| Message ID | 20181115085306.9910-5-ming.lei@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | block: support multi-page bvec | expand |
On Thu, Nov 15, 2018 at 04:52:51PM +0800, Ming Lei wrote: > It is more efficient to use bio_for_each_bvec() to map sg, meantime > we have to consider splitting multipage bvec as done in blk_bio_segment_split(). > > Cc: Dave Chinner <dchinner@redhat.com> > Cc: Kent Overstreet <kent.overstreet@gmail.com> > Cc: Mike Snitzer <snitzer@redhat.com> > Cc: dm-devel@redhat.com > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > Cc: linux-fsdevel@vger.kernel.org > Cc: Shaohua Li <shli@kernel.org> > Cc: linux-raid@vger.kernel.org > Cc: linux-erofs@lists.ozlabs.org > Cc: David Sterba <dsterba@suse.com> > Cc: linux-btrfs@vger.kernel.org > Cc: Darrick J. Wong <darrick.wong@oracle.com> > Cc: linux-xfs@vger.kernel.org > Cc: Gao Xiang <gaoxiang25@huawei.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Theodore Ts'o <tytso@mit.edu> > Cc: linux-ext4@vger.kernel.org > Cc: Coly Li <colyli@suse.de> > Cc: linux-bcache@vger.kernel.org > Cc: Boaz Harrosh <ooo@electrozaur.com> > Cc: Bob Peterson <rpeterso@redhat.com> > Cc: cluster-devel@redhat.com Reviewed-by: Omar Sandoval <osandov@fb.com> > Signed-off-by: Ming Lei <ming.lei@redhat.com> > --- > block/blk-merge.c | 72 +++++++++++++++++++++++++++++++++++++++---------------- > 1 file changed, 52 insertions(+), 20 deletions(-) > > diff --git a/block/blk-merge.c b/block/blk-merge.c > index 6f7deb94a23f..cb9f49bcfd36 100644 > --- a/block/blk-merge.c > +++ b/block/blk-merge.c > @@ -473,6 +473,56 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, > return biovec_phys_mergeable(q, &end_bv, &nxt_bv); > } > > +static struct scatterlist *blk_next_sg(struct scatterlist **sg, > + struct scatterlist *sglist) > +{ > + if (!*sg) > + return sglist; > + else { > + /* > + * If the driver previously mapped a shorter > + * list, we could see a termination bit > + * prematurely unless it fully inits the sg > + * table on each mapping. We KNOW that there > + * must be more entries here or the driver > + * would be buggy, so force clear the > + * termination bit to avoid doing a full > + * sg_init_table() in drivers for each command. > + */ > + sg_unmark_end(*sg); > + return sg_next(*sg); > + } > +} > + > +static unsigned blk_bvec_map_sg(struct request_queue *q, > + struct bio_vec *bvec, struct scatterlist *sglist, > + struct scatterlist **sg) > +{ > + unsigned nbytes = bvec->bv_len; > + unsigned nsegs = 0, total = 0; > + > + while (nbytes > 0) { > + unsigned seg_size; > + struct page *pg; > + unsigned offset, idx; > + > + *sg = blk_next_sg(sg, sglist); > + > + seg_size = min(nbytes, queue_max_segment_size(q)); > + offset = (total + bvec->bv_offset) % PAGE_SIZE; > + idx = (total + bvec->bv_offset) / PAGE_SIZE; > + pg = nth_page(bvec->bv_page, idx); > + > + sg_set_page(*sg, pg, seg_size, offset); > + > + total += seg_size; > + nbytes -= seg_size; > + nsegs++; > + } > + > + return nsegs; > +} > + > static inline void > __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, > struct scatterlist *sglist, struct bio_vec *bvprv, > @@ -490,25 +540,7 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, > (*sg)->length += nbytes; > } else { > new_segment: > - if (!*sg) > - *sg = sglist; > - else { > - /* > - * If the driver previously mapped a shorter > - * list, we could see a termination bit > - * prematurely unless it fully inits the sg > - * table on each mapping. We KNOW that there > - * must be more entries here or the driver > - * would be buggy, so force clear the > - * termination bit to avoid doing a full > - * sg_init_table() in drivers for each command. > - */ > - sg_unmark_end(*sg); > - *sg = sg_next(*sg); > - } > - > - sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); > - (*nsegs)++; > + (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg); > } > *bvprv = *bvec; > } > @@ -530,7 +562,7 @@ static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, > int cluster = blk_queue_cluster(q), nsegs = 0; > > for_each_bio(bio) > - bio_for_each_segment(bvec, bio, iter) > + bio_for_each_bvec(bvec, bio, iter) > __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, > &nsegs, &cluster); > > -- > 2.9.5 >
> + if (!*sg) > + return sglist; > + else { No need for an else after an early return.
