contrib: add script to dump filesystem details in btrfs fs_uuids cache

Btrfs maintains a fs_uuids cache, but there is no defined way to look into it. This script reads the cache and prints details of the filesystems present in it. Signed-off-by: Srivathsa Dara <[email protected]>
osandov · Aug 7, 2024 · 3ecda77 · 3ecda77
1 parent 9ad29fd
commit 3ecda77
Showing 1 changed file with 204 additions and 0 deletions.
diff --git a/contrib/btrfs_print_fs_uuids_cache.py b/contrib/btrfs_print_fs_uuids_cache.py
@@ -0,0 +1,204 @@
+#!/usr/bin/env drgn
+# Copyright (c) 2024, Oracle and/or its affiliates.
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+"""
+Print key details of the filesystems in the btrfs fs_uuids cache
+
+Usage:
+* drgn -s <btrfs.ko.debug> -s <vmlinux> -c <vmcore> btrfs_print_fs_uuids_cache.py
+    - This only prints key details of the filesystems
+* drgn -s <btrfs.ko.debug> -s <vmlinux> -c <vmcore> btrfs_print_fs_uuids_cache.py -d yes
+    - This dumps all the structures. The output will be enormous,
+    so it's recommended to redirect it to a file and read it from there.
+"""
+
+import drgn
+import argparse
+
+from drgn.helpers.common import *
+from drgn.helpers.linux import (
+    list_for_each_entry,
+    for_each_possible_cpu,
+    per_cpu_ptr,
+)
+
+parser = argparse.ArgumentParser()
+parser.add_argument("-d", "--dump", required = False, help = "Dump all structure data")
+
+args = parser.parse_args()
+
+def format(uuid_list):
+    """Helper to format uuid from list representation"""
+    part = ""
+    for ele in uuid_list:
+        part += "%02x" %ele
+    return part
+
+def get_uuid_from_list(uuid_list):
+    """Helper to format uuid from list representation"""
+    uuid = ""
+    uuid += format(uuid_list[0:4]) + "-"
+    uuid += format(uuid_list[4:6]) + "-"
+    uuid += format(uuid_list[6:8]) + "-"
+    uuid += format(uuid_list[8:10]) + "-"
+    uuid += format(uuid_list[10:])
+    return uuid
+
+def print_mount_info(mnt):
+    """Print key fields of `struct mount`"""
+    print(f"Mount Info:")
+    print(f"\tMount Point: {mnt.mnt_mountpoint.d_iname.string_().decode('utf-8')}")
+    print(f"\tVFS Mount Flags: {mnt.mnt.mnt_flags}")
+    print(f"\tDevice Name: {mnt.mnt_devname.string_().decode('utf-8')}")
+    if mnt.mnt_mp:
+        print(f"\tMount Point Count: {mnt.mnt_mp.m_count.value_()}")
+    else:
+        print("\tMount Point is NULL")
+    print(f"\tMount ID: {mnt.mnt_id}")
+    print(f"\tMount Group ID: {mnt.mnt_group_id}")
+    print(f"\tMount Expiry Mark: {mnt.mnt_expiry_mark}")
+    return
+
+def print_super_block_info(sb):
+    """Print key fields of `struct super_block`"""
+    print("Super Block:")
+    if not sb:
+        print("\tSuper block is NULL")
+        return
+    print(f"\tsb ref count: {sb.s_active.counter}")
+    print(f"\tsb s_count: {sb.s_count}")
+    print(f"\tsb umount rw_sem counter {sb.s_umount.count.counter}")
+    print(f"\tsb s_flags: {sb.s_flags}")
+    print(f"\tsb s_dev {sb.s_dev}")
+    print(f"\tsb s_id {sb.s_id}")
+    print(f"\tsb i_flags {sb.s_iflags}")
+
+    for mnt in list_for_each_entry("struct mount", sb.s_mounts.address_of_(), "mnt_instance"):
+        if not mnt.mnt_master:
+            print_mount_info(mnt)
+            break
+
+    return
+
+def print_fs_info(fs_info):
+    """Print key fields of `struct btrfs_fs_info`"""
+    print("FS Info:")
+    if not fs_info:
+        print("\tfs_info is NULL")
+        return
+
+    print(f"\tFS State: {fs_info.fs_state}")
+    print(f"\tFlags: {fs_info.flags}")
+    print(f"\tmount opt: {fs_info.mount_opt}")
+
+    print_super_block_info(fs_info.sb)
+    return
+
+def print_fs_devices_info(fs_dev):
+    """"Print key fields of `struct btrfs_fs_devices`"""
+    print("FS Devices:")
+    print(f"\tFS UUID: {get_uuid_from_list(list(fs_dev.fsid))}")
+    print(f"\tMETADATA UUID: {get_uuid_from_list(list(fs_dev.metadata_uuid))}")
+    print(f"\tnum_devices: {fs_dev.num_devices}")
