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From:   David Howells <dhowells@redhat.com>
In-Reply-To: <a60594ef-ff85-498f-a1c4-0fcb9586621c@mattwhitlock.name>
References: <a60594ef-ff85-498f-a1c4-0fcb9586621c@mattwhitlock.name> <ZJq6nJBoX1m6Po9+@casper.infradead.org> <ec804f26-fa76-4fbe-9b1c-8fbbd829b735@mattwhitlock.name> <ZJp4Df8MnU8F3XAt@dread.disaster.area> <3299543.1687933850@warthog.procyon.org.uk>
To:     Matt Whitlock <kernel@mattwhitlock.name>
Cc:     dhowells@redhat.com, Matthew Wilcox <willy@infradead.org>,
        Dave Chinner <david@fromorbit.com>,
        linux-fsdevel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Jens Axboe <axboe@kernel.dk>, Al Viro <viro@zeniv.linux.org.uk>
Subject: Re: [Reproducer] Corruption, possible race between splice and FALLOC_FL_PUNCH_HOLE
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Date:   Wed, 28 Jun 2023 19:27:26 +0100
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Matt Whitlock <kernel@mattwhitlock.name> wrote:

> In other words, the currently implemented behavior is appropriate for
> SPLICE_F_MOVE, but it is not appropriate for ~SPLICE_F_MOVE.

The problems with SPLICE_F_MOVE is that it's only applicable to splicing *out*
of a pipe.  By the time you get that far the pages can already be corrupted by
a shared-writable mmap or write().

David