On 2020/06/30 12:09, Herbert Xu wrote: > On Tue, Jun 30, 2020 at 02:51:17AM +0000, Damien Le Moal wrote: >> >>> @@ -1463,12 +1465,12 @@ static void crypt_alloc_req_skcipher(struct crypt_config *cc, >>> * requests if driver request queue is full. >>> */ >>> skcipher_request_set_callback(ctx->r.req, >>> - CRYPTO_TFM_REQ_MAY_BACKLOG, >>> + nobacklog ? 0 : CRYPTO_TFM_REQ_MAY_BACKLOG, >>> kcryptd_async_done, dmreq_of_req(cc, ctx->r.req)); >> >> Will not specifying CRYPTO_TFM_REQ_MAY_BACKLOG always cause the crypto API to >> return -EBUSY ? From the comment above the skcipher_request_set_callback(), it >> seems that this will be the case only if the skcipher diver queue is full. So in >> other word, keeping the kcryptd_async_done() callback and executing the skcipher >> request through crypt_convert() and crypt_convert_block_skcipher() may still end >> up being an asynchronous operation. Can you confirm this and is it what you >> intended to implement ? > > The purpose of MAY_BACKLOG is to make the crypto request reliable. > It has nothing to do with whether the request will be synchronous > or not. > > Without the backlog flag, if the hardware queue is full the request > will simply be dropped, which is appropriate in the network stack > with IPsec where congestion can be dealt with at the source. > > Block layer on the other hand should always use the backlog flag > and stop sending more requests to the crypto API until the congestion > goes away. OK. Thanks for the information. So it sounds like this patch still needs some more fixes. > > Cheers, > -- Damien Le Moal Western Digital Research -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
