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dm crypt: add comments to better describe crypto processing logic

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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: Milan Broz <mbroz@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Milan Broz 2015-05-15 17:00:25 +02:00 committed by Mike Snitzer
parent ed63287dd6
commit 54cea3f668
1 changed files with 24 additions and 6 deletions
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30
drivers/md/dm-crypt.c
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@ -1,7 +1,7 @@
/*
* 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*/
/* 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;