linux-kernel - Re: [PATCH] kcmp: add separate Kconfig symbol for kcmp syscall

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Date:   Fri, 10 Jul 2020 11:30:25 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kcmp: add separate Kconfig symbol for kcmp syscall

On Fri, Jul 10, 2020 at 09:56:31AM +0200, Rasmus Villemoes wrote:
> The ability to check open file descriptions for equality (without
> resorting to unreliable fstat() and fcntl(F_GETFL) comparisons) can be
> useful outside of the checkpoint/restore use case - for example,
> systemd uses kcmp() to deduplicate the per-service file descriptor
> store.
> 
> Make it possible to have the kcmp() syscall without the full
> CONFIG_CHECKPOINT_RESTORE.
> 
> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> ---
> I deliberately drop the ifdef in the eventpoll.h header rather than
> replace with KCMP_SYSCALL; it's harmless to declare a function that
> isn't defined anywhere.

Could you please point why setting #fidef KCMP_SYSCALL in eventpoll.h
is not suitable? Still the overall idea is fine for me, thanks!

Reviewed-by: Cyrill Gorcunov <gorcunov@...il.com>