From: Keith Busch <kbusch@xxxxxxxxxx> At LSFMM nearly 2 months ago, I discussed how some storage hardware supports the ability to read at granularities smaller than a sector, and the nvme protocol feature that enables this capability, "bit buckets". This is useful in scenarios where only parts of sectors are used by the application, and the primary benefits to support this are: * Improved link bandwidth usage * Reduced memory utilization This series enables the block layer and nvme to set up bit bucket descriptors for read commands, then enables user space direct-io to make use of this capability by allowing the user to specify an arbitrary offset and length. This allows truncating an arbitrary number of bytes off sectors from the front and end of the transfer. There are no current in-kernel users beyond the direct-io cases, but this could also be used for to truncate bytes out of the middle of a transfer as well. For example, if you wanted to read a page and knew you wer going to immediately dirty some number of bytes in the middle, you could set up a read request to skip those in the data transfer. Keith Busch (12): block: move direct io alignment check to common iomap: save copy of bdev for direct io iomap: get logical block size directly iomap: use common blkdev alignment check block: add bit bucket capabilities nvme: add support for bit buckets block: allow copying pre-registered bvecs block: add bio number of vecs helper for partials block: add partial sector parameter helper block: add direct-io partial sector read support iomap: add direct io partial sector read support block: export and document bit_bucket attribute Documentation/ABI/stable/sysfs-block | 9 +++ block/bio.c | 42 +++++++++++- block/blk-core.c | 5 ++ block/blk-merge.c | 3 +- block/blk-mq.c | 2 + block/blk-sysfs.c | 3 + block/fops.c | 97 ++++++++++++++++++---------- drivers/nvme/host/core.c | 3 + drivers/nvme/host/nvme.h | 6 ++ drivers/nvme/host/pci.c | 17 ++++- fs/iomap/direct-io.c | 43 ++++++++---- include/linux/bio.h | 11 ++++ include/linux/blk-mq.h | 2 + include/linux/blk_types.h | 1 + include/linux/blkdev.h | 41 ++++++++++++ include/linux/nvme.h | 2 + 16 files changed, 236 insertions(+), 51 deletions(-) -- 2.30.2
