Hi Vyacheslav,
On Fri, 26 Jul 2013 17:59:14 +0400, Vyacheslav Dubeyko wrote:
> Hi Ryusuke,
>
> I changed place of increment operation of segbuf->sb_nbio in
> nilfs_segbuf_submit_bio() and adding decrement operation for
> BIO_EOPNOTSUPP case in second version of the patch.
>
> Could you share your opinion about this version of the patch?
>
> With the best regards,
> Vyacheslav Dubeyko.
> ---
> From: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
> Subject: [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error
>
> This patch removes double call of bio_put() in nilfs_end_bio_write()
> for the case of BIO_EOPNOTSUPP error detection. The issue was found
> by Dan Carpenter and he suggests first version of the fix too.
>
> Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> Signed-off-by: Vyacheslav Dubeyko <slava@xxxxxxxxxxx>
> CC: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>
> ---
> fs/nilfs2/segbuf.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
> index dc9a913..0b09ec9 100644
> --- a/fs/nilfs2/segbuf.c
> +++ b/fs/nilfs2/segbuf.c
> @@ -345,8 +345,7 @@ static void nilfs_end_bio_write(struct bio *bio, int err)
>
> if (err == -EOPNOTSUPP) {
> set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
> - bio_put(bio);
> - /* to be detected by submit_seg_bio() */
> + /* to be detected by nilfs_segbuf_submit_bio() */
> }
>
> if (!uptodate)
> @@ -377,12 +376,13 @@ 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)) {
> + segbuf->sb_nbio--;
This decrement looks wrong.
Otherwise, your change of nilfs_segbuf_submit_bio() is just a
equivalent transformation and doesn't fix problem, that is, a mismatch
of the number of calls between complete() and wait_for_completion().
In your patch, nilfs_end_bio_write() function calls the complete()
routine as before even if it received an EOPNOTSUPP error.
In that case, segbuf->sb_nbio must be incremented to call
wait_for_completion() the right number of times.
Note that wait_for_completion() is called based on the count of
segbuf->sb_nbio even if nilfs_segbuf_submit_bio() returns an error.
This is performed through the following path:
nilfs_segbuf_submit_bio
nilfs_segbuf_submit_bh
nilfs_segbuf_write
nilfs_write_logs
nilfs_segctor_write
nilfs_segctor_do_construct
nilfs_segctor_abort_construction
nilfs_wait_on_logs
nilfs_segbuf_wait
wait_for_completion
(repeated for the number of times of segbuf->sb_nbio)
If you think this is a separate problem, then it should be fixed in
another patch and nilfs_segbuf_submit_bio() should not be touched in
this patch.
Regards,
Ryusuke Konishi
> bio_put(bio);
> err = -EOPNOTSUPP;
> goto failed;
> }
> - segbuf->sb_nbio++;
> bio_put(bio);
>
> wi->bio = NULL;
> --
> 1.7.9.5
>
>
>
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