Hi Jens, We want to improve Android performance by increasing the page size from 4 KiB to 16 KiB. However, some of the storage controllers we care about do not support DMA segments larger than 4 KiB. Hence the need support for DMA segments that are smaller than the size of one virtual memory page. This patch series implements that support. Please consider this patch series for the next merge window. Thanks, Bart. Changes compared to v3: - Removed CONFIG_BLK_SUB_PAGE_SEGMENTS and QUEUE_FLAG_SUB_PAGE_SEGMENTS. Replaced these by a new member in struct queue_limits and a static branch. - The static branch that controls whether or not sub-page limits are enabled is set by the block layer core instead of by block drivers. - Dropped the patches that are no longer needed (SCSI core and UFS Exynos driver). Changes compared to v2: - For SCSI drivers, only set flag QUEUE_FLAG_SUB_PAGE_SEGMENTS if necessary. - In the scsi_debug patch, sorted kernel module parameters alphabetically. Only set flag QUEUE_FLAG_SUB_PAGE_SEGMENTS if necessary. - Added a patch for the UFS Exynos driver that enables CONFIG_BLK_SUB_PAGE_SEGMENTS if the page size exceeds 4 KiB. Changes compared to v1: - Added a CONFIG variable that controls whether or not small segment support is enabled. - Improved patch descriptions. Bart Van Assche (7): block: Introduce blk_mq_debugfs_init() block: Support configuring limits below the page size block: Support submitting passthrough requests with small segments block: Add support for filesystem requests and small segments block: Add support for small segments in blk_rq_map_user_iov() scsi_debug: Support configuring the maximum segment size null_blk: Support configuring the maximum segment size block/blk-core.c | 4 +- block/blk-map.c | 29 ++++++++--- block/blk-merge.c | 7 ++- block/blk-mq-debugfs.c | 10 ++++ block/blk-mq-debugfs.h | 6 +++ block/blk-mq.c | 2 + block/blk-settings.c | 82 ++++++++++++++++++++++++++++--- block/blk.h | 39 ++++++++++++--- drivers/block/null_blk/main.c | 19 +++++-- drivers/block/null_blk/null_blk.h | 1 + drivers/scsi/scsi_debug.c | 4 ++ include/linux/blkdev.h | 2 + 12 files changed, 179 insertions(+), 26 deletions(-)
