From b5bc885ba703533b52ad092d3ee9a3090c00e499 Mon Sep 17 00:00:00 2001 From: Ed Bartosh Date: Mon, 3 Apr 2017 18:31:00 +0300 Subject: Revert "filemap: remove FilemapSeek class" FIEMAP API is not supported by tmpfs file system, but SEEK_HOLE/SEEK_DATA is supported. Returned back FilemapSeek class that implements support of SEEK_HOLE/SEEK_DATA API to make sparse_copy API working on tmpfs again. This reverts commit 6b80c13f7a82a312a3b981de5a56c66466ba1fac. (From OE-Core rev: e75bd6a7dd5c1b4bad039c35cf4a2ffc2f77c60a) Signed-off-by: Ed Bartosh Signed-off-by: Ross Burton Signed-off-by: Richard Purdie --- scripts/lib/wic/filemap.py | 309 ++++++++++++++++++++++++++++++++++++++------- 1 file changed, 260 insertions(+), 49 deletions(-) (limited to 'scripts') diff --git a/scripts/lib/wic/filemap.py b/scripts/lib/wic/filemap.py index 34523c02b6..080668e7c2 100644 --- a/scripts/lib/wic/filemap.py +++ b/scripts/lib/wic/filemap.py @@ -54,46 +54,24 @@ class Error(Exception): """A class for all the other exceptions raised by this module.""" pass -# Below goes the FIEMAP ioctl implementation, which 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. - -# 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 -# This FIEMAP ioctl flag which instructs the kernel to sync the file before -# reading the block map -_FIEMAP_FLAG_SYNC = 0x00000001 -# 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. -_FIEMAP_BUFFER_SIZE = 256 * 1024 -class FilemapFiemap: +class _FilemapBase(object): """ - This class provides API to the FIEMAP ioctl. Namely, it allows to iterate - over all mapped blocks and over all holes. - - This class synchronizes the image file every time it invokes the FIEMAP - ioctl in order to work-around early FIEMAP implementation kernel bugs. + This is a base class for a couple of other classes in this module. This + class simply performs the common parts of the initialization process: opens + the image file, gets its size, etc. The 'log' parameter is the logger object + to use for printing messages. """ - def __init__(self, image): + def __init__(self, image, log=None): """ - Initialize a class instance. The 'image' argument is full the file - object to operate on. + Initialize a class instance. The 'image' argument is full path to the + file or file object to operate on. """ - self._log = logging.getLogger(__name__) - self._log.debug("FilemapFiemap: initializing") + self._log = log + if self._log is None: + self._log = logging.getLogger(__name__) self._f_image_needs_close = False @@ -135,21 +113,6 @@ class FilemapFiemap: self._log.debug("block size %d, blocks count %d, image size %d" % (self.block_size, self.blocks_cnt, self.image_size)) - self._buf_size = _FIEMAP_BUFFER_SIZE - - # Calculate how many 'struct fiemap_extent' elements fit the buffer - self._buf_size -= _FIEMAP_SIZE - self._fiemap_extent_cnt = self._buf_size // _FIEMAP_EXTENT_SIZE - assert self._fiemap_extent_cnt > 0 - 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) - - # Check if the FIEMAP ioctl