linux-kernel - [088/121] nilfs2: fix issue with counting number of bio requests for BIO

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Message-ID: <lsq.1378608721.460181979@decadent.org.uk>
Date:	Sun, 08 Sep 2013 03:52:01 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Ryusuke Konishi" <konishi.ryusuke@....ntt.co.jp>,
	"Dan Carpenter" <dan.carpenter@...cle.com>,
	"Vyacheslav Dubeyko" <slava@...eyko.com>
Subject: [088/121] nilfs2: fix issue with counting number of bio requests
 for BIO_EOPNOTSUPP error detection

3.2.51-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Vyacheslav Dubeyko <slava@...eyko.com>

commit 4bf93b50fd04118ac7f33a3c2b8a0a1f9fa80bc9 upstream.

Fix the issue with improper counting number of flying bio requests for
BIO_EOPNOTSUPP error detection case.

The sb_nbio must be incremented exactly the same number of times as
complete() function was called (or will be called) because
nilfs_segbuf_wait() will call wail_for_completion() for the number of
times set to sb_nbio:

  do {
      wait_for_completion(&segbuf->sb_bio_event);
  } while (--segbuf->sb_nbio > 0);

Two functions complete() and wait_for_completion() must be called the
same number of times for the same sb_bio_event.  Otherwise,
wait_for_completion() will hang or leak.

Signed-off-by: Vyacheslav Dubeyko <slava@...eyko.com>
Cc: Dan Carpenter <dan.carpenter@...cle.com>
Acked-by: Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
Tested-by: Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/nilfs2/segbuf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/nilfs2/segbuf.c
+++ b/fs/nilfs2/segbuf.c
@@ -376,12 +376,12 @@ static int nilfs_segbuf_submit_bio(struc
 	bio->bi_private = segbuf;
 	bio_get(bio);
 	submit_bio(mode, bio);
+	segbuf->sb_nbio++;
 	if (bio_flagged(bio, BIO_EOPNOTSUPP)) {
 		bio_put(bio);
 		err = -EOPNOTSUPP;
 		goto failed;
 	}
-	segbuf->sb_nbio++;
 	bio_put(bio);
 
 	wi->bio = NULL;

--
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