linux-kernel - Re: [RFC PATCH 11/10] pipe: Add fsync() support [ver #2]

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Message-ID: <25886.1572723272@warthog.procyon.org.uk>
Date:   Sat, 02 Nov 2019 19:34:32 +0000
From:   David Howells <dhowells@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     dhowells@...hat.com,
        Konstantin Khlebnikov <khlebnikov@...dex-team.ru>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>, raven@...maw.net,
        Christian Brauner <christian@...uner.io>,
        keyrings@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-block <linux-block@...r.kernel.org>,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 11/10] pipe: Add fsync() support [ver #2]

Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> > > Similar synchronization is required for reusing memory after vmsplice()?
> > > I don't see other way how sender could safely change these pages.

Actually, it's probably worse than that.  If the output of the pipe gets teed
or spliced somewhere else, you still don't know when the vmspliced pages are
finished with.

David