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

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Commit b32d45824a ("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: b32d45824a ("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>
This commit is contained in:
Mikulas Patocka 2022-08-10 16:16:34 -04:00 committed by Mike Snitzer
parent b7f362d641
commit e3a7c2947b
1 changed files with 9 additions and 1 deletions
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10
drivers/md/dm-bufio.c
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@ -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))