From e3a7c2947b9e01b9cedd3f67849c0ae95f0fadfa Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <mpatocka@redhat.com>
Date: Wed, 10 Aug 2022 16:16:34 -0400
Subject: [PATCH] dm bufio: fix some cases where the code sleeps with spinlock
held
Git-commit: e3a7c2947b9e01b9cedd3f67849c0ae95f0fadfa
Patch-mainline: v6.0-rc1
References: jsc#PED-2765
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>
Signed-off-by: Coly Li <colyli@suse.de>
---
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 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) {
__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))
--
2.35.3