linux-ext4 - Re: (subset) [PATCH v6 0/7] fs: implement multigrain timestamps

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Date:   Fri, 28 Jul 2023 13:00:37 +0200
From:   Christian Brauner <brauner@...nel.org>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Christian Brauner <brauner@...nel.org>,
        Dave Chinner <david@...morbit.com>,
        Anthony Iliopoulos <ailiop@...e.com>, v9fs@...ts.linux.dev,
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Subject: Re: (subset) [PATCH v6 0/7] fs: implement multigrain timestamps

On Tue, 25 Jul 2023 10:58:13 -0400, Jeff Layton wrote:
> The VFS always uses coarse-grained timestamps when updating the
> ctime and mtime after a change. This has the benefit of allowing
> filesystems to optimize away a lot metadata updates, down to around 1
> per jiffy, even when a file is under heavy writes.
> 
> Unfortunately, this coarseness has always been an issue when we're
> exporting via NFSv3, which relies on timestamps to validate caches. A
> lot of changes can happen in a jiffy, so timestamps aren't sufficient to
> help the client decide to invalidate the cache.
> 
> [...]

Survives xfstests (tmpfs, ext4, overlayfs) and the fs portions of LTP.
Let's keep our eyes open for any potential issues. Past suspects has
been IMA interacting with overlayfs. We'll see. Picked everything minus
the tmpfs-writepage patch that was contentious.

---

Applied to the vfs.ctime branch of the vfs/vfs.git tree.
Patches in the vfs.ctime branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs.ctime

[1/7] fs: pass the request_mask to generic_fillattr
      https://git.kernel.org/vfs/vfs/c/0a6ab6dc6958
[2/7] fs: add infrastructure for multigrain timestamps
      https://git.kernel.org/vfs/vfs/c/d242b98ac3e9
[4/7] tmpfs: add support for multigrain timestamps
      https://git.kernel.org/vfs/vfs/c/1f31c58cf032
[5/7] xfs: switch to multigrain timestamps
      https://git.kernel.org/vfs/vfs/c/859dd91017dd
[6/7] ext4: switch to multigrain timestamps
      https://git.kernel.org/vfs/vfs/c/093af249eab4
[7/7] btrfs: convert to multigrain timestamps
      https://git.kernel.org/vfs/vfs/c/b90a04d1c30c