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eventfs: Use simple_recursive_removal() to clean up dentries
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commit 407c672 upstream

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: 5bdcd5f ("eventfs: Implement removal of meta data from eventfs")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@rostedt @gregkh
rostedt authored and gregkh committed Nov 8, 2023
1 parent ea4c30a commit 055907a
Showing 1 changed file with 33 additions and 38 deletions.
71 changes: 33 additions & 38 deletions fs/tracefs/event_inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -54,12 +54,10 @@ 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;
Expand Down Expand Up @@ -276,7 +274,6 @@ 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;

Expand All @@ -297,10 +294,6 @@ 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;
Expand Down Expand Up @@ -873,30 +866,29 @@ 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
* @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, struct list_head *head, int level)
static void eventfs_remove_rec(struct eventfs_file *ef, int level)
{
struct eventfs_file *ef_child;

Expand All @@ -916,14 +908,16 @@ static void eventfs_remove_rec(struct eventfs_file *ef, struct list_head *head,
/* 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, head, level + 1);
eventfs_remove_rec(ef_child, level + 1);
}
}

ef->is_freed = 1;

unhook_dentry(ef->dentry);

list_del_rcu(&ef->list);
list_add_tail(&ef->del_list, head);
call_srcu(&eventfs_srcu, &ef->rcu, free_rcu_ef);
}

/**
Expand All @@ -934,28 +928,22 @@ static void eventfs_remove_rec(struct eventfs_file *ef, struct list_head *head,
*/
void eventfs_remove(struct eventfs_file *ef)
{
struct eventfs_file *tmp;
LIST_HEAD(ef_del_list);
struct dentry *dentry;

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);
eventfs_remove_rec(ef, &ef_del_list, 0);
dentry = ef->dentry;
eventfs_remove_rec(ef, 0);
mutex_unlock(&eventfs_mutex);

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);
}
/*
* If any of the ei children has a dentry, then the ei itself
* must have a dentry.
*/
if (dentry)
simple_recursive_removal(dentry, NULL);
}

/**
Expand All @@ -966,6 +954,8 @@ 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)
Expand All @@ -975,6 +965,11 @@ void eventfs_remove_events_dir(struct dentry *dentry)
if (!ti || !(ti->flags & TRACEFS_EVENT_INODE))
return;

d_invalidate(dentry);
dput(dentry);
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);
}

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