From 497280509f32340d90feac030bce18006a3e3605 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 15 Mar 2017 14:05:12 +1100 Subject: [PATCH] md/raid5: use md_write_start to count stripes, not bios We use md_write_start() to increase the count of pending writes, and md_write_end() to decrement the count. We currently count bios submitted to md/raid5. Change it count stripe_heads that a WRITE bio has been attached to. So now, raid5_make_request() calls md_write_start() and then md_write_end() to keep the count elevated during the setup of the request. add_stripe_bio() calls md_write_start() for each stripe_head, and the completion routines always call md_write_end(), instead of only calling it when raid5_dec_bi_active_stripes() returns 0. make_discard_request also calls md_write_start/end(). The parallel between md_write_{start,end} and use of bi_phys_segments can be seen in that: Whenever we set bi_phys_segments to 1, we now call md_write_start. Whenever we increment it on non-read requests with raid5_inc_bi_active_stripes(), we now call md_write_start(). Whenever we decrement bi_phys_segments on non-read requsts with raid5_dec_bi_active_stripes(), we now call md_write_end(). This reduces our dependence on keeping a per-bio count of active stripes in bi_phys_segments. md_write_inc() is added which parallels md_write_start(), but requires that a write has already been started, and is certain never to sleep. This can be used inside a spinlocked region when adding to a write request. Signed-off-by: NeilBrown Signed-off-by: Shaohua Li --- drivers/md/md.c | 17 +++++++++++++++++ drivers/md/md.h | 1 + drivers/md/raid5-cache.c | 2 +- drivers/md/raid5.c | 27 +++++++++++++-------------- 4 files changed, 32 insertions(+), 15 deletions(-) diff --git a/drivers/md/md.c b/drivers/md/md.c index 42e68b2..41f766a 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -7907,6 +7907,23 @@ void md_write_start(struct mddev *mddev, struct bio *bi) } EXPORT_SYMBOL(md_write_start); +/* md_write_inc can only be called when md_write_start() has + * already been called at least once of the current request. + * It increments the counter and is useful when a single request + * is split into several parts. Each part causes an increment and + * so needs a matching md_write_end(). + * Unlike md_write_start(), it is safe to call md_write_inc() inside + * a spinlocked region. + */ +void md_write_inc(struct mddev *mddev, struct bio *bi) +{ + if (bio_data_dir(bi) != WRITE) + return; + WARN_ON_ONCE(mddev->in_sync || mddev->ro); + atomic_inc(&mddev->writes_pending); +} +EXPORT_SYMBOL(md_write_inc); + void md_write_end(struct mddev *mddev) { if (atomic_dec_and_test(&mddev->writes_pending)) { diff --git a/drivers/md/md.h b/drivers/md/md.h index e094006..0cd1272 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -648,6 +648,7 @@ extern void md_wakeup_thread(struct md_thread *thread); extern void md_check_recovery(struct mddev *mddev); extern void md_reap_sync_thread(struct mddev *mddev); extern void md_write_start(struct mddev *mddev, struct bio *bi); +extern void md_write_inc(struct mddev *mddev, struct bio *bi); extern void md_write_end(struct mddev *mddev); extern void md_done_sync(struct mddev *mddev, int blocks, int ok); extern void md_error(struct mddev *mddev, struct md_rdev *rdev); diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c index 6449313..f5034ec 100644 --- a/drivers/md/raid5-cache.c +++ b/drivers/md/raid5-cache.c @@ -318,8 +318,8 @@ r5c_return_dev_pending_writes(struct