linux/drivers/md/dm-writecache.c, branch v5.6

dm: bump version of core and various targets

2020-03-03T16:10:21Z

Changes made during the 5.6 cycle warrant bumping the version number for DM core and the targets modified by this commit. It should be noted that dm-thin, dm-crypt and dm-raid already had their target version bumped during the 5.6 merge window. Signed-off-by; Mike Snitzer

dm writecache: verify watermark during resume

2020-02-27T21:44:24Z

Verify the watermark upon resume - so that if the target is reloaded with lower watermark, it will start the cleanup process immediately. Fixes: 48debafe4f2f ("dm: add writecache target") Cc: stable@vger.kernel.org # 4.18+ Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm: report suspended device during destroy

2020-02-27T21:40:58Z

The function dm_suspended returns true if the target is suspended. However, when the target is being suspended during unload, it returns false. An example where this is a problem: the test "!dm_suspended(wc->ti)" in writecache_writeback is not sufficient, because dm_suspended returns zero while writecache_suspend is in progress. As is, without an enhanced dm_suspended, simply switching from flush_workqueue to drain_workqueue still emits warnings: workqueue writecache-writeback: drain_workqueue() isn't complete after 10 tries workqueue writecache-writeback: drain_workqueue() isn't complete after 100 tries workqueue writecache-writeback: drain_workqueue() isn't complete after 200 tries workqueue writecache-writeback: drain_workqueue() isn't complete after 300 tries workqueue writecache-writeback: drain_workqueue() isn't complete after 400 tries writecache_suspend calls flush_workqueue(wc->writeback_wq) - this function flushes the current work. However, the workqueue may re-queue itself and flush_workqueue doesn't wait for re-queued works to finish. Because of this - the function writecache_writeback continues execution after the device was suspended and then concurrently with writecache_dtr, causing a crash in writecache_writeback. We must use drain_workqueue - that waits until the work and all re-queued works finish. As a prereq for switching to drain_workqueue, this commit fixes dm_suspended to return true after the presuspend hook and before the postsuspend hook - just like during a normal suspend. It allows simplifying the dm-integrity and dm-writecache targets so that they don't have to maintain suspended flags on their own. With this change use of drain_workqueue() can be used effectively. This change was tested with the lvm2 testsuite and cryptsetup testsuite and the are no regressions. Fixes: 48debafe4f2f ("dm: add writecache target") Cc: stable@vger.kernel.org # 4.18+ Reported-by: Corey Marthaler Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm writecache: improve performance of large linear writes on SSDs

2020-01-16T18:34:17Z

When dm-writecache is used with SSD as a cache device, it would submit a separate bio for each written block. The I/Os would be merged by the disk scheduler, but this merging degrades performance. Improve dm-writecache performance by submitting larger bios - this is possible as long as there is consecutive free space on the cache device. Benchmark (arm64 with 64k page size, using /dev/ram0 as a cache device): fio --bs=512k --iodepth=32 --size=400M --direct=1 \ --filename=/dev/mapper/cache --rw=randwrite --numjobs=1 --name=test block old new size MiB/s MiB/s --------------------- 512 181 700 1k 347 1256 2k 644 2020 4k 1183 2759 8k 1852 3333 16k 2469 3509 32k 2974 3670 64k 3404 3810 Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm writecache: fix incorrect flush sequence when doing SSD mode commit

2020-01-15T01:22:48Z

When committing state, the function writecache_flush does the following: 1. write metadata (writecache_commit_flushed) 2. flush disk cache (writecache_commit_flushed) 3. wait for data writes to complete (writecache_wait_for_ios) 4. increase superblock seq_count 5. write the superblock 6. flush disk cache It may happen that at step 3, when we wait for some write to finish, the disk may report the write as finished, but the write only hit the disk cache and it is not yet stored in persistent storage. At step 5 we write the superblock - it may happen that the superblock is written before the write that we waited for in step 3. If the machine crashes, it may result in incorrect data being returned after reboot. In order to fix the bug, we must swap steps 2 and 3 in the above sequence, so that we first wait for writes to complete and then flush the disk cache. Fixes: 48debafe4f2f ("dm: add writecache target") Cc: stable@vger.kernel.org # 4.18+ Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm writecache: handle REQ_FUA

