d_invalidate(): unhash immediately

Once that is done, we can just hunt mountpoints down one by one;
no new mountpoints can be added from now on, so we don't need
anything tricky in finish() callback, etc.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 16 insertions, 46 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 86d2de63461e..449d0f895e6f 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1542,78 +1542,48 @@ void shrink_dcache_for_umount(struct super_block *sb)
         }
 }
 
-struct detach_data {
-        struct select_data select;
-        struct dentry *mountpoint;
-};
-static enum d_walk_ret detach_and_collect(void *_data, struct dentry *dentry)
+static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
 {
-        struct detach_data *data = _data;
-
+        struct dentry **victim = _data;
         if (d_mountpoint(dentry)) {
                 __dget_dlock(dentry);
-                data->mountpoint = dentry;
+                *victim = dentry;
                 return D_WALK_QUIT;
         }
-
-        return select_collect(&data->select, dentry);
-}
-
-static void check_and_drop(void *_data)
-{
-        struct detach_data *data = _data;
-
-        if (!data->mountpoint && list_empty(&data->select.dispose))
-                __d_drop(data->select.start);
+        return D_WALK_CONTINUE;
 }
 
 /**
  * d_invalidate - detach submounts, prune dcache, and drop
  * @dentry: dentry to invalidate (aka detach, prune and drop)
- *
- * no dcache lock.
- *
- * The final d_drop is done as an atomic operation relative to
- * rename_lock ensuring there are no races with d_set_mounted.  This
- * ensures there are no unhashed dentries on the path to a mountpoint.
  */
 void d_invalidate(struct dentry *dentry)
 {
-        /*
-         * If it's already been dropped, return OK.
-         */
+        bool had_submounts = false;
         spin_lock(&dentry->d_lock);
         if (d_unhashed(dentry)) {
                 spin_unlock(&dentry->d_lock);
                 return;
         }
+        __d_drop(dentry);
         spin_unlock(&dentry->d_lock);
 
         /* Negative dentries can be dropped without further checks */
-        if (!dentry->d_inode) {
-                d_drop(dentry);
+        if (!dentry->d_inode)
                 return;
-        }
 
+        shrink_dcache_parent(dentry);
         for (;;) {
-                struct detach_data data;
-
-                data.mountpoint = NULL;
-                INIT_LIST_HEAD(&data.select.dispose);
-                data.select.start = dentry;
-                data.select.found = 0;
-
-                d_walk(dentry, &data, detach_and_collect, check_and_drop);
-
-                if (!list_empty(&data.select.dispose))
-                        shrink_dentry_list(&data.select.dispose);
-                else if (!data.mountpoint)
+                struct dentry *victim = NULL;
+                d_walk(dentry, &victim, find_submount, NULL);
+                if (!victim) {
+                        if (had_submounts)
+                                shrink_dcache_parent(dentry);
                         return;
-
-                if (data.mountpoint) {
-                        detach_mounts(data.mountpoint);
-                        dput(data.mountpoint);
                 }
+                had_submounts = true;
+                detach_mounts(victim);
+                dput(victim);
         }
 }
 EXPORT_SYMBOL(d_invalidate);