From e3a7c2947b9e01b9cedd3f67849c0ae95f0fadfa Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Wed, 10 Aug 2022 16:16:34 -0400 Subject: [PATCH] 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 Signed-off-by: Mike Snitzer --- drivers/md/dm-bufio.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c index bef8c6e..7999152 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) { __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)) -- 2.7.4