From 2ded370373a400c20cf0c6e941e724e61582a867 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Thu, 17 Nov 2016 15:24:38 -0800 Subject: 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 Signed-off-by: Shaohua Li --- drivers/md/raid5.h | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) (limited to 'drivers/md/raid5.h') 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 -- cgit v1.2.3