On Tue, Sep 23, 2014 at 10:39 AM, Chris Mason <clm@xxxxxx> wrote:
>
> 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@xxxxxx>
> ---
> btrfs-debugfs | 296 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 296 insertions(+)
> create mode 100755 btrfs-debugfs
>
> diff --git a/btrfs-debugfs b/btrfs-debugfs
> new file mode 100755
> index 0000000..cf1d285
> --- /dev/null
> +++ b/btrfs-debugfs
> @@ -0,0 +1,296 @@
> +#!/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):
Put comments like these in triple-quoted strings just inside the class
or function you're defining; this makes them accessible using the
standard help() system:
class foo(bar):
"""
In the kernel sources, this is
> + _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)
> --
> 1.8.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
