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Song Liu 03b047f45c md/r5cache: enable chunk_aligned_read with write back cache 
Chunk aligned read significantly reduces CPU usage of raid456.
However, it is not safe to fully bypass the write back cache.
This patch enables chunk aligned read with write back cache.

For chunk aligned read, we track stripes in write back cache at
a bigger granularity, "big_stripe". Each chunk may contain more
than one stripe (for example, a 256kB chunk contains 64 4kB-page,
so this chunk contain 64 stripes). For chunk_aligned_read, these
stripes are grouped into one big_stripe, so we only need one lookup
for the whole chunk.

For each big_stripe, struct big_stripe_info tracks how many stripes
of this big_stripe are in the write back cache. We count how many
stripes of this big_stripe are in the write back cache. These
counters are tracked in a radix tree (big_stripe_tree).
r5c_tree_index() is used to calculate keys for the radix tree.

chunk_aligned_read() calls r5c_big_stripe_cached() to look up
big_stripe of each chunk in the tree. If this big_stripe is in the
tree, chunk_aligned_read() aborts. This look up is protected by
rcu_read_lock().

It is necessary to remember whether a stripe is counted in
big_stripe_tree. Instead of adding new flag, we reuses existing flags:
STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE. If either of these
two flags are set, the stripe is counted in big_stripe_tree. This
requires moving set_bit(STRIPE_R5C_PARTIAL_STRIPE) to
r5c_try_caching_write(); and moving clear_bit of
STRIPE_R5C_PARTIAL_STRIPE and STRIPE_R5C_FULL_STRIPE to
r5c_finish_stripe_write_out().