2019-11-05T19:21:40Z

Call writecache_flush() on REQ_FUA in writecache_map(). Cc: stable@vger.kernel.org # 4.18+ Signed-off-by: Maged Mokhtar Acked-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm writecache: fix uninitialized variable warning

2019-11-05T19:11:44Z

This fixes coverity warning CID 1454301. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm writecache: skip writecache_wait for pmem mode

2019-09-05T17:22:05Z

The array bio_in_progress[2] only have chance to be increased and decreased with ssd mode. For pmem mode, they are not involved at all. So skip writecache_wait_for_ios in writecache_flush for pmem. Suggested-by: Doris Yu Signed-off-by: Huaisheng Ye Acked-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm writecache: optimize performance by sorting the blocks for writeback_all

2019-08-26T14:59:00Z

During the process of writeback, the blocks, which have been placed in wbl.list for writeback soon, are partially ordered for the contiguous ones. When writeback_all has been set, for most cases, also by default, there will be a lot of blocks in pmem need to writeback at the same time. For this case, we could optimize the performance by sorting all blocks in wbl.list. writecache_writeback doesn't need to get blocks from the tail of wc->lru, whereas from the first rb_node from the rb_tree. The benefit is that, writecache_writeback doesn't need to have any cost to sort the blocks, because of all blocks are incremental originally in rb_tree. There will be a writecache_flush when writeback_all begins to work, that will eliminate duplicate blocks in cache by committed/uncommitted. Testing platform: Thinksystem SR630 with persistent memory. The cache comes from pmem, which has 1006MB size. The origin device is HDD, 2GB of which for using. Testing steps: 1) dmsetup create mycache --table '0 4194304 writecache p /dev/sdb1 /dev/pmem4 4096 0' 2) fio -filename=/dev/mapper/mycache -direct=1 -iodepth=20 -rw=randwrite -ioengine=libaio -bs=4k -loops=1 -size=2g -group_reporting -name=mytest1 3) time dmsetup message /dev/mapper/mycache 0 flush Here is the results below, With the patch: # fio -filename=/dev/mapper/mycache -direct=1 -iodepth=20 -rw=randwrite -ioengine=libaio -bs=4k -loops=1 -size=2g -group_reporting -name=mytest1 iops : min= 1582, max=199470, avg=5305.94, stdev=21273.44, samples=197 # time dmsetup message /dev/mapper/mycache 0 flush real 0m44.020s user 0m0.002s sys 0m0.003s Without the patch: # fio -filename=/dev/mapper/mycache -direct=1 -iodepth=20 -rw=randwrite -ioengine=libaio -bs=4k -loops=1 -size=2g -group_reporting -name=mytest1 iops : min= 1202, max=197650, avg=4968.67, stdev=20480.17, samples=211 # time dmsetup message /dev/mapper/mycache 0 flush real 1m39.221s user 0m0.001s sys 0m0.003s I also have checked the data accuracy with this patch by making EXT4 filesystem on mycache, then mount it for checking md5 of files on that. The test result is positive, with this patch it could save more than half of time when writeback_all. Signed-off-by: Huaisheng Ye Signed-off-by: Mike Snitzer

dm writecache: add unlikely for getting two block with same LBA

2019-08-26T14:54:41Z

In function writecache_writeback, entries g and f has same original sector only happens at entry f has been committed, but entry g has NOT yet. The probability of this happening is very low in the following 256 blocks at most of entry e. Signed-off-by: Huaisheng Ye Acked-by: Mikulas Patocka Signed-off-by: Mike Snitzer