* [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error
@ 2013-07-26 13:59 Vyacheslav Dubeyko
2013-07-27 3:02 ` Ryusuke Konishi
0 siblings, 1 reply; 5+ messages in thread
From: Vyacheslav Dubeyko @ 2013-07-26 13:59 UTC (permalink / raw)
To: KONISHI Ryusuke
Cc: DanCarpenter, linux-nilfs, Linux FS Devel, kernel-janitors,
Andrew Morton
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@dubeyko.com>
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@oracle.com>
Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
CC: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
---
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--;
bio_put(bio);
err = -EOPNOTSUPP;
goto failed;
}
- segbuf->sb_nbio++;
bio_put(bio);
wi->bio = NULL;
--
1.7.9.5
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error
2013-07-26 13:59 [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error Vyacheslav Dubeyko
@ 2013-07-27 3:02 ` Ryusuke Konishi
2013-07-31 10:36 ` Vyacheslav Dubeyko
[not found] ` <20130727.120232.356926182.konishi.ryusuke-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>
0 siblings, 2 replies; 5+ messages in thread
From: Ryusuke Konishi @ 2013-07-27 3:02 UTC (permalink / raw)
To: Vyacheslav Dubeyko
Cc: DanCarpenter, linux-nilfs, Linux FS Devel,
kernel-janitors-u79uwXL29TY76Z2rM5mHXA,
akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b
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-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org>
> 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-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 | 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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> the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error
2013-07-27 3:02 ` Ryusuke Konishi
@ 2013-07-31 10:36 ` Vyacheslav Dubeyko
[not found] ` <20130727.120232.356926182.konishi.ryusuke-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>
1 sibling, 0 replies; 5+ messages in thread
From: Vyacheslav Dubeyko @ 2013-07-31 10:36 UTC (permalink / raw)
To: Ryusuke Konishi
Cc: DanCarpenter, linux-nilfs, Linux FS Devel, kernel-janitors, akpm,
Jérôme Poulin
Hi Ryusuke,
On Sat, 2013-07-27 at 12:02 +0900, Ryusuke Konishi wrote:
[snip]
>
> 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.
>
Sorry for delay with working on this patch. Now I am investigating
the issue (Kernel Bug: unable to handle kernel paging request) that it
was reported by Jérôme Poulin <jeromepoulin@gmail.com>. I suspect that
the reported issue is related to this patch. So, I feel a necessity to
investigate the issue more deeply before continuation to work on this
patch.
With the best regards,
Vyacheslav Dubeyko.
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error
[not found] ` <20130727.120232.356926182.konishi.ryusuke-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>
@ 2013-08-12 13:16 ` Vyacheslav Dubeyko
2013-08-12 14:57 ` Ryusuke Konishi
0 siblings, 1 reply; 5+ messages in thread
From: Vyacheslav Dubeyko @ 2013-08-12 13:16 UTC (permalink / raw)
To: Ryusuke Konishi
Cc: DanCarpenter, linux-nilfs, Linux FS Devel,
kernel-janitors-u79uwXL29TY76Z2rM5mHXA,
akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b
Hi Ryusuke,
On Sat, 2013-07-27 at 12:02 +0900, Ryusuke Konishi wrote:
> > From: Vyacheslav Dubeyko <slava-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org>
> > 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-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 | 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.
>
I tried to understand your vision but I am thinking that my patch is
correct. Maybe, I missed something in my considerations. I describe my
vision in more details.
> 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.
>
I moved incrementing of sb_nbio nearly after submit_bio(mode, bio). So,
firstly, we call submit_bio(mode, bio) and segbuf->sb_nbio++. Then,
because of asynchronous nature of nilfs_end_bio_write() call, we have
two alternatives: (1) nilfs_end_bio_write() detects that BIO_EOPNOTSUPP
flag is set; (2) BIO_EOPNOTSUPP flag isn't set because bio is not
processed yet or we haven't error.
