On 05/29/2014 12:59 AM, Ming Lei wrote:
> On Wed, May 28, 2014 at 11:42 PM, Ming Lei <tom.leim...@gmail.com> wrote:
>> Hi Dongsu,
>>
>> On Wed, May 28, 2014 at 11:09 PM, Dongsu Park
>> <dongsu.p...@profitbricks.com> wrote:
>>> From: Dongsu Park <dongsu.p...@profitbricks.com>
>>>
>>> Commit 3979ef4dcf3d1de55a560a3a4016c30a835df44d ("bio-modify-
>>> __bio_add_page-to-accept-pages-that-dont-start-a-new-segment-v3")
>>> introduced a regression as reported by Jet Chen.
>>> That results in a kernel BUG at drivers/block/virtio_blk.c:166.
>>>
>>> To fix that, bi_iter.bi_size must be decreased by len, before
>>> recounting the number of physical segments.
>>>
>>> Tested on with kernel 3.15.0-rc7-next-20140527 on qemu guest,
>>> by running xfstests/ext4/271.
>>>
>>> Cc: Jens Axboe <ax...@kernel.dk>
>>> Cc: Jet Chen <jet.c...@intel.com>
>>> Cc: Maurizio Lombardi <mlomb...@redhat.com>
>>> Signed-off-by: Dongsu Park <dongsu.p...@profitbricks.com>
>>> ---
>>> block/bio.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/block/bio.c b/block/bio.c
>>> index 0443694ccbb4..67d7cba1e5fd 100644
>>> --- a/block/bio.c
>>> +++ b/block/bio.c
>>> @@ -810,6 +810,7 @@ static int __bio_add_page(struct request_queue *q,
>>> struct bio *bio, struct page
>>> bvec->bv_len = 0;
>>> bvec->bv_offset = 0;
>>> bio->bi_vcnt--;
>>> + bio->bi_iter.bi_size -= len;
>>
>> Would you mind explaining why bi_iter.bi_size need to be
>> decreased by 'len'? In the failure path, it wasn't added by
>> 'len', was it?
>
> Actually, the correct thing may be like what did in the
> attached patch, as Maurizio discussed with me[1].
>
> Very interestingly, I have reproduced the problem one time
> with ext4/271 ext4/301 ext4/305, but won't with the attached
> patch after running it for 3 rounds.
>
> [tom@localhost xfstests]$ sudo ./check ext4/271 ext4/301 ext4/305
> FSTYP -- ext4
> PLATFORM -- Linux/x86_64 localhost 3.15.0-rc7-next-20140527+
> MKFS_OPTIONS -- /dev/vdc
> MOUNT_OPTIONS -- -o acl,user_xattr /dev/vdc /mnt/scratch
>
> ext4/271 1s ... 1s
> ext4/301 31s ... 32s
> ext4/305 181s ... 180s
> Ran: ext4/271 ext4/301 ext4/305
> Passed all 3 tests
>
> Jet, could you test the attached patch?
sorry, could you specify which patch need me to test ?
actually I got confused. I only find
[PATCH V3] bio: modify __bio_add_page() to accept pages that don't
start a new segment
in this mail thread. is it need to be tested ?
on next/master branch,
commit 3979ef4dcf3d1de55a560a3a4016c30a835df44d
Author: Maurizio Lombardi <mlomb...@redhat.com>
Date: Sat May 17 23:17:30 2014 +1000
bio-modify-__bio_add_page-to-accept-pages-that-dont-start-a-new-segment-v3
Changes in V3:
In case of error, V2 restored the previous number of segments but left
the BIO_SEG_FLAG set.
To avoid problems, after the page is removed from the bio vec,
V3 performs a recount of the segments in the error code path.
Signed-off-by: Maurizio Lombardi <mlomb...@redhat.com>
Cc: Al Viro <v...@zeniv.linux.org.uk>
Cc: Christoph Hellwig <h...@lst.de>
Cc: Kent Overstreet <k...@daterainc.com>
Cc: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Andrew Morton <a...@linux-foundation.org>
commit fceb38f36f4fecabf9ca33aa44a3f943f133cb78
Author: Maurizio Lombardi <mlomb...@redhat.com>
Date: Sat May 17 23:17:30 2014 +1000
bio: modify __bio_add_page() to accept pages that don't start a new segment
The original behaviour is to refuse to add a new page if the maximum
number of segments has been reached, regardless of the fact the page we
3979ef4dcf3d1de55a560a3a4016c30a835df44d is the first bad commit.
>
> [1], https://lkml.org/lkml/2014/5/27/327
>
>
> Thanks,
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
