From: Al Viro <viro@ZenIV.linux.org.uk>
To: Ian Kent <raven@themaw.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
autofs mailing list <autofs@vger.kernel.org>,
Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Omar Sandoval <osandov@osandov.com>
Subject: Re: [PATCH 6/8] autofs - use path_is_mountpoint() to fix unreliable d_mountpoint() checks
Date: Thu, 27 Oct 2016 03:17:53 +0100 [thread overview]
Message-ID: <20161027021753.GJ19539@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20161011053418.27645.15241.stgit@pluto.themaw.net>
On Tue, Oct 11, 2016 at 01:34:18PM +0800, Ian Kent wrote:
> + path = file->f_path;
> +
> /*
> * An empty directory in an autofs file system is always a
> * mount point. The daemon must have failed to mount this
> @@ -123,7 +126,7 @@ static int autofs4_dir_open(struct inode *inode, struct file *file)
> * it.
> */
> spin_lock(&sbi->lookup_lock);
> - if (!d_mountpoint(dentry) && simple_empty(dentry)) {
> + if (!path_is_mountpoint(&path) && simple_empty(dentry)) {
Why not &file->f_path, provided that you constify that thing properly?
> + if (rcu_walk) {
> + if (!path_is_mountpoint_rcu(path))
> + return -EISDIR;
> + } else {
> + if (!path_is_mountpoint(path))
> + return -EISDIR;
IDGI. What's the point of _having_ the _rcu() variant, anyway? Here you
are probably paying more in terms of i-cache footprint/branch prediction
than you win on not doing that rcu_read_lock()/rcu_read_unlock()...
_rcu variants make sense when non-RCU case does something you can't do
under RCU; here your path_is_mountpoint() is pretty close to being
rcu_read_lock()+path_is_mountpoint_rcu()+rcu_read_unlock() anyway...
next prev parent reply other threads:[~2016-10-27 2:17 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-11 5:33 [PATCH 1/8] vfs - change d_manage() to take a struct path Ian Kent
2016-10-11 5:33 ` [PATCH 2/8] vfs - add path_is_mountpoint() helper Ian Kent
2016-10-11 5:34 ` [PATCH 3/8] vfs - add path_has_submounts() Ian Kent
2016-10-11 5:34 ` [PATCH 4/8] autofs - change autofs4_expire_wait() to take struct path Ian Kent
2016-10-11 5:34 ` [PATCH 5/8] autofs - change autofs4_wait() " Ian Kent
2016-10-11 5:34 ` [PATCH 6/8] autofs - use path_is_mountpoint() to fix unreliable d_mountpoint() checks Ian Kent
2016-10-27 2:17 ` Al Viro [this message]
2016-10-27 2:51 ` Ian Kent
2016-10-11 5:34 ` [PATCH 7/8] autofs - use path_has_submounts() to fix unreliable have_submount() checks Ian Kent
2016-10-11 5:34 ` [PATCH 8/8] vfs - remove unused have_submounts() function Ian Kent
2016-10-11 16:04 ` [PATCH 1/8] vfs - change d_manage() to take a struct path Eric W. Biederman
2016-10-11 23:47 ` Ian Kent
2016-10-19 19:40 ` Andrew Morton
2016-10-20 23:39 ` Ian Kent
2016-10-27 2:11 ` Al Viro
2016-10-27 2:47 ` Ian Kent
2016-10-27 6:50 ` Ian Kent
2016-11-01 2:02 ` Ian Kent
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