From: Matthew Wilcox <willy@infradead.org>
To: Trond Myklebust <trondmy@kernel.org>
Cc: Anna Schumaker <anna@kernel.org>,
linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
Mike Snitzer <snitzer@kernel.org>
Subject: Re: [PATCH v3 2/2] NFS: Enable the RWF_DONTCACHE flag for the NFS client
Date: Mon, 18 Aug 2025 16:58:08 +0100 [thread overview]
Message-ID: <aKNNkFJ3mt0svnyw@casper.infradead.org> (raw)
In-Reply-To: <88e2e70a827618b5301d92b094ef07efacba0577.camel@kernel.org>
On Mon, Aug 18, 2025 at 08:56:31AM -0700, Trond Myklebust wrote:
> On Mon, 2025-08-18 at 16:21 +0100, Matthew Wilcox wrote:
> > I don't think this technique is "safe". By clearing the flag early,
> > the page cache can't see that a folio that was created by dropbehind
> > has now been reused and should have its dropbehind flag cleared. So
> > we
> > might see pages dropped from the cache that really should not be.
>
> The only alternative would be to add back in a helper in mm/filemap.c
> that does the normal folio_end_writeback() routine, but ignores the
> dropbehind flag. (folio_end_writeback_ignore_dropbehind()?)
Can you remind me why we clear the writeback flag as soon as the WRITE
completes instead of leaving it set until the COMMIT completes?
next prev parent reply other threads:[~2025-08-18 15:58 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-08-18 14:39 [PATCH v3 0/2] Initial NFS client support for RWF_DONTCACHE Trond Myklebust
2025-08-18 14:39 ` [PATCH v3 1/2] filemap: Add a helper for filesystems implementing dropbehind Trond Myklebust
2025-08-18 14:51 ` Matthew Wilcox
2025-08-18 15:59 ` Trond Myklebust
2025-08-18 16:08 ` Matthew Wilcox
2025-08-18 14:39 ` [PATCH v3 2/2] NFS: Enable the RWF_DONTCACHE flag for the NFS client Trond Myklebust
2025-08-18 15:21 ` Matthew Wilcox
2025-08-18 15:56 ` Trond Myklebust
2025-08-18 15:58 ` Matthew Wilcox [this message]
2025-08-18 16:49 ` Trond Myklebust
2025-08-18 17:04 ` Matthew Wilcox
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