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4ad8d880b6
linux/drivers/md
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Nikos Tsironis 4ad8d880b6 dm snapshot: Replace mutex with rw semaphore 
dm-snapshot uses a single mutex to serialize every access to the
snapshot state. This includes all accesses to the complete and pending
exception tables, which occur at every origin write, every snapshot
read/write and every exception completion.

The lock statistics indicate that this mutex is a bottleneck (average
wait time ~480 usecs for 8 processes doing random 4K writes to the
origin device) preventing dm-snapshot to scale as the number of threads
doing IO increases.

The major contention points are __origin_write()/snapshot_map() and
pending_complete(), i.e., the submission and completion of pending
exceptions.

Replace this mutex with a rw semaphore.

We essentially revert commit ae1093be5a ("dm snapshot: use mutex
instead of rw_semaphore") and together with the next two patches we
substitute the single mutex with a fine-grained locking scheme, where we
use a read-write semaphore to protect the mostly read fields of the
snapshot structure, e.g., valid, active, etc., and per-bucket bit
spinlocks to protect accesses to the complete and pending exception
tables.

Co-developed-by: Ilias Tsitsimpis <iliastsi@arrikto.com>
Signed-off-by: Nikos Tsironis <ntsironis@arrikto.com>
Acked-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2019-04-18 16:18:28 -04:00
..
bcache block: allow bio_for_each_segment_all() to iterate over multi-page bvec 2019-02-15 08:40:11 -07:00
persistent-data dm block manager: remove redundant unlikely annotation 2019-03-05 14:53:48 -05:00
dm-bio-prison-v1.c dm: adjust structure members to improve alignment 2018-06-08 11:53:14 -04:00
dm-bio-prison-v1.h
dm-bio-prison-v2.c dm: adjust structure members to improve alignment 2018-06-08 11:53:14 -04:00
dm-bio-prison-v2.h
dm-bio-record.h block: replace bi_bdev with a gendisk pointer and partitions index 2017-08-23 12:49:55 -06:00
dm-bufio.c Merge branch 'akpm' (patches from Andrew) 2018-12-28 16:55:46 -08:00
dm-builtin.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dm-cache-background-tracker.c dm cache background tracker: fix sparse warning 2018-04-30 15:40:40 -04:00
dm-cache-background-tracker.h
dm-cache-block-types.h
dm-cache-metadata.c dm cache metadata: Fix loading discard bitset 2019-04-18 16:18:25 -04:00
dm-cache-metadata.h
dm-cache-policy-internal.h
dm-cache-policy-smq.c dm: remove unnecessary unlikely() around WARN_ON_ONCE() 2018-10-16 14:34:59 -04:00
dm-cache-policy.c
dm-cache-policy.h
dm-cache-target.c dm cache: add support for discard passdown to the origin device 2019-03-05 14:53:52 -05:00
dm-core.h dm: disable DISCARD if the underlying storage no longer supports it 2019-04-04 15:33:59 -04:00
dm-crypt.c dm crypt: fix endianness annotations around org_sector_of_dmreq 2019-04-18 16:16:01 -04:00
dm-delay.c dm: Check for device sector overflow if CONFIG_LBDAF is not set 2018-12-18 09:02:26 -05:00
dm-era-target.c dm: allow targets to return output from messages they are sent 2018-04-03 15:04:10 -04:00
dm-exception-store.c
dm-exception-store.h
dm-flakey.c dm flakey: Properly corrupt multi-page bios. 2018-12-18 09:02:27 -05:00
dm-init.c dm init: fix const confusion for dm_allowed_targets array 2019-04-01 16:16:37 -04:00
dm-integrity.c dm integrity: fix deadlock with overlapping I/O 2019-04-05 18:49:08 -04:00
dm-io.c dm: Use kzalloc for all structs with embedded biosets/mempools 2018-06-05 08:47:43 -06:00
dm-ioctl.c dm: add support to directly boot to a mapped device 2019-03-05 14:53:50 -05:00
dm-kcopyd.c dm kcopyd: Fix bug causing workqueue stalls 2018-12-18 09:02:26 -05:00
dm-linear.c dm: Check for device sector overflow if CONFIG_LBDAF is not set 2018-12-18 09:02:26 -05:00
dm-log-userspace-base.c dm: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
dm-log-userspace-transfer.c
dm-log-userspace-transfer.h
dm-log-writes.c dax: Introduce a ->copy_to_iter dax operation 2018-05-22 23:18:31 -07:00
dm-log.c
dm-mpath.c dm mpath: only flush workqueue when needed 2018-12-18 09:02:25 -05:00
dm-mpath.h
dm-path-selector.c
dm-path-selector.h
dm-queue-length.c dm mpath selector: more evenly distribute ties 2018-01-29 13:44:58 -05:00
dm-raid1.c dm: Check for device sector overflow if CONFIG_LBDAF is not set 2018-12-18 09:02:26 -05:00
dm-raid.c dm: eliminate 'split_discard_bios' flag from DM target interface 2019-02-20 23:24:55 -05:00
