Chris Mason
2014-Sep-23 16:39 UTC
[PATCH RFC] 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>
---
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):
+ _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
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