Commit 88903dae authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

eventfs: Remove expectation that ei->is_freed means ei->dentry == NULL 

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.

Link: https://lkml.kernel.org/r/20231120235154.265826243@goodmis.org



Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Fixes: 020010fb ("eventfs: Delete eventfs_inode when the last dentry is freed")
Reported-by: default avatarMark Rutland <mark.rutland@arm.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 98b1cc82

fs/tracefs/event_inode.c

+12 −10
Original line number Diff line number Diff line
@@ -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)