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eventfs: Use simple_recursive_removal() to clean up dentries 

Looking at how dentry is removed via the tracefs system, I found that
eventfs does not do everything that it did under tracefs. The tracefs
removal of a dentry calls simple_recursive_removal() that does a lot more
than a simple d_invalidate().

As it should be a requirement that any eventfs_inode that has a dentry, so
does its parent. When removing a eventfs_inode, if it has a dentry, a call
to simple_recursive_removal() on that dentry should clean up all the
dentries underneath it.

Add WARN_ON_ONCE() to check for the parent having a dentry if any children
do.

Link: https://lore.kernel.org/all/20231101022553.GE1957730@ZenIV/
Link: https://lkml.kernel.org/r/20231101172650.552471568@goodmis.org

Cc: stable@vger.kernel.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Fixes: 5bdcd5f533 ("eventfs: Implement removal of meta data from eventfs")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (Google) 2023-11-01 13:25:49 -04:00
parent 62d65cac11
commit 407c6726ca
2 changed files with 44 additions and 35 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

77
fs/tracefs/event_inode.c
View File

@ -967,30 +967,29 @@ static void unhook_dentry(struct dentry *dentry)
{
if (!dentry)
return;
/* Keep the dentry from being freed yet (see eventfs_workfn()) */
/*
* Need to add a reference to the dentry that is expected by
* simple_recursive_removal(), which will include a dput().
*/
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);
/*
* 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.
*/
dget(dentry);
}
/**
* eventfs_remove_rec - remove eventfs dir or file from list
* @ei: eventfs_inode to be removed.
* @head: the list head to place the deleted @ei and children
* @level: prevent recursion from going more than 3 levels deep.
*
* This function recursively removes eventfs_inodes which
* contains info of files and/or directories.
*/
static void eventfs_remove_rec(struct eventfs_inode *ei, struct list_head *head, int level)
static void eventfs_remove_rec(struct eventfs_inode *ei, int level)
{
struct eventfs_inode *ei_child;
@ -1009,13 +1008,26 @@ static void eventfs_remove_rec(struct eventfs_inode *ei, struct list_head *head,
/* search for nested folders or files */
list_for_each_entry_srcu(ei_child, &ei->children, list,
lockdep_is_held(&eventfs_mutex)) {
eventfs_remove_rec(ei_child, head, level + 1);
/* Children only have dentry if parent does */
WARN_ON_ONCE(ei_child->dentry && !ei->dentry);
eventfs_remove_rec(ei_child, level + 1);
}
ei->is_freed = 1;
for (int i = 0; i < ei->nr_entries; i++) {
if (ei->d_children[i]) {
/* Children only have dentry if parent does */
WARN_ON_ONCE(!ei->dentry);
unhook_dentry(ei->d_children[i]);
}
}
unhook_dentry(ei->dentry);
list_del_rcu(&ei->list);
list_add_tail(&ei->del_list, head);
call_srcu(&eventfs_srcu, &ei->rcu, free_rcu_ei);
}
/**
@ -1026,30 +1038,22 @@ static void eventfs_remove_rec(struct eventfs_inode *ei, struct list_head *head,
*/
void eventfs_remove_dir(struct eventfs_inode *ei)
{
struct eventfs_inode *tmp;
LIST_HEAD(ei_del_list);
struct dentry *dentry;
if (!ei)
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);
eventfs_remove_rec(ei, &ei_del_list, 0);
dentry = ei->dentry;
eventfs_remove_rec(ei, 0);
mutex_unlock(&eventfs_mutex);
list_for_each_entry_safe(ei, tmp, &ei_del_list, del_list) {
for (int i = 0; i < ei->nr_entries; i++)
unhook_dentry(ei->d_children[i]);
unhook_dentry(ei->dentry);
list_del(&ei->del_list);
call_srcu(&eventfs_srcu, &ei->rcu, free_rcu_ei);
}
/*
* If any of the ei children has a dentry, then the ei itself
* must have a dentry.
*/
if (dentry)
simple_recursive_removal(dentry, NULL);
}
/**
@ -1060,10 +1064,17 @@ void eventfs_remove_dir(struct eventfs_inode *ei)
*/
void eventfs_remove_events_dir(struct eventfs_inode *ei)
{
struct dentry *dentry = ei->dentry;
struct dentry *dentry;
dentry = ei->dentry;
eventfs_remove_dir(ei);
/* Matches the dget() from eventfs_create_events_dir() */
/*
* Matches the dget() done by tracefs_start_creating()
* in eventfs_create_events_dir() when it the dentry was
* created. In other words, it's a normal dentry that
* sticks around while the other ei->dentry are created
* and destroyed dynamically.
*/
dput(dentry);
}

2
fs/tracefs/internal.h
View File

@ -55,12 +55,10 @@ struct eventfs_inode {
/*
* Union - used for deletion
* @llist: for calling dput() if needed after RCU
* @del_list: list of eventfs_inode to delete
* @rcu: eventfs_inode to delete in RCU
*/
union {
struct llist_node llist;
struct list_head del_list;
struct rcu_head rcu;
};
unsigned int is_freed:1;