From: Christian Schoenebeck <linux_oss@crudebyte.com>
To: asmadeus@codewreck.org, Christoph Hellwig <hch@infradead.org>
Cc: Eric Van Hensbergen <ericvh@kernel.org>,
Latchesar Ionkov <lucho@ionkov.net>,
v9fs@lists.linux.dev, linux-kernel@vger.kernel.org,
David Howells <dhowells@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
linux-fsdevel@vger.kernel.org,
Chris Arges <carges@cloudflare.com>
Subject: Re: [PATCH] 9p/virtio: restrict page pinning to user_backed_iter() iovec
Date: Wed, 10 Dec 2025 14:33:56 +0100 [thread overview]
Message-ID: <3385064.aeNJFYEL58@weasel> (raw)
In-Reply-To: <aTkNbptI5stvpBPn@infradead.org>
On Wednesday, 10 December 2025 07:04:30 CET Christoph Hellwig wrote:
> On Wed, Dec 10, 2025 at 06:04:23AM +0900, Dominique Martinet via B4 Relay
> wrote:
[...]
> > The problem is that iov_iter_get_pages_alloc2() apparently cannot be
> > called on folios (as illustrated by the backtrace below), so limit what
> > iov we can pin from !iov_iter_is_kvec() to user_backed_iter()
>
> As willy pointed out this is a kmalloc.
>
> And 9p (just like NFS) really needs to switch away from
> iov_iter_get_pages_alloc2 to iov_iter_extract_pages, which handles not
> just this perfectly fine but also fixes various other issues.
>
> Note that the networking code still wants special treatment for kmalloc
> pages, so you might have more work there.
But couldn't this patch be used as a preliminary solution for this issue
before switching to iov_iter_extract_pages(), as the latter does not look like
a trivial change?
Maybe I'm still missing something important here, not sure.
/Christian
next prev parent reply other threads:[~2025-12-10 13:34 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-09 21:04 [PATCH] 9p/virtio: restrict page pinning to user_backed_iter() iovec Dominique Martinet via B4 Relay
2025-12-10 4:21 ` Matthew Wilcox
2025-12-10 6:04 ` Christoph Hellwig
2025-12-10 7:38 ` asmadeus
2025-12-10 8:32 ` Christoph Hellwig
2025-12-13 13:28 ` asmadeus
2025-12-15 5:55 ` Christoph Hellwig
2025-12-15 7:34 ` Dominique Martinet
2025-12-15 11:16 ` Christian Schoenebeck
2025-12-15 14:37 ` Christoph Hellwig
2025-12-19 12:03 ` David Howells
2025-12-19 12:00 ` David Howells
2025-12-19 11:26 ` David Howells
2025-12-10 13:33 ` Christian Schoenebeck [this message]
2025-12-17 13:41 ` Christian Schoenebeck
2025-12-17 21:49 ` asmadeus
2025-12-18 14:21 ` asmadeus
2025-12-18 15:14 ` Christian Schoenebeck
2025-12-18 23:14 ` asmadeus
2025-12-19 4:09 ` 9p read corruption of mmaped content (Was: [PATCH] 9p/virtio: restrict page pinning to user_backed_iter() iovec) Dominique Martinet
2025-12-19 11:53 ` Dominique Martinet
2025-12-19 13:46 ` Dominique Martinet
2025-12-19 14:01 ` David Howells
2025-12-19 12:06 ` [PATCH] 9p/virtio: restrict page pinning to user_backed_iter() iovec David Howells
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