From: Song Liu Date: Thu, 17 Nov 2016 23:24:38 +0000 (-0800) Subject: md/r5cache: State machine for raid5-cache write back mode X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=2ded370373a400c20cf0c6e941e724e61582a867;p=linux-beck.git 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 --- diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c index 33fc85015147..02a554434747 100644 --- a/drivers/md/raid5-cache.c +++ b/drivers/md/raid5-cache.c @@ -40,6 +40,47 @@ */ #define R5L_POOL_SIZE 4 +/* + * r5c journal modes of the array: write-back or write-through. + * write-through mode has identical behavior as existing log only + * implementation. + */ +enum r5c_journal_mode { + R5C_JOURNAL_MODE_WRITE_THROUGH = 0, + R5C_JOURNAL_MODE_WRITE_BACK = 1, +}; + +/* + * 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_try_caching_write). 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 + */ + struct r5l_log { struct md_rdev *rdev; @@ -96,6 +137,9 @@ struct r5l_log { spinlock_t no_space_stripes_lock; bool need_cache_flush; + + /* for r5c_cache */ + enum r5c_journal_mode r5c_journal_mode; }; /* @@ -133,6 +177,12 @@ enum r5l_io_unit_state { IO_UNIT_STRIPE_END = 3, /* stripes data finished writing to raid */ }; +bool r5c_is_writeback(struct r5l_log *log) +{ + return (log != NULL && + log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_BACK); +} + static sector_t r5l_ring_add(struct r5l_log *log, sector_t start, sector_t inc) { start += inc; @@ -168,12 +218,51 @@ static void __r5l_set_io_unit_state(struct r5l_io_unit *io, io->state = state; } +/* + * Put the stripe into writing-out phase by clearing STRIPE_R5C_CACHING. + * This function should only be called in write-back mode. + */ +static void r5c_make_stripe_write_out(struct stripe_head *sh) +{ + struct r5conf *conf = sh->raid_conf; + struct r5l_log *log = conf->log; + + BUG_ON(!r5c_is_writeback(log)); + + WARN_ON(!test_bit(STRIPE_R5C_CACHING, &sh->state)); + clear_bit(STRIPE_R5C_CACHING, &sh->state); +} + +/* + * Setting proper flags after writing (or flushing) data and/or parity to the + * log device. This is called from r5l_log_endio() or r5l_log_flush_endio(). + */ +static void r5c_finish_cache_stripe(struct stripe_head *sh) +{ + struct r5l_log *log = sh->raid_conf->log; + + if (log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) { + BUG_ON(test_bit(STRIPE_R5C_CACHING, &sh->state)); + /* + * Set R5_InJournal for parity dev[pd_idx]. This means + * all data AND parity in the journal. For RAID 6, it is + * NOT necessary to set the flag for dev[qd_idx], as the + * two parities are written out together. + */ + set_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags); + } else + BUG(); /* write-back logic in next patch */ +} + static void r5l_io_run_stripes(struct r5l_io_unit *io) { struct stripe_head *sh, *next; list_for_each_entry_safe(sh, next, &io->stripe_list, log_list) { list_del_init(&sh->log_list); + + r5c_finish_cache_stripe(sh); + set_bit(STRIPE_HANDLE, &sh->state); raid5_release_stripe(sh); } @@ -412,18 +501,19 @@ static int r5l_log_stripe(struct r5l_log *log, struct stripe_head *sh, r5l_append_payload_page(log, sh->dev[i].page); } - if (sh->qd_idx >= 0) { + if (parity_pages == 2) { r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY, sh->sector, sh->dev[sh->pd_idx].log_checksum, sh->dev[sh->qd_idx].log_checksum, true); r5l_append_payload_page(log, sh->dev[sh->pd_idx].page); r5l_append_payload_page(log, sh->dev[sh->qd_idx].page); - } else { + } else if (parity_pages == 1) { r5l_append_payload_meta(log, R5LOG_PAYLOAD_PARITY, sh->sector, sh->dev[sh->pd_idx].log_checksum, 0, false); r5l_append_payload_page(log, sh->dev[sh->pd_idx].page); - } + } else /* Just writing data, not parity, in caching phase */ + BUG_ON(parity_pages != 0); list_add_tail(&sh->log_list, &io->stripe_list); atomic_inc(&io->pending_stripe); @@ -455,6 +545,8 @@ int r5l_write_stripe(struct r5l_log *log, struct stripe_head *sh) return -EAGAIN; } + WARN_ON(test_bit(STRIPE_R5C_CACHING, &sh->state)); + for (i = 0; i < sh->disks; i++) { void *addr; @@ -1112,6 +1204,49 @@ static void