From 0021b7bc045e4b0b85d8c53614342aaf84ca96a5 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 31 Jul 2012 09:08:14 +0200 Subject: md: remove plug_cnt feature of plugging. This seemed like a good idea at the time, but after further thought I cannot see it making a difference other than very occasionally and testing to try to exercise the case it is most likely to help did not show any performance difference by removing it. So remove the counting of active plugs and allow 'pending writes' to be activated at any time, not just when no plugs are active. This is only relevant when there is a write-intent bitmap, and the updating of the bitmap will likely introduce enough delay that the single-threading of bitmap updates will be enough to collect large numbers of updates together. Removing this will make it easier to centralise the unplug code, and will clear the other for other unplug enhancements which have a measurable effect. Signed-off-by: NeilBrown Signed-off-by: Jens Axboe --- drivers/md/md.c | 5 +---- drivers/md/md.h | 3 --- drivers/md/raid1.c | 3 +-- drivers/md/raid10.c | 3 +-- drivers/md/raid5.c | 5 ++--- 5 files changed, 5 insertions(+), 14 deletions(-) (limited to 'drivers/md') diff --git a/drivers/md/md.c b/drivers/md/md.c index d5ab4493c8be..34381172a947 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -514,8 +514,7 @@ struct md_plug_cb { static void plugger_unplug(struct blk_plug_cb *cb) { struct md_plug_cb *mdcb = container_of(cb, struct md_plug_cb, cb); - if (atomic_dec_and_test(&mdcb->mddev->plug_cnt)) - md_wakeup_thread(mdcb->mddev->thread); + md_wakeup_thread(mdcb->mddev->thread); kfree(mdcb); } @@ -548,7 +547,6 @@ int mddev_check_plugged(struct mddev *mddev) mdcb->mddev = mddev; mdcb->cb.callback = plugger_unplug; - atomic_inc(&mddev->plug_cnt); list_add(&mdcb->cb.list, &plug->cb_list); return 1; } @@ -602,7 +600,6 @@ void mddev_init(struct mddev *mddev) atomic_set(&mddev->active, 1); atomic_set(&mddev->openers, 0); atomic_set(&mddev->active_io, 0); - atomic_set(&mddev->plug_cnt, 0); spin_lock_init(&mddev->write_lock); atomic_set(&mddev->flush_pending, 0); init_waitqueue_head(&mddev->sb_wait); diff --git a/drivers/md/md.h b/drivers/md/md.h index 7b4a3c318cae..91786c46b85c 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -266,9 +266,6 @@ struct mddev { int new_chunk_sectors; int reshape_backwards; - atomic_t plug_cnt; /* If device is expecting - * more bios soon. - */ struct md_thread *thread; /* management thread */ struct md_thread *sync_thread; /* doing resync or reconstruct */ sector_t curr_resync; /* last block scheduled */ diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index cacd008d6864..36a8fc059ac3 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -2173,8 +2173,7 @@ static void raid1d(struct mddev *mddev) blk_start_plug(&plug); for (;;) { - if (atomic_read(&mddev->plug_cnt) == 0) - flush_pending_writes(conf); + flush_pending_writes(conf); spin_lock_irqsave(&conf->device_lock, flags); if (list_empty(head)) { diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index 8da6282254c3..5d33603a497d 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -2660,8 +2660,7 @@ static void raid10d(struct mddev *mddev) blk_start_plug(&plug); for (;;) { - if (atomic_read(&mddev->plug_cnt) == 0) - flush_pending_writes(conf); + flush_pending_writes(conf); spin_lock_irqsave(&conf->device_lock, flags); if (list_empty(head)) { diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c index 04348d76bb30..bde9da2baa39 100644 --- a/drivers/md/raid5.c +++ b/drivers/md/raid5.c @@ -4543,7 +4543,7 @@ static void raid5d(struct mddev *mddev) while (1) { struct bio *bio; - if (atomic_read(&mddev->plug_cnt) == 0 && + if ( !list_empty(&conf->bitmap_list)) { /* Now is a good time to flush some bitmap updates */ conf->seq_flush++; @@ -4553,8 +4553,7 @@ static void raid5d(struct mddev *mddev) conf->seq_write = conf->seq_flush; activate_bit_delay(conf); } - if (atomic_read(&mddev->plug_cnt) == 0) - raid5_activate_delayed(conf); + raid5_activate_delayed(conf); while ((bio = remove_bio_from_retry(conf))) { int ok; -- cgit v1.2.3-55-g7522 From 9cbb17508808f8a6bdd83354b61e126ac4fa6fed Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 31 Jul 2012 09:08:14 +0200 Subject: blk: centralize non-request unplug handling. Both md and umem has similar code for getting notified on an blk_finish_plug event. Centralize this code in block/ and allow each driver to provide its distinctive difference. Signed-off-by: NeilBrown