+    print(f"\topen_devices: {fs_dev.open_devices}")
+    print(f"\trw_devices: {fs_dev.rw_devices}")
+    print(f"\tmissing_devices: {fs_dev.missing_devices}")
+    print(f"\ttotal_rw_bytes: {fs_dev.total_rw_bytes}")
+    print(f"\ttotal_devices: {fs_dev.total_devices}")
+    print(f"\tlatest_generation: {fs_dev.latest_generation}")
+    print(f"\topened: {fs_dev.opened}")
+    try:
+        print(f"\tfsid_change: {fs_dev.fsid_change}")
+    except AttributeError:
+        pass
+    return
+
+def print_dev_info(dev):
+    """Print key fields of `struct btrfs_device`"""
+    print("Device Info:")
+    print(f"\tName: {str(dev.name.str)}")
+    print(f"\tstate: {dev.dev_state}")
+    print(f"\tdevid: {dev.devid}")
+    print(f"\tgeneration: {dev.generation}")
+    print(f"\ttype: {dev.type}")
+    if not dev.bdev:
+        print(f"\tbdev: NULL")
+    else:
+        print(f"\tbd_dev: {dev.bdev.bd_dev}")
+        print(f"\tbd_partno: {dev.bdev.bd_partno}")
+    return
+
+def dump_mounts(s_mounts):
+    """Dump master `struct mount` of a mount point"""
+    for mnt in list_for_each_entry("struct mount", s_mounts.address_of_(), "mnt_instance"):
+        if not mnt.mnt_master:
+            print(f"struct mount:\n{mnt}")
+            print(f"Mount Point Dentry:\n{mnt.mnt_mountpoint}")
+            print(f"Namespace:\n{mnt.mnt_ns}")
+            print(f"Mount Point Struct:\n{mnt.mnt_mp}")
+            for cpu in for_each_possible_cpu(prog):
+                print(f"mnt_pcp {cpu}:\n{per_cpu_ptr(mnt.mnt_pcp, cpu)}")
+            break
+    return
+
+def dump_all(fs_uuids):
+    """
+    Dump all structure data of:
+        - struct btrfs_fs_devices
+        - struct btrfs_device
+        - struct btrfs_fs_info
+        - Running transaction => struct btrfs_transaction
+        - struct btrfs_super_block
+        - struct super_block
+        - struct file_system_type
+        - Root Dentry => struct dentry
+        - Root Inode => struct inode
+        - struct user_namespace
+    """
+    for fs_dev in list_for_each_entry("struct btrfs_fs_devices", fs_uuids.address_of_(), "fs_list"):
+        print("-"*30 + f"{get_uuid_from_list(list(fs_dev.fsid))}" + '-'*30)
+        print("FS Devices:\n", fs_dev)
+        print("fs_dev.latest_bdev:", fs_dev.latest_bdev)
+        if fs_dev.fs_info:
+            print("FS Info:\n", fs_dev.fs_info)
+            print("fs_info Running transaction:\n", fs_dev.fs_info.running_transaction)
+            print("Disk superblock:\n", fs_dev.fs_info.super_copy)
+            if fs_dev.fs_info.sb:
+                print("Superblock:\n", fs_dev.fs_info.sb)
+                print("Fs Type:\n", fs_dev.fs_info.sb.s_type)
+                print("Root Dentry:\n", fs_dev.fs_info.sb.s_root)
+                print("Root Inode:\n", fs_dev.fs_info.sb.s_root.d_inode)
+                print("sb user namespace:\n", fs_dev.fs_info.sb.s_user_ns)
+                dump_mounts(fs_dev.fs_info.sb.s_mounts)
+            else:
+                print("Superblock: NULL")
+        else:
+            print("FS Info: NULL")
+
+        for dev in list_for_each_entry("struct btrfs_device", fs_dev.devices.address_of_(), "dev_list"):
+            print("Device:\n", dev)
+            print("Block Device:\n", dev.bdev)
+            print("dev.flush_bio:\n", dev.flush_bio) 
+        print("\n")
+    return
+
+def print_btrfs_cache(fs_uuids):
+    """
+    Iterate through the fs_uuids cache and print the details of each filesystem.
+    """
+    for fs_dev in list_for_each_entry("struct btrfs_fs_devices", fs_uuids.address_of_(), "fs_list"):
+        print("-"*60)
+        print_fs_devices_info(fs_dev)
+        print_fs_info(fs_dev.fs_info)
+
+        for dev in list_for_each_entry("struct btrfs_device", fs_dev.devices.address_of_(), "dev_list"):
+            print_dev_info(dev)
+    return
+
+fs_uuids = prog['fs_uuids']
+
+if args.dump == "yes":
+    dump_all(fs_uuids)
+else:
+    print_btrfs_cache(fs_uuids)