Messages in this thread Patch in this message | | | Date | Sat, 12 Mar 2016 22:25:48 +0800 | From | Ming Lei <> | Subject | Re: e827091cb1 "block: merge: get the 1st and last bvec via helpers" broken |
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On Sat, 12 Mar 2016 05:02:56 -0900 Kent Overstreet <kent.overstreet@gmail.com> wrote:
> Here's the output of the patch below: > > generic/036 11s ...run fstests generic/036 at 2016-03-12 13:58:21 > end 4096 0 ffffea0001d611c0 end2 1024 0 ffffea0001d611c0 > len 1024 offset 0 page ffffea0001d611c0 > KGDB: Waiting for remote debugger > > Your code gives a biovec with bv_len of 4096, the old code gives a biovec with > bv_len of 1024 (and then we dump every biovec, we see that the bio had only a > single biovec that did indeed have bv_len == 1024).
I guess we shouldn't have optimized for the case of non-cloned bio, could you try the following patch?
-- diff --git a/include/linux/bio.h b/include/linux/bio.h index 1e7248f..4abc129 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -267,11 +267,6 @@ static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv) struct bvec_iter iter = bio->bi_iter; int idx; - if (!bio_flagged(bio, BIO_CLONED)) { - *bv = bio->bi_io_vec[bio->bi_vcnt - 1]; - return; - } - if (unlikely(!bio_multiple_segments(bio))) { *bv = bio_iovec(bio); return; Thanks, Ming
> > bio_get_last_bvec() is broken, please revert your patch for v4.5. > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 261353166d..231aec4fa3 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -318,6 +318,34 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, > bio_get_last_bvec(bio, &end_bv); > bio_get_first_bvec(nxt, &nxt_bv); > > + { > + struct bvec_iter iter; > + struct bio_vec end2, bv; > + > + bio_for_each_segment(end2, bio, iter) > + if (end2.bv_len == iter.bi_size) > + break; > + > + if (end_bv.bv_len != end2.bv_len || > + end_bv.bv_offset != end2.bv_offset || > + end_bv.bv_page != end2.bv_page) { > + printk(KERN_ERR "end %u %u %p end2 %u %u %p\n", > + end_bv.bv_len, > + end_bv.bv_offset, > + end_bv.bv_page, > + end2.bv_len, > + end2.bv_offset, > + end2.bv_page); > + > + bio_for_each_segment(bv, bio, iter) > + printk(KERN_ERR "len %u offset %u page %p\n", > + bv.bv_len, > + bv.bv_offset, > + bv.bv_page); > + BUG(); > + } > + } > + > if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv)) > return 0; >
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