On Thu, May 29, 2014 at 1:21 AM, Maurizio Lombardi <mlomb...@redhat.com> wrote: > Hi Ming, > > On Thu, May 29, 2014 at 12:59:19AM +0800, Ming Lei wrote: >> >> 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? >> >> [1], https://lkml.org/lkml/2014/5/27/327 > > There is a little mistake in your patch, you removed bio->bi_iter.bi_size += > len; > after the "done" label, > but be careful that at line 747 there is a "goto done"... bi_size should be > incremented > before jumping there.
Good catch, thanks Maurizio. Jet, please test the attached patch in this mail and ignore previous one. The story behind the patch should be like below: - one page is added in __bio_add_page() 'successfully', and bio->bi_phys_segments is equal to queue_max_segments(q), but it should have been rejected since the last vector isn't covered - next time, __bio_add_page() is called to add one page, but this time blk_recount_segments() can figure out the actual physical segments and find it is more than max segments, so failure is triggered, but the bio->bi_phys_segments is updated with max segments plus one - the oops is triggered and reported by Jet, :-) Thanks, -- Ming Lei
diff --git a/block/bio.c b/block/bio.c index 0443694..f9bae56 100644 --- a/block/bio.c +++ b/block/bio.c @@ -744,6 +744,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page } } + bio->bi_iter.bi_size += len; goto done; } } @@ -761,6 +762,7 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page bvec->bv_offset = offset; bio->bi_vcnt++; bio->bi_phys_segments++; + bio->bi_iter.bi_size += len; /* * Perform a recount if the number of segments is greater @@ -802,7 +804,6 @@ static int __bio_add_page(struct request_queue *q, struct bio *bio, struct page bio->bi_flags &= ~(1 << BIO_SEG_VALID); done: - bio->bi_iter.bi_size += len; return len; failed: @@ -810,6 +811,7 @@ 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; blk_recount_segments(q, bio); return 0; }
