Commit e3a7c294 authored by Mikulas Patocka's avatar Mikulas Patocka Committed by Mike Snitzer
Browse files

dm bufio: fix some cases where the code sleeps with spinlock held 



Commit b32d4582 ("dm bufio: Add DM_BUFIO_CLIENT_NO_SLEEP flag")
added a "NO_SLEEP" mode, it replaces a mutex with a spinlock, and it
is only usable when the device is in read-only mode (because the write
path may be sleeping while holding the dm_bufio_client lock).

However, there are still two points where the code could sleep even in
read-only mode. One is in __get_unclaimed_buffer -> __make_buffer_clean.
The other is in __try_evict_buffer -> __make_buffer_clean. These functions
will call __make_buffer_clean which sleeps if the buffer is being read.

Fix these cases so that if c->no_sleep is set __make_buffer_clean
will not be called and the buffer will be skipped instead.

Fixes: b32d4582 ("dm bufio: Add DM_BUFIO_CLIENT_NO_SLEEP flag")
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent b7f362d6

drivers/md/dm-bufio.c

+9 −1
Original line number Diff line number Diff line
@@ -815,6 +815,10 @@ static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c) 
		BUG_ON(test_bit(B_WRITING, &b->state));

		BUG_ON(test_bit(B_DIRTY, &b->state));



		if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep &&

		    unlikely(test_bit(B_READING, &b->state)))

			continue;



		if (!b->hold_count) {

			__make_buffer_clean(b);

			__unlink_buffer(b);
@@ -823,6 +827,9 @@ static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c) 
		cond_resched();

	}



	if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)

		return NULL;



	list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {

		BUG_ON(test_bit(B_READING, &b->state));
@@ -1632,7 +1639,8 @@ static void drop_buffers(struct dm_bufio_client *c) 
 */

static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)

{

	if (!(gfp & __GFP_FS)) {

	if (!(gfp & __GFP_FS) ||

	    (static_branch_unlikely(&no_sleep_enabled) && b->c->no_sleep)) {

		if (test_bit(B_READING, &b->state) ||

		    test_bit(B_WRITING, &b->state) ||

		    test_bit(B_DIRTY, &b->state))