[PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Vyacheslav Dubeyko]

From: Vyacheslav Dubeyko <slava-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org>
Subject: [PATCH] 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-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
Signed-off-by: Vyacheslav Dubeyko <slava-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org>
CC: Ryusuke Konishi <konishi.ryusuke-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>
---
 fs/nilfs2/segbuf.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
index dc9a913..5bacf46 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)
-- 
1.7.9.5



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[PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Vyacheslav Dubeyko]

From: Vyacheslav Dubeyko <slava@dubeyko.com>
Subject: [PATCH] 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@oracle.com>
Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
CC: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
---
 fs/nilfs2/segbuf.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
index dc9a913..5bacf46 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)
-- 
1.7.9.5

Re: [PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Ryusuke Konishi]

Hi Vyacheslav,
On Mon, 22 Jul 2013 12:02:14 +0400, Vyacheslav Dubeyko wrote:
> From: Vyacheslav Dubeyko <slava-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org>
> Subject: [PATCH] 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-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Vyacheslav Dubeyko <slava-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org>
> CC: Ryusuke Konishi <konishi.ryusuke-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>

Thank you for following the issue.  I reviewed the code around bio.

In conclusion, Dan Carpenter's patch looks correct because
nilfs_segbuf_submit_bio() does not increment the number of flying bio
(segbuf->sb_nbio) for EOPNOTSUPP/BIO_EOPNOTSUPP case.

If nilfs_end_bio_write() function reaches the complete() call for the
EOPNOTSUPP/BIO_EOPNOTSUPP case (as the current implementation), the
number of complete() calls and that of wait_for_complete() will not
balance.

Do you have a comment?

Regards,
Ryusuke Konishi

> ---
>  fs/nilfs2/segbuf.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
> index dc9a913..5bacf46 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)
> -- 
> 1.7.9.5
> 
> 
> 
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> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
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Re: [PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Ryusuke Konishi]

Hi Vyacheslav,
On Mon, 22 Jul 2013 12:02:14 +0400, Vyacheslav Dubeyko wrote:
> From: Vyacheslav Dubeyko <slava@dubeyko.com>
> Subject: [PATCH] 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@oracle.com>
> Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
> CC: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

Thank you for following the issue.  I reviewed the code around bio.

In conclusion, Dan Carpenter's patch looks correct because
nilfs_segbuf_submit_bio() does not increment the number of flying bio
(segbuf->sb_nbio) for EOPNOTSUPP/BIO_EOPNOTSUPP case.

If nilfs_end_bio_write() function reaches the complete() call for the
EOPNOTSUPP/BIO_EOPNOTSUPP case (as the current implementation), the
number of complete() calls and that of wait_for_complete() will not
balance.

Do you have a comment?

Regards,
Ryusuke Konishi

> ---
>  fs/nilfs2/segbuf.c |    3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
> index dc9a913..5bacf46 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)
> -- 
> 1.7.9.5
> 
> 
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Vyacheslav Dubeyko]

Hi Ryusuke,

On Tue, 2013-07-23 at 03:24 +0900, Ryusuke Konishi wrote:

[snip]
> 
> Thank you for following the issue.  I reviewed the code around bio.
> 
> In conclusion, Dan Carpenter's patch looks correct because
> nilfs_segbuf_submit_bio() does not increment the number of flying bio
> (segbuf->sb_nbio) for EOPNOTSUPP/BIO_EOPNOTSUPP case.
> 

I worry that nilfs_end_bio_write() is called asynchronously. And, as I
understand, the BIO_EOPNOTSUPP flag is set during nilfs_end_bio_write()
call. It means for me that sometimes segbuf->sb_nbio will be not
incremented in nilfs_segbuf_submit_bio() but sometimes this field can be
incremented and for BIO_EOPNOTSUPP case.

> If nilfs_end_bio_write() function reaches the complete() call for the
> EOPNOTSUPP/BIO_EOPNOTSUPP case (as the current implementation), the
> number of complete() calls and that of wait_for_complete() will not
> balance.
> 

I think that it is dangerous to return without complete() call because
of asynchronous nature of nilfs_end_bio_write() call.

What do you think?

With the best regards,
Vyacheslav Dubeyko.

> Do you have a comment?
> 
> Regards,
> Ryusuke Konishi
> 
> > ---
> >  fs/nilfs2/segbuf.c |    3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
> > index dc9a913..5bacf46 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)
> > -- 
> > 1.7.9.5
> > 
> > 
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Vyacheslav Dubeyko]

Hi Ryusuke,

On Tue, 2013-07-23 at 03:24 +0900, Ryusuke Konishi wrote:

[snip]
> 
> Thank you for following the issue.  I reviewed the code around bio.
> 
> In conclusion, Dan Carpenter's patch looks correct because
> nilfs_segbuf_submit_bio() does not increment the number of flying bio
> (segbuf->sb_nbio) for EOPNOTSUPP/BIO_EOPNOTSUPP case.
> 

I worry that nilfs_end_bio_write() is called asynchronously. And, as I
understand, the BIO_EOPNOTSUPP flag is set during nilfs_end_bio_write()
call. It means for me that sometimes segbuf->sb_nbio will be not
incremented in nilfs_segbuf_submit_bio() but sometimes this field can be
incremented and for BIO_EOPNOTSUPP case.

