linux-ext4 - Re: [PATCH 12/19] mm: Define MAP_SYNC and VM

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Date:   Fri, 13 Oct 2017 13:44:44 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-xfs@...r.kernel.org, Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>,
        Ted Tso <tytso@....edu>,
        "Darrick J. Wong" <darrick.wong@...cle.com>
Subject: Re: [PATCH 12/19] mm: Define MAP_SYNC and VM_SYNC flags

On Wed, Oct 11, 2017 at 10:05:56PM +0200, Jan Kara wrote:
> Define new MAP_SYNC flag and corresponding VMA VM_SYNC flag. As the
> MAP_SYNC flag is not part of LEGACY_MAP_MASK, currently it will be
> refused by all MAP_SHARED_VALIDATE map attempts and silently ignored for
> everything else.
> 
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  arch/xtensa/include/uapi/asm/mman.h | 1 +
>  fs/proc/task_mmu.c                  | 1 +
>  include/linux/mm.h                  | 1 +
>  include/linux/mman.h                | 3 ++-
>  include/uapi/asm-generic/mman.h     | 1 +
>  5 files changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/xtensa/include/uapi/asm/mman.h b/arch/xtensa/include/uapi/asm/mman.h
> index ec597900eec7..b62a7ce166fb 100644
> --- a/arch/xtensa/include/uapi/asm/mman.h
> +++ b/arch/xtensa/include/uapi/asm/mman.h
> @@ -56,6 +56,7 @@
>  #define MAP_NONBLOCK	0x20000		/* do not block on IO */
>  #define MAP_STACK	0x40000		/* give out an address that is best suited for process/thread stacks */
>  #define MAP_HUGETLB	0x80000		/* create a huge page mapping */
> +#define MAP_SYNC	0x100000	/* perform synchronous page faults for the mapping */

Why define MAP_SYNC for this one architecture, but not for the rest that have
their own arch/*/include/uapi/asm/mman.h?  AFAIK xtensa doesn't support DAX,
so has no need for MAP_SYNC?

Other than this one question, this patch looks fine:

Reviewed-by: Ross Zwisler <ross.zwisler@...ux.intel.com>