diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2022-10-18 10:06:45 -0400 |
|---|---|---|
| committer | Mike Snitzer <snitzer@kernel.org> | 2022-10-18 12:38:16 -0400 |
| commit | 141b3523e9be6f15577acf4bbc3bc1f82d81d6d1 (patch) | |
| tree | 66e3b3ea3e39a1d3f818d4de600e5e2546eb9bf3 /drivers | |
| parent | bb1a1146467ad812bb65440696df0782e2bc63c8 (diff) | |
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')
| -rw-r--r-- | drivers/md/dm-bufio.c | 13 |
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; |