[dm-devel] [PATCH] disallow FS recursion from sb_issue_discard allocation

[Mike Snitzer]

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 at redhat.com>
Signed-off-by: Mike Snitzer <snitzer at redhat.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);
 }