linux-kernel - Re: [patch V3 01/10] rslib: Add GFP aware init function

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Date:   Wed, 25 Apr 2018 11:16:17 +1000
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kees Cook <keescook@...omium.org>,
        Segher Boessenkool <segher@...nel.crashing.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Andrew Morton <akpm@...uxfoundation.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Alasdair Kergon <agk@...hat.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>, Neil Brown <neilb@...e.com>
Subject: Re: [patch V3 01/10] rslib: Add GFP aware init function

Hi Thomas,

On Sun, 22 Apr 2018 18:23:46 +0200 Thomas Gleixner <tglx@...utronix.de> wrote:
>
> The rslib usage in dm/verity_fec is broken because init_rs() can nest in
> GFP_NOIO mempool allocations as init_rs() is invoked from the mempool alloc
> callback.
> 
> Provide a variant which takes gfp_t flags as argument.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Mike Snitzer <snitzer@...hat.com>
> Cc: Alasdair Kergon <agk@...hat.com>
> Cc: Neil Brown <neilb@...e.com>
> ---
>  include/linux/rslib.h           |   26 +++++++++++++++++++++++---
>  lib/reed_solomon/reed_solomon.c |   36 ++++++++++++++++++++----------------
>  2 files changed, 43 insertions(+), 19 deletions(-)
> 
> --- a/include/linux/rslib.h
> +++ b/include/linux/rslib.h
> @@ -77,10 +77,30 @@ int decode_rs16(struct rs_control *rs, u
>  #endif
>  
>  /* Create or get a matching rs control structure */
> -struct rs_control *init_rs(int symsize, int gfpoly, int fcr, int prim,
> -			   int nroots);
> +struct rs_control *init_rs_gfp(int symsize, int gfpoly, int fcr, int prim,
> +			       int nroots, gfp_t gfp);
> +
> +/**
> + * init_rs - Create a RS control struct and initialize it
> + *  @symsize:	the symbol size (number of bits)
> + *  @gfpoly:	the extended Galois field generator polynomial coefficients,
> + *		with the 0th coefficient in the low order bit. The polynomial
> + *		must be primitive;
> + *  @fcr:	the first consecutive root of the rs code generator polynomial
> + *		in index form
> + *  @prim:	primitive element to generate polynomial roots
> + *  @nroots:	RS code generator polynomial degree (number of roots)
> + *
> + * Allocations use GFP_KERNEL.
> + */
> +static inline struct rs_control *init_rs(int symsize, int gfpoly, int fcr,
> +					 int prim, int nroots)
> +{
> +	return init_rs_gfp(symsize, gfpoly, fcr, prim, nroots, GFP_KERNEL);
> +}
> +

The version of this patch that Kees has committed to his kspp tree in linux-next has

#include <linux/slab.h>

why not just

#include <linux/types.h>	/* for gpf_t */
#include <linux/gpf.h>		/* for GFP_KERNEL */

?
-- 
Cheers,
Stephen Rothwell

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