Btrfs: catch invalid free space trees

[mirror_ubuntu-eoan-kernel.git] / include / uapi / linux / btrfs.h

diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
index ac5eacd3055b503f9b95e330600608bf5a018cec..db4c253f8011b2f483ddd1ffc09f4f04a93fdc0a 100644 (file)
--- a/include/uapi/linux/btrfs.h
+++ b/include/uapi/linux/btrfs.h
@@ -239,7 +239,17 @@ struct btrfs_ioctl_fs_info_args {
  * Used by:
  * struct btrfs_ioctl_feature_flags
  */
-#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE        (1ULL << 0)
+#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE                (1ULL << 0)
+/*
+ * Older kernels (< 4.9) on big-endian systems produced broken free space tree
+ * bitmaps, and btrfs-progs also used to corrupt the free space tree (versions
+ * < 4.7.3).  If this bit is clear, then the free space tree cannot be trusted.
+ * btrfs-progs can also intentionally clear this bit to ask the kernel to
+ * rebuild the free space tree, however this might not work on older kernels
+ * that do not know about this bit. If not sure, clear the cache manually on
+ * first mount when booting older kernel versions.
+ */
+#define BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE_VALID  (1ULL << 1)
 
 #define BTRFS_FEATURE_INCOMPAT_MIXED_BACKREF   (1ULL << 0)
 #define BTRFS_FEATURE_INCOMPAT_DEFAULT_SUBVOL  (1ULL << 1)