Hello, This patchset replaces the current barrier implementation with sequenced flush which doesn't impose any restriction on ordering around the flush requests. This patchst is result of the following discussion thread. http://thread.gmane.org/gmane.linux.file-systems/43877 In summary, filesystems can take over the ordering of requests around commit writes and the block layer should just supply a mechanism to perform the commit writes themselves. This would greatly lessen tha stall caused by queue dumping and draining used by the current barrier implementation for request ordering. This patchset converts barrier mechanism to sequenced flush/fua mechanism in the following steps. 1. Kill the mostly unused ORDERED_BY_TAG support. 2. Deprecate REQ_HARDBARRIER support. All hard barrier requests are failed with -EOPNOTSUPP. 3. Drop barrier ordering by queue draining mechanism. 4. Rename barrier to flush and implement new interface based on REQ_FLUSH and REQ_FUA as suggested by Christoph. blkdev_issue_flush() is converted to use the new mechanism but all the filesystems still use the deprecated REQ_HARDBARRIER which always fails. Each filesystem needs to be updated to enforce request ordering themselves and then to use REQ_FLUSH/FUA mechanism. loop, md, dm, etc... haven't been converted yet and REQ_FLUSH/FUA doesn't work with them yet. I'll convert most of them soonish if this patchset is generally agreed upon. This patchset contains the following patches. 0001-block-loop-queue-ordered-mode-should-be-DRAIN_FLUSH.patch 0002-block-kill-QUEUE_ORDERED_BY_TAG.patch 0003-block-deprecate-barrier-and-replace-blk_queue_ordere.patch 0004-block-remove-spurious-uses-of-REQ_HARDBARRIER.patch 0005-block-misc-cleanups-in-barrier-code.patch 0006-block-drop-barrier-ordering-by-queue-draining.patch 0007-block-rename-blk-barrier.c-to-blk-flush.c.patch 0008-block-rename-barrier-ordered-to-flush.patch 0009-block-implement-REQ_FLUSH-FUA-based-interface-for-FL.patch 0010-fs-block-propagate-REQ_FLUSH-FUA-interface-to-upper-.patch 0011-block-use-REQ_FLUSH-in-blkdev_issue_flush.patch and is also available in the following git tree. git://git.kernel.org/pub/scm/linux/kernel/git/tj/misc.git flush-fua and contains the following changes. block/Makefile | 2 block/blk-barrier.c | 350 ------------------------------------ block/blk-core.c | 55 ++--- block/blk-flush.c | 248 +++++++++++++++++++++++++ block/blk-settings.c | 20 ++ block/blk.h | 8 block/elevator.c | 79 -------- drivers/block/brd.c | 1 drivers/block/loop.c | 2 drivers/block/osdblk.c | 5 drivers/block/pktcdvd.c | 1 drivers/block/ps3disk.c | 2 drivers/block/virtio_blk.c | 34 --- drivers/block/xen-blkfront.c | 47 +--- drivers/ide/ide-disk.c | 13 - drivers/md/dm.c | 2 drivers/mmc/card/queue.c | 1 drivers/s390/block/dasd.c | 1 drivers/scsi/aic7xxx_old.c | 21 -- drivers/scsi/libsas/sas_scsi_host.c | 13 - drivers/scsi/sd.c | 18 - fs/buffer.c | 27 +- include/linux/blk_types.h | 4 include/linux/blkdev.h | 73 +------ include/linux/buffer_head.h | 8 include/linux/fs.h | 20 +- include/scsi/scsi_tcq.h | 6 27 files changed, 402 insertions(+), 659 deletions(-) Thanks. -- tejun -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
