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eventfs: Remove "is_freed" union with rcu head

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commit f2f496370afcbc5227d7002da28c74b91fed12ff upstream.

The eventfs_inode->is_freed was a union with the rcu_head with the
assumption that when it was on the srcu list the head would contain a
pointer which would make "is_freed" true. But that was a wrong assumption
as the rcu head is a single link list where the last element is NULL.

Instead, split the nr_entries integer so that "is_freed" is one bit and
the nr_entries is the next 31 bits. As there shouldn't be more than 10
(currently there's at most 5 to 7 depending on the config), this should
not be a problem.

Link: https://lkml.kernel.org/r/20231101172649.049758712@goodmis.org

Cc: stable@vger.kernel.org
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ajay Kaher <akaher@vmware.com>
Fixes: 63940449555e7 ("eventfs: Implement eventfs lookup, read, open functions")
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Steven Rostedt (Google) 2024-02-06 07:09:21 -05:00 committed by Greg Kroah-Hartman
parent 773cd7dfd0
commit 4bb123ce29
2 changed files with 5 additions and 3 deletions
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2
fs/tracefs/event_inode.c
View File

@ -824,6 +824,8 @@ static void eventfs_remove_rec(struct eventfs_inode *ei, struct list_head *head,
eventfs_remove_rec(ei_child, head, level + 1);
}
ei->is_freed = 1;
list_del_rcu(&ei->list);
list_add_tail(&ei->del_list, head);
}

6
fs/tracefs/internal.h
View File

@ -23,6 +23,7 @@ struct tracefs_inode {
* @d_parent: pointer to the parent's dentry
* @d_children: The array of dentries to represent the files when created
* @data: The private data to pass to the callbacks
* @is_freed: Flag set if the eventfs is on its way to be freed
* @nr_entries: The number of items in @entries
*/
struct eventfs_inode {
@ -38,14 +39,13 @@ struct eventfs_inode {
* Union - used for deletion
* @del_list: list of eventfs_inode to delete
* @rcu: eventfs_inode to delete in RCU
* @is_freed: node is freed if one of the above is set
*/
union {
struct list_head del_list;
struct rcu_head rcu;
unsigned long is_freed;
};
int nr_entries;
unsigned int is_freed:1;
unsigned int nr_entries:31;
};
static inline struct tracefs_inode *get_tracefs(const struct inode *inode)