[1.x] Fix for block blkdev_ro() miss reports disk's readonly status

drgn_tools/block.py

@@ -11,6 +11,7 @@
 
 import drgn
 from drgn import cast
+from drgn import container_of
 from drgn import Object
 from drgn import TypeKind
 from drgn.helpers.common.format import decode_enum_type_flags
@@ -51,18 +52,60 @@ def for_each_badblocks(bb: Object) -> Iterable[Object]:
 
 def blkdev_ro(bdev: Object) -> int:
     """
-    Check whether ``struct block_device *`` is read only
+    Check whether ``struct block_device *`` is read only, which could be
+    user set it to readonly through ioctl, or its underlying disk is set
+    to readonly by disk driver.
 
     :param bdev: ``struct block_device *``
-    :returns: 1 if readonly, 0 if readwrite, -1 if unknown
+    :returns: 1 if readonly, 0 if readwrite, -1 if unknown which is possible
+        for kernel before v5.11 if the block_deivce has not be opened yet.
+    """
+    ro = -1
+    if has_member(bdev, "__bd_flags"):
+        # v6.10: 01e198f01d55 ("bdev: move ->bd_read_only to ->__bd_flags")
+        BD_READ_ONLY = 1 << 8
+        ro = int(bool(bdev.__bd_flags.counter & BD_READ_ONLY))
+    elif has_member(bdev, "bd_read_only"):
+        # v5.11: 83950d359010 ("block: move the policy field to struct
+        # block_device")
+        ro = int(bool(bdev.bd_read_only.value_()))
+
+    # For v5.11 and up
+    if ro != -1:
+        # check whether disk driver set disk to readonly.
+        # v5.12: 52f019d43c22 ("block: add a hard-readonly flag to struct gendisk")
+        # introduced this flag to mark disk driver setting disk to readonly.
+        GD_READ_ONLY = 1 << 1
+        # v5.10: 38430f0876fa ("block: move the NEED_PART_SCAN flag to struct gendisk")
+        # add memeber "state" for "struct gendisk", not necessary to check whether
+        # this member exist since this branch is for v5.11+
+        ro |= int(bool(bdev.bd_disk.state & GD_READ_ONLY))
+        return ro
+    else:  # for v5.10 and below
+        # "bd_part" is NULL if bdev was not opened yet, this can only happen
+        # for the kernel before this commit:
+        # v5.11 0d02129e76ed ("block: merge struct block_device and struct hd_struct")
+        if bdev.bd_part:
+            return int(bdev.bd_part.policy != 0)
+        else:
+            return -1
+
+
+def BD_INODE(bdev: Object) -> Object:
+    """
+    Return the inode associated with a block device. Analogous to the kernel
+    function of the same name.
+
+    :param bdev: ``struct block_device *``
+    :returns: ``struct inode *``
     """
-    if has_member(bdev, "bd_read_only"):
-        return bool(bdev.bd_read_only.value_())
-    # "bd_part" is NULL if bdev was not opened yet.
-    if bdev.bd_part:
-        return bdev.bd_part.policy != 0
+    if has_member(bdev, "bd_inode"):
+        return bdev.bd_inode
     else:
-        return -1
+        # v6.10: 203c1ce0bb06 ("RIP ->bd_inode")
+        return container_of(
+            bdev, "struct bdev_inode", "bdev"
+        ).vfs_inode.address_of_()
 
 
 def blkdev_size(bdev: Object) -> int:
@@ -72,7 +115,7 @@ def blkdev_size(bdev: Object) -> int:
     :param bdev: ``struct block_device *``
     :returns: device size
     """
-    return int(bdev.bd_inode.i_size)
+    return BD_INODE(bdev).i_size.value_()
 
 
 def blkdev_name(bdev: Object) -> str:
@@ -84,6 +127,9 @@ def blkdev_name(bdev: Object) -> str:
     """
     if has_member(bdev, "bd_partno"):
         partno = int(bdev.bd_partno)
+    elif has_member(bdev, "__bd_flags"):
+        # v6.10: 1116b9fa15c0 ("bdev: infrastructure for flags")
+        partno = int(bdev.__bd_flags.counter & 0xFF)
     else:
         partno = int(bdev.bd_part.partno)