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| -rw-r--r-- | scripts/lib/mic/utils/Fiemap.py | 252 |
1 files changed, 0 insertions, 252 deletions
diff --git a/scripts/lib/mic/utils/Fiemap.py b/scripts/lib/mic/utils/Fiemap.py deleted file mode 100644 index f2db6ff..0000000 --- a/scripts/lib/mic/utils/Fiemap.py +++ /dev/null @@ -1,252 +0,0 @@ -""" This module implements python API for the FIEMAP ioctl. The FIEMAP ioctl -allows to find holes and mapped areas in a file. """ - -# Note, a lot of code in this module is not very readable, because it deals -# with the rather complex FIEMAP ioctl. To understand the code, you need to -# know the FIEMAP interface, which is documented in the -# Documentation/filesystems/fiemap.txt file in the Linux kernel sources. - -# Disable the following pylint recommendations: -# * Too many instance attributes (R0902) -# pylint: disable=R0902 - -import os -import struct -import array -import fcntl -from mic.utils.misc import get_block_size - -# Format string for 'struct fiemap' -_FIEMAP_FORMAT = "=QQLLLL" -# sizeof(struct fiemap) -_FIEMAP_SIZE = struct.calcsize(_FIEMAP_FORMAT) -# Format string for 'struct fiemap_extent' -_FIEMAP_EXTENT_FORMAT = "=QQQQQLLLL" -# sizeof(struct fiemap_extent) -_FIEMAP_EXTENT_SIZE = struct.calcsize(_FIEMAP_EXTENT_FORMAT) -# The FIEMAP ioctl number -_FIEMAP_IOCTL = 0xC020660B - -# Minimum buffer which is required for 'class Fiemap' to operate -MIN_BUFFER_SIZE = _FIEMAP_SIZE + _FIEMAP_EXTENT_SIZE -# The default buffer size for 'class Fiemap' -DEFAULT_BUFFER_SIZE = 256 * 1024 - -class Error(Exception): - """ A class for exceptions generated by this module. We currently support - only one type of exceptions, and we basically throw human-readable problem - description in case of errors. """ - pass - -class Fiemap: - """ This class provides API to the FIEMAP ioctl. Namely, it allows to - iterate over all mapped blocks and over all holes. """ - - def _open_image_file(self): - """ Open the image file. """ - - try: - self._f_image = open(self._image_path, 'rb') - except IOError as err: - raise Error("cannot open image file '%s': %s" \ - % (self._image_path, err)) - - self._f_image_needs_close = True - - def __init__(self, image, buf_size = DEFAULT_BUFFER_SIZE): - """ Initialize a class instance. The 'image' argument is full path to - the file to operate on, or a file object to operate on. - - The 'buf_size' argument is the size of the buffer for 'struct - fiemap_extent' elements which will be used when invoking the FIEMAP - ioctl. The larger is the buffer, the less times the FIEMAP ioctl will - be invoked. """ - - self._f_image_needs_close = False - - if hasattr(image, "fileno"): - self._f_image = image - self._image_path = image.name - else: - self._image_path = image - self._open_image_file() - - # Validate 'buf_size' - if buf_size < MIN_BUFFER_SIZE: - raise Error("too small buffer (%d bytes), minimum is %d bytes" \ - % (buf_size, MIN_BUFFER_SIZE)) - - # How many 'struct fiemap_extent' elements fit the buffer - buf_size -= _FIEMAP_SIZE - self._fiemap_extent_cnt = buf_size / _FIEMAP_EXTENT_SIZE - self._buf_size = self._fiemap_extent_cnt * _FIEMAP_EXTENT_SIZE - self._buf_size += _FIEMAP_SIZE - - # Allocate a mutable buffer for the FIEMAP ioctl - self._buf = array.array('B', [0] * self._buf_size) - - self.image_size = os.fstat(self._f_image.fileno()).st_size - - try: - self.block_size = get_block_size(self._f_image) - except IOError as err: - raise Error("cannot get block size for '%s': %s" \ - % (self._image_path, err)) - - self.blocks_cnt = self.image_size + self.block_size - 1 - self.blocks_cnt /= self.block_size - - # Synchronize the image file to make sure FIEMAP returns correct values - try: - self._f_image.flush() - except IOError as err: - raise Error("cannot flush image file '%s': %s" \ - % (self._image_path, err)) - try: - os.fsync(self._f_image.fileno()), - except OSError as err: - raise Error("cannot synchronize image file '%s': %s " \ - % (self._image_path, err.strerror)) - - # Check if the FIEMAP ioctl is supported - self.block_is_mapped(0) - - def __del__(self): - """ The class destructor which closes the opened files. """ - - if self._f_image_needs_close: - self._f_image.close() - - def _invoke_fiemap(self, block, count): - """ Invoke the FIEMAP ioctl for 