Signed-off-by: Song Liu <songliubraving@fb.com>
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
 		2017-02-13 09:17:51 -08:00
..
bcache bcache: partition support: add 16 minors per bcacheN device 2016-12-17 13:02:00 -07:00
persistent-data dm space map: always set ev if sm_ll_mutate() succeeds 2016-12-08 14:13:15 -05:00
Kconfig dm block manager: make block locking optional 2016-11-14 15:17:47 -05:00
Makefile dm: move request-based code out to dm-rq.[hc] 2016-06-10 15:15:44 -04:00
bitmap.c md: separate flags for superblock changes 2016-12-08 22:01:47 -08:00
bitmap.h md-cluster: sync bitmap when node received RESYNCING msg 2016-05-04 12:39:35 -07:00
dm-bio-prison.c block: add a bi_error field to struct bio 2015-07-29 08:55:15 -06:00
dm-bio-prison.h
…
dm-bio-record.h
…
dm-bufio.c . various fixes and improvements to request-based DM and DM multipath 2016-12-14 11:01:00 -08:00
dm-bufio.h
…
dm-builtin.c dm: move request-based code out to dm-rq.[hc] 2016-06-10 15:15:44 -04:00
dm-cache-block-types.h linux: drop __bitwise__ everywhere 2016-12-16 00:13:41 +02:00
dm-cache-metadata.c dm cache metadata: remove an extra newline in DMERR and code 2016-11-21 09:52:02 -05:00
dm-cache-metadata.h dm cache: make sure every metadata function checks fail_io 2016-03-10 17:12:12 -05:00
dm-cache-policy-cleaner.c dm cache: speed up writing of the hint array 2016-09-22 11:15:02 -04:00
dm-cache-policy-internal.h dm cache: speed up writing of the hint array 2016-09-22 11:15:02 -04:00
dm-cache-policy-smq.c dm cache policy smq: use hash_32() instead of hash_32_generic() 2016-12-08 19:42:37 -05:00
dm-cache-policy.c
…
dm-cache-policy.h dm cache: speed up writing of the hint array 2016-09-22 11:15:02 -04:00
dm-cache-target.c dm cache: add missing cache device name to DMERR in set_cache_mode() 2016-11-21 09:52:03 -05:00
dm-core.h dm: move request-based code out to dm-rq.[hc] 2016-06-10 15:15:44 -04:00
dm-crypt.c dm crypt: replace RCU read-side section with rwsem 2017-02-03 10:26:14 -05:00
dm-delay.c dm: rename target's per_bio_data_size to per_io_data_size 2016-02-22 22:34:37 -05:00
dm-era-target.c block: rename bio bi_rw to bi_opf 2016-08-07 14:41:02 -06:00
dm-exception-store.c - Revert a dm-multipath change that caused a regression for unprivledged 2015-11-04 21:19:53 -08:00
dm-exception-store.h dm snapshot: fix hung bios when copy error occurs 2016-01-08 20:03:05 -05:00
dm-flakey.c dm flakey: introduce "error_writes" feature 2016-12-13 15:01:31 -05:00
dm-io.c dm io: use bvec iterator helpers to implement .get_page and .next_page 2016-11-21 09:51:57 -05:00
dm-ioctl.c Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
dm-kcopyd.c dm: move request-based code out to dm-rq.[hc] 2016-06-10 15:15:44 -04:00
dm-linear.c libnvdimm for 4.8 2016-07-28 17:38:16 -07:00
dm-log-userspace-base.c dm: drop NULL test before kmem_cache_destroy() and mempool_destroy() 2015-10-31 19:06:00 -04:00
dm-log-userspace-transfer.c
…
dm-log-userspace-transfer.h
…
dm-log-writes.c Merge branch 'for-4.9/block' of git://git.kernel.dk/linux-block 2016-10-07 14:42:05 -07:00
dm-log.c block,fs: use REQ_* flags directly 2016-11-01 09:43:26 -06:00
dm-mpath.c dm mpath: cleanup -Wbool-operation warning in choose_pgpath() 2017-02-03 10:18:37 -05:00
dm-mpath.h
…
dm-path-selector.c
…
dm-path-selector.h dm path selector: remove 'repeat_count' return from .select_path hook 2016-02-22 22:34:42 -05:00
dm-queue-length.c dm path selector: remove 'repeat_count' return from .select_path hook 2016-02-22 22:34:42 -05:00
dm-raid.c . various fixes and improvements to request-based DM and DM multipath 2016-12-14 11:01:00 -08:00
dm-raid1.c Merge branch 'for-4.10/block' of git://git.kernel.dk/linux-block 2016-12-13 10:19:16 -08:00
dm-region-hash.c block: rename bio bi_rw to bi_opf 2016-08-07 14:41:02 -06:00
dm-round-robin.c dm round robin: do not use this_cpu_ptr() without having preemption disabled 2016-08-15 09:23:14 -04:00
dm-rq.c dm rq: cope with DM device destruction while in dm_old_request_fn() 2017-02-03 10:18:43 -05:00
dm-rq.h dm rq: introduce dm_mq_kick_requeue_list() 2016-09-15 11:16:05 -04:00
dm-service-time.c dm path selector: remove 'repeat_count' return from .select_path hook 2016-02-22 22:34:42 -05:00
dm-snap-persistent.c block,fs: use REQ_* flags directly 2016-11-01 09:43:26 -06:00
dm-snap-transient.c dm snapshot: fix hung bios when copy error occurs 2016-01-08 20:03:05 -05:00
dm-snap.c block: rename bio bi_rw to bi_opf 2016-08-07 14:41:02 -06:00
dm-stats.c dm: move request-based code out to dm-rq.[hc] 2016-06-10 15:15:44 -04:00
dm-stats.h
…
dm-stripe.c block: rename bio bi_rw to bi_opf 2016-08-07 14:41:02 -06:00
dm-switch.c dm switch: simplify conditional in alloc_region_table() 2015-10-31 19:06:06 -04:00
dm-sysfs.c dm: move request-based code out to dm-rq.[hc] 2016-06-10 15:15:44 -04:00
dm-table.c dm table: simplify dm_table_determine_type() 2016-12-08 14:13:03 -05:00
dm-target.c libnvdimm for 4.8 2016-07-28 17:38:16 -07:00
dm-thin-metadata.c dm thin: fix a race condition between discarding and provisioning a block 2016-07-20 12:43:35 -04:00
dm-thin-metadata.h dm thin: fix a race condition between discarding and provisioning a block 2016-07-20 12:43:35 -04:00
dm-thin.c block: rename bio bi_rw to bi_opf 2016-08-07 14:41:02 -06:00
dm-uevent.c
…
dm-uevent.h
…
dm-verity-fec.c dm verity fec: fix block calculation 2016-07-01 23:29:08 -04:00
dm-verity-fec.h dm verity: add support for forward error correction 2015-12-10 10:39:03 -05:00
dm-verity-target.c dm verity: fix incorrect error message 2016-11-21 09:52:01 -05:00
dm-verity.h dm verity: add ignore_zero_blocks feature 2015-12-10 10:39:03 -05:00
dm-zero.c block: rename bio bi_rw to bi_opf 2016-08-07 14:41:02 -06:00
dm.c . various fixes and improvements to request-based DM and DM multipath 2016-12-14 11:01:00 -08:00
dm.h dm: add infrastructure for DAX support 2016-07-20 23:49:49 -04:00
faulty.c MD: rename some functions 2016-01-20 13:52:20 -08:00
linear.c md linear: fix a race between linear_add() and linear_congested() 2017-02-13 09:17:50 -08:00
linear.h md linear: fix a race between linear_add() and linear_congested() 2017-02-13 09:17:50 -08:00
md-cluster.c md-cluster: make resync lock also could be interruptted 2016-09-21 09:09:44 -07:00
md-cluster.h md-cluster: gather resync infos and enable recv_thread after bitmap is ready 2016-05-09 09:24:03 -07:00
md.c md/r5cache: flush data only stripes in r5l_recovery_log() 2017-01-24 11:20:15 -08:00
md.h md: cleanup mddev flag clear for takeover 2017-01-05 11:45:18 -08:00
multipath.c Merge branch 'md-next' into md-linus 2016-12-13 12:40:15 -08:00
multipath.h
…
raid0.c md: cleanup mddev flag clear for takeover 2017-01-05 11:45:18 -08:00
raid0.h block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
raid1.c md: cleanup mddev flag clear for takeover 2017-01-05 11:45:18 -08:00
raid1.h md/raid1: add failfast handling for reads. 2016-11-22 09:13:18 -08:00
raid5-cache.c md/r5cache: enable chunk_aligned_read with write back cache 2017-02-13 09:17:51 -08:00
raid5.c md/r5cache: enable chunk_aligned_read with write back cache 2017-02-13 09:17:51 -08:00
raid5.h md/r5cache: enable chunk_aligned_read with write back cache 2017-02-13 09:17:51 -08:00
raid10.c md/raid10: Refactor raid10_make_request 2017-01-03 08:56:52 -08:00
raid10.h md/raid10: add failfast handling for reads. 2016-11-22 09:14:28 -08:00