linux-kernel - [RFC -v2 6/8] ext3: Do not abort journal prematurely

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Date:	Tue, 18 Aug 2015 12:39:37 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Dave Chinner <david@...morbit.com>,
	Theodore Ts'o <tytso@....edu>, linux-btrfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [RFC -v2 6/8] ext3: Do not abort journal prematurely

From: Michal Hocko <mhocko@...e.com>

journal_get_undo_access is relying on GFP_NOFS allocation yet it is
essential for the journal transaction:

[   83.256914] journal_get_undo_access: No memory for committed data
[   83.258022] EXT3-fs: ext3_free_blocks_sb: aborting transaction: Out
of memory in __ext3_journal_get_undo_access
[   83.259785] EXT3-fs (hdb1): error in ext3_free_blocks_sb: Out of
memory
[   83.267130] Aborting journal on device hdb1.
[   83.292308] EXT3-fs (hdb1): error: ext3_journal_start_sb: Detected
aborted journal
[   83.293630] EXT3-fs (hdb1): error: remounting filesystem read-only

Since "mm: page_alloc: do not lock up GFP_NOFS allocations upon OOM"
these allocation requests are allowed to fail so we need to use
__GFP_NOFAIL to imitate the previous behavior.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 fs/jbd/transaction.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
index bf7474deda2f..2151b80276c3 100644
--- a/fs/jbd/transaction.c
+++ b/fs/jbd/transaction.c
@@ -886,15 +886,8 @@ int journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
 		goto out;
 
 repeat:
-	if (!jh->b_committed_data) {
-		committed_data = jbd_alloc(jh2bh(jh)->b_size, GFP_NOFS);
-		if (!committed_data) {
-			printk(KERN_ERR "%s: No memory for committed data\n",
-				__func__);
-			err = -ENOMEM;
-			goto out;
-		}
-	}
+	if (!jh->b_committed_data)
+		committed_data = jbd_alloc(jh2bh(jh)->b_size, GFP_NOFS | __GFP_NOFAIL);
 
 	jbd_lock_bh_state(bh);
 	if (!jh->b_committed_data) {
-- 
2.5.0

-- 
Michal Hocko
SUSE Labs
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