'count' blocks of the file starting from - block number 'block'. - - The full result of the operation is stored in 'self._buf' on exit. - Returns the unpacked 'struct fiemap' data structure in form of a python - list (just like 'struct.upack()'). """ - - if block < 0 or block >= self.blocks_cnt: - raise Error("bad block number %d, should be within [0, %d]" \ - % (block, self.blocks_cnt)) - - # Initialize the 'struct fiemap' part of the buffer - struct.pack_into(_FIEMAP_FORMAT, self._buf, 0, block * self.block_size, - count * self.block_size, 0, 0, - self._fiemap_extent_cnt, 0) - - try: - fcntl.ioctl(self._f_image, _FIEMAP_IOCTL, self._buf, 1) - except IOError as err: - error_msg = "the FIEMAP ioctl failed for '%s': %s" \ - % (self._image_path, err) - if err.errno == os.errno.EPERM or err.errno == os.errno.EACCES: - # The FIEMAP ioctl was added in kernel version 2.6.28 in 2008 - error_msg += " (looks like your kernel does not support FIEMAP)" - - raise Error(error_msg) - - return struct.unpack(_FIEMAP_FORMAT, self._buf[:_FIEMAP_SIZE]) - - def block_is_mapped(self, block): - """ This function returns 'True' if block number 'block' of the image - file is mapped and 'False' otherwise. """ - - struct_fiemap = self._invoke_fiemap(block, 1) - - # The 3rd element of 'struct_fiemap' is the 'fm_mapped_extents' field. - # If it contains zero, the block is not mapped, otherwise it is - # mapped. - return bool(struct_fiemap[3]) - - def block_is_unmapped(self, block): - """ This function returns 'True' if block number 'block' of the image - file is not mapped (hole) and 'False' otherwise. """ - - return not self.block_is_mapped(block) - - def _unpack_fiemap_extent(self, index): - """ Unpack a 'struct fiemap_extent' structure object number 'index' - from the internal 'self._buf' buffer. """ - - offset = _FIEMAP_SIZE + _FIEMAP_EXTENT_SIZE * index - return struct.unpack(_FIEMAP_EXTENT_FORMAT, - self._buf[offset : offset + _FIEMAP_EXTENT_SIZE]) - - def _do_get_mapped_ranges(self, start, count): - """ Implements most the functionality for the 'get_mapped_ranges()' - generator: invokes the FIEMAP ioctl, walks through the mapped - extents and yields mapped block ranges. However, the ranges may be - consecutive (e.g., (1, 100), (100, 200)) and 'get_mapped_ranges()' - simply merges them. """ - - block = start - while block < start + count: - struct_fiemap = self._invoke_fiemap(block, count) - - mapped_extents = struct_fiemap[3] - if mapped_extents == 0: - # No more mapped blocks - return - - extent = 0 - while extent < mapped_extents: - fiemap_extent = self._unpack_fiemap_extent(extent) - - # Start of the extent - extent_start = fiemap_extent[0] - # Starting block number of the extent - extent_block = extent_start / self.block_size - # Length of the extent - extent_len = fiemap_extent[2] - # Count of blocks in the extent - extent_count = extent_len / self.block_size - - # Extent length and offset have to be block-aligned - assert extent_start % self.block_size == 0 - assert extent_len % self.block_size == 0 - - if extent_block > start + count - 1: - return - - first = max(extent_block, block) - last = min(extent_block + extent_count, start + count) - 1 - yield (first, last) - - extent += 1 - - block = extent_block + extent_count - - def get_mapped_ranges(self, start, count): - """ A generator which yields ranges of mapped blocks in the file. The - ranges are tuples of 2 elements: [first, last], where 'first' is the - first mapped block and 'last' is the last mapped block. - - The ranges are yielded for the area of the file of size 'count' blocks, - starting from block 'start'. """ - - iterator = self._do_get_mapped_ranges(start, count) - - first_prev, last_prev = iterator.next() - - for first, last in iterator: - if last_prev == first - 1: - last_prev = last - else: - yield (first_prev, last_prev) - first_prev, last_prev = first, last - - yield (first_prev, last_prev) - - def get_unmapped_ranges(self, start, count): - """ Just like 'get_mapped_ranges()', but yields unmapped block ranges - instead (holes). """ - - hole_first = start - for first, last in self._do_get_mapped_ranges(start, count): - if first > hole_first: - yield (hole_first, first - 1) - - hole_first = last + 1 - - if hole_first < start + count: - yield (hole_first, start + count - 1) |
