Commit 45150c43 authored Sep 09, 2013 by Olof Johansson Committed by Linus Torvalds Sep 09, 2013

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>

parent ef9a61be

fs/direct-io.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

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