From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi 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 Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- Documentation/filesystems/btrfs.rst | 43 +++++++++++++++++++++++++++++++++++++ 1 file changed, 43 insertions(+) create mode 100644 Documentation/filesystems/btrfs.rst (limited to 'Documentation/filesystems/btrfs.rst') 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. -- cgit v1.3.1