[PATCH v3 2/2] nilfs2: fix issue with counting number of bio requests for BIO_EOPNOTSUPP error detection

[PATCH v3 2/2] nilfs2: fix issue with counting number of bio requests for BIO_EOPNOTSUPP error detection

[Vyacheslav Dubeyko]

From: Vyacheslav Dubeyko <slava@dubeyko.com>
Subject: [PATCH v3 2/2] nilfs2: fix issue with counting number of bio requests for BIO_EOPNOTSUPP error detection

This patch fixes 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@dubeyko.com>
CC: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
CC: Dan Carpenter <dan.carpenter@oracle.com>
---
 fs/nilfs2/segbuf.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
index 5bacf46..2d8be51 100644
--- a/fs/nilfs2/segbuf.c
+++ b/fs/nilfs2/segbuf.c
@@ -376,12 +376,12 @@ static int nilfs_segbuf_submit_bio(struct nilfs_segment_buffer *segbuf,
 	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;
-- 
1.7.9.5

Re: [PATCH v3 2/2] nilfs2: fix issue with counting number of bio requests for BIO_EOPNOTSUPP error detection

[Ryusuke Konishi]

On Tue, 13 Aug 2013 17:50:51 +0400, Vyacheslav Dubeyko wrote:
> From: Vyacheslav Dubeyko <slava@dubeyko.com>
> Subject: [PATCH v3 2/2] nilfs2: fix issue with counting number of bio requests for BIO_EOPNOTSUPP error detection
> 
> This patch fixes 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@dubeyko.com>
> CC: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Acked-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Tested-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

I confirmed that this fixes the leak of wait_for_completion() for the
BIO_EOPNOTSUPP error detection case.

Andrew, please send this upstream along with the companion patch
titled "nilfs2: remove double bio_put() in nilfs_end_bio_write() for
BIO_EOPNOTSUPP error".


Thanks,
Ryusuke Konishi


> CC: Dan Carpenter <dan.carpenter@oracle.com>
> ---
>  fs/nilfs2/segbuf.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
> index 5bacf46..2d8be51 100644
> --- a/fs/nilfs2/segbuf.c
> +++ b/fs/nilfs2/segbuf.c
> @@ -376,12 +376,12 @@ static int nilfs_segbuf_submit_bio(struct nilfs_segment_buffer *segbuf,
>  	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;
> -- 
> 1.7.9.5
> 
> 
> 
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