linux-ext4 - [PATCH] disallow FS recursion from sb_issue

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Date:	Tue, 6 Jul 2010 12:11:56 -0400
From:	Mike Snitzer <snitzer@...hat.com>
To:	Jens Axboe <jaxboe@...ionio.com>
Cc:	Mikulas Patocka <mpatocka@...hat.com>, dm-devel@...hat.com,
	Alasdair G Kergon <agk@...hat.com>,
	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: [PATCH] disallow FS recursion from sb_issue_discard allocation

Filesystems can call sb_issue_discard on a memory reclaim path
(e.g. ext4 calls sb_issue_discard during journal commit).

Use GFP_NOFS in sb_issue_discard to avoid recursing back into the FS.

Reported-by: Mikulas Patocka <mpatocka@...hat.com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
---
 include/linux/blkdev.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index baf5258..dbb510c 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -933,7 +933,7 @@ static inline int sb_issue_discard(struct super_block *sb,
 {
 	block <<= (sb->s_blocksize_bits - 9);
 	nr_blocks <<= (sb->s_blocksize_bits - 9);
-	return blkdev_issue_discard(sb->s_bdev, block, nr_blocks, GFP_KERNEL,
+	return blkdev_issue_discard(sb->s_bdev, block, nr_blocks, GFP_NOFS,
 				   BLKDEV_IFL_WAIT | BLKDEV_IFL_BARRIER);
 }
 
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