From: "Steven Rostedt (Google)" <rost...@goodmis.org>
The logic to free the eventfs_inode (ei) use to set is_freed and clear the
"dentry" field under the eventfs_mutex. But that changed when a race was
found where the ei->dentry needed to be cleared when the last dput() was
called on it. But there was still logic that checked if ei->dentry was not
NULL and is_freed is set, and would warn if it was.
But since that situation was changed and the ei->dentry isn't cleared
until the last dput() is called on it while the ei->is_freed is set, do
not test for that condition anymore, and change the comments to reflect
that.
Fixes: 020010fbfa20 ("eventfs: Delete eventfs_inode when the last dentry is
freed")
Reported-by: Mark Rutland <mark.rutl...@arm.com>
Signed-off-by: Steven Rostedt (Google) <rost...@goodmis.org>
---
fs/tracefs/event_inode.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
index f8a594a50ae6..f239b2b507a4 100644
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -27,16 +27,16 @@
/*
* eventfs_mutex protects the eventfs_inode (ei) dentry. Any access
* to the ei->dentry must be done under this mutex and after checking
- * if ei->is_freed is not set. The ei->dentry is released under the
- * mutex at the same time ei->is_freed is set. If ei->is_freed is set
- * then the ei->dentry is invalid.
+ * if ei->is_freed is not set. When ei->is_freed is set, the dentry
+ * is on its way to being freed after the last dput() is made on it.
*/
static DEFINE_MUTEX(eventfs_mutex);
/*
* The eventfs_inode (ei) itself is protected by SRCU. It is released from
* its parent's list and will have is_freed set (under eventfs_mutex).
- * After the SRCU grace period is over, the ei may be freed.
+ * After the SRCU grace period is over and the last dput() is called
+ * the ei is freed.
*/
DEFINE_STATIC_SRCU(eventfs_srcu);
@@ -365,12 +365,14 @@ create_file_dentry(struct eventfs_inode *ei, int idx,
* created the dentry for this e_dentry. In which case
* use that one.
*
- * Note, with the mutex held, the e_dentry cannot have content
- * and the ei->is_freed be true at the same time.
+ * If ei->is_freed is set, the e_dentry is currently on its
+ * way to being freed, don't return it. If e_dentry is NULL
+ * it means it was already freed.
*/
- dentry = *e_dentry;
- if (WARN_ON_ONCE(dentry && ei->is_freed))
+ if (ei->is_freed)
dentry = NULL;
+ else
+ dentry = *e_dentry;
/* The lookup does not need to up the dentry refcount */
if (dentry && !lookup)
dget(dentry);
@@ -473,8 +475,8 @@ create_dir_dentry(struct eventfs_inode *pei, struct
eventfs_inode *ei,
* created the dentry for this e_dentry. In which case
* use that one.
*
- * Note, with the mutex held, the e_dentry cannot have content
- * and the ei->is_freed be true at the same time.
+ * If ei->is_freed is set, the e_dentry is currently on its
+ * way to being freed.
*/
dentry = ei->dentry;
if (dentry && !lookup)
--
2.42.0
