[PATCH 3.4 045/146] dm crypt: fix deadlock when async crypto algorithm returns -EBUSY

lizf
2015-09-15T09:47:46Z

From: Ben Collins <ben.c@servergy.com>

3.4.109-rc1 review patch. If anyone has any objections, please let me know.

------------------

commit 0618764cb25f6fa9fb31152995de42a8a0496475 upstream.

I suspect this doesn't show up for most anyone because software
algorithms typically don't have a sense of being too busy. However,
when working with the Freescale CAAM driver it will return -EBUSY on
occasion under heavy -- which resulted in dm-crypt deadlock.

After checking the logic in some other drivers, the scheme for
crypt_convert() and it's callback, kcryptd_async_done(), were not
correctly laid out to properly handle -EBUSY or -EINPROGRESS.

Fix this by using the completion for both -EBUSY and -EINPROGRESS. Now
crypt_convert()'s use of completion is comparable to
af_alg_wait_for_completion(). Similarly, kcryptd_async_done() follows
the pattern used in af_alg_complete().

Before this fix dm-crypt would lockup within 1-2 minutes running with
the CAAM driver. Fix was regression tested against software algorithms
on PPC32 and x86_64, and things seem perfectly happy there as well.

Signed-off-by: Ben Collins <ben.c@servergy.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
[lizf: Backported to 3.4: adjust context]
Signed-off-by: Zefan Li <lizefan@huawei.com>
---
drivers/md/dm-crypt.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index 926989d..a1bd688 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -782,11 +782,10 @@ static int crypt_convert(struct crypt_config *cc,

switch (r) {
/* async */
+ case -EINPROGRESS:
case -EBUSY:
wait_for_completion(&ctx->restart);
INIT_COMPLETION(ctx->restart);
- /* fall through*/
- case -EINPROGRESS:
this_cc->req = NULL;
ctx->sector++;
continue;
@@ -1195,10 +1194,8 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
struct dm_crypt_io *io = container_of(ctx, struct dm_crypt_io, ctx);
struct crypt_config *cc = io->target->private;

- if (error == -EINPROGRESS) {
- complete(&ctx->restart);
+ if (error == -EINPROGRESS)
return;
- }

if (!error && cc->iv_gen_ops && cc->iv_gen_ops->post)
error = cc->iv_gen_ops->post(cc, iv_of_dmreq(cc, dmreq), dmreq);
@@ -1209,12 +1206,15 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
mempool_free(req_of_dmreq(cc, dmreq), cc->req_pool);

if (!atomic_dec_and_test(&ctx->pending))
- return;
+ goto done;

if (bio_data_dir(io->base_bio) == READ)
kcryptd_crypt_read_done(io);
else
kcryptd_crypt_write_io_submit(io, 1);
+done:
+ if (!completion_done(&ctx->restart))
+ complete(&ctx->restart);
}

static void kcryptd_crypt(struct work_struct *work)
--
1.9.1