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Date: Fri, 7 Nov 2025 13:10:56 +0100
From: Christoph Hellwig <hch@lst.de>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Jens Axboe <axboe@kernel.dk>,
	Vlastimil Babka <vbabka@suse.cz>,
	Andrew Morton <akpm@linux-foundation.org>,
	Christoph Lameter <cl@gentwo.org>,
	David Rientjes <rientjes@google.com>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Harry Yoo <harry.yoo@oracle.com>, linux-block@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-fscrypt@vger.kernel.org,
	linux-mm@kvack.org
Subject: Re: [PATCH 8/9] blk-crypto: use on-stack skciphers for fallback
 en/decryption
Message-ID: <20251107121056.GF30551@lst.de>
References: <20251031093517.1603379-1-hch@lst.de> <20251031093517.1603379-9-hch@lst.de> <20251107041859.GD47797@sol>
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User-Agent: Mutt/1.5.17 (2007-11-01)

On Thu, Nov 06, 2025 at 08:18:59PM -0800, Eric Biggers wrote:
> On Fri, Oct 31, 2025 at 10:34:38AM +0100, Christoph Hellwig wrote:
> > Allocating a skcipher dynamically can deadlock or cause unexpected
> > I/O failures when called from writeback context.  Sidestep the
> > allocation by using on-stack skciphers, similar to what the non
> > blk-crypto fscrypt already does.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> It might be worth leaving a note in the commit message that this also
> drops the incomplete support for asynchronous algorithms.  ("Incomplete"
> in the sense that they could be used, but only synchronously.)

sure.

> Also note that with asynchronous algorithms no being longer supported,
> the code can actually be simplified further because the
> DECLARE_CRYPTO_WAIT(wait) objects are no longer necessary.  The sequence
> of crypto_sync_skcipher calls that is used should be similar to what
> fscrypt_crypt_data_unit() does.

Ok.