autofs4: make "autofs4_can_expire" idempotent.

Have a "test" function change the value it is testing can be confusing,
particularly as a future patch will be calling this function twice.

So move the update for 'last_used' to avoid repeat expiry to the place
where the final determination on what to expire is known.

Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Ian Kent <raven@themaw.net>
Tested-by: Ian Kent <raven@themaw.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/autofs4/expire.c

@@ -30,12 +30,6 @@ static inline int autofs4_can_expire(struct dentry *dentry,
 		/* Too young to die */
 		if (!timeout || time_after(ino->last_used + timeout, now))
 			return 0;
-
-		/* update last_used here :-
-		   - obviously makes sense if it is in use now
-		   - less obviously, prevents rapid-fire expire
-		     attempts if expire fails the first time */
-		ino->last_used = now;
 	}
 	return 1;
 }
@@ -535,6 +529,8 @@ int autofs4_expire_run(struct super_block *sb,
 
 	spin_lock(&sbi->fs_lock);
 	ino = autofs4_dentry_ino(dentry);
+	/* avoid rapid-fire expire attempts if expiry fails */
+	ino->last_used = now;
 	ino->flags &= ~AUTOFS_INF_EXPIRING;
 	complete_all(&ino->expire_complete);
 	spin_unlock(&sbi->fs_lock);
@@ -561,6 +557,8 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
 		ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
 
 		spin_lock(&sbi->fs_lock);
+		/* avoid rapid-fire expire attempts if expiry fails */
+		ino->last_used = now;
 		ino->flags &= ~AUTOFS_INF_EXPIRING;
 		complete_all(&ino->expire_complete);
 		spin_unlock(&sbi->fs_lock);