linux-kernel - Re: [PATCH v2] mm: Move MAP_SYNC to asm-generic/mman-common.h

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Message-ID: <20190528092748.GE9607@quack2.suse.cz>
Date:   Tue, 28 May 2019 11:27:48 +0200
From:   Jan Kara <jack@...e.cz>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
Cc:     akpm@...ux-foundation.org, jack@...e.cz, mpe@...erman.id.au,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2] mm: Move MAP_SYNC to asm-generic/mman-common.h

On Tue 28-05-19 14:41:20, Aneesh Kumar K.V wrote:
> This enables support for synchronous DAX fault on powerpc
> 
> The generic changes are added as part of
> commit b6fb293f2497 ("mm: Define MAP_SYNC and VM_SYNC flags")
> 
> Without this, mmap returns EOPNOTSUPP for MAP_SYNC with MAP_SHARED_VALIDATE
> 
> Instead of adding MAP_SYNC with same value to
> arch/powerpc/include/uapi/asm/mman.h, I am moving the #define to
> asm-generic/mman-common.h. Two architectures using mman-common.h directly are
> sparc and powerpc. We should be able to consloidate more #defines to
> mman-common.h. That can be done as a separate patch.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.ibm.com>

Looks good to me FWIW (I don't have much experience with mmap flags and
their peculirarities). So feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
> Changes from V1:
> * Move #define to mman-common.h instead of powerpc specific mman.h change
> 
> 
>  include/uapi/asm-generic/mman-common.h | 3 ++-
>  include/uapi/asm-generic/mman.h        | 1 -
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h
> index abd238d0f7a4..bea0278f65ab 100644
> --- a/include/uapi/asm-generic/mman-common.h
> +++ b/include/uapi/asm-generic/mman-common.h
> @@ -25,7 +25,8 @@
>  # define MAP_UNINITIALIZED 0x0		/* Don't support this flag */
>  #endif
>  
> -/* 0x0100 - 0x80000 flags are defined in asm-generic/mman.h */
> +/* 0x0100 - 0x40000 flags are defined in asm-generic/mman.h */
> +#define MAP_SYNC		0x080000 /* perform synchronous page faults for the mapping */
>  #define MAP_FIXED_NOREPLACE	0x100000	/* MAP_FIXED which doesn't unmap underlying mapping */
>  
>  /*
> diff --git a/include/uapi/asm-generic/mman.h b/include/uapi/asm-generic/mman.h
> index 653687d9771b..2dffcbf705b3 100644
> --- a/include/uapi/asm-generic/mman.h
> +++ b/include/uapi/asm-generic/mman.h
> @@ -13,7 +13,6 @@
>  #define MAP_NONBLOCK	0x10000		/* do not block on IO */
>  #define MAP_STACK	0x20000		/* give out an address that is best suited for process/thread stacks */
>  #define MAP_HUGETLB	0x40000		/* create a huge page mapping */
> -#define MAP_SYNC	0x80000		/* perform synchronous page faults for the mapping */
>  
>  /* Bits [26:31] are reserved, see mman-common.h for MAP_HUGETLB usage */
>  
> -- 
> 2.21.0
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR