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btrfs-progs: Add simple python front end to the search ioctl 

This is a starting point for a debugfs style python interface using
the search ioctl.  For now it can only do one thing, which is to
print out all the extents in a file and calculate the compression ratio.

Over time it will grow more features, especially for the kinds of things
we might run btrfs-debug-tree to find out.  Expect the usage and output
to change dramatically over time (don't hard code to it).

Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
This commit is contained in:
Chris Mason 2014-09-23 12:39:23 -04:00 committed by David Sterba
parent 7269fa1570
commit 05063de62c
1 changed files with 296 additions and 0 deletions
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#!/usr/bin/env python2
#
# Simple python program to print out all the extents of a single file
# LGPLv2 license
# Copyright Facebook 2014
import sys,os,struct,fcntl,ctypes,stat
# helpers for max ints
maxu64 = (1L << 64) - 1
maxu32 = (1L << 32) - 1
# the inode (like form stat)
BTRFS_INODE_ITEM_KEY = 1
# backref to the directory
BTRFS_INODE_REF_KEY = 12
# backref to the directory v2
BTRFS_INODE_EXTREF_KEY = 13
# xattr items
BTRFS_XATTR_ITEM_KEY = 24
# orphans for list files
BTRFS_ORPHAN_ITEM_KEY = 48
# treelog items for dirs
BTRFS_DIR_LOG_ITEM_KEY = 60
BTRFS_DIR_LOG_INDEX_KEY = 72
# dir items and dir indexes both hold filenames
BTRFS_DIR_ITEM_KEY = 84
BTRFS_DIR_INDEX_KEY = 96
# these are the file extent pointers
BTRFS_EXTENT_DATA_KEY = 108
# csums
BTRFS_EXTENT_CSUM_KEY = 128
# root item for subvols and snapshots
BTRFS_ROOT_ITEM_KEY = 132
# root item backrefs
BTRFS_ROOT_BACKREF_KEY = 144
BTRFS_ROOT_REF_KEY = 156
# each allocated extent has an extent item
BTRFS_EXTENT_ITEM_KEY = 168
# optimized extents for metadata only
BTRFS_METADATA_ITEM_KEY = 169
# backrefs for extents
BTRFS_TREE_BLOCK_REF_KEY = 176
BTRFS_EXTENT_DATA_REF_KEY = 178
BTRFS_EXTENT_REF_V0_KEY = 180
BTRFS_SHARED_BLOCK_REF_KEY = 182
BTRFS_SHARED_DATA_REF_KEY = 184
# one of these for each block group
BTRFS_BLOCK_GROUP_ITEM_KEY = 192
# dev extents records which part of each device is allocated
BTRFS_DEV_EXTENT_KEY = 204
# dev items describe devs
BTRFS_DEV_ITEM_KEY = 216
# one for each chunk
BTRFS_CHUNK_ITEM_KEY = 228
# qgroup info
BTRFS_QGROUP_STATUS_KEY = 240
BTRFS_QGROUP_INFO_KEY = 242
BTRFS_QGROUP_LIMIT_KEY = 244
BTRFS_QGROUP_RELATION_KEY = 246
# records balance progress
BTRFS_BALANCE_ITEM_KEY = 248
# stats on device errors
BTRFS_DEV_STATS_KEY = 249
BTRFS_DEV_REPLACE_KEY = 250
BTRFS_STRING_ITEM_KEY = 253
# in the kernel sources, this is flattened
# btrfs_ioctl_search_args_v2. It includes both the btrfs_ioctl_search_key
# and the buffer. We're using a 64K buffer size.
#
args_buffer_size = 65536
class btrfs_ioctl_search_args(ctypes.Structure):
_pack_ = 1
_fields_ = [ ("tree_id", ctypes.c_ulonglong),
("min_objectid", ctypes.c_ulonglong),
("max_objectid", ctypes.c_ulonglong),
("min_offset", ctypes.c_ulonglong),
("max_offset", ctypes.c_ulonglong),
("min_transid", ctypes.c_ulonglong),
("max_transid", ctypes.c_ulonglong),
("min_type", ctypes.c_uint),
("max_type", ctypes.c_uint),
("nr_items", ctypes.c_uint),
("unused", ctypes.c_uint),
("unused1", ctypes.c_ulonglong),
("unused2", ctypes.c_ulonglong),
("unused3", ctypes.c_ulonglong),
("unused4", ctypes.c_ulonglong),
("buf_size", ctypes.c_ulonglong),
("buf", ctypes.c_ubyte * args_buffer_size),
]
# the search ioctl resturns one header for each item
#
class btrfs_ioctl_search_header(ctypes.Structure):
_pack_ = 1
_fields_ = [ ("transid", ctypes.c_ulonglong),
("objectid", ctypes.c_ulonglong),
("offset", ctypes.c_ulonglong),
("type", ctypes.c_uint),
("len", ctypes.c_uint),
]
# the type field in btrfs_file_extent_item
BTRFS_FILE_EXTENT_INLINE = 0
BTRFS_FILE_EXTENT_REG = 1
BTRFS_FILE_EXTENT_PREALLOC = 2
class btrfs_file_extent_item(ctypes.LittleEndianStructure):
_pack_ = 1
_fields_ = [ ("generation", ctypes.c_ulonglong),
("ram_bytes", ctypes.c_ulonglong),
("compression", ctypes.c_ubyte),
("encryption", ctypes.c_ubyte),
("other_encoding", ctypes.c_ubyte * 2),
("type", ctypes.c_ubyte),
("disk_bytenr", ctypes.c_ulonglong),
("disk_num_bytes", ctypes.c_ulonglong),
("offset", ctypes.c_ulonglong),
("num_bytes", ctypes.c_ulonglong),
]
class btrfs_ioctl_search():
def __init__(self):
