This is a note to let you know that I've just added the patch titled bcache: improve multithreaded bch_btree_check() to the 5.17-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: bcache-improve-multithreaded-bch_btree_check.patch and it can be found in the queue-5.17 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 622536443b6731ec82c563aae7807165adbe9178 Mon Sep 17 00:00:00 2001 From: Coly Li <colyli@xxxxxxx> Date: Tue, 24 May 2022 18:23:33 +0800 Subject: bcache: improve multithreaded bch_btree_check() From: Coly Li <colyli@xxxxxxx> commit 622536443b6731ec82c563aae7807165adbe9178 upstream. Commit 8e7102273f59 ("bcache: make bch_btree_check() to be multithreaded") makes bch_btree_check() to be much faster when checking all btree nodes during cache device registration. But it isn't in ideal shap yet, still can be improved. This patch does the following thing to improve current parallel btree nodes check by multiple threads in bch_btree_check(), - Add read lock to root node while checking all the btree nodes with multiple threads. Although currently it is not mandatory but it is good to have a read lock in code logic. - Remove local variable 'char name[32]', and generate kernel thread name string directly when calling kthread_run(). - Allocate local variable "struct btree_check_state check_state" on the stack and avoid unnecessary dynamic memory allocation for it. - Reduce BCH_BTR_CHKTHREAD_MAX from 64 to 12 which is enough indeed. - Increase check_state->started to count created kernel thread after it succeeds to create. - When wait for all checking kernel threads to finish, use wait_event() to replace wait_event_interruptible(). With this change, the code is more clear, and some potential error conditions are avoided. Fixes: 8e7102273f59 ("bcache: make bch_btree_check() to be multithreaded") Signed-off-by: Coly Li <colyli@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/20220524102336.10684-2-colyli@xxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/bcache/btree.c | 58 ++++++++++++++++++++-------------------------- drivers/md/bcache/btree.h | 2 - 2 files changed, 27 insertions(+), 33 deletions(-) --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -2006,8 +2006,7 @@ int bch_btree_check(struct cache_set *c) int i; struct bkey *k = NULL; struct btree_iter iter; - struct btree_check_state *check_state; - char name[32]; + struct btree_check_state check_state; /* check and mark root node keys */ for_each_key_filter(&c->root->keys, k, &iter, bch_ptr_invalid) @@ -2018,63 +2017,58 @@ int bch_btree_check(struct cache_set *c) if (c->root->level == 0) return 0; - check_state = kzalloc(sizeof(struct btree_check_state), GFP_KERNEL); - if (!check_state) - return -ENOMEM; - - check_state->c = c; - check_state->total_threads = bch_btree_chkthread_nr(); - check_state->key_idx = 0; - spin_lock_init(&check_state->idx_lock); - atomic_set(&check_state->started, 0); - atomic_set(&check_state->enough, 0); - init_waitqueue_head(&check_state->wait); + check_state.c = c; + check_state.total_threads = bch_btree_chkthread_nr(); + check_state.key_idx = 0; + spin_lock_init(&check_state.idx_lock); + atomic_set(&check_state.started, 0); + atomic_set(&check_state.enough, 0); + init_waitqueue_head(&check_state.wait); + rw_lock(0, c->root, c->root->level); /* * Run multiple threads to check btree nodes in parallel, - * if check_state->enough is non-zero, it means current + * if check_state.enough is non-zero, it means current * running check threads are enough, unncessary to create * more. */ - for (i = 0; i < check_state->total_threads; i++) { - /* fetch latest check_state->enough earlier */ + for (i = 0; i < check_state.total_threads; i++) { + /* fetch latest check_state.enough earlier */ smp_mb__before_atomic(); - if (atomic_read(&check_state->enough)) + if (atomic_read(&check_state.enough)) break; - check_state->infos[i].result = 0; - check_state->infos[i].state = check_state; - snprintf(name, sizeof(name), "bch_btrchk[%u]", i); - atomic_inc(&check_state->started); + check_state.infos[i].result = 0; + check_state.infos[i].state = &check_state; - check_state->infos[i].thread = + check_state.infos[i].thread = kthread_run(bch_btree_check_thread, - &check_state->infos[i], - name); - if (IS_ERR(check_state->infos[i].thread)) { + &check_state.infos[i], + "bch_btrchk[%d]", i); + if (IS_ERR(check_state.infos[i].thread)) { pr_err("fails to run thread bch_btrchk[%d]\n", i); for (--i; i >= 0; i--) - kthread_stop(check_state->infos[i].thread); + kthread_stop(check_state.infos[i].thread); ret = -ENOMEM; goto out; } + atomic_inc(&check_state.started); } /* * Must wait for all threads to stop. */ - wait_event_interruptible(check_state->wait, - atomic_read(&check_state->started) == 0); + wait_event(check_state.wait, atomic_read(&check_state.started) == 0); - for (i = 0; i < check_state->total_threads; i++) { - if (check_state->infos[i].result) { - ret = check_state->infos[i].result; + for (i = 0; i < check_state.total_threads; i++) { + if (check_state.infos[i].result) { + ret = check_state.infos[i].result; goto out; } } out: - kfree(check_state); + rw_unlock(0, c->root); return ret; } --- a/drivers/md/bcache/btree.h +++ b/drivers/md/bcache/btree.h @@ -226,7 +226,7 @@ struct btree_check_info { int result; }; -#define BCH_BTR_CHKTHREAD_MAX 64 +#define BCH_BTR_CHKTHREAD_MAX 12 struct btree_check_state { struct cache_set *c; int total_threads; Patches currently in stable-queue which might be from colyli@xxxxxxx are queue-5.17/bcache-avoid-journal-no-space-deadlock-by-reserving-1-journal-bucket.patch queue-5.17/bcache-improve-multithreaded-bch_btree_check.patch queue-5.17/bcache-remove-incremental-dirty-sector-counting-for-bch_sectors_dirty_init.patch queue-5.17/bcache-improve-multithreaded-bch_sectors_dirty_init.patch