Signed-off-by: Jens Axboe --- block/blk-core.c | 25 ++++++++++++++++++++++ drivers/block/umem.c | 35 ++++++------------------------- drivers/md/md.c | 56 +++++--------------------------------------------- drivers/md/md.h | 8 +++++++- include/linux/blkdev.h | 8 ++++++-- 5 files changed, 49 insertions(+), 83 deletions(-) (limited to 'drivers/md') diff --git a/block/blk-core.c b/block/blk-core.c index dd134d834d58..177ddcf356e6 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2927,6 +2927,31 @@ static void flush_plug_callbacks(struct blk_plug *plug) } } +struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data, + int size) +{ + struct blk_plug *plug = current->plug; + struct blk_plug_cb *cb; + + if (!plug) + return NULL; + + list_for_each_entry(cb, &plug->cb_list, list) + if (cb->callback == unplug && cb->data == data) + return cb; + + /* Not currently on the callback list */ + BUG_ON(size < sizeof(*cb)); + cb = kzalloc(size, GFP_ATOMIC); + if (cb) { + cb->data = data; + cb->callback = unplug; + list_add(&cb->list, &plug->cb_list); + } + return cb; +} +EXPORT_SYMBOL(blk_check_plugged); + void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) { struct request_queue *q; diff --git a/drivers/block/umem.c b/drivers/block/umem.c index 9a72277a31df..6ef3489568e3 100644 --- a/drivers/block/umem.c +++ b/drivers/block/umem.c @@ -513,42 +513,19 @@ static void process_page(unsigned long data) } } -struct mm_plug_cb { - struct blk_plug_cb cb; - struct cardinfo *card; -}; - static void mm_unplug(struct blk_plug_cb *cb) { - struct mm_plug_cb *mmcb = container_of(cb, struct mm_plug_cb, cb); + struct cardinfo *card = cb->data; - spin_lock_irq(&mmcb->card->lock); - activate(mmcb->card); - spin_unlock_irq(&mmcb->card->lock); - kfree(mmcb); + spin_lock_irq(&card->lock); + activate(card); + spin_unlock_irq(&card->lock); + kfree(cb); } static int mm_check_plugged(struct cardinfo *card) { - struct blk_plug *plug = current->plug; - struct mm_plug_cb *mmcb; - - if (!plug) - return 0; - - list_for_each_entry(mmcb, &plug->cb_list, cb.list) { - if (mmcb->cb.callback == mm_unplug && mmcb->card == card) - return 1; - } - /* Not currently on the callback list */ - mmcb = kmalloc(sizeof(*mmcb), GFP_ATOMIC); - if (!mmcb) - return 0; - - mmcb->card = card; - mmcb->cb.callback = mm_unplug; - list_add(&mmcb->cb.list, &plug->cb_list); - return 1; + return !!blk_check_plugged(mm_unplug, card, sizeof(struct blk_plug_cb)); } static void mm_make_request(struct request_queue *q, struct bio *bio) diff --git a/drivers/md/md.c b/drivers/md/md.c index 34381172a947..b493fa417387 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -498,59 +498,13 @@ void md_flush_request(struct mddev *mddev, struct bio *bio) } EXPORT_SYMBOL(md_flush_request); -/* Support for plugging. - * This mirrors the plugging support in request_queue, but does not - * require having a whole queue or request structures. - * We allocate an md_plug_cb for each md device and each thread it gets - * plugged on. This links tot the private plug_handle structure in the - * personality data where we keep a count of the number of outstanding - * plugs so other code can see if a plug is active. - */ -struct md_plug_cb { - struct blk_plug_cb cb; - struct mddev *mddev; -}; - -static void plugger_unplug(struct blk_plug_cb *cb) +void md_unplug(struct blk_plug_cb *cb) { - struct md_plug_cb *mdcb = container_of(cb, struct md_plug_cb, cb); - md_wakeup_thread(mdcb->mddev->thread); - kfree(mdcb); -} - -/* Check that an unplug wakeup will come shortly. - * If not, wakeup the md thread immediately - */ -int mddev_check_plugged(struct mddev *mddev) -{ - struct blk_plug *plug = current->plug; - struct md_plug_cb *mdcb; - - if (!plug) - return 0; - - list_for_each_entry(mdcb, &plug->cb_list, cb.list) { - if (mdcb->cb.callback == plugger_unplug && - mdcb->mddev == mddev) { - /* Already on the list, move to top */ - if (mdcb != list_first_entry(&plug->cb_list, - struct md_plug_cb, - cb.list)) - list_move(&mdcb->cb.list, &plug->cb_list); - return 1; - } - } - /* Not currently on the callback list */ - mdcb = kmalloc(sizeof(*mdcb), GFP_ATOMIC); - if (!mdcb) - return 0; - - mdcb->mddev = mddev; - mdcb->cb.callback = plugger_unplug; - list_add(&mdcb->cb.list, &plug->cb_list); - return 1; + struct mddev *mddev = cb->data; + md_wakeup_thread(mddev->thread); + kfree(cb); } -EXPORT_SYMBOL_GPL(mddev_check_plugged); +EXPORT_SYMBOL(md_unplug); static inline struct mddev *mddev_get(struct mddev *mddev) { diff --git