selftests/bpf: Reject graph kptr use after RCU unlockgrafted

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>

1 files changed, 31 insertions, 0 deletions

diff --git a/fs/btrfs/defrag.h b/fs/btrfs/defrag.h
new file mode 100644
index 000000000..a7f917a38
--- /dev/null
+++ b/fs/btrfs/defrag.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef BTRFS_DEFRAG_H
+#define BTRFS_DEFRAG_H
+
+#include <linux/types.h>
+#include <linux/compiler_types.h>
+
+struct file_ra_state;
+struct btrfs_inode;
+struct btrfs_fs_info;
+struct btrfs_root;
+struct btrfs_trans_handle;
+struct btrfs_ioctl_defrag_range_args;
+
+int btrfs_defrag_file(struct btrfs_inode *inode, struct file_ra_state *ra,
+		      struct btrfs_ioctl_defrag_range_args *range,
+		      u64 newer_than, unsigned long max_to_defrag);
+int __init btrfs_auto_defrag_init(void);
+void __cold btrfs_auto_defrag_exit(void);
+void btrfs_add_inode_defrag(struct btrfs_inode *inode, u32 extent_thresh);
+int btrfs_run_defrag_inodes(struct btrfs_fs_info *fs_info);
+void btrfs_cleanup_defrag_inodes(struct btrfs_fs_info *fs_info);
+int btrfs_defrag_root(struct btrfs_root *root);
+
+static inline int btrfs_defrag_cancelled(struct btrfs_fs_info *fs_info)
+{
+	return signal_pending(current);
+}
+
+#endif