[PATCH] AUTOFS: Make sure all dentries refs are released before calling kill_anon_super()

Make sure all dentries refs are released before calling kill_anon_super() so
that the assumption that generic_shutdown_super() can completely destroy the
dentry tree for there will be no external references holds true.

What was being done in the put_super() superblock op, is now done in the
kill_sb() filesystem op instead, prior to calling kill_anon_super().

This makes the struct autofs_sb_info::root member variable redundant (since
sb->s_root is still available), and so that is removed.  The calls to
shrink_dcache_sb() are also removed since they're also redundant as
shrink_dcache_for_umount() will now be called after the cleanup routine.

Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Ian Kent <raven@themaw.net>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 6 insertions, 22 deletions

diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
index 480ab178cba5..b13f32c8aeee 100644
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -94,7 +94,6 @@ struct autofs_wait_queue {
 
 struct autofs_sb_info {
         u32 magic;
-        struct dentry *root;
         int pipefd;
         struct file *pipe;
         pid_t oz_pgrp;
@@ -229,4 +228,4 @@ out:
 }
 
 void autofs4_dentry_release(struct dentry *);
-
+extern void autofs4_kill_sb(struct super_block *);
diff --git a/fs/autofs4/init.c b/fs/autofs4/init.c
index 5d9193332bef..723a1c5e361b 100644
--- a/fs/autofs4/init.c
+++ b/fs/autofs4/init.c
@@ -24,7 +24,7 @@ static struct file_system_type autofs_fs_type = {
         .owner          = THIS_MODULE,
         .name           = "autofs",
         .get_sb         = autofs_get_sb,
-        .kill_sb        = kill_anon_super,
+        .kill_sb        = autofs4_kill_sb,
 };
 
 static int __init init_autofs4_fs(void)
diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
index 800ce876caec..51fd8595bf85 100644
--- a/fs/autofs4/inode.c
+++ b/fs/autofs4/inode.c
@@ -96,7 +96,7 @@ void autofs4_free_ino(struct autofs_info *ino)
  */
 static void autofs4_force_release(struct autofs_sb_info *sbi)
 {
-        struct dentry *this_parent = sbi->root;
+        struct dentry *this_parent = sbi->sb->s_root;
         struct list_head *next;
 
         spin_lock(&dcache_lock);
@@ -127,7 +127,7 @@ resume:
                 spin_lock(&dcache_lock);
         }
 
-        if (this_parent != sbi->root) {
+        if (this_parent != sbi->sb->s_root) {
                 struct dentry *dentry = this_parent;
 
                 next = this_parent->d_u.d_child.next;
@@ -140,15 +140,9 @@ resume:
                 goto resume;
         }
         spin_unlock(&dcache_lock);
-
-        dput(sbi->root);
-        sbi->root = NULL;
-        shrink_dcache_sb(sbi->sb);
-
-        return;
 }
 
-static void autofs4_put_super(struct super_block *sb)
+void autofs4_kill_sb(struct super_block *sb)
 {
         struct autofs_sb_info *sbi = autofs4_sbi(sb);
 
@@ -163,6 +157,7 @@ static void autofs4_put_super(struct super_block *sb)
         kfree(sbi);
 
         DPRINTK("shutting down");
+        kill_anon_super(sb);
 }
 
 static int autofs4_show_options(struct seq_file *m, struct vfsmount *mnt)
@@ -189,7 +184,6 @@ static int autofs4_show_options(struct seq_file *m, struct vfsmount *mnt)
 }
 
 static struct super_operations autofs4_sops = {
-        .put_super      = autofs4_put_super,
         .statfs         = simple_statfs,
         .show_options   = autofs4_show_options,
 };
@@ -315,7 +309,6 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
 
         s->s_fs_info = sbi;
         sbi->magic = AUTOFS_SBI_MAGIC;
-        sbi->root = NULL;
         sbi->pipefd = -1;
         sbi->catatonic = 0;
         sbi->exp_timeout = 0;
@@ -397,13 +390,6 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
         sbi->pipefd = pipefd;
 
         /*
-         * Take a reference to the root dentry so we get a chance to
-         * clean up the dentry tree on umount.
-         * See autofs4_force_release.
-         */
-        sbi->root = dget(root);
-
-        /*
          * Success! Install the root dentry now to indicate completion.
          */
         s->s_root = root;
diff --git a/fs/autofs4/waitq.c b/fs/autofs4/waitq.c
index ce103e7b0bc3..c0a6c8d445c7 100644
--- a/fs/autofs4/waitq.c
+++ b/fs/autofs4/waitq.c
@@ -45,7 +45,6 @@ void autofs4_catatonic_mode(struct autofs_sb_info *sbi)
                 fput(sbi->pipe);        /* Close the pipe */
                 sbi->pipe = NULL;
         }
-        shrink_dcache_sb(sbi->sb);
 }
 
 static int autofs4_write(struct file *file, const void *addr, int bytes)