dm-region-hash.c - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
dm-round-robin.c
dm-rq.c dm: disable DISCARD if the underlying storage no longer supports it 2019-04-04 15:33:59 -04:00
dm-rq.h dm: remove unused _rq_tio_cache and _rq_cache 2019-03-05 14:48:50 -05:00
dm-service-time.c dm mpath selector: more evenly distribute ties 2018-01-29 13:44:58 -05:00
dm-snap-persistent.c dm bufio: move dm-bufio.h to include/linux/ 2018-04-03 15:04:23 -04:00
dm-snap-transient.c
dm-snap.c dm snapshot: Replace mutex with rw semaphore 2019-04-18 16:18:28 -04:00
dm-stats.c mm: convert totalram_pages and totalhigh_pages variables to atomic 2018-12-28 12:11:47 -08:00
dm-stats.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dm-stripe.c dax: Introduce a ->copy_to_iter dax operation 2018-05-22 23:18:31 -07:00
dm-switch.c dm switch: use struct_size() in kzalloc() 2019-03-05 14:48:51 -05:00
dm-sysfs.c dm: remove legacy request-based IO path 2018-10-11 11:36:09 -04:00
dm-table.c dm table: propagate BDI_CAP_STABLE_WRITES to fix sporadic checksum errors 2019-04-01 16:26:02 -04:00
dm-target.c dm: remove unused macro DM_MOD_NAME_SIZE 2018-04-03 15:04:15 -04:00
dm-thin-metadata.c dm thin: fix passdown_double_checking_shared_status() 2019-01-15 16:10:41 -05:00
dm-thin-metadata.h dm thin: fix passdown_double_checking_shared_status() 2019-01-15 16:10:41 -05:00
dm-thin.c dm thin: add sanity checks to thin-pool and external snapshot creation 2019-03-05 14:53:49 -05:00
dm-uevent.c
dm-uevent.h
dm-unstripe.c dm: Check for device sector overflow if CONFIG_LBDAF is not set 2018-12-18 09:02:26 -05:00
dm-verity-fec.c dm verity fec: remove redundant unlikely annotation 2019-03-05 14:53:48 -05:00
dm-verity-fec.h dm: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
dm-verity-target.c dm verity: log the hash algorithm implementation 2018-12-18 09:02:27 -05:00
dm-verity.h dm verity: add 'check_at_most_once' option to only validate hashes once 2018-04-03 15:04:29 -04:00
dm-writecache.c dm writecache: fix typo in name for writeback_wq 2019-03-05 14:53:51 -05:00
dm-zero.c
dm-zoned-metadata.c dm zoned: Fix zone report handling 2019-04-18 16:17:58 -04:00
dm-zoned-reclaim.c dm kcopyd: return void from dm_kcopyd_copy() 2018-07-31 17:33:21 -04:00
dm-zoned-target.c dm zoned: Silence a static checker warning 2019-04-18 16:16:01 -04:00
dm-zoned.h
dm.c dm: disable DISCARD if the underlying storage no longer supports it 2019-04-04 15:33:59 -04:00
dm.h dm: remove legacy request-based IO path 2018-10-11 11:36:09 -04:00
Kconfig dm: add support to directly boot to a mapped device 2019-03-05 14:53:50 -05:00
Makefile dm: add support to directly boot to a mapped device 2019-03-05 14:53:50 -05:00
md-bitmap.c md/bitmap: use mddev_suspend/resume instead of ->quiesce() 2018-10-10 11:03:34 -07:00
md-bitmap.h md: Avoid namespace collision with bitmap API 2018-08-01 15:49:39 -07:00
md-cluster.c md-cluster: remove suspend_info 2018-10-18 09:41:25 -07:00
md-cluster.h md-cluster: introduce resync_info_get interface for sanity check 2018-10-18 09:36:35 -07:00
md-faulty.c md: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
md-linear.c md-linear: use struct_size() in kzalloc() 2019-02-04 10:37:11 -08:00
md-linear.h Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/shli/md 2017-11-14 16:07:26 -08:00
md-multipath.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
md-multipath.h md: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
md.c md: Make bio_alloc_mddev use bio_alloc_bioset 2019-01-14 06:31:56 -07:00
md.h md-cluster/raid10: support add disk under grow mode 2018-10-18 09:34:56 -07:00
raid0.c blkcg: remove bio->bi_css and instead use bio->bi_blkg 2018-12-07 22:26:37 -07:00
raid0.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
raid1-10.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
raid1.c for-5.1/block-20190302 2019-03-08 14:12:17 -08:00
raid1.h md: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00
raid5-cache.c md/raid5: fix 'out of memory' during raid cache recovery 2019-01-28 11:44:40 -08:00
raid5-log.h raid5: set write hint for PPL 2019-03-12 10:15:18 -07:00
raid5-ppl.c for-5.1/block-post-20190315 2019-03-16 12:36:39 -07:00
raid5.c for-5.1/block-post-20190315 2019-03-16 12:36:39 -07:00
raid5.h md: convert to kvmalloc 2019-03-12 10:04:02 -07:00
raid10.c md: Fix failed allocation of md_register_thread 2019-03-12 10:15:18 -07:00
raid10.h md: convert to bioset_init()/mempool_init() 2018-05-30 15:33:32 -06:00