diff options
| author | Coly Li <colyli@suse.de> | 2019-06-28 14:59:56 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-09-16 09:22:23 +0300 |
| commit | f73c35d9297698cb9ce03dc84eaae19e2e1cd7a7 (patch) | |
| tree | 647f76da6b3700a034fdab954a4a17d6873c996a | |
| parent | 7989a5026fd12c7208448b66c51402a65a8a7f16 (diff) | |
| download | linux-f73c35d9297698cb9ce03dc84eaae19e2e1cd7a7.tar.xz | |
bcache: add comments for mutex_lock(&b->write_lock)
[ Upstream commit 41508bb7d46b74dba631017e5a702a86caf1db8c ]
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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -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 8c80833e73a9..e0468fd41b6e 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -649,6 +649,11 @@ 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); @@ -772,6 +777,11 @@ 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); |