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

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Date:	Mon, 18 May 2015 23:58:12 -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 02:32:11PM +0800, Herbert Xu wrote:
> On Mon, May 18, 2015 at 11:24:30PM -0700, Jaegeuk Kim wrote:
> >
> > The call path in fs/ext4/crypto.c is:
> >  - writepage
> >   - ext4_encrypt
> >    - ext4_get_crypto_ctx
> >     - crypto_alloc_ablkcipher
> > 
> > AFAIK, this way can achieve to reduce memory footprint gracefully.
> > Just before submitting bios, fs allocates the required memory, and then end_io
> > will free them in pair.
> 
> So where does the key get generated? The crypto tfm should be
> allocated when you generate the key.

In fs/ext4/crypto.c,

 - writepage
   - ext4_encrypt
     - ext4_get_crypto_ctx
       - crypto_alloc_ablkcipher
     - ext4_page_crypto
       - crypto_ablkcipher_setkey
       - ablkcipher_request_alloc(GFP_NOFS)
       - ablkcipher_request_set_crypt(PAGE_CACHE_SIZE)
       - crypto_ablkcipher_encrypt

 - end_io
   - crypto_free_tfm

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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