ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/Documentation/filesystems/btrfs.rst b/Documentation/filesystems/btrfs.rst
new file mode 100644
index 000000000..a81db8f54
--- /dev/null
+++ b/Documentation/filesystems/btrfs.rst
@@ -0,0 +1,43 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=====
+BTRFS
+=====
+
+Btrfs is a copy on write filesystem for Linux aimed at implementing advanced
+features while focusing on fault tolerance, repair and easy administration.
+Jointly developed by several companies, licensed under the GPL and open for
+contribution from anyone.
+
+The main Btrfs features include:
+
+    * Extent based file storage (2^64 max file size)
+    * Space efficient packing of small files
+    * Space efficient indexed directories
+    * Dynamic inode allocation
+    * Writable snapshots
+    * Subvolumes (separate internal filesystem roots)
+    * Object level mirroring and striping
+    * Checksums on data and metadata (multiple algorithms available)
+    * Compression (multiple algorithms available)
+    * Reflink, deduplication
+    * Scrub (on-line checksum verification)
+    * Hierarchical quota groups (subvolume and snapshot support)
+    * Integrated multiple device support, with several raid algorithms
+    * Offline filesystem check
+    * Efficient incremental backup and FS mirroring (send/receive)
+    * Trim/discard
+    * Online filesystem defragmentation
+    * Swapfile support
+    * Zoned mode
+    * Read/write metadata verification
+    * Online resize (shrink, grow)
+
+For more information please refer to the documentation site or wiki
+
+  https://btrfs.readthedocs.io
+
+
+that maintains information about administration tasks, frequently asked
+questions, use cases, mount options, comprehensible changelogs, features,
+manual pages, source code repositories, contacts etc.