linux-kernel - Re: [PATCH] VFS: change try_lookup

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Message-ID: <20250611-leisten-vokal-55db13cc534e@brauner>
Date: Wed, 11 Jun 2025 12:03:53 +0200
From: Christian Brauner <brauner@...nel.org>
To: NeilBrown <neil@...wn.name>
Cc: Christian Brauner <brauner@...nel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	CIFS <linux-cifs@...r.kernel.org>,
	Bharath S M <bharathsm@...rosoft.com>,
	Steve French <smfrench@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jan Kara <jack@...e.com>
Subject: Re: [PATCH] VFS: change try_lookup_noperm() to skip revalidation

On Tue, 10 Jun 2025 11:04:04 +1000, NeilBrown wrote:
> The recent change from using d_hash_and_lookup() to using
> try_lookup_noperm() inadvertently introduce a d_revalidate() call when
> the lookup was successful.  Steven French reports that this resulted in
> worse than halving of performance in some cases.
> 
> Prior to the offending patch the only caller of try_lookup_noperm() was
> autofs which does not need the d_revalidate().  So it is safe to remove
> the d_revalidate() call providing we stop using try_lookup_noperm() to
> implement lookup_noperm().
> 
> [...]

Applied to the vfs.fixes branch of the vfs/vfs.git tree.
Patches in the vfs.fixes 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.fixes

[1/1] VFS: change try_lookup_noperm() to skip revalidation
      https://git.kernel.org/vfs/vfs/c/ad5a0351064c