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Commit 54cea3f6 authored by Milan Broz's avatar Milan Broz Committed by Mike Snitzer
Browse files

dm crypt: add comments to better describe crypto processing logic 



A crypto driver can process requests synchronously or asynchronously
and can use an internal driver queue to backlog requests.
Add some comments to clarify internal logic and completion return codes.

Signed-off-by: default avatarMilan Broz <mbroz@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@redhat.com>
parent ed63287d

drivers/md/dm-crypt.c

+24 −6
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2003 Jana Saout <jana@saout.de>

 * Copyright (C) 2004 Clemens Fruhwirth <clemens@endorphin.org>

 * Copyright (C) 2006-2009 Red Hat, Inc. All rights reserved.

 * Copyright (C) 2006-2015 Red Hat, Inc. All rights reserved.

 * Copyright (C) 2013 Milan Broz <gmazyland@gmail.com>

 *

 * This file is released under the GPL.
@@ -891,6 +891,11 @@ static void crypt_alloc_req(struct crypt_config *cc, 
		ctx->req = mempool_alloc(cc->req_pool, GFP_NOIO);



	ablkcipher_request_set_tfm(ctx->req, cc->tfms[key_index]);



	/*

	 * Use REQ_MAY_BACKLOG so a cipher driver internally backlogs

	 * requests if driver request queue is full.

	 */

	ablkcipher_request_set_callback(ctx->req,

	    CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,

	    kcryptd_async_done, dmreq_of_req(cc, ctx->req));
@@ -924,24 +929,32 @@ static int crypt_convert(struct crypt_config *cc, 
		r = crypt_convert_block(cc, ctx, ctx->req);



		switch (r) {

		/* async */

		/*

		 * The request was queued by a crypto driver

		 * but the driver request queue is full, let's wait.

		 */

		case -EBUSY:

			wait_for_completion(&ctx->restart);

			reinit_completion(&ctx->restart);

			/* fall through */

		/*

		 * The request is queued and processed asynchronously,

		 * completion function kcryptd_async_done() will be called.

		 */

		case -EINPROGRESS:

			ctx->req = NULL;

			ctx->cc_sector++;

			continue;



		/* sync */

		/*

		 * The request was already processed (synchronously).

		 */

		case 0:

			atomic_dec(&ctx->cc_pending);

			ctx->cc_sector++;

			cond_resched();

			continue;



		/* error */

		/* There was an error while processing the request. */

		default:

			atomic_dec(&ctx->cc_pending);

			return r;
@@ -1346,6 +1359,11 @@ 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;



	/*

	 * A request from crypto driver backlog is going to be processed now,

	 * finish the completion and continue in crypt_convert().

	 * (Callback will be called for the second time for this request.)

	 */

	if (error == -EINPROGRESS) {

		complete(&ctx->restart);

		return;