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authorMikulas Patocka <mpatocka@redhat.com>2022-10-18 17:06:45 +0300
committerMike Snitzer <snitzer@kernel.org>2022-10-18 19:38:16 +0300
commit141b3523e9be6f15577acf4bbc3bc1f82d81d6d1 (patch)
tree66e3b3ea3e39a1d3f818d4de600e5e2546eb9bf3 /drivers/md
parentbb1a1146467ad812bb65440696df0782e2bc63c8 (diff)
downloadlinux-141b3523e9be6f15577acf4bbc3bc1f82d81d6d1.tar.xz
dm bufio: use the acquire memory barrier when testing for B_READING
The function test_bit doesn't provide any memory barrier. It may be possible that the read requests that follow test_bit(B_READING, &b->state) are reordered before the test, reading invalid data that existed before B_READING was cleared. Fix this bug by changing test_bit to test_bit_acquire. This is particularly important on arches with weak(er) memory ordering (e.g. arm64). Depends-On: 8238b4579866 ("wait_on_bit: add an acquire memory barrier") Depends-On: d6ffe6067a54 ("provide arch_test_bit_acquire for architectures that define test_bit") Cc: stable@vger.kernel.org Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-bufio.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index 09c7ed2650ca..9c5ef818ca36 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -795,7 +795,8 @@ static void __make_buffer_clean(struct dm_buffer *b)
{
BUG_ON(b->hold_count);
- if (!b->state) /* fast case */
+ /* smp_load_acquire() pairs with read_endio()'s smp_mb__before_atomic() */
+ if (!smp_load_acquire(&b->state)) /* fast case */
return;
wait_on_bit_io(&b->state, B_READING, TASK_UNINTERRUPTIBLE);
@@ -816,7 +817,7 @@ static struct dm_buffer *__get_unclaimed_buffer(struct dm_bufio_client *c)
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)))
+ unlikely(test_bit_acquire(B_READING, &b->state)))
continue;
if (!b->hold_count) {
@@ -1058,7 +1059,7 @@ found_buffer:
* If the user called both dm_bufio_prefetch and dm_bufio_get on
* the same buffer, it would deadlock if we waited.
*/
- if (nf == NF_GET && unlikely(test_bit(B_READING, &b->state)))
+ if (nf == NF_GET && unlikely(test_bit_acquire(B_READING, &b->state)))
return NULL;
b->hold_count++;
@@ -1218,7 +1219,7 @@ void dm_bufio_release(struct dm_buffer *b)
* invalid buffer.
*/
if ((b->read_error || b->write_error) &&
- !test_bit(B_READING, &b->state) &&
+ !test_bit_acquire(B_READING, &b->state) &&
!test_bit(B_WRITING, &b->state) &&
!test_bit(B_DIRTY, &b->state)) {
__unlink_buffer(b);
@@ -1479,7 +1480,7 @@ EXPORT_SYMBOL_GPL(dm_bufio_release_move);
static void forget_buffer_locked(struct dm_buffer *b)
{
- if (likely(!b->hold_count) && likely(!b->state)) {
+ if (likely(!b->hold_count) && likely(!smp_load_acquire(&b->state))) {
__unlink_buffer(b);
__free_buffer_wake(b);
}
@@ -1639,7 +1640,7 @@ static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
{
if (!(gfp & __GFP_FS) ||
(static_branch_unlikely(&no_sleep_enabled) && b->c->no_sleep)) {
- if (test_bit(B_READING, &b->state) ||
+ if (test_bit_acquire(B_READING, &b->state) ||
test_bit(B_WRITING, &b->state) ||
test_bit(B_DIRTY, &b->state))
return false;