linux-kernel - Re: [dm-crypt] Kernel 2.6.25-rc4: lock up when writing onto DM-Crypt volume

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Date:	Fri, 14 Mar 2008 10:19:24 +0100
From:	Milan Broz <mbroz@...hat.com>
To:	dm-crypt@...ut.de
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Alasdair G Kergon <agk@...hat.com>
Subject: Re: [dm-crypt] Kernel 2.6.25-rc4: lock up when writing onto DM-Crypt
 volume

Ulrich Lukas wrote:

> I observed a reproducible bug after switching from Linux 2.6.24 to the
> latest 2.6.25-rc4 kernel. On Linux 2.6.24 I had no such problem.
>
> When writing to a slightly bigger DM-Crypt-LUKS volume, I experience
> lock-ups in the form of stuck, non-terminating, non-"kill -9"-able
> processes
Please could you try patch below?
Milan

--
dm-crypt: Fix reference counting in crypto context.

Fix regression in dm-crypt introduced in commit
3a7f6c990ad04e6f576a159876c602d14d6f7fef
(dm crypt: use async crypto).

If the write request is splitted, ctx->context
is not properly initialized again and crypt_convert
return incorrectly processed return value like
asynchronous request.

Fix by moving pending counter manipulation
directly to crypt_convert call.

Signed-off-by: Milan Broz <mbroz@...hat.com>
---
 drivers/md/dm-crypt.c |   18 ++++++++++--------
 1 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index b04f98d..47bbb03 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -331,14 +331,7 @@ static void crypt_convert_init(struct crypt_config *cc,
 	ctx->idx_out = bio_out ? bio_out->bi_idx : 0;
 	ctx->sector = sector + cc->iv_offset;
 	init_completion(&ctx->restart);
-	/*
-	 * Crypto operation can be asynchronous,
-	 * ctx->pending is increased after request submission.
-	 * We need to ensure that we don't call the crypt finish
-	 * operation before pending got incremented
-	 * (dependent on crypt submission return code).
-	 */
-	atomic_set(&ctx->pending, 2);
+	atomic_set(&ctx->pending, 0);
 }
 
 static int crypt_convert_block(struct crypt_config *cc,
@@ -413,6 +406,15 @@ static int crypt_convert(struct crypt_config *cc,
 {
 	int r = 0;
 
+	/*
+	 * Crypto operation can be asynchronous,
+	 * ctx->pending is increased after request submission.
+	 * We need to ensure that we don't call the crypt finish
+	 * operation before pending got incremented
+	 * (dependent on crypt submission return code).
+	 */
+	atomic_add(2, &ctx->pending);
+
 	while(ctx->idx_in < ctx->bio_in->bi_vcnt &&
 	      ctx->idx_out < ctx->bio_out->bi_vcnt) {
 


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