If nilfs_end_bio_write() method would detect -EOPNOTSUPP error then it
set BIO_EOPNOTSUPP flag, increment sb_err field and to call complete().
So, if we detect that BIO_EOPNOTSUPP flag is set in
nilfs_segbuf_submit_bio() then we decrement sb_nbio and to return from
nilfs_segbuf_submit_bio() with error. And if we had submitted
successfully some bios before then it will need to wait theirs
completion.
Otherwise, if BIO_EOPNOTSUPP flag is not set yet during check in
nilfs_segbuf_submit_bio() then sb_nbio is remained incremented. And, for
example, nilfs_segbuf_wait() can end correctly the cycle with
wait_for_completion() call. We will know about error during bio
processing because of sb_err was incremented in nilfs_end_bio_write().
So, I suppose that my logic is right. Please, correct me if I am wrong.
What do you think?
By the way, why sb_err has atomic_t type but sb_nbio is simple int type?
Maybe, sb_nbio should be atomic_t type too?
With the best regards,
Vyacheslav Dubeyko.
> 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.
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^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error
2013-08-12 13:16 ` Vyacheslav Dubeyko
@ 2013-08-12 14:57 ` Ryusuke Konishi
0 siblings, 0 replies; 5+ messages in thread
From: Ryusuke Konishi @ 2013-08-12 14:57 UTC (permalink / raw)
To: Vyacheslav Dubeyko
Cc: DanCarpenter, linux-nilfs-u79uwXL29TY76Z2rM5mHXA, Linux FS Devel,
kernel-janitors-u79uwXL29TY76Z2rM5mHXA,
akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b
On Mon, 12 Aug 2013 17:16:28 +0400, Vyacheslav Dubeyko wrote:
>> 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.
>>
>
> I moved incrementing of sb_nbio nearly after submit_bio(mode, bio). So,
> firstly, we call submit_bio(mode, bio) and segbuf->sb_nbio++. Then,
> because of asynchronous nature of nilfs_end_bio_write() call, we have
> two alternatives: (1) nilfs_end_bio_write() detects that BIO_EOPNOTSUPP
> flag is set; (2) BIO_EOPNOTSUPP flag isn't set because bio is not
> processed yet or we haven't error.
>
> If nilfs_end_bio_write() method would detect -EOPNOTSUPP error then it
> set BIO_EOPNOTSUPP flag, increment sb_err field and to call complete().
>
> So, if we detect that BIO_EOPNOTSUPP flag is set in
> nilfs_segbuf_submit_bio() then we decrement sb_nbio and to return from
> nilfs_segbuf_submit_bio() with error. And if we had submitted
> successfully some bios before then it will need to wait theirs
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.
In your patch, nilfs_end_bio_write() will call complete() even in the
case "(1) nilfs_end_bio_write() detects that BIO_EOPNOTSUPP flag is
set" (like the current implementation). Therefore, sb_nbio must be
incremented for that count.
This looks another issue of the current implemention and the second
bug can be fixed as follows:
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);
> By the way, why sb_err has atomic_t type but sb_nbio is simple int type?
> Maybe, sb_nbio should be atomic_t type too?
No, the current implementation is correct.
sb_err is incremented asynchronously by nilfs_end_bio_write(), so it
is implemented with atomic_t type. On the other hand, sb_nbio is
operated sequentially and therefore it doesn't need to use atomic_t
type.
Regards,
Ryusuke Konishi
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^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2013-08-12 14:57 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2013-07-26 13:59 [PATCH v2] nilfs2: remove double bio_put() in nilfs_end_bio_write() for BIO_EOPNOTSUPP error Vyacheslav Dubeyko
2013-07-27 3:02 ` Ryusuke Konishi
2013-07-31 10:36 ` Vyacheslav Dubeyko
[not found] ` <20130727.120232.356926182.konishi.ryusuke-Zyj7fXuS5i5L9jVzuh4AOg@public.gmane.org>
2013-08-12 13:16 ` Vyacheslav Dubeyko
2013-08-12 14:57 ` Ryusuke Konishi
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