diff options
author | Song Liu <songliubraving@fb.com> | 2016-11-17 15:24:38 -0800 |
---|---|---|
committer | Shaohua Li <shli@fb.com> | 2016-11-18 13:26:07 -0800 |
commit | 2ded370373a400c20cf0c6e941e724e61582a867 (patch) | |
tree | 704038326bbbe6f2e7fddd1b98b1f0ae1d3d9f44 /drivers/md/raid5.h | |
parent | 937621c36e0ea1af2aceeaea412ba3bd80247199 (diff) |
md/r5cache: State machine for raid5-cache write back mode
This patch adds state machine for raid5-cache. With log device, the
raid456 array could operate in two different modes (r5c_journal_mode):
- write-back (R5C_MODE_WRITE_BACK)
- write-through (R5C_MODE_WRITE_THROUGH)
Existing code of raid5-cache only has write-through mode. For write-back
cache, it is necessary to extend the state machine.
With write-back cache, every stripe could operate in two different
phases:
- caching
- writing-out
In caching phase, the stripe handles writes as:
- write to journal
- return IO
In writing-out phase, the stripe behaviors as a stripe in write through
mode R5C_MODE_WRITE_THROUGH.
STRIPE_R5C_CACHING is added to sh->state to differentiate caching and
writing-out phase.
Please note: this is a "no-op" patch for raid5-cache write-through
mode.
The following detailed explanation is copied from the raid5-cache.c:
/*
* raid5 cache state machine
*
* With rhe RAID cache, each stripe works in two phases:
* - caching phase
* - writing-out phase
*
* These two phases are controlled by bit STRIPE_R5C_CACHING:
* if STRIPE_R5C_CACHING == 0, the stripe is in writing-out phase
* if STRIPE_R5C_CACHING == 1, the stripe is in caching phase
*
* When there is no journal, or the journal is in write-through mode,
* the stripe is always in writing-out phase.
*
* For write-back journal, the stripe is sent to caching phase on write
* (r5c_handle_stripe_dirtying). r5c_make_stripe_write_out() kicks off
* the write-out phase by clearing STRIPE_R5C_CACHING.
*
* Stripes in caching phase do not write the raid disks. Instead, all
* writes are committed from the log device. Therefore, a stripe in
* caching phase handles writes as:
* - write to log device
* - return IO
*
* Stripes in writing-out phase handle writes as:
* - calculate parity
* - write pending data and parity to journal
* - write data and parity to raid disks
* - return IO for pending writes
*/
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Diffstat (limited to 'drivers/md/raid5.h')
-rw-r--r-- | drivers/md/raid5.h | 31 |
1 files changed, 30 insertions, 1 deletions
diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h index ffc13c4d7e63..c9590a8e1425 100644 --- a/drivers/md/raid5.h +++ b/drivers/md/raid5.h @@ -264,6 +264,7 @@ struct stripe_head_state { int syncing, expanding, expanded, replacing; int locked, uptodate, to_read, to_write, failed, written; int to_fill, compute, req_compute, non_overwrite; + int injournal; int failed_num[2]; int p_failed, q_failed; int dec_preread_active; @@ -313,6 +314,11 @@ enum r5dev_flags { */ R5_Discard, /* Discard the stripe */ R5_SkipCopy, /* Don't copy data from bio to stripe cache */ + R5_InJournal, /* data being written is in the journal device. + * if R5_InJournal is set for parity pd_idx, all the + * data and parity being written are in the journal + * device + */ }; /* @@ -345,7 +351,23 @@ enum { STRIPE_BITMAP_PENDING, /* Being added to bitmap, don't add * to batch yet. */ - STRIPE_LOG_TRAPPED, /* trapped into log */ + STRIPE_LOG_TRAPPED, /* trapped into log (see raid5-cache.c) + * this bit is used in two scenarios: + * + * 1. write-out phase + * set in first entry of r5l_write_stripe + * clear in second entry of r5l_write_stripe + * used to bypass logic in handle_stripe + * + * 2. caching phase + * set in r5c_try_caching_write() + * clear when journal write is done + * used to initiate r5c_cache_data() + * also used to bypass logic in handle_stripe + */ + STRIPE_R5C_CACHING, /* the stripe is in caching phase + * see more detail in the raid5-cache.c + */ }; #define STRIPE_EXPAND_SYNC_FLAGS \ @@ -710,4 +732,11 @@ extern void r5l_stripe_write_finished(struct stripe_head *sh); extern int r5l_handle_flush_request(struct r5l_log *log, struct bio *bio); extern void r5l_quiesce(struct r5l_log *log, int state); extern bool r5l_log_disk_error(struct r5conf *conf); +extern bool r5c_is_writeback(struct r5l_log *log); +extern int +r5c_try_caching_write(struct r5conf *conf, struct stripe_head *sh, + struct stripe_head_state *s, int disks); +extern void +r5c_finish_stripe_write_out(struct r5conf *conf, struct stripe_head *sh, + struct stripe_head_state *s); #endif |