Hi, This patchset brings multipage bvec into block layer. Basic xfstests(-a auto) over virtio-blk/virtio-scsi have been run and no regression is found, so it should be good enough to show the approach now, and any comments are welcome! 1) what is multipage bvec? Multipage bvecs means that one 'struct bio_bvec' can hold multiple pages which are physically contiguous instead of one single page used in linux kernel for long time. 2) why is multipage bvec introduced? Kent proposed the idea[1] first. As system's RAM becomes much bigger than before, and at the same time huge page, transparent huge page and memory compaction are widely used, it is a bit easy now to see physically contiguous pages inside fs/block stack. On the other hand, from block layer's view, it isn't necessary to store intermediate pages into bvec, and it is enough to just store the physicallly contiguous 'segment'. Also huge pages are being brought to filesystem[2], we can do IO a hugepage a time[3], requires that one bio can transfer at least one huge page one time. Turns out it isn't flexiable to change BIO_MAX_PAGES simply[3]. Multipage bvec can fit in this case very well. With multipage bvec: - bio size can be increased and it should improve some high-bandwidth IO case in theory[4]. - Inside block layer, both bio splitting and sg map can become more efficient than before by just traversing the physically contiguous 'segment' instead of each page. - there is possibility in future to improve memory footprint of bvecs usage. 3) how is multipage bvec implemented in this patchset? The 1st 22 patches cleanup on direct access to bvec table, and comments on some special cases. With this approach, most of cases are found as safe for multipage bvec, only fs/buffer, pktcdvd, dm-io, MD and btrfs need to deal with. Given a little more work is involved to cleanup pktcdvd, MD and btrfs, this patchset introduces QUEUE_FLAG_NO_MP for them, and these components can still see/use singlepage bvec. In the future, once the cleanup is done, the flag can be killed. The 2nd part(23 ~ 60) implements multipage bvec in block: - put all tricks into bvec/bio/rq iterators, and as far as drivers and fs use these standard iterators, they are happy with multipage bvec - bio_for_each_segment_all() changes this helper pass pointer of each bvec directly to user, and it has to be changed. Two new helpers(bio_for_each_segment_all_rd() and bio_for_each_segment_all_wt()) are introduced. - bio_clone() changes At default bio_clone still clones one new bio in multipage bvec way. Also single page version of bio_clone() is introduced for some special cases, such as only single page bvec is used for the new cloned bio(bio bounce, ...) These patches can be found in the following git tree: https://github.com/ming1/linux/tree/mp-bvec-0.3-v4.9 Thanks Christoph for looking at the early version and providing very good suggestions, such as: introduce bio_init_with_vec_table(), remove another unnecessary helpers for cleanup and so on. TODO: - cleanup direct access to bvec table for MD & btrfs [1], http://marc.info/?l=linux-kernel&m=141680246629547&w=2 [2], http://lwn.net/Articles/700781/ [3], http://marc.info/?t=147735447100001&r=1&w=2 [4], http://marc.info/?l=linux-mm&m=147745525801433&w=2 Ming Lei (60): block: bio: introduce bio_init_with_vec_table() block drivers: convert to bio_init_with_vec_table() block: drbd: remove impossible failure handling block: floppy: use bio_add_page() target: avoid to access .bi_vcnt directly bcache: debug: avoid to access .bi_io_vec directly dm: crypt: use bio_add_page() dm: use bvec iterator helpers to implement .get_page and .next_page dm: dm.c: replace 'bio->bi_vcnt == 1' with !bio_multiple_segments fs: logfs: convert to bio_add_page() in sync_request() fs: logfs: use bio_add_page() in __bdev_writeseg() fs: logfs: use bio_add_page() in do_erase() fs: logfs: