From: Mikulas Patocka <mpatocka@redhat.com>
To: Ignat Korchagin <ignat@cloudflare.com>
Cc: Damien.LeMoal@wdc.com, herbert@gondor.apana.org.au,
snitzer@redhat.com, kernel-team@cloudflare.com,
dm-crypt@saout.de, linux-kernel@vger.kernel.org,
stable@vger.kernel.org, nobuto.murata@canonical.com,
ebiggers@kernel.org, clm@fb.com, dm-devel@redhat.com,
linux-btrfs@vger.kernel.org, dsterba@suse.com,
josef@toxicpanda.com, mail@maciej.szmigiero.name, agk@redhat.com
Subject: Re: [dm-crypt] [PATCH v2 1/2] dm crypt: use GFP_ATOMIC when allocating crypto requests from softirq
Date: Fri, 1 Jan 2021 05:00:18 -0500 (EST) [thread overview]
Message-ID: <alpine.LRH.2.02.2101010450460.31009@file01.intranet.prod.int.rdu2.redhat.com> (raw)
In-Reply-To: <20201230214520.154793-2-ignat@cloudflare.com>
On Wed, 30 Dec 2020, Ignat Korchagin wrote:
> diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
> index 53791138d78b..e4fd690c70e1 100644
> --- a/drivers/md/dm-crypt.c
> +++ b/drivers/md/dm-crypt.c
> @@ -1539,7 +1549,10 @@ static blk_status_t crypt_convert(struct crypt_config *cc,
>
> while (ctx->iter_in.bi_size && ctx->iter_out.bi_size) {
>
> - crypt_alloc_req(cc, ctx);
> + r = crypt_alloc_req(cc, ctx);
> + if (r)
> + return BLK_STS_RESOURCE;
> +
> atomic_inc(&ctx->cc_pending);
>
> if (crypt_integrity_aead(cc))
> --
> 2.20.1
I'm not quite convinced that returning BLK_STS_RESOURCE will help. The
block layer will convert this value back to -ENOMEM and return it to the
caller, resulting in an I/O error.
Note that GFP_ATOMIC allocations may fail anytime and you must handle
allocation failure gracefully - i.e. process the request without any
error.
An acceptable solution would be to punt the request to a workqueue and do
GFP_NOIO allocation from the workqueue. Or add the request to some list
and process the list when some other request completes.
You should write a test that simulates allocation failure and verify that
the kernel handles it gracefully without any I/O error.
Mikulas
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next prev parent reply other threads:[~2021-01-01 10:56 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-30 21:45 [dm-crypt] [PATCH v2 0/2] dm crypt: some fixes to support dm-crypt running in softirq context Ignat Korchagin
2020-12-30 21:45 ` [dm-crypt] [PATCH v2 1/2] dm crypt: use GFP_ATOMIC when allocating crypto requests from softirq Ignat Korchagin
2021-01-01 10:00 ` Mikulas Patocka [this message]
2021-01-01 10:26 ` Ignat Korchagin
2020-12-30 21:45 ` [dm-crypt] [PATCH v2 2/2] dm crypt: do not wait for backlogged crypto request completion in softirq Ignat Korchagin
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