linux-kernel - Re: [PATCH] mm: save two stranding bit in gfp

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Date:   Wed, 16 May 2018 22:46:44 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Greg Thelen <gthelen@...gle.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Vlastimil Babka <vbabka@...e.cz>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm: save two stranding bit in gfp_mask

On Wed 16-05-18 13:20:23, Shakeel Butt wrote:
> ___GFP_COLD and ___GFP_OTHER_NODE were removed but their bits were
> stranded. Slide existing gfp masks to make those two bits available.

Could you make the patch a bit smaller smaller? E.g.

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 1a4582b44d32..92c82ac8420f 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -24,6 +24,7 @@ struct vm_area_struct;
 #define ___GFP_HIGH		0x20u
 #define ___GFP_IO		0x40u
 #define ___GFP_FS		0x80u
+#define ___GFP_WRITE		0x100u
 #define ___GFP_NOWARN		0x200u
 #define ___GFP_RETRY_MAYFAIL	0x400u
 #define ___GFP_NOFAIL		0x800u
@@ -36,11 +37,10 @@ struct vm_area_struct;
 #define ___GFP_THISNODE		0x40000u
 #define ___GFP_ATOMIC		0x80000u
 #define ___GFP_ACCOUNT		0x100000u
-#define ___GFP_DIRECT_RECLAIM	0x400000u
-#define ___GFP_WRITE		0x800000u
-#define ___GFP_KSWAPD_RECLAIM	0x1000000u
+#define ___GFP_DIRECT_RECLAIM	0x200000u
+#define ___GFP_KSWAPD_RECLAIM	0x400000u
 #ifdef CONFIG_LOCKDEP
-#define ___GFP_NOLOCKDEP	0x2000000u
+#define ___GFP_NOLOCKDEP	0x800000u
 #else
 #define ___GFP_NOLOCKDEP	0
 #endif

> Signed-off-by: Shakeel Butt <shakeelb@...gle.com>

Other than that I have no real objections. It is good to see how many
bits we are using. So
Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  include/linux/gfp.h | 42 +++++++++++++++++++++---------------------
>  1 file changed, 21 insertions(+), 21 deletions(-)
> 
> diff --git a/include/linux/gfp.h b/include/linux/gfp.h
> index 1a4582b44d32..8edf72d32411 100644
> --- a/include/linux/gfp.h
> +++ b/include/linux/gfp.h
> @@ -16,31 +16,31 @@ struct vm_area_struct;
>   */
>  
>  /* Plain integer GFP bitmasks. Do not use this directly. */
> -#define ___GFP_DMA		0x01u
> -#define ___GFP_HIGHMEM		0x02u
> -#define ___GFP_DMA32		0x04u
> -#define ___GFP_MOVABLE		0x08u
> +#define ___GFP_DMA		0x1u
> +#define ___GFP_HIGHMEM		0x2u
> +#define ___GFP_DMA32		0x4u
> +#define ___GFP_MOVABLE		0x8u
>  #define ___GFP_RECLAIMABLE	0x10u
>  #define ___GFP_HIGH		0x20u
>  #define ___GFP_IO		0x40u
>  #define ___GFP_FS		0x80u
> -#define ___GFP_NOWARN		0x200u
> -#define ___GFP_RETRY_MAYFAIL	0x400u
> -#define ___GFP_NOFAIL		0x800u
> -#define ___GFP_NORETRY		0x1000u
> -#define ___GFP_MEMALLOC		0x2000u
> -#define ___GFP_COMP		0x4000u
> -#define ___GFP_ZERO		0x8000u
> -#define ___GFP_NOMEMALLOC	0x10000u
> -#define ___GFP_HARDWALL		0x20000u
> -#define ___GFP_THISNODE		0x40000u
> -#define ___GFP_ATOMIC		0x80000u
> -#define ___GFP_ACCOUNT		0x100000u
> -#define ___GFP_DIRECT_RECLAIM	0x400000u
> -#define ___GFP_WRITE		0x800000u
> -#define ___GFP_KSWAPD_RECLAIM	0x1000000u
> +#define ___GFP_NOWARN		0x100u
> +#define ___GFP_RETRY_MAYFAIL	0x200u
> +#define ___GFP_NOFAIL		0x400u
> +#define ___GFP_NORETRY		0x800u
> +#define ___GFP_MEMALLOC		0x1000u
> +#define ___GFP_COMP		0x2000u
> +#define ___GFP_ZERO		0x4000u
> +#define ___GFP_NOMEMALLOC	0x8000u
> +#define ___GFP_HARDWALL		0x10000u
> +#define ___GFP_THISNODE		0x20000u
> +#define ___GFP_ATOMIC		0x40000u
> +#define ___GFP_ACCOUNT		0x80000u
> +#define ___GFP_DIRECT_RECLAIM	0x100000u
> +#define ___GFP_WRITE		0x200000u
> +#define ___GFP_KSWAPD_RECLAIM	0x400000u
>  #ifdef CONFIG_LOCKDEP
> -#define ___GFP_NOLOCKDEP	0x2000000u
> +#define ___GFP_NOLOCKDEP	0x800000u
>  #else
>  #define ___GFP_NOLOCKDEP	0
>  #endif
> @@ -205,7 +205,7 @@ struct vm_area_struct;
>  #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP)
>  
>  /* Room for N __GFP_FOO bits */
> -#define __GFP_BITS_SHIFT (25 + IS_ENABLED(CONFIG_LOCKDEP))
> +#define __GFP_BITS_SHIFT (23 + IS_ENABLED(CONFIG_LOCKDEP))
>  #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))
>  
>  /*
> -- 
> 2.17.0.441.gb46fe60e1d-goog

-- 
Michal Hocko
SUSE Labs