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

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Date:	Wed, 20 May 2015 09:21:20 +0200
From:	Steffen Klassert <steffen.klassert@...unet.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
CC:	Theodore Ts'o <tytso@....edu>, Jaegeuk Kim <jaegeuk@...nel.org>,
	<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 10:27:55PM +0800, Herbert Xu wrote:
> On Tue, May 19, 2015 at 10:14:30AM -0400, Theodore Ts'o wrote:
> > 
> > There can be multiple reads going on in parallel, so we're currently
> > creating tfm's as necessary.  In fact one of the things that we've
> 
> A single tfm is fully-reentrant (as long as you don't change the
> key).  So multiple reads/writes on a single file can all use one
> tfm with no locking at all.
> 
> There should be a single tfm per key.  As your code appears to use
> one key per inode, that translates to one tfm per inode.
> 
> > talked about doing is since there are some ARM cores where their
> > "hardware acceleration" is slower than optimized software (sigh), and
> > there are some Android applications (such as Facebook) that read
> > *vast* quantities of data from flash on startup before painting a
> > single pixel, that we might want to consider in some cases,
> > parallelizing the decryption across multiple ARM cores.  Figuring out
> > when to do this, both in terms of the workload, how many cores to use
> > to balance off against power utilization, how much (if ever) to use
> > the hardware "accelerator", and just plain lack of time caused us not
> > to go down that particular path.
> 
> We already have some support for such parallelisation in the form of
> pcrypt.  It has been used on IPsec and I believe dmcrypt.

The current pcrypt version is used just for IPsec because it supports
only AEAD type algorithms and does not support request backlog. But
I have patches to support ablkcipher algorithms and request backlog.
I could provide them if there is interest in it.
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