This is a note to let you know that I've just added the patch titled
eventfs: Keep all directory links at 1
to the 6.7-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-keep-all-directory-links-at-1.patch
and it can be found in the queue-6.7 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 12:35:18 2024
From: Steven Rostedt <rostedt@xxxxxxxxxxx>
Date: Tue, 06 Feb 2024 06:32:21 -0500
Subject: eventfs: Keep all directory links at 1
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>, Christian Brauner <brauner@xxxxxxxxxx>, Al Viro <viro@xxxxxxxxxxxxxxxxxx>, Ajay Kaher <ajay.kaher@xxxxxxxxxxxx>, Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Message-ID: <20240206113401.818811467@xxxxxxxxxxxxxxxxxxxxx>
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
commit ca185770db914869ff9fe773bac5e0e5e4165b83 upstream.
The directory link count in eventfs was somewhat bogus. It was only being
updated when a directory child was being looked up and not on creation.
One solution would be to update in get_attr() the link count by iterating
the ei->children list and then adding 2. But that could slow down simple
stat() calls, especially if it's done on all directories in eventfs.
Another solution would be to add a parent pointer to the eventfs_inode
and keep track of the number of sub directories it has on creation. But
this adds overhead for something not really worthwhile.
The solution decided upon is to keep all directory links in eventfs as 1.
This tells user space not to rely on the hard links of directories. Which
in this case it shouldn't.
Link: https://lore.kernel.org/linux-trace-kernel/20240201002719.GS2087318@ZenIV/
Link: https://lore.kernel.org/linux-trace-kernel/20240201161617.339968298@xxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Ajay Kaher <ajay.kaher@xxxxxxxxxxxx>
Fixes: c1504e510238 ("eventfs: Implement eventfs dir creation functions")
Suggested-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/tracefs/event_inode.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- a/fs/tracefs/event_inode.c
+++ b/fs/tracefs/event_inode.c
@@ -404,9 +404,7 @@ static struct dentry *lookup_dir_entry(s
dentry->d_fsdata = get_ei(ei);
- inc_nlink(inode);
d_add(dentry, inode);
- inc_nlink(dentry->d_parent->d_inode);
return NULL;
}
@@ -769,9 +767,17 @@ struct eventfs_inode *eventfs_create_eve
dentry->d_fsdata = get_ei(ei);
- /* directory inodes start off with i_nlink == 2 (for "." entry) */
- inc_nlink(inode);
+ /*
+ * Keep all eventfs directories with i_nlink == 1.
+ * Due to the dynamic nature of the dentry creations and not
+ * wanting to add a pointer to the parent eventfs_inode in the
+ * eventfs_inode structure, keeping the i_nlink in sync with the
+ * number of directories would cause too much complexity for
+ * something not worth much. Keeping directory links at 1
+ * tells userspace not to trust the link number.
+ */
d_instantiate(dentry, inode);
+ /* The dentry of the "events" parent does keep track though */
inc_nlink(dentry->d_parent->d_inode);
fsnotify_mkdir(dentry->d_parent->d_inode, dentry);
tracefs_end_creating(dentry);
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxx are
queue-6.7/eventfs-keep-all-directory-links-at-1.patch
queue-6.7/eventfs-save-directory-inodes-in-the-eventfs_inode-structure.patch
queue-6.7/tracefs-zero-out-the-tracefs_inode-when-allocating-it.patch
queue-6.7/eventfs-read-ei-entries-before-ei-children-in-eventfs_iterate.patch
queue-6.7/eventfs-remove-lookup-parameter-from-create_dir-file_dentry.patch
queue-6.7/eventfs-remove-fsnotify-functions-from-lookup.patch
queue-6.7/eventfs-stop-using-dcache_readdir-for-getdents.patch
queue-6.7/tracefs-avoid-using-the-ei-dentry-pointer-unnecessarily.patch
queue-6.7/eventfs-initialize-the-tracefs-inode-properly.patch
queue-6.7/eventfs-do-ctx-pos-update-for-all-iterations-in-eventfs_iterate.patch
queue-6.7/tracefs-dentry-lookup-crapectomy.patch
queue-6.7/eventfs-have-the-inodes-all-for-files-and-directories-all-be-the-same.patch
queue-6.7/eventfs-use-kcalloc-instead-of-kzalloc.patch
queue-6.7/eventfs-shortcut-eventfs_iterate-by-skipping-entries-already-read.patch
queue-6.7/eventfs-do-not-create-dentries-nor-inodes-in-iterate_shared.patch
queue-6.7/eventfs-have-eventfs_iterate-stop-immediately-if-ei-is_freed-is-set.patch
queue-6.7/eventfs-restructure-eventfs_inode-structure-to-be-more-condensed.patch
queue-6.7/eventfs-warn-if-an-eventfs_inode-is-freed-without-is_freed-being-set.patch
queue-6.7/eventfs-get-rid-of-dentry-pointers-without-refcounts.patch
queue-6.7/eventfs-remove-unused-d_parent-pointer-field.patch
queue-6.7/eventfs-clean-up-dentry-ops-and-add-revalidate-function.patch
