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 v5: - Rebased the entire series on top of the block layer for-next branch. - Dropped patch "block: Add support for small segments in blk_rq_map_user_iov()" because that patch prepares for a patch that has already been dropped. - Modified a source code comment in patch 3/9 such that it fits in 80 columns. Changes compared to v4: - Fixed the debugfs patch such that the behavior for creating the block debugfs directory is retained. - Made the description of patch "Support configuring limits below the page size" more detailed. Split that patch into two patches. - Added patch "Use pr_info() instead of printk(KERN_INFO ...)". 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 (8): block: Use pr_info() instead of printk(KERN_INFO ...) block: Prepare for supporting sub-page limits block: Support configuring limits below the page size block: Make sub_page_limit_queues available in debugfs block: Support submitting passthrough requests with small segments block: Add support for filesystem requests and small segments 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 | 2 +- block/blk-merge.c | 8 ++- block/blk-mq-debugfs.c | 9 +++ block/blk-mq-debugfs.h | 6 ++ block/blk-mq.c | 2 + block/blk-settings.c | 91 +++++++++++++++++++++++++++---- 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, 163 insertions(+), 24 deletions(-)
