From: Matthew Wilcox <willy@infradead.org>
To: Josef Bacik <josef@toxicpanda.com>
Cc: Joanne Koong <joannelkoong@gmail.com>,
miklos@szeredi.hu, linux-fsdevel@vger.kernel.org,
bernd.schubert@fastmail.fm, jefflexu@linux.alibaba.com,
shakeel.butt@linux.dev, kernel-team@meta.com
Subject: Re: [PATCH v2 10/12] fuse: support large folios for direct io
Date: Mon, 9 Dec 2024 15:54:51 +0000 [thread overview]
Message-ID: <Z1cSy1OUxPZ2kzYT@casper.infradead.org> (raw)
In-Reply-To: <20241209155042.GB2843669@perftesting>
On Mon, Dec 09, 2024 at 10:50:42AM -0500, Josef Bacik wrote:
> As we've noticed in the upstream bug report for your initial work here, this
> isn't quite correct, as we could have gotten a large folio in from userspace. I
> think the better thing here is to do the page extraction, and then keep track of
> the last folio we saw, and simply skip any folios that are the same for the
> pages we have. This way we can handle large folios correctly. Thanks,
Some people have in the past thought that they could skip subsequent
page lookup if the folio they get back is large. This is an incorrect
optimisation. Userspace may mmap() a file PROT_WRITE, MAP_PRIVATE.
If they store to the middle of a large folio (the file that is mmaped
may be on a filesystem that does support large folios, rather than
fuse), then we'll have, eg:
folio A page 0
folio A page 1
folio B page 0
folio A page 3
where folio A belongs to the file and folio B is an anonymous COW page.
next prev parent reply other threads:[~2024-12-09 15:54 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-25 22:05 [PATCH v2 00/12] fuse: support large folios Joanne Koong
2024-11-25 22:05 ` [PATCH v2 01/12] fuse: support copying " Joanne Koong
2024-11-25 22:05 ` [PATCH v2 02/12] fuse: support large folios for retrieves Joanne Koong
2024-11-25 22:05 ` [PATCH v2 03/12] fuse: refactor fuse_fill_write_pages() Joanne Koong
2024-11-25 22:05 ` [PATCH v2 04/12] fuse: support large folios for writethrough writes Joanne Koong
2024-11-25 22:05 ` [PATCH v2 05/12] fuse: support large folios for folio reads Joanne Koong
2024-11-25 22:05 ` [PATCH v2 06/12] fuse: support large folios for symlinks Joanne Koong
2024-11-25 22:05 ` [PATCH v2 07/12] fuse: support large folios for stores Joanne Koong
2024-11-25 22:05 ` [PATCH v2 08/12] fuse: support large folios for queued writes Joanne Koong
2024-11-25 22:05 ` [PATCH v2 09/12] fuse: support large folios for readahead Joanne Koong
2024-11-25 22:05 ` [PATCH v2 10/12] fuse: support large folios for direct io Joanne Koong
2024-12-09 15:50 ` Josef Bacik
2024-12-09 15:54 ` Matthew Wilcox [this message]
2024-12-11 21:04 ` Joanne Koong
2024-12-11 21:11 ` Matthew Wilcox
2024-12-11 21:35 ` Joanne Koong
2024-11-25 22:05 ` [PATCH v2 11/12] fuse: support large folios for writeback Joanne Koong
2024-11-25 22:05 ` [PATCH v2 12/12] fuse: enable large folios Joanne Koong
2024-12-06 9:50 ` [PATCH v2 00/12] fuse: support " Jingbo Xu
2024-12-06 17:41 ` Joanne Koong
2024-12-06 20:36 ` Shakeel Butt
2024-12-06 22:11 ` Joanne Koong
2024-12-06 22:27 ` Shakeel Butt
2024-12-06 22:33 ` Matthew Wilcox
2024-12-09 17:23 ` Shakeel Butt
2024-12-06 22:25 ` Matthew Wilcox
2024-12-10 0:31 ` Joanne Koong
2025-01-08 21:03 ` Joanne Koong
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