> If nilfs_end_bio_write() function reaches the complete() call for the
> EOPNOTSUPP/BIO_EOPNOTSUPP case (as the current implementation), the
> number of complete() calls and that of wait_for_complete() will not
> balance.
> 

I think that it is dangerous to return without complete() call because
of asynchronous nature of nilfs_end_bio_write() call.

What do you think?

With the best regards,
Vyacheslav Dubeyko.

> Do you have a comment?
> 
> Regards,
> Ryusuke Konishi
> 
> > ---
> >  fs/nilfs2/segbuf.c |    3 +--
> >  1 file changed, 1 insertion(+), 2 deletions(-)
> > 
> > diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
> > index dc9a913..5bacf46 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)
> > -- 
> > 1.7.9.5
> > 
> > 
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Ryusuke Konishi]

On Tue, 23 Jul 2013 11:46:51 +0400, Vyacheslav Dubeyko wrote:
> Hi Ryusuke,
> 
> On Tue, 2013-07-23 at 03:24 +0900, Ryusuke Konishi wrote:
> 
> [snip]
>> 
>> Thank you for following the issue.  I reviewed the code around bio.
>> 
>> In conclusion, Dan Carpenter's patch looks correct because
>> nilfs_segbuf_submit_bio() does not increment the number of flying bio
>> (segbuf->sb_nbio) for EOPNOTSUPP/BIO_EOPNOTSUPP case.
>> 
> 
> I worry that nilfs_end_bio_write() is called asynchronously. And, as I
> understand, the BIO_EOPNOTSUPP flag is set during nilfs_end_bio_write()
> call. It means for me that sometimes segbuf->sb_nbio will be not
> incremented in nilfs_segbuf_submit_bio() but sometimes this field can be
> incremented and for BIO_EOPNOTSUPP case.
> 
>> If nilfs_end_bio_write() function reaches the complete() call for the
>> EOPNOTSUPP/BIO_EOPNOTSUPP case (as the current implementation), the
>> number of complete() calls and that of wait_for_complete() will not
>> balance.
>> 
> 
> I think that it is dangerous to return without complete() call because
> of asynchronous nature of nilfs_end_bio_write() call.
> 
> What do you think?

nilfs_end_bio_write() may be called either synchronously or
asynchronously as bio->bi_end_io().  It may be called when
submit_bio() fails or when bio is terminated asynchronously.

Yes, the current nilfs_end_bio_write() implementation is confusing
and dangerous for the EOPNOTSUPP case.

I think nilfs_end_bio_write() should be modified so that
segbuf->sb_nbio is incremented in either case.


Thanks,
Ryusuke Konishi

Re: [PATCH] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error

[Ryusuke Konishi]

On Tue, 23 Jul 2013 11:46:51 +0400, Vyacheslav Dubeyko wrote:
> Hi Ryusuke,
> 
> On Tue, 2013-07-23 at 03:24 +0900, Ryusuke Konishi wrote:
> 
> [snip]
>> 
>> Thank you for following the issue.  I reviewed the code around bio.
>> 
>> In conclusion, Dan Carpenter's patch looks correct because
>> nilfs_segbuf_submit_bio() does not increment the number of flying bio
>> (segbuf->sb_nbio) for EOPNOTSUPP/BIO_EOPNOTSUPP case.
>> 
> 
> I worry that nilfs_end_bio_write() is called asynchronously. And, as I
> understand, the BIO_EOPNOTSUPP flag is set during nilfs_end_bio_write()
> call. It means for me that sometimes segbuf->sb_nbio will be not
> incremented in nilfs_segbuf_submit_bio() but sometimes this field can be
> incremented and for BIO_EOPNOTSUPP case.
> 
>> If nilfs_end_bio_write() function reaches the complete() call for the
>> EOPNOTSUPP/BIO_EOPNOTSUPP case (as the current implementation), the
>> number of complete() calls and that of wait_for_complete() will not
>> balance.
>> 
> 
> I think that it is dangerous to return without complete() call because
> of asynchronous nature of nilfs_end_bio_write() call.
> 
> What do you think?

nilfs_end_bio_write() may be called either synchronously or
asynchronously as bio->bi_end_io().  It may be called when
submit_bio() fails or when bio is terminated asynchronously.

Yes, the current nilfs_end_bio_write() implementation is confusing
and dangerous for the EOPNOTSUPP case.

I think nilfs_end_bio_write() should be modified so that
segbuf->sb_nbio is incremented in either case.


Thanks,
Ryusuke Konishi