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| author | Coly Li <colyli@suse.de> | 2019-06-28 14:59:56 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2019-06-28 16:39:17 +0300 |
| commit | 41508bb7d46b74dba631017e5a702a86caf1db8c (patch) | |
| tree | 72a7cc87407d048751e2ab6e676a3969f3b6caa4 | |
| parent | e5ec5f4765ada9c75fb3eee93a6e72f0e50599d5 (diff) | |
| download | linux-41508bb7d46b74dba631017e5a702a86caf1db8c.tar.xz | |
bcache: add comments for mutex_lock(&b->write_lock)
When accessing or modifying BTREE_NODE_dirty bit, it is not always
necessary to acquire b->write_lock. In bch_btree_cache_free() and
mca_reap() acquiring b->write_lock is necessary, and this patch adds
comments to explain why mutex_lock(&b->write_lock) is necessary for
checking or clearing BTREE_NODE_dirty bit there.
Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | drivers/md/bcache/btree.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index 88e5aa3fbb07..846306c3a887 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -659,6 +659,11 @@ static int mca_reap(struct btree *b, unsigned int min_order, bool flush) up(&b->io_mutex); } + /* + * BTREE_NODE_dirty might be cleared in btree_flush_btree() by + * __bch_btree_node_write(). To avoid an extra flush, acquire + * b->write_lock before checking BTREE_NODE_dirty bit. + */ mutex_lock(&b->write_lock); if (btree_node_dirty(b)) __bch_btree_node_write(b, &cl); @@ -782,6 +787,11 @@ void bch_btree_cache_free(struct cache_set *c) while (!list_empty(&c->btree_cache)) { b = list_first_entry(&c->btree_cache, struct btree, list); + /* + * This function is called by cache_set_free(), no I/O + * request on cache now, it is unnecessary to acquire + * b->write_lock before clearing BTREE_NODE_dirty anymore. + */ if (btree_node_dirty(b)) { btree_complete_write(b, btree_current_write(b)); clear_bit(BTREE_NODE_dirty, &b->flags); |