From: Bernd Schubert <bernd.schubert@fastmail.fm>
To: Miklos Szeredi <miklos@szeredi.hu>, David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Christoph Hellwig <hch@lst.de>,
Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>,
Jeff Layton <jlayton@kernel.org>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
netfs@lists.linux.dev, v9fs@lists.linux.dev,
linux-afs@lists.infradead.org, ceph-devel@vger.kernel.org,
linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] mm: Replace ->launder_folio() with flush and wait
Date: Tue, 19 Mar 2024 17:59:42 +0100 [thread overview]
Message-ID: <63e67db9-7425-4928-afb2-cbe7cc6232bb@fastmail.fm> (raw)
In-Reply-To: <CAJfpegsCBEm11OHS8bfQdgossOgofPcYhLTFtw7_+T66iBvznw@mail.gmail.com>
On 3/19/24 17:40, Miklos Szeredi wrote:
> On Tue, 19 Mar 2024 at 17:13, Miklos Szeredi <miklos@szeredi.hu> wrote:
>>
>> On Tue, 19 Mar 2024 at 15:15, David Howells <dhowells@redhat.com> wrote:
>>
>>> What particular usage case of invalidate_inode_pages2() are you thinking of?
>>
>> FUSE_NOTIFY_INVAL_INODE will trigger invalidate_inode_pages2_range()
>> to clean up the cache.
>>
>> The server is free to discard writes resulting from this invalidation
>> and delay reads in the region until the invalidation finishes. This
>> would no longer work with your change, since the mapping could
>> silently be reinstated between the writeback and the removal from the
>> cache due to the page being unlocked/relocked.
>
> This would also matter if a distributed filesystem wanted to implement
> coherence even if there are mmaps. I.e. a client could get exclusive
> access to a region by issuing FUSE_NOTIFY_INVAL_INODE on all other
> clients and blocking reads. With your change this would fail.
>
> Again, this is purely theoretical, and without a way to differentiate
> between the read-only and write cases it has limited usefulness.
> Adding leases to fuse (which I plan to do) would make this much more
> useful.
Thanks Miklos! Fyi, we are actually planning to extend fuse
notifications from inode to page ranges.
Thanks,
Bernd
next prev parent reply other threads:[~2024-03-19 16:59 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-06 22:39 [RFC PATCH] mm: Replace ->launder_folio() with flush and wait David Howells
2024-03-07 4:45 ` Matthew Wilcox
2024-03-07 8:26 ` David Howells
2024-03-07 10:36 ` David Howells
2024-03-07 14:54 ` Christoph Hellwig
2024-03-08 7:52 ` Miklos Szeredi
2024-03-19 14:14 ` David Howells
2024-03-19 16:13 ` Miklos Szeredi
2024-03-19 16:40 ` Miklos Szeredi
2024-03-19 16:59 ` Bernd Schubert [this message]
2024-03-07 16:15 ` [RFC PATCH v2] mm: Kill ->launder_folio() David Howells
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