bcache: add code comments for state->pool in __btree_sort()

To explain the pages allocated from mempool state->pool can be
swapped in __btree_sort(), because state->pool is a page pool,
which allocates pages by alloc_pages() indeed.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/md/bcache/bset.c b/drivers/md/bcache/bset.c
index cffcdc9..4385303 100644 (file)
--- a/drivers/md/bcache/bset.c
+++ b/drivers/md/bcache/bset.c
@@ -1257,6 +1257,11 @@ static void __btree_sort(struct btree_keys *b, struct btree_iter *iter,
                 * Our temporary buffer is the same size as the btree node's
                 * buffer, we can just swap buffers instead of doing a big
                 * memcpy()
+                *
+                * Don't worry event 'out' is allocated from mempool, it can
+                * still be swapped here. Because state->pool is a page mempool
+                * creaated by by mempool_init_page_pool(), which allocates
+                * pages by alloc_pages() indeed.
                 */
 
                out->magic      = b->set->data->magic;