linux-kernel - Re: [PATCH 1/2] audit: Quit audit_free

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Message-ID: <20260121052623.GC3183987@ZenIV>
Date: Wed, 21 Jan 2026 05:26:23 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Waiman Long <llong@...hat.com>
Cc: Paul Moore <paul@...l-moore.com>, Eric Paris <eparis@...hat.com>,
	Christian Brauner <brauner@...nel.org>,
	linux-kernel@...r.kernel.org, audit@...r.kernel.org,
	Richard Guy Briggs <rgb@...hat.com>,
	Ricardo Robaina <rrobaina@...hat.com>
Subject: Re: [PATCH 1/2] audit: Quit audit_free_names() early if name list
 empty

On Tue, Jan 20, 2026 at 11:08:45PM -0500, Waiman Long wrote:
> 
> On 1/20/26 10:11 PM, Al Viro wrote:
> > On Tue, Jan 20, 2026 at 09:35:08PM -0500, Waiman Long wrote:
> > > Optimize audit_free_names() by quitting early if the name list is empty.
> > > This eliminates the need to acquire and release the fs_struct spinlock
> > > in path_put().
> > Why would path_put() go anywhere need fs_struct spinlock???
> > 
> path_put() is defined in include/linux/fs_struct.h. It calls
> read_seq{un}lock_excl(&fs->seq) which, in turn, acquires the releases the
> spinlock underneath the seqlock_t.

Really?  Which kernel would that be?  On mainline we have

; git grep -n -w path_put include/linux/fs_struct.h
; $ git grep -C 6 'void path_put\>' fs/namei.c
fs/namei.c-/**
fs/namei.c- * path_put - put a reference to a path
fs/namei.c- * @path: path to put the reference to
fs/namei.c- *
fs/namei.c- * Given a path decrement the reference count to the dentry and the vfsmount.
fs/namei.c- */
fs/namei.c:void path_put(const struct path *path)
fs/namei.c-{
fs/namei.c-     dput(path->dentry);
fs/namei.c-     mntput(path->mnt);
fs/namei.c-}
fs/namei.c-EXPORT_SYMBOL(path_put);
fs/namei.c-
;