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authorOlof Johansson <olof@lixom.net>2013-09-09 10:34:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-09-09 10:47:42 -0700
commit45150c43b1b0c16e665fd0a5cdcca128b8192db1 (patch)
treee1faec166f3edb5974829d9f7ec4c25e02fd1572
parentef9a61bef917e38f8e096f6df303329aed6cf467 (diff)
downloadlinux-45150c43b1b0c16e665fd0a5cdcca128b8192db1.tar.bz2
direct-io: Use return from cmpxchg to decide of assignment happened
Not using the return value can in the generic case be racy, so it's in general good practice to check the return value instead. This also resolved the warning caused on ARM and other architectures: fs/direct-io.c: In function 'sb_init_dio_done_wq': fs/direct-io.c:557:2: warning: value computed is not used [-Wunused-value] Signed-off-by: Olof Johansson <olof@lixom.net> Reviewed-by: Jan Kara <jack@suse.cz> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Stephen Rothwell <sfr@canb.auug.org.au> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Christoph Hellwig <hch@infradead.org> Cc: Russell King <linux@arm.linux.org.uk> Cc: H Peter Anvin <hpa@zytor.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/direct-io.c5
1 files changed, 3 insertions, 2 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 1782023bd68a..0e04142d5962 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -544,6 +544,7 @@ static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio)
*/
static int sb_init_dio_done_wq(struct super_block *sb)
{
+ struct workqueue_struct *old;
struct workqueue_struct *wq = alloc_workqueue("dio/%s",
WQ_MEM_RECLAIM, 0,
sb->s_id);
@@ -552,9 +553,9 @@ static int sb_init_dio_done_wq(struct super_block *sb)
/*
* This has to be atomic as more DIOs can race to create the workqueue
*/
- cmpxchg(&sb->s_dio_done_wq, NULL, wq);
+ old = cmpxchg(&sb->s_dio_done_wq, NULL, wq);
/* Someone created workqueue before us? Free ours... */
- if (wq != sb->s_dio_done_wq)
+ if (old)
destroy_workqueue(wq);
return 0;
}