Patch "autofs: revert "autofs: take more care to not update last_used on path walk"" has been added to the 4.14-stable tree

Patch "autofs: revert "autofs: take more care to not update last_used on path walk"" has been added to the 4.14-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    autofs: revert "autofs: take more care to not update last_used on path walk"

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     autofs-revert-autofs-take-more-care-to-not-update-last_used-on-path-walk.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 43694d4bf843ddd34519e8e9de983deefeada699 Mon Sep 17 00:00:00 2001
From: Ian Kent <raven@themaw.net>
Date: Wed, 29 Nov 2017 16:11:23 -0800
Subject: autofs: revert "autofs: take more care to not update last_used on path walk"

From: Ian Kent <raven@themaw.net>

commit 43694d4bf843ddd34519e8e9de983deefeada699 upstream.

While commit 092a53452bb7 ("autofs: take more care to not update
last_used on path walk") helped (partially) resolve a problem where
automounts were not expiring due to aggressive accesses from user space
it has a side effect for very large environments.

This change helps with the expire problem by making the expire more
aggressive but, for very large environments, that means more mount
requests from clients.  When there are a lot of clients that can mean
fairly significant server load increases.

It turns out I put the last_used in this position to solve this very
problem and failed to update my own thinking of the autofs expire
policy.  So the patch being reverted introduces a regression which
should be fixed.

Link: http://lkml.kernel.org/r/151174729420.6162.1832622523537052460.stgit@pluto.themaw.net
Fixes: 092a53452b ("autofs: take more care to not update last_used on path walk")
Signed-off-by: Ian Kent <raven@themaw.net>
Reviewed-by: NeilBrown <neilb@suse.com>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Colin Walters <walters@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Ondrej Holy <oholy@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/autofs4/root.c |   17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -281,8 +281,8 @@ static int autofs4_mount_wait(const stru
 		pr_debug("waiting for mount name=%pd\n", path->dentry);
 		status = autofs4_wait(sbi, path, NFY_MOUNT);
 		pr_debug("mount wait done status=%d\n", status);
-		ino->last_used = jiffies;
 	}
+	ino->last_used = jiffies;
 	return status;
 }
 
@@ -321,21 +321,16 @@ static struct dentry *autofs4_mountpoint
 	 */
 	if (autofs_type_indirect(sbi->type) && d_unhashed(dentry)) {
 		struct dentry *parent = dentry->d_parent;
+		struct autofs_info *ino;
 		struct dentry *new;
 
 		new = d_lookup(parent, &dentry->d_name);
 		if (!new)
 			return NULL;
-		if (new == dentry)
-			dput(new);
-		else {
-			struct autofs_info *ino;
-
-			ino = autofs4_dentry_ino(new);
-			ino->last_used = jiffies;
-			dput(path->dentry);
-			path->dentry = new;
-		}
+		ino = autofs4_dentry_ino(new);
+		ino->last_used = jiffies;
+		dput(path->dentry);
+		path->dentry = new;
 	}
 	return path->dentry;
 }


Patches currently in stable-queue which might be from raven@themaw.net are

queue-4.14/autofs-revert-autofs-fix-at_no_automount-not-being-honored.patch
queue-4.14/autofs-revert-autofs-take-more-care-to-not-update-last_used-on-path-walk.patch