In order to improve the IO performance of the dm-crypt
implementation, the commit 39d42fa96ba1 ("dm crypt:
add flags to optionally bypass kcryptd workqueues")
adds tasklet to do the crypto operations.
The tasklet callback function kcryptd_crypt_tasklet()
calls kcryptd_crypt() which is an original workqueue
callback function that may sleep. As a result, the
sleep-in-atomic-context bug may happen. The process
is shown below.
(atomic context)
kcryptd_crypt_tasklet()
kcryptd_crypt()
kcryptd_crypt_write_convert()
wait_for_completion() //may sleep
The wait_for_completion() is a function that may sleep.
In order to mitigate the bug, this patch changes
wait_for_completion() to try_wait_for_completion().
Fixes: 39d42fa96ba1 ("dm crypt: add flags to optionally bypass kcryptd workqueues")
Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
---
drivers/md/dm-crypt.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 8b47b913ee8..5e2b2463d87 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -2085,7 +2085,8 @@ static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
crypt_finished = atomic_dec_and_test(&ctx->cc_pending);
if (!crypt_finished && kcryptd_crypt_write_inline(cc, ctx)) {
/* Wait for completion signaled by kcryptd_async_done() */
- wait_for_completion(&ctx->restart);
+ while (!try_wait_for_completion(&ctx->restart))
+ ;
crypt_finished = 1;
}
--
2.17.1
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