a/drivers/md/md.h b/drivers/md/md.h index 91786c46b85c..8f998e08fb87 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -627,6 +627,12 @@ extern struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask, struct mddev *mddev); extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs, struct mddev *mddev); -extern int mddev_check_plugged(struct mddev *mddev); extern void md_trim_bio(struct bio *bio, int offset, int size); + +extern void md_unplug(struct blk_plug_cb *cb); +static inline int mddev_check_plugged(struct mddev *mddev) +{ + return !!blk_check_plugged(md_unplug, mddev, + sizeof(struct blk_plug_cb)); +} #endif /* _MD_MD_H */ diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 3816ce8a08fc..607ca228f47e 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -922,11 +922,15 @@ struct blk_plug { }; #define BLK_MAX_REQUEST_COUNT 16 +struct blk_plug_cb; +typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *); struct blk_plug_cb { struct list_head list; - void (*callback)(struct blk_plug_cb *); + blk_plug_cb_fn callback; + void *data; }; - +extern struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, + void *data, int size); extern void blk_start_plug(struct blk_plug *); extern void blk_finish_plug(struct blk_plug *); extern void blk_flush_plug_list(struct blk_plug *, bool); -- cgit v1.2.3-55-g7522 From 74018dc3063a2c729fc73041c0a9f03aac995920 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Tue, 31 Jul 2012 09:08:15 +0200 Subject: blk: pass from_schedule to non-request unplug functions. This will allow md/raid to know why the unplug was called, and will be able to act according - if !from_schedule it is safe to perform tasks which could themselves schedule. Signed-off-by: NeilBrown Signed-off-by: Jens Axboe --- block/blk-core.c | 6 +++--- drivers/block/umem.c | 2 +- drivers/md/md.c | 2 +- drivers/md/md.h | 2 +- include/linux/blkdev.h | 2 +- 5 files changed, 7 insertions(+), 7 deletions(-) (limited to 'drivers/md') diff --git a/block/blk-core.c b/block/blk-core.c index 35bf4fe8234c..4b4dbdfbca89 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2909,7 +2909,7 @@ static void queue_unplugged(struct request_queue *q, unsigned int depth, } -static void flush_plug_callbacks(struct blk_plug *plug) +static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule) { LIST_HEAD(callbacks); @@ -2921,7 +2921,7 @@ static void flush_plug_callbacks(struct blk_plug *plug) struct blk_plug_cb, list); list_del(&cb->list); - cb->callback(cb); + cb->callback(cb, from_schedule); } } } @@ -2961,7 +2961,7 @@ void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) BUG_ON(plug->magic != PLUG_MAGIC); - flush_plug_callbacks(plug); + flush_plug_callbacks(plug, from_schedule); if (list_empty(&plug->list)) return; diff --git a/drivers/block/umem.c b/drivers/block/umem.c index 6ef3489568e3..eb0d8216f557 100644 --- a/drivers/block/umem.c +++ b/drivers/block/umem.c @@ -513,7 +513,7 @@ static void process_page(unsigned long data) } } -static void mm_unplug(struct blk_plug_cb *cb) +static void mm_unplug(struct blk_plug_cb *cb, bool from_schedule) { struct cardinfo *card = cb->data; diff --git a/drivers/md/md.c b/drivers/md/md.c index b493fa417387..db02d2efb76f 100644 --- a/drivers/md/md.c +++ b/drivers/md/md.c @@ -498,7 +498,7 @@ void md_flush_request(struct mddev *mddev, struct bio *bio) } EXPORT_SYMBOL(md_flush_request); -void md_unplug(struct blk_plug_cb *cb) +void md_unplug(struct blk_plug_cb *cb, bool from_schedule) { struct mddev *mddev = cb->data; md_wakeup_thread(mddev->thread); diff --git a/drivers/md/md.h b/drivers/md/md.h index 8f998e08fb87..f385b038589d 100644 --- a/drivers/md/md.h +++ b/drivers/md/md.h @@ -629,7 +629,7 @@ extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs, struct mddev *mddev); extern void md_trim_bio(struct bio *bio, int offset, int size); -extern void md_unplug(struct blk_plug_cb *cb); +extern void md_unplug(struct blk_plug_cb *cb, bool from_schedule); static inline int mddev_check_plugged(struct mddev *mddev) { return !!blk_check_plugged(md_unplug, mddev, diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 607ca228f47e..4e72a9d48232 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -923,7 +923,7 @@ struct blk_plug { #define BLK_MAX_REQUEST_COUNT 16 struct blk_plug_cb; -typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *); +typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *, bool); struct blk_plug_cb { struct list_head list; blk_plug_cb_fn callback; -- cgit v1.2.3-55-g7522