Add btrfs helpers

contrib/dump_btrfs_bgs.py

@@ -12,32 +12,6 @@
 from drgn.helpers.linux import *
 from drgn.helpers.common import decode_flags
 
-BTRFS_BLOCK_GROUP_FLAGS = [
-        ("BTRFS_BLOCK_GROUP_DATA", 0),
-        ("BTRFS_BLOCK_GROUP_SYSTEM", 1),
-        ("BTRFS_BLOCK_GROUP_METADATA", 2),
-        ("BTRFS_BLOCK_GROUP_RAID0", 3),
-        ("BTRFS_BLOCK_GROUP_RAID1", 4),
-        ("BTRFS_BLOCK_GROUP_DUP", 5),
-        ("BTRFS_BLOCK_GROUP_RAID10", 6),
-        ("BTRFS_BLOCK_GROUP_RAID5", 9),
-        ("BTRFS_BLOCK_GROUP_RAID6", 8),
-        ("BTRFS_BLOCK_GROUP_RAID1C3", 9),
-        ("BTRFS_BLOCK_GROUP_RAID1C4", 10)
-        ]
-
-BTRFS_BLOCK_GROUP_RUNTIME_FLAGS = [
-        ("BLOCK_GROUP_FLAG_IREF", 0),
-        ("BLOCK_GROUP_FLAG_REMOVED", 1),
-        ("BLOCK_GROUP_FLAG_TO_COPY", 2),
-        ("BLOCK_GROUP_FLAG_RELOCATING_REPAIR", 3),
-        ("BLOCK_GROUP_FLAG_CHUNK_ITEM_INSERTED", 4),
-        ("BLOCK_GROUP_FLAG_ZONE_IS_ACTIVE", 5),
-        ("BLOCK_GROUP_FLAG_ZONED_DATA_RELOC", 6),
-        ("BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE", 7),
-        ("BLOCK_GROUP_FLAG_SEQUENTIAL_ZONE", 8)
-        ]
-
 if len(sys.argv) > 1:
     mnt_path = sys.argv[1]
     mnt_path = mnt_path.rstrip('/')

drgn/helpers/linux/btrfs.py

@@ -0,0 +1,82 @@
+# Copyright (c) Western Digital Corporation, and affiliates.
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+"""
+BTRFS File System
+-----------------
+
+The ``drgn.helpers.linux.btrfs`` module provides helpers for working with the
+Linux BTRFS filesystem.
+"""
+
+from drgn import Object, Program
+from drgn.helpers.common.prog import takes_program_or_default
+from drgn.helpers.linux.mm import page_to_virt
+
+__all__ = (
+    "BTRFS_BLOCK_GROUP_FLAGS",
+    "BTRFS_BLOCK_GROUP_RUNTIME_FLAGS",
+    "BTRFS_EXTENT_BUFFER_FLAGS",
+    "btrfs_header",
+)
+
+BTRFS_BLOCK_GROUP_FLAGS = [
+    ("BTRFS_BLOCK_GROUP_DATA", 0),
+    ("BTRFS_BLOCK_GROUP_SYSTEM", 1),
+    ("BTRFS_BLOCK_GROUP_METADATA", 2),
+    ("BTRFS_BLOCK_GROUP_RAID0", 3),
+    ("BTRFS_BLOCK_GROUP_RAID1", 4),
+    ("BTRFS_BLOCK_GROUP_DUP", 5),
+    ("BTRFS_BLOCK_GROUP_RAID10", 6),
+    ("BTRFS_BLOCK_GROUP_RAID5", 9),
+    ("BTRFS_BLOCK_GROUP_RAID6", 8),
+    ("BTRFS_BLOCK_GROUP_RAID1C3", 9),
+    ("BTRFS_BLOCK_GROUP_RAID1C4", 10),
+]
+
+BTRFS_BLOCK_GROUP_RUNTIME_FLAGS = [
+    ("BLOCK_GROUP_FLAG_IREF", 0),
+    ("BLOCK_GROUP_FLAG_REMOVED", 1),
+    ("BLOCK_GROUP_FLAG_TO_COPY", 2),
+    ("BLOCK_GROUP_FLAG_RELOCATING_REPAIR", 3),
+    ("BLOCK_GROUP_FLAG_CHUNK_ITEM_INSERTED", 4),
+    ("BLOCK_GROUP_FLAG_ZONE_IS_ACTIVE", 5),
+    ("BLOCK_GROUP_FLAG_ZONED_DATA_RELOC", 6),
+    ("BLOCK_GROUP_FLAG_NEEDS_FREE_SPACE", 7),
+    ("BLOCK_GROUP_FLAG_SEQUENTIAL_ZONE", 8),
+]
+
+
+# Extent Buffer Flags used for decoding
+# >>> print(hex(eb.bflags))
+# 0x85
+# >>> decode_flags(eb.bflags, BTRFS_EXTENT_BUFFER_FLAGS)
+# 'EXTENT_BUFFER_UPTODATE|EXTENT_BUFFER_TREE_REF|EXTENT_BUFFER_ZONED_ZEROOUT'
+BTRFS_EXTENT_BUFFER_FLAGS = [
+    ("EXTENT_BUFFER_UPTODATE", 0),
+    ("EXTENT_BUFFER_DIRTY", 1),
+    ("EXTENT_BUFFER_TREE_REF", 2),
+    ("EXTENT_BUFFER_STALE", 3),
+    ("EXTENT_BUFFER_WRITEBACK", 4),
+    ("EXTENT_BUFFER_UNMAPPED", 5),
+    ("EXTENT_BUFFER_WRITE_ERR", 6),
+    ("EXTENT_BUFFER_ZONED_ZEROOUT", 7),
+    ("EXTENT_BUFFER_READING", 8),
+]
+
+
+def _offset_in_page(prog: Program, p: int) -> int:
+    return int(p & ~prog["PAGE_MASK"])
+
+
+@takes_program_or_default
+def btrfs_header(prog: Program, eb: Object) -> Object:
+    """
+    Lookup ``struct btrfs_header`` from a given exent_buffer
+
+    :param eb: ``struct btrfs_extent_buffer *`` to get the header from.
+    :return: ``struct btrfs_header *``
+    """
+    page = eb.folios[0].page
+    addr = page_to_virt(page.address_of_()) + _offset_in_page(prog, int(eb.start))
+    return Object(prog, "struct btrfs_header", address=addr)