[dm-devel] [PATCH v2] dm crypt: fix deadlock when algo returns -EBUSY

[Ben Collins]

> On Apr 7, 2015, at 11:28 AM, Mike Snitzer <snitzer at redhat.com> wrote:
> 
> On Tue, Apr 07 2015 at 11:55P -0400,
> Mike Snitzer <snitzer at redhat.com> wrote:
> 
>> It looks like you're _always_ using the completion regardless of whether
>> crypt_convert() will be waiting (e.g. even if error is 0).
>> 
>> I can see this "working" but it seems less than ideal.  Would it be
>> better to record the need to use the completion in ctx and then
>> conditionally call complete()?
> 
> Actually, how about using !completion_done() before calling complete()?
> If you think this would be OK, any chance you could re-test with this?

I'll be able to test it before Friday (out of town). Thanks



> From: Ben Collins <ben.c at servergy.com>
> Date: Fri, 3 Apr 2015 16:09:46 +0000
> Subject: [PATCH] dm crypt: fix deadlock when algo returns -EBUSY
> 
> 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.
> 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 at servergy.com>
> Signed-off-by: Mike Snitzer <snitzer at redhat.com>
> Cc: stable at vger.kernel.org
> ---
> 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 ea09d54..cab96ca 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -925,11 +925,10 @@ static int crypt_convert(struct crypt_config *cc,
> 
> 		switch (r) {
> 		/* async */
> +		case -EINPROGRESS:
> 		case -EBUSY:
> 			wait_for_completion(&ctx->restart);
> 			reinit_completion(&ctx->restart);
> -			/* fall through*/
> -		case -EINPROGRESS:
> 			ctx->req = NULL;
> 			ctx->cc_sector++;
> 			continue;
> @@ -1346,10 +1345,8 @@ 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->cc;
> 
> -	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);
> @@ -1360,12 +1357,15 @@ static void kcryptd_async_done(struct crypto_async_request *async_req,
> 	crypt_free_req(cc, req_of_dmreq(cc, dmreq), io->base_bio);
> 
> 	if (!atomic_dec_and_test(&ctx->cc_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)
> --
> 1.9.5 (Apple Git-50.3)
> 

——
Ben Collins
Cyphre Champion
————————————————
Principal Architect
Servergy, Inc.
469-919-5634 (O)
757-243-7557 (M)

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