linux-ext4 - Re: [PATCH] crypto: allow to assign gfp_t for __crypto_alloc

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Message-ID: <20150519072740.GA40281@jaegeuk-mac02.hsd1.ca.comcast.net>
Date:	Tue, 19 May 2015 00:27:40 -0700
From:	Jaegeuk Kim <jaegeuk@...nel.org>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	davem@...emloft.net, linux-crypto@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-f2fs-devel@...ts.sourceforge.net, ecryptfs@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] crypto: allow to assign gfp_t for __crypto_alloc_tfm

On Tue, May 19, 2015 at 03:15:21PM +0800, Herbert Xu wrote:
> On Tue, May 19, 2015 at 12:13:17AM -0700, Jaegeuk Kim wrote:
> >
> > The key generation is done by ext4_generate_encryption_key in
> > fs/ext4/crypto_key.c.
> > And, ext4_file_mmap and ext4_file_open trigger it.
> 
> Well that's where you should be doing crypto_alloc_ablkcipher
> and crypto_ablkcipher_setkey.
> 
> The whole point of a crypto tfm is to represent a key so any time
> you get one you should create a crypto tfm.  Carrying around a raw
> key is just wrong.

So, IMHO, it can consume memory too much, since tfm should be allocated for
every inodes and be alive until inode eviction.
Apart from giving GFP_NOFS, do you mean that it is a wrong approach?

Thanks,

> 
> Cheers,
> -- 
> Email: Herbert Xu <herbert@...dor.apana.org.au>
> Home Page: http://gondor.apana.org.au/~herbert/
> PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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