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, 61 insertions, 0 deletions

diff --git a/Documentation/admin-guide/device-mapper/striped.rst b/Documentation/admin-guide/device-mapper/striped.rst
new file mode 100644
index 000000000..e9a8da192
--- /dev/null
+++ b/Documentation/admin-guide/device-mapper/striped.rst
@@ -0,0 +1,61 @@
+=========
+dm-stripe
+=========
+
+Device-Mapper's "striped" target is used to create a striped (i.e. RAID-0)
+device across one or more underlying devices. Data is written in "chunks",
+with consecutive chunks rotating among the underlying devices. This can
+potentially provide improved I/O throughput by utilizing several physical
+devices in parallel.
+
+Parameters: <num devs> <chunk size> [<dev path> <offset>]+
+    <num devs>:
+	Number of underlying devices.
+    <chunk size>:
+	Size of each chunk of data. Must be at least as
+        large as the system's PAGE_SIZE.
+    <dev path>:
+	Full pathname to the underlying block-device, or a
+	"major:minor" device-number.
+    <offset>:
+	Starting sector within the device.
+
+One or more underlying devices can be specified. The striped device size must
+be a multiple of the chunk size multiplied by the number of underlying devices.
+
+
+Example scripts
+===============
+
+::
+
+  #!/usr/bin/perl -w
+  # Create a striped device across any number of underlying devices. The device
+  # will be called "stripe_dev" and have a chunk-size of 128k.
+
+  my $chunk_size = 128 * 2;
+  my $dev_name = "stripe_dev";
+  my $num_devs = @ARGV;
+  my @devs = @ARGV;
+  my ($min_dev_size, $stripe_dev_size, $i);
+
+  if (!$num_devs) {
+          die("Specify at least one device\n");
+  }
+
+  $min_dev_size = `blockdev --getsz $devs[0]`;
+  for ($i = 1; $i < $num_devs; $i++) {
+          my $this_size = `blockdev --getsz $devs[$i]`;
+          $min_dev_size = ($min_dev_size < $this_size) ?
+                          $min_dev_size : $this_size;
+  }
+
+  $stripe_dev_size = $min_dev_size * $num_devs;
+  $stripe_dev_size -= $stripe_dev_size % ($chunk_size * $num_devs);
+
+  $table = "0 $stripe_dev_size striped $num_devs $chunk_size";
+  for ($i = 0; $i < $num_devs; $i++) {
+          $table .= " $devs[$i] 0";
+  }
+
+  `echo $table | dmsetup create $dev_name`;