Revert "eventfs: Use simple_recursive_removal() to clean up dentries"

This reverts commit 055907ad2c14838c90d63297f7bab8d180a5d844.

The eventfs was not designed properly and may have some hidden bugs in it.
Linus rewrote it properly and I trust his version more than this one. Revert
the backported patches for 6.6 and re-apply all the changes to make it
equivalent to Linus's version.

Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index 5fcfb634fec26a7606113db7b8ec196d8f3e5e96..7aa92b8ebc51f8a26725c52408f8c0615c29e64d 100644 (file)
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -54,10 +54,12 @@ struct eventfs_file {
        /*
         * Union - used for deletion
         * @llist:      for calling dput() if needed after RCU
+        * @del_list:   list of eventfs_file to delete
         * @rcu:        eventfs_file to delete in RCU
         */
        union {
                struct llist_node       llist;
+               struct list_head        del_list;
                struct rcu_head         rcu;
        };
        void                            *data;
@@ -274,6 +276,7 @@ static void free_ef(struct eventfs_file *ef)
  */
 void eventfs_set_ef_status_free(struct tracefs_inode *ti, struct dentry *dentry)
 {
+       struct tracefs_inode *ti_parent;
        struct eventfs_inode *ei;
        struct eventfs_file *ef;
 
@@ -294,6 +297,10 @@ void eventfs_set_ef_status_free(struct tracefs_inode *ti, struct dentry *dentry)
 
        mutex_lock(&eventfs_mutex);
 
+       ti_parent = get_tracefs(dentry->d_parent->d_inode);
+       if (!ti_parent || !(ti_parent->flags & TRACEFS_EVENT_INODE))
+               goto out;
+
        ef = dentry->d_fsdata;
        if (!ef)
                goto out;
@@ -866,29 +873,30 @@ static void unhook_dentry(struct dentry *dentry)
 {
        if (!dentry)
                return;
-       /*
-        * Need to add a reference to the dentry that is expected by
-        * simple_recursive_removal(), which will include a dput().
-        */
-       dget(dentry);
 
-       /*
-        * Also add a reference for the dput() in eventfs_workfn().
-        * That is required as that dput() will free the ei after
-        * the SRCU grace period is over.
-        */
+       /* Keep the dentry from being freed yet (see eventfs_workfn()) */
        dget(dentry);
+
+       dentry->d_fsdata = NULL;
+       d_invalidate(dentry);
+       mutex_lock(&eventfs_mutex);
+       /* dentry should now have at least a single reference */
+       WARN_ONCE((int)d_count(dentry) < 1,
+                 "dentry %px (%s) less than one reference (%d) after invalidate\n",
+                 dentry, dentry->d_name.name, d_count(dentry));
+       mutex_unlock(&eventfs_mutex);
 }
 
 /**
  * eventfs_remove_rec - remove eventfs dir or file from list
  * @ef: eventfs_file to be removed.
+ * @head: to create list of eventfs_file to be deleted
  * @level: to check recursion depth
  *
  * The helper function eventfs_remove_rec() is used to clean up and free the
  * associated data from eventfs for both of the added functions.
  */
-static void eventfs_remove_rec(struct eventfs_file *ef, int level)
+static void eventfs_remove_rec(struct eventfs_file *ef, struct list_head *head, int level)
 {
        struct eventfs_file *ef_child;
 
@@ -908,16 +916,14 @@ static void eventfs_remove_rec(struct eventfs_file *ef, int level)
                /* search for nested folders or files */
                list_for_each_entry_srcu(ef_child, &ef->ei->e_top_files, list,
                                         lockdep_is_held(&eventfs_mutex)) {
-                       eventfs_remove_rec(ef_child, level + 1);
+                       eventfs_remove_rec(ef_child, head, level + 1);
                }
        }
 
        ef->is_freed = 1;
 
-       unhook_dentry(ef->dentry);
-
        list_del_rcu(&ef->list);
-       call_srcu(&eventfs_srcu, &ef->rcu, free_rcu_ef);
+       list_add_tail(&ef->del_list, head);
 }
 
 /**
@@ -928,22 +934,28 @@ static void eventfs_remove_rec(struct eventfs_file *ef, int level)
  */
 void eventfs_remove(struct eventfs_file *ef)
 {
-       struct dentry *dentry;
+       struct eventfs_file *tmp;
+       LIST_HEAD(ef_del_list);
 
        if (!ef)
                return;
 
+       /*
+        * Move the deleted eventfs_inodes onto the ei_del_list
+        * which will also set the is_freed value. Note, this has to be
+        * done under the eventfs_mutex, but the deletions of
+        * the dentries must be done outside the eventfs_mutex.
+        * Hence moving them to this temporary list.
+        */
        mutex_lock(&eventfs_mutex);
-       dentry = ef->dentry;
-       eventfs_remove_rec(ef, 0);
+       eventfs_remove_rec(ef, &ef_del_list, 0);
        mutex_unlock(&eventfs_mutex);
 
-       /*
-        * If any of the ei children has a dentry, then the ei itself
-        * must have a dentry.
-        */
-       if (dentry)
-               simple_recursive_removal(dentry, NULL);
+       list_for_each_entry_safe(ef, tmp, &ef_del_list, del_list) {
+               unhook_dentry(ef->dentry);
+               list_del(&ef->del_list);
+               call_srcu(&eventfs_srcu, &ef->rcu, free_rcu_ef);
+       }
 }
 
 /**
@@ -954,8 +966,6 @@ void eventfs_remove(struct eventfs_file *ef)
  */
 void eventfs_remove_events_dir(struct dentry *dentry)
 {
-       struct eventfs_file *ef_child;
-       struct eventfs_inode *ei;
        struct tracefs_inode *ti;
 
        if (!dentry || !dentry->d_inode)
@@ -965,11 +975,6 @@ void eventfs_remove_events_dir(struct dentry *dentry)
        if (!ti || !(ti->flags & TRACEFS_EVENT_INODE))
                return;
 
-       mutex_lock(&eventfs_mutex);
-       ei = ti->private;
-       list_for_each_entry_srcu(ef_child, &ei->e_top_files, list,
-                                lockdep_is_held(&eventfs_mutex)) {
-               eventfs_remove_rec(ef_child, 0);
-       }
-       mutex_unlock(&eventfs_mutex);
+       d_invalidate(dentry);
+       dput(dentry);
 }