r5l_write_super(struct r5l_log *log, sector_t cp) set_bit(MD_CHANGE_DEVS, &mddev->flags); } +/* + * Try handle write operation in caching phase. This function should only + * be called in write-back mode. + * + * If all outstanding writes can be handled in caching phase, returns 0 + * If writes requires write-out phase, call r5c_make_stripe_write_out() + * and returns -EAGAIN + */ +int r5c_try_caching_write(struct r5conf *conf, + struct stripe_head *sh, + struct stripe_head_state *s, + int disks) +{ + struct r5l_log *log = conf->log; + + BUG_ON(!r5c_is_writeback(log)); + + /* more write-back logic in next patches */ + r5c_make_stripe_write_out(sh); + return -EAGAIN; +} + +/* + * clean up the stripe (clear R5_InJournal for dev[pd_idx] etc.) after the + * stripe is committed to RAID disks. + */ +void r5c_finish_stripe_write_out(struct r5conf *conf, + struct stripe_head *sh, + struct stripe_head_state *s) +{ + if (!conf->log || + !test_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags)) + return; + + WARN_ON(test_bit(STRIPE_R5C_CACHING, &sh->state)); + clear_bit(R5_InJournal, &sh->dev[sh->pd_idx].flags); + + if (conf->log->r5c_journal_mode == R5C_JOURNAL_MODE_WRITE_THROUGH) + return; + BUG(); /* write-back logic in following patches */ +} + + static int r5l_load_log(struct r5l_log *log) { struct md_rdev *rdev = log->rdev; @@ -1249,6 +1384,8 @@ int r5l_init_log(struct r5conf *conf, struct md_rdev *rdev) INIT_LIST_HEAD(&log->no_space_stripes); spin_lock_init(&log->no_space_stripes_lock); + log->r5c_journal_mode = R5C_JOURNAL_MODE_WRITE_THROUGH; + if (r5l_load_log(log)) goto error; diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 34895f3218d9..7c98eb06d1b2 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -4107,6 +4107,9 @@ static void analyse_stripe(struct stripe_head *sh, struct stripe_head_state *s) if (rdev && !test_bit(Faulty, &rdev->flags)) do_recovery = 1; } + + if (test_bit(R5_InJournal, &dev->flags)) + s->injournal++; } if (test_bit(STRIPE_SYNCING, &sh->state)) { /* If there is a failed device being replaced, @@ -4386,14 +4389,47 @@ static void handle_stripe(struct stripe_head *sh) || s.expanding) handle_stripe_fill(sh, &s, disks); - /* Now to consider new write requests and what else, if anything - * should be read. We do not handle new writes when: + /* + * When the stripe finishes full journal write cycle (write to journal + * and raid disk), this is the clean up procedure so it is ready for + * next operation. + */ + r5c_finish_stripe_write_out(conf, sh, &s); + + /* + * Now to consider new write requests, cache write back and what else, + * if anything should be read. We do not handle new writes when: * 1/ A 'write' operation (copy+xor) is already in flight. * 2/ A 'check' operation is in flight, as it may clobber the parity * block. + * 3/ A r5c cache log write is in flight. */ - if (s.to_write && !sh->reconstruct_state && !sh->check_state) - handle_stripe_dirtying(conf, sh, &s, disks); + + if (!sh->reconstruct_state && !sh->check_state && !sh->log_io) { + if (!r5c_is_writeback(conf->log)) { + if (s.to_write) + handle_stripe_dirtying(conf, sh, &s, disks); + } else { /* write back cache */ + int ret = 0; + + /* First, try handle writes in caching phase */ + if (s.to_write) + ret = r5c_try_caching_write(conf, sh, &s, + disks); + /* + * If caching phase failed: ret == -EAGAIN + * OR + * stripe under reclaim: !caching && injournal + * + * fall back to handle_stripe_dirtying() + */ + if (ret == -EAGAIN || + /* stripe under reclaim: !caching && injournal */ + (!test_bit(STRIPE_R5C_CACHING, &sh->state) && + s.injournal > 0)) + handle_stripe_dirtying(conf, sh, &s, disks); + } + } /* maybe we need to check and possibly fix the parity for this stripe * Any reads will already have been scheduled, so we just see if enough @@ -5110,6 +5146,7 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi) * data on failed drives. */ if (rw == READ && mddev->degraded == 0 && + !r5c_is_writeback(conf->log) && mddev->reshape_position == MaxSector) { bi = chunk_aligned_read(mddev, bi); if (!bi) 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