self.args = btrfs_ioctl_search_args()
self.args.tree_id = 0
self.args.min_objectid = 0
self.args.max_objectid = maxu64
self.args.min_offset = 0
self.args.max_offset = maxu64
self.args.min_transid = 0
self.args.max_transid = maxu64
self.args.min_type = 0
self.args.max_type = maxu32
self.args.nr_items = 0
self.args.buf_size = args_buffer_size
# magic encoded for x86_64 this is the v2 search ioctl
self.ioctl_num = 3228603409L
# the results of the search get stored into args.buf
def search(self, fd, nritems=65536):
self.args.nr_items = nritems
fcntl.ioctl(fd, self.ioctl_num, self.args, 1)
# this moves the search key forward by one. If the end result is
# still a valid search key (all mins less than all maxes), we return
# True. Otherwise False
#
def advance_search(search):
if search.args.min_offset < maxu64:
search.args.min_offset += 1
elif search.args.min_type < 255:
search.args.min_type += 1
elif search.args.min_objectid < maxu64:
search.args.min_objectid += 1
else:
return False
if search.args.min_offset > search.args.max_offset:
return False
if search.args.min_type > search.args.max_type:
return False
if search.args.min_objectid > search.args.max_objectid:
return False
return True
# given one search_header and one file_item, print the details. This
# also tosses the [disk_bytenr,disk_num_bytes] into extent_hash to record
# which extents were used by this file
#
def print_one_extent(header, fi, extent_hash):
# we're ignoring inline items for now
if fi.type == BTRFS_FILE_EXTENT_INLINE:
# header.len is the length of the item returned. We subtract
# the part of the file item header that is actually used (21 bytes)
# and we get the length of the inlined data.
# this may or may not be compressed
inline_len = header.len - 21
if fi.compression:
ram_bytes = fi.ram_bytes
else:
ram_bytes = inline_len
print "(%Lu %Lu): ram %Lu disk 0 disk_size %Lu -- inline" % \
(header.objectid, header.offset, ram_bytes, inline_len)
extent_hash[-1] = inline_len
return
if fi.disk_bytenr == 0:
tag = " -- hole"
else:
tag = ""
print "(%Lu %Lu): ram %Lu disk %Lu disk_size %Lu%s" % (header.objectid,
header.offset, fi.num_bytes, fi.disk_bytenr, fi.disk_num_bytes, tag)
if fi.disk_bytenr:
extent_hash[fi.disk_bytenr] = fi.disk_num_bytes
# open 'filename' and run the search ioctl against it, printing all the extents
# we find
def print_file_extents(filename):
extent_hash = {}
s = btrfs_ioctl_search()
s.args.min_type = BTRFS_EXTENT_DATA_KEY
s.args.max_type = BTRFS_EXTENT_DATA_KEY
try:
fd = os.open(filename, os.O_RDONLY)
st = os.fstat(fd)
except Exception, e:
sys.stderr.write("Failed to open %s (%s)\n" % (filename, e))
return -1
if not stat.S_ISREG(st.st_mode):
sys.stderr.write("%s not a regular file\n" % filename)
return 0
s.args.min_objectid = st.st_ino
s.args.max_objectid = st.st_ino
size = st.st_size
while True:
try:
s.search(fd)
except Exception, e:
sys.stderr.write("Search ioctl failed for %s (%s)\n" % (filename, e))
return -1
if s.args.nr_items == 0:
break
# p is the results buffer from the kernel
p = ctypes.addressof(s.args.buf)
header = btrfs_ioctl_search_header()
header_size = ctypes.sizeof(header)
h = ctypes.addressof(header)
p_left = args_buffer_size
for x in xrange(0, s.args.nr_items):
# for each item, copy the header from the buffer into
# our header struct.
ctypes.memmove(h, p, header_size)
p += header_size
p_left -= header_size
# this would be a kernel bug it shouldn't be sending malformed
# items
if p_left <= 0:
break
if header.type == BTRFS_EXTENT_DATA_KEY:
fi = btrfs_file_extent_item()
# this would also be a kernel bug
if p_left < ctypes.sizeof(fi):
break
# Copy the file item out of the results buffer
ctypes.memmove(ctypes.addressof(fi), p, ctypes.sizeof(fi))
print_one_extent(header, fi, extent_hash)
p += header.len
p_left -= header.len
if p_left <= 0:
break
s.args.min_offset = header.offset
if not advance_search(s):
break
total_on_disk = 0
total_extents = 0
for x in extent_hash.itervalues():
total_on_disk += x
total_extents += 1
# don't divide by zero
if total_on_disk == 0:
total_on_disk = 1
print "file: %s extents %Lu disk size %Lu logical size %Lu ratio %.2f" % \
(filename, total_extents, total_on_disk, st.st_size,
float(st.st_size) / float(total_on_disk))
return 0
if len(sys.argv) == 1:
sys.stderr.write("Usage: btrfs-debug filename ...\n")
sys.exit(1)
for f in sys.argv[1:]:
print_file_extents(f)