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Date: Thu, 27 Oct 2016 10:51:40 +0800 From: Ian Kent <raven@...maw.net> To: Al Viro <viro@...IV.linux.org.uk> Cc: Andrew Morton <akpm@...ux-foundation.org>, autofs mailing list <autofs@...r.kernel.org>, Kernel Mailing List <linux-kernel@...r.kernel.org>, "Eric W. Biederman" <ebiederm@...ssion.com>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Omar Sandoval <osandov@...ndov.com> Subject: Re: [PATCH 6/8] autofs - use path_is_mountpoint() to fix unreliable d_mountpoint() checks On Thu, 2016-10-27 at 03:17 +0100, Al Viro wrote: > 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? Yep, my bad, as pointed out by Eric. Patches to fix that and constify a bunch of things will follow. > > > > > + 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... Again, my bad, I'll merge these two and post along with the follow up patches above. Thanks Al, Ian
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