Mikulas Patocka 141b3523e9 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: 8238b45798 ("wait_on_bit: add an acquire memory barrier")
Depends-On: d6ffe6067a ("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>

2022-10-18 12:38:16 -04:00

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