This is a note to let you know that I've just added the patch titled
eventfs: Remove expectation that ei->is_freed means ei->dentry == NULL
to the 6.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
eventfs-remove-expectation-that-ei-is_freed-means-ei-dentry-null.patch
and it can be found in the queue-6.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From SRS0=eEWY=JP=rostedt.homelinux.com=rostedt@xxxxxxxxxx Tue Feb 6 13:11:18 2024
From: Steven Rostedt <rostedt@xxxxxxxxxxx>
Date: Tue, 06 Feb 2024 07:09:29 -0500
Subject: eventfs: Remove expectation that ei->is_freed means ei->dentry == NULL
To: linux-kernel@xxxxxxxxxxxxxxx, stable@xxxxxxxxxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, Sasha Levin <sashal@xxxxxxxxxx>, Masami Hiramatsu <mhiramat@xxxxxxxxxx>, Mark Rutland <mark.rutland@xxxxxxx>, Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Message-ID: <20240206120950.284520771@xxxxxxxxxxxxxxxxxxxxx>
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
commit 88903daecacf03b1e5636e1b5f18bda5b07030fc upstream.
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@xxxxxxxxxxx
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Fixes: 020010fbfa20 ("eventfs: Delete eventfs_inode when the last dentry is freed")
Reported-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/tracefs/event_inode.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
--- 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
* 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 *
* 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)
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxx are
queue-6.6/eventfs-keep-all-directory-links-at-1.patch
queue-6.6/eventfs-make-sure-that-parent-d_inode-is-locked-in-creating-files-dirs.patch
queue-6.6/eventfs-save-directory-inodes-in-the-eventfs_inode-structure.patch
queue-6.6/revert-eventfs-save-ownership-and-mode.patch
queue-6.6/tracefs-zero-out-the-tracefs_inode-when-allocating-it.patch
queue-6.6/eventfs-read-ei-entries-before-ei-children-in-eventfs_iterate.patch
queue-6.6/eventfs-do-not-invalidate-dentry-in-create_file-dir_dentry.patch
queue-6.6/eventfs-fix-file-and-directory-uid-and-gid-ownership.patch
queue-6.6/eventfs-remove-lookup-parameter-from-create_dir-file_dentry.patch
queue-6.6/eventfs-use-gfp_nofs-for-allocation-when-eventfs_mutex-is-held.patch
queue-6.6/eventfs-remove-fsnotify-functions-from-lookup.patch
queue-6.6/eventfs-use-err_cast-in-eventfs_create_events_dir.patch
queue-6.6/revert-eventfs-use-simple_recursive_removal-to-clean-up-dentries.patch
queue-6.6/eventfs-use-simple_recursive_removal-to-clean-up-dentries.patch
queue-6.6/eventfs-stop-using-dcache_readdir-for-getdents.patch
queue-6.6/eventfs-have-event-files-and-directories-default-to-parent-uid-and-gid.patch
queue-6.6/eventfs-use-eventfs_remove_events_dir.patch
queue-6.6/eventfs-delete-eventfs_inode-when-the-last-dentry-is-freed.patch
queue-6.6/tracefs-avoid-using-the-ei-dentry-pointer-unnecessarily.patch
queue-6.6/tracefs-remove-stale-update_gid-code.patch
queue-6.6/eventfs-initialize-the-tracefs-inode-properly.patch
queue-6.6/eventfs-remove-special-processing-of-dput-of-events-directory.patch
queue-6.6/eventfs-save-ownership-and-mode.patch
queue-6.6/tracefs-check-for-dentry-d_inode-exists-in-set_gid.patch
queue-6.6/eventfs-do-ctx-pos-update-for-all-iterations-in-eventfs_iterate.patch
queue-6.6/tracefs-dentry-lookup-crapectomy.patch
queue-6.6/eventfs-move-taking-of-inode_lock-into-dcache_dir_open_wrapper.patch
queue-6.6/eventfs-have-a-free_ei-that-just-frees-the-eventfs_inode.patch
queue-6.6/revert-eventfs-remove-is_freed-union-with-rcu-head.patch
queue-6.6/eventfs-have-the-inodes-all-for-files-and-directories-all-be-the-same.patch
queue-6.6/eventfs-use-kcalloc-instead-of-kzalloc.patch
queue-6.6/eventfs-test-for-ei-is_freed-when-accessing-ei-dentry.patch
queue-6.6/eventfs-fix-bitwise-fields-for-is_events.patch
queue-6.6/eventfs-fix-warn_on-in-create_file_dentry.patch
queue-6.6/eventfs-fix-events-beyond-name_max-blocking-tasks.patch
queue-6.6/eventfs-shortcut-eventfs_iterate-by-skipping-entries-already-read.patch
queue-6.6/revert-eventfs-do-not-allow-null-parent-to-eventfs_start_creating.patch
queue-6.6/eventfs-do-not-allow-null-parent-to-eventfs_start_creating.patch
queue-6.6/eventfs-do-not-create-dentries-nor-inodes-in-iterate_shared.patch
queue-6.6/eventfs-have-eventfs_iterate-stop-immediately-if-ei-is_freed-is-set.patch
queue-6.6/eventfs-fix-typo-in-eventfs_inode-union-comment.patch
queue-6.6/eventfs-remove-expectation-that-ei-is_freed-means-ei-dentry-null.patch
queue-6.6/eventfs-restructure-eventfs_inode-structure-to-be-more-condensed.patch
queue-6.6/eventfs-warn-if-an-eventfs_inode-is-freed-without-is_freed-being-set.patch
queue-6.6/eventfs-get-rid-of-dentry-pointers-without-refcounts.patch
queue-6.6/eventfs-remove-unused-d_parent-pointer-field.patch
queue-6.6/eventfs-hold-eventfs_mutex-when-calling-callback-functions.patch
queue-6.6/eventfs-remove-is_freed-union-with-rcu-head.patch
queue-6.6/tracefs-eventfs-modify-mismatched-function-name.patch
queue-6.6/eventfs-fix-kerneldoc-of-eventfs_remove_rec.patch
queue-6.6/tracefs-eventfs-use-root-and-instance-inodes-as-default-ownership.patch
queue-6.6/revert-eventfs-check-for-null-ef-in-eventfs_set_attr.patch
queue-6.6/eventfs-fix-failure-path-in-eventfs_create_events_dir.patch
queue-6.6/eventfs-clean-up-dentry-ops-and-add-revalidate-function.patch
