doesn't
adjust refcounts) will likely result in the file system eventually
deadlocking since the current transaction will never be able to close,
it's much cleaner to call let ext4's error handling system deal with
this situation.

There's a separate bug here which is that if certain jbd2 errors
errors occur and file system is mounted errors=continue, the file
system will probably eventually end grind to a halt as described
above.  But things have been this way in a long time, and usually when
we have these sorts of errors it's pretty much a disaster --- and
that's why the jbd2 layer aggressively retries memory allocations,
which is the most likely cause of these jbd2 errors.

Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
Reviewed-by: Jan Kara <jack at suse.cz>
[ kamal: backport to 3.8 (print available struct members only) ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/ext4/ext4_jbd2.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/ext4_jbd2.c b/fs/ext4/ext4_jbd2.c
index 6d7abb1..ee73a81 100644
--- a/fs/ext4/ext4_jbd2.c
+++ b/fs/ext4/ext4_jbd2.c
@@ -113,6 +113,11 @@ int __ext4_handle_dirty_metadata(const char *where, unsigned int line,
 		if (WARN_ON_ONCE(err)) {
 			ext4_journal_abort_handle(where, line, __func__, bh,
 						  handle, err);
+			ext4_error_inode(inode, where, line,
+					 bh->b_blocknr,
+					 "journal_dirty_metadata failed: "
+					 "credits %u, errcode %d",
+					 handle->h_buffer_credits, err);
 		}
 	} else {
 		if (inode)
--
1.8.3.2