remove unnecesary check block: drbd: comment on direct access bvec table block: loop: comment on direct access to bvec table block: pktcdvd: comment on direct access to bvec table kernel/power/swap.c: comment on direct access to bvec table mm: page_io.c: comment on direct access to bvec table fs/buffer: comment on direct access to bvec table f2fs: f2fs_read_end_io: comment on direct access to bvec table bcache: comment on direct access to bvec table block: comment on bio_alloc_pages() block: introduce flag QUEUE_FLAG_NO_MP md: set NO_MP for request queue of md block: pktcdvd: set NO_MP for pktcdvd request queue btrfs: set NO_MP for request queues behind BTRFS block: introduce BIO_SP_MAX_SECTORS block: introduce QUEUE_FLAG_SPLIT_MP dm: limit the max bio size as BIO_SP_MAX_SECTORS << SECTOR_SHIFT bcache: set flag of QUEUE_FLAG_SPLIT_MP block: introduce multipage/single page bvec helpers block: implement sp version of bvec iterator helpers block: introduce bio_for_each_segment_mp() block: introduce bio_clone_sp() bvec_iter: introduce BVEC_ITER_ALL_INIT block: bounce: avoid direct access to bvec from bio->bi_io_vec block: bounce: don't access bio->bi_io_vec in copy_to_high_bio_irq block: bounce: convert multipage bvecs into singlepage bcache: debug: switch to bio_clone_sp() blk-merge: compute bio->bi_seg_front_size efficiently block: blk-merge: try to make front segments in full size block: use bio_for_each_segment_mp() to compute segments count block: use bio_for_each_segment_mp() to map sg block: introduce bvec_for_each_sp_bvec() block: bio: introduce bio_for_each_segment_all_rd() and its write pair block: deal with dirtying pages for multipage bvec block: convert to bio_for_each_segment_all_rd() fs/mpage: convert to bio_for_each_segment_all_rd() fs/direct-io: convert to bio_for_each_segment_all_rd() ext4: convert to bio_for_each_segment_all_rd() xfs: convert to bio_for_each_segment_all_rd() logfs: convert to bio_for_each_segment_all_rd() gfs2: convert to bio_for_each_segment_all_rd() f2fs: convert to bio_for_each_segment_all_rd() exofs: convert to bio_for_each_segment_all_rd() fs: crypto: convert to bio_for_each_segment_all_rd() bcache: convert to bio_for_each_segment_all_rd() dm-crypt: convert to bio_for_each_segment_all_rd() fs/buffer.c: use bvec iterator to truncate the bio block: enable multipage bvecs block/bio.c | 104 ++++++++++++++---- block/blk-merge.c | 216 +++++++++++++++++++++++++++++-------- block/bounce.c | 80 ++++++++++---- drivers/block/drbd/drbd_bitmap.c | 1 + drivers/block/drbd/drbd_receiver.c | 14 +-- drivers/block/floppy.c | 10 +- drivers/block/loop.c | 5 + drivers/block/pktcdvd.c | 8 ++ drivers/md/bcache/btree.c | 4 +- drivers/md/bcache/debug.c | 19 +++- drivers/md/bcache/io.c | 4 +- drivers/md/bcache/journal.c | 4 +- drivers/md/bcache/movinggc.c | 7 +- drivers/md/bcache/super.c | 25 +++-- drivers/md/bcache/util.c | 7 ++ drivers/md/bcache/writeback.c | 6 +- drivers/md/dm-bufio.c | 4 +- drivers/md/dm-crypt.c | 11 +- drivers/md/dm-io.c | 34 ++++-- drivers/md/dm-rq.c | 3 +- drivers/md/dm.c | 11 +- drivers/md/md.c | 12 +++ drivers/md/raid5.c | 9 +- drivers/nvme/target/io-cmd.c | 4 +- drivers/target/target_core_pscsi.c | 8 +- fs/btrfs/volumes.c | 3 + fs/buffer.c | 24 +++-- fs/crypto/crypto.c | 3 +- fs/direct-io.c | 4 +- fs/exofs/ore.c | 3 +- fs/exofs/ore_raid.c | 3 +- fs/ext4/page-io.c | 3 +- fs/ext4/readpage.c | 3 +- fs/f2fs/data.c | 13 ++- fs/gfs2/lops.c | 3 +- fs/gfs2/meta_io.c | 3 +- fs/logfs/dev_bdev.c | 110 +++++++------------ fs/mpage.c | 3 +- fs/xfs/xfs_aops.c | 3 +- include/linux/bio.h | 108 +++++++++++++++++-- include/linux/blk_types.h | 6 ++ include/linux/blkdev.h | 4 + include/linux/bvec.h | 123 +++++++++++++++++++-- kernel/power/swap.c | 2 + mm/page_io.c | 1 + 45 files changed, 759 insertions(+), 276 deletions(-) -- 2.7.4 -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
