From: "J. Bruce Fields" <bfields@fieldses.org>
To: David Howells <dhowells@redhat.com>
Cc: Amir Goldstein <amir73il@gmail.com>,
linux-cachefs@redhat.com, Jeff Layton <jlayton@redhat.com>,
David Wysochanski <dwysocha@redhat.com>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
Dave Chinner <dchinner@redhat.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
linux-afs@lists.infradead.org,
Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
CIFS <linux-cifs@vger.kernel.org>,
ceph-devel <ceph-devel@vger.kernel.org>,
v9fs-developer@lists.sourceforge.net,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Miklos Szeredi <miklos@szeredi.hu>
Subject: Re: fscache: Redesigning the on-disk cache
Date: Mon, 8 Mar 2021 13:54:10 -0500 [thread overview]
Message-ID: <20210308185410.GE7284@fieldses.org> (raw)
In-Reply-To: <517184.1615194835@warthog.procyon.org.uk>
On Mon, Mar 08, 2021 at 09:13:55AM +0000, David Howells wrote:
> Amir Goldstein <amir73il@gmail.com> wrote:
> > With ->fiemap() you can at least make the distinction between a non existing
> > and an UNWRITTEN extent.
>
> I can't use that for XFS, Ext4 or btrfs, I suspect. Christoph and Dave's
> assertion is that the cache can't rely on the backing filesystem's metadata
> because these can arbitrarily insert or remove blocks of zeros to bridge or
> split extents.
Could you instead make some sort of explicit contract with the
filesystem? Maybe you'd flag it at mkfs time and query for it before
allowing a filesystem to be used for fscache. You don't need every
filesystem to support fscache, right, just one acceptable one?
--b.
next prev parent reply other threads:[~2021-03-08 18:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-03 23:20 fscache: Redesigning the on-disk cache David Howells
2021-03-04 13:47 ` fscache: Redesigning the on-disk cache - LRU handling David Howells
2021-03-05 9:46 ` fscache: Redesigning the on-disk cache Amir Goldstein
2021-03-08 9:13 ` David Howells
2021-03-08 10:35 ` Amir Goldstein
2021-03-08 11:28 ` Metadata writtenback notification? -- was " David Howells
2021-03-08 22:32 ` Dave Chinner
2021-03-08 23:20 ` Matthew Wilcox
2021-03-09 11:27 ` David Howells
2021-03-08 18:54 ` J. Bruce Fields [this message]
2021-03-08 19:08 ` David Howells
2021-03-08 21:55 ` Dave Chinner
2021-03-09 9:21 ` David Howells
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