From: Linus Torvalds <torvalds@linux-foundation.org>
To: David Howells <dhowells@redhat.com>
Cc: netdev@vger.kernel.org, Matthew Wilcox <willy@infradead.org>,
Dave Chinner <david@fromorbit.com>,
Matt Whitlock <kernel@mattwhitlock.name>,
Jens Axboe <axboe@kernel.dk>,
linux-fsdevel@kvack.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 0/4] splice: Fix corruption in data spliced to pipe
Date: Thu, 29 Jun 2023 10:56:04 -0700 [thread overview]
Message-ID: <CAHk-=wiDwfyj0CCupT-oEToqsNLcbsTQdcgDupF=ZETUjJQJtQ@mail.gmail.com> (raw)
In-Reply-To: <20230629155433.4170837-1-dhowells@redhat.com>
On Thu, 29 Jun 2023 at 08:55, David Howells <dhowells@redhat.com> wrote:
>
> Matt Whitlock, Matthew Wilcox and Dave Chinner are of the opinion that data
> in the pipe must not be seen to change and that if it does, this is a bug.
I'm not convinced.
The whole *point* of vmsplice (and splicing from a file) is the zero-copy.
If you don't want the zero-copy, then you should use just "write()".
So I disagree violently. This is not a bug unless you can point to
some other correctness issues.
The "stableness" of the data is literally the *only* difference
between vmsplice() and write().
> Whilst this does allow the code to be somewhat simplified, it also results
> in a loss of performance: stolen pages have to be reloaded in accessed
> again; more data has to be copied.
No. It literally results in a loss of THE WHOLE POINT of vmsplice().
Linus
next prev parent reply other threads:[~2023-06-29 17:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-29 15:54 David Howells
2023-06-29 15:54 ` [RFC PATCH 1/4] splice: Fix corruption of spliced data after splice() returns David Howells
2023-07-19 10:17 ` Miklos Szeredi
2023-07-19 17:59 ` Matt Whitlock
2023-07-19 19:35 ` Miklos Szeredi
2023-07-19 19:44 ` Matthew Wilcox
2023-07-19 19:56 ` Miklos Szeredi
2023-07-19 20:04 ` Matthew Wilcox
2023-07-19 20:16 ` Linus Torvalds
2023-07-19 21:02 ` Matt Whitlock
2023-07-19 23:20 ` Linus Torvalds
2023-07-19 23:41 ` Matt Whitlock
2023-07-20 0:00 ` Linus Torvalds
2023-07-19 23:48 ` Linus Torvalds
2023-07-24 9:44 ` David Howells
2023-07-24 13:55 ` Miklos Szeredi
2023-07-24 16:15 ` David Howells
2023-06-29 15:54 ` [RFC PATCH 2/4] splice: Make vmsplice() steal or copy David Howells
2023-06-30 13:44 ` Simon Horman
2023-06-30 15:29 ` David Howells
2023-06-30 17:32 ` Simon Horman
2023-06-29 15:54 ` [RFC PATCH 3/4] splice: Remove some now-unused bits David Howells
2023-06-29 15:54 ` [RFC PATCH 4/4] splice: Record some statistics David Howells
2023-06-29 17:56 ` Linus Torvalds [this message]
2023-06-29 18:05 ` [RFC PATCH 0/4] splice: Fix corruption in data spliced to pipe Matt Whitlock
2023-06-29 18:19 ` Linus Torvalds
2023-06-29 18:34 ` Matthew Wilcox
2023-06-29 18:53 ` Linus Torvalds
2023-06-30 16:50 ` David Howells
2023-06-29 18:42 ` Linus Torvalds
2023-06-29 18:16 ` Matt Whitlock
2023-06-30 0:01 ` Jakub Kicinski
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