Messages in this thread | | | Date | Thu, 29 May 2014 12:13:16 +0800 | Subject | Re: [PATCH] bio: decrease bi_iter.bi_size by len in the fail path | From | Ming Lei <> |
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On Thu, May 29, 2014 at 11:35 AM, Jet Chen <jet.chen@intel.com> wrote: > On 05/29/2014 12:59 AM, Ming Lei wrote: >> On Wed, May 28, 2014 at 11:42 PM, Ming Lei <tom.leiming@gmail.com> wrote: >>> Hi Dongsu, >>> >>> On Wed, May 28, 2014 at 11:09 PM, Dongsu Park >>> <dongsu.park@profitbricks.com> wrote: >>>> From: Dongsu Park <dongsu.park@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 <axboe@kernel.dk> >>>> Cc: Jet Chen <jet.chen@intel.com> >>>> Cc: Maurizio Lombardi <mlombard@redhat.com> >>>> Signed-off-by: Dongsu Park <dongsu.park@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
Firstly, dongsu's patch is wrong, and it doesn't make sense to test that.
Secondly, it is the patch attached in my last email, and the name is 'fix_compute_segments.patch'.
Please let me know if you can find the patch, if you still can't, I may resend to you.
Thanks, -- Ming Lei
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