r5conf *conf, struct r5dev *dev, while (wbi && wbi->bi_iter.bi_sector < dev->sector + STRIPE_SECTORS) { wbi2 = r5_next_bio(wbi, dev->sector); + md_write_end(conf->mddev); if (!raid5_dec_bi_active_stripes(wbi)) { - md_write_end(conf->mddev); bio_list_add(return_bi, wbi); } wbi = wbi2; diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 88cc898..a684003 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -3274,6 +3274,7 @@ static int add_stripe_bio(struct stripe_head *sh, struct bio *bi, int dd_idx, bi->bi_next = *bip; *bip = bi; raid5_inc_bi_active_stripes(bi); + md_write_inc(conf->mddev, bi); if (forwrite) { /* check if page is covered */ @@ -3397,10 +3398,9 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, struct bio *nextbi = r5_next_bio(bi, sh->dev[i].sector); bi->bi_error = -EIO; - if (!raid5_dec_bi_active_stripes(bi)) { - md_write_end(conf->mddev); + md_write_end(conf->mddev); + if (!raid5_dec_bi_active_stripes(bi)) bio_list_add(return_bi, bi); - } bi = nextbi; } if (bitmap_end) @@ -3421,10 +3421,9 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh, struct bio *bi2 = r5_next_bio(bi, sh->dev[i].sector); bi->bi_error = -EIO; - if (!raid5_dec_bi_active_stripes(bi)) { - md_write_end(conf->mddev); + md_write_end(conf->mddev); + if (!raid5_dec_bi_active_stripes(bi)) bio_list_add(return_bi, bi); - } bi = bi2; } @@ -3781,10 +3780,9 @@ returnbi: while (wbi && wbi->bi_iter.bi_sector < dev->sector + STRIPE_SECTORS) { wbi2 = r5_next_bio(wbi, dev->sector); - if (!raid5_dec_bi_active_stripes(wbi)) { - md_write_end(conf->mddev); + md_write_end(conf->mddev); + if (!raid5_dec_bi_active_stripes(wbi)) bio_list_add(return_bi, wbi); - } wbi = wbi2; } bitmap_endwrite(conf->mddev->bitmap, sh->sector, @@ -5487,6 +5485,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi) bi->bi_next = NULL; bi->bi_phys_segments = 1; /* over-loaded to count active stripes */ + md_write_start(mddev, bi); stripe_sectors = conf->chunk_sectors * (conf->raid_disks - conf->max_degraded); @@ -5533,6 +5532,7 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi) sh->dev[d].towrite = bi; set_bit(R5_OVERWRITE, &sh->dev[d].flags); raid5_inc_bi_active_stripes(bi); + md_write_inc(mddev, bi); sh->overwrite_disks++; } spin_unlock_irq(&sh->stripe_lock); @@ -5555,9 +5555,9 @@ static void make_discard_request(struct mddev *mddev, struct bio *bi) release_stripe_plug(mddev, sh); } + md_write_end(mddev); remaining = raid5_dec_bi_active_stripes(bi); if (remaining == 0) { - md_write_end(mddev); bio_endio(bi); } } @@ -5592,8 +5592,6 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi) do_flush = bi->bi_opf & REQ_PREFLUSH; } - md_write_start(mddev, bi); - /* * If array is degraded, better not do chunk aligned read because * later we might have to read it again in order to reconstruct @@ -5615,6 +5613,7 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi) last_sector = bio_end_sector(bi); bi->bi_next = NULL; bi->bi_phys_segments = 1; /* over-loaded to count active stripes */ + md_write_start(mddev, bi); prepare_to_wait(&conf->wait_for_overlap, &w, TASK_UNINTERRUPTIBLE); for (;logical_sector < last_sector; logical_sector += STRIPE_SECTORS) { @@ -5749,11 +5748,11 @@ static void raid5_make_request(struct mddev *mddev, struct bio * bi) } finish_wait(&conf->wait_for_overlap, &w); + if (rw == WRITE) + md_write_end(mddev); remaining = raid5_dec_bi_active_stripes(bi); if (remaining == 0) { - if ( rw == WRITE ) - md_write_end(mddev); trace_block_bio_complete(bdev_get_queue(bi->bi_bdev), bi, 0); -- 2.7.4