path: root/drivers
diff options
authorMikulas Patocka <mpatocka@redhat.com>2022-08-10 16:16:34 -0400
committerMike Snitzer <snitzer@kernel.org>2022-08-11 11:10:42 -0400
commite3a7c2947b9e01b9cedd3f67849c0ae95f0fadfa (patch)
treec7710728a55e2a9b042beda3c95b6ab28cd609b8 /drivers
parentb7f362d6413ebd0167ac5a9f09ad5dca5490ac1a (diff)
dm bufio: fix some cases where the code sleeps with spinlock held
Commit b32d45824aa7 ("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: b32d45824aa7 ("dm bufio: Add DM_BUFIO_CLIENT_NO_SLEEP flag") Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Diffstat (limited to 'drivers')
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index bef8c6eb5bdb..799915220e6c 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -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) {
@@ -823,6 +827,9 @@ static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
+ 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))

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