On Fri, Nov 16, 2018 at 02:33:14PM +0100, Christoph Hellwig wrote: > > + if (!*sg) > > + return sglist; > > + else { > > No need for an else after an early return. OK, good catch! Thanks, Ming
diff --git a/block/blk-merge.c b/block/blk-merge.c index 6f7deb94a23f..cb9f49bcfd36 100644 --- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -473,6 +473,56 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio, return biovec_phys_mergeable(q, &end_bv, &nxt_bv); } +static struct scatterlist *blk_next_sg(struct scatterlist **sg, + struct scatterlist *sglist) +{ + if (!*sg) + return sglist; + else { + /* + * If the driver previously mapped a shorter + * list, we could see a termination bit + * prematurely unless it fully inits the sg + * table on each mapping. We KNOW that there + * must be more entries here or the driver + * would be buggy, so force clear the + * termination bit to avoid doing a full + * sg_init_table() in drivers for each command. + */ + sg_unmark_end(*sg); + return sg_next(*sg); + } +} + +static unsigned blk_bvec_map_sg(struct request_queue *q, + struct bio_vec *bvec, struct scatterlist *sglist, + struct scatterlist **sg) +{ + unsigned nbytes = bvec->bv_len; + unsigned nsegs = 0, total = 0; + + while (nbytes > 0) { + unsigned seg_size; + struct page *pg; + unsigned offset, idx; + + *sg = blk_next_sg(sg, sglist); + + seg_size = min(nbytes, queue_max_segment_size(q)); + offset = (total + bvec->bv_offset) % PAGE_SIZE; + idx = (total + bvec->bv_offset) / PAGE_SIZE; + pg = nth_page(bvec->bv_page, idx); + + sg_set_page(*sg, pg, seg_size, offset); + + total += seg_size; + nbytes -= seg_size; + nsegs++; + } + + return nsegs; +} + static inline void __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, struct scatterlist *sglist, struct bio_vec *bvprv, @@ -490,25 +540,7 @@ __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec, (*sg)->length += nbytes; } else { new_segment: - if (!*sg) - *sg = sglist; - else { - /* - * If the driver previously mapped a shorter - * list, we could see a termination bit - * prematurely unless it fully inits the sg - * table on each mapping. We KNOW that there - * must be more entries here or the driver - * would be buggy, so force clear the - * termination bit to avoid doing a full - * sg_init_table() in drivers for each command. - */ - sg_unmark_end(*sg); - *sg = sg_next(*sg); - } - - sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset); - (*nsegs)++; + (*nsegs) += blk_bvec_map_sg(q, bvec, sglist, sg); } *bvprv = *bvec; } @@ -530,7 +562,7 @@ static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, int cluster = blk_queue_cluster(q), nsegs = 0; for_each_bio(bio) - bio_for_each_segment(bvec, bio, iter) + bio_for_each_bvec(bvec, bio, iter) __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg, &nsegs, &cluster);
It is more efficient to use bio_for_each_bvec() to map sg, meantime we have to consider splitting multipage bvec as done in blk_bio_segment_split(). Cc: Dave Chinner <dchinner@redhat.com> Cc: Kent Overstreet <kent.overstreet@gmail.com> Cc: Mike Snitzer <snitzer@redhat.com> Cc: dm-devel@redhat.com Cc: Alexander Viro <viro@zeniv.linux.org.uk> Cc: linux-fsdevel@vger.kernel.org Cc: Shaohua Li <shli@kernel.org> Cc: linux-raid@vger.kernel.org Cc: linux-erofs@lists.ozlabs.org Cc: David Sterba <dsterba@suse.com> Cc: linux-btrfs@vger.kernel.org Cc: Darrick J. Wong <darrick.wong@oracle.com> Cc: linux-xfs@vger.kernel.org Cc: Gao Xiang <gaoxiang25@huawei.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Theodore Ts'o <tytso@mit.edu> Cc: linux-ext4@vger.kernel.org Cc: Coly Li <colyli@suse.de> Cc: linux-bcache@vger.kernel.org Cc: Boaz Harrosh <ooo@electrozaur.com> Cc: Bob Peterson <rpeterso@redhat.com> Cc: cluster-devel@redhat.com Signed-off-by: Ming Lei <ming.lei@redhat.com> --- block/blk-merge.c | 72 +++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 52 insertions(+), 20 deletions(-)