linux-kernel - Re: copy on write for splice() from file to pipe?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Y+VYfHcNdvez6M2a@jeremy-acer>
Date:   Thu, 9 Feb 2023 12:33:00 -0800
From:   Jeremy Allison <jra@...ba.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Stefan Metzmacher <metze@...ba.org>, Jens Axboe <axboe@...nel.dk>,
        Linux API Mailing List <linux-api@...r.kernel.org>,
        Samba Technical <samba-technical@...ts.samba.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        io-uring <io-uring@...r.kernel.org>
Subject: Re: copy on write for splice() from file to pipe?

On Thu, Feb 09, 2023 at 11:48:35AM -0800, Linus Torvalds via samba-technical wrote:
>
>So this is exactly *why* splicing from a file all the way to the
>network will then show any file changes that have happened in between
>that "splice started" and "network card got the data". You're supposed
>to use splice only when you can guarantee the data stability (or,
>alternatively, when you simply don't care about the data stability,
>and getting the changed data is perfectly fine).

Metze, correct me if I'm wrong but isn't this exactly the "file
is leased in SMB3" case ?

We already know if a file is leased, and so only use the splice calls
for I/O in that case, and fall back to the slower calls in the
non-leased case.