This is a note to let you know that I've just added the patch titled bcache: remove incremental dirty sector counting for bch_sectors_dirty_init() to the 5.10-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-remove-incremental-dirty-sector-counting-for-bch_sectors_dirty_init.patch and it can be found in the queue-5.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 80db4e4707e78cb22287da7d058d7274bd4cb370 Mon Sep 17 00:00:00 2001 From: Coly Li <colyli@xxxxxxx> Date: Tue, 24 May 2022 18:23:35 +0800 Subject: bcache: remove incremental dirty sector counting for bch_sectors_dirty_init() From: Coly Li <colyli@xxxxxxx> commit 80db4e4707e78cb22287da7d058d7274bd4cb370 upstream. After making bch_sectors_dirty_init() being multithreaded, the existing incremental dirty sector counting in bch_root_node_dirty_init() doesn't release btree occupation after iterating 500000 (INIT_KEYS_EACH_TIME) bkeys. Because a read lock is added on btree root node to prevent the btree to be split during the dirty sectors counting, other I/O requester has no chance to gain the write lock even restart bcache_btree(). That is to say, the incremental dirty sectors counting is incompatible to the multhreaded bch_sectors_dirty_init(). We have to choose one and drop another one. In my testing, with 512 bytes random writes, I generate 1.2T dirty data and a btree with 400K nodes. With single thread and incremental dirty sectors counting, it takes 30+ minites to register the backing device. And with multithreaded dirty sectors counting, the backing device registration can be accomplished within 2 minutes. The 30+ minutes V.S. 2- minutes difference makes me decide to keep multithreaded bch_sectors_dirty_init() and drop the incremental dirty sectors counting. This is what this patch does. But INIT_KEYS_EACH_TIME is kept, in sectors_dirty_init_fn() the CPU will be released by cond_resched() after every INIT_KEYS_EACH_TIME keys iterated. This is to avoid the watchdog reports a bogus soft lockup warning. Fixes: b144e45fc576 ("bcache: make bch_sectors_dirty_init() to be multithreaded") Signed-off-by: Coly Li <colyli@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lore.kernel.org/r/20220524102336.10684-4-colyli@xxxxxxx Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/md/bcache/writeback.c | 39 ++++++++++++--------------------------- 1 file changed, 12 insertions(+), 27 deletions(-) --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -756,13 +756,11 @@ static int bch_writeback_thread(void *ar /* Init */ #define INIT_KEYS_EACH_TIME 500000 -#define INIT_KEYS_SLEEP_MS 100 struct sectors_dirty_init { struct btree_op op; unsigned int inode; size_t count; - struct bkey start; }; static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b, @@ -778,11 +776,8 @@ static int sectors_dirty_init_fn(struct KEY_START(k), KEY_SIZE(k)); op->count++; - if (atomic_read(&b->c->search_inflight) && - !(op->count % INIT_KEYS_EACH_TIME)) { - bkey_copy_key(&op->start, k); - return -EAGAIN; - } + if (!(op->count % INIT_KEYS_EACH_TIME)) + cond_resched(); return MAP_CONTINUE; } @@ -797,24 +792,16 @@ static int bch_root_node_dirty_init(stru bch_btree_op_init(&op.op, -1); op.inode = d->id; op.count = 0; - op.start = KEY(op.inode, 0, 0); - do { - ret = bcache_btree(map_keys_recurse, - k, - c->root, - &op.op, - &op.start, - sectors_dirty_init_fn, - 0); - if (ret == -EAGAIN) - schedule_timeout_interruptible( - msecs_to_jiffies(INIT_KEYS_SLEEP_MS)); - else if (ret < 0) { - pr_warn("sectors dirty init failed, ret=%d!\n", ret); - break; - } - } while (ret == -EAGAIN); + ret = bcache_btree(map_keys_recurse, + k, + c->root, + &op.op, + &KEY(op.inode, 0, 0), + sectors_dirty_init_fn, + 0); + if (ret < 0) + pr_warn("sectors dirty init failed, ret=%d!\n", ret); return ret; } @@ -858,7 +845,6 @@ static int bch_dirty_init_thread(void *a goto out; } skip_nr--; - cond_resched(); } if (p) { @@ -868,7 +854,6 @@ static int bch_dirty_init_thread(void *a p = NULL; prev_idx = cur_idx; - cond_resched(); } out: @@ -907,11 +892,11 @@ void bch_sectors_dirty_init(struct bcach bch_btree_op_init(&op.op, -1); op.inode = d->id; op.count = 0; - op.start = KEY(op.inode, 0, 0); for_each_key_filter(&c->root->keys, k, &iter, bch_ptr_invalid) sectors_dirty_init_fn(&op.op, c->root, k); + rw_unlock(0, c->root); return; } Patches currently in stable-queue which might be from colyli@xxxxxxx are queue-5.10/bcache-avoid-journal-no-space-deadlock-by-reserving-1-journal-bucket.patch queue-5.10/bcache-improve-multithreaded-bch_btree_check.patch queue-5.10/bcache-remove-incremental-dirty-sector-counting-for-bch_sectors_dirty_init.patch queue-5.10/bcache-improve-multithreaded-bch_sectors_dirty_init.patch