From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Fri, 4 Sep 2026 10:43:19 +0200
Subject: selftests/bpf: Reject graph kptr use after RCU unlock

Add a sleepable verifier test that loads a graph-node local kptr in an
explicit RCU read-side critical section, then passes its node to
bpf_rbtree_remove() after the section ends.

Before the verifier fix, the stale NON_OWN_REF flag makes the node look like
a live borrowed reference and the program is accepted. After the fix, the
pointer is demoted without NON_OWN_REF and the graph kfunc argument is
rejected.

Also exercise a graph kptr loaded while a spin lock provides implicit RCU
protection. The pointer must be invalidated when the lock is released, which
guards the required ordering between non-owning-reference invalidation and
RCU demotion.

Update the existing fault-protected load test state description. The
post-unlock pointer no longer carries NON_OWN_REF, but remains readable
because the load is rewritten to use BPF_PROBE_MEM.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
 .../admin-guide/device-mapper/striped.rst          | 61 ++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 Documentation/admin-guide/device-mapper/striped.rst

(limited to 'Documentation/admin-guide/device-mapper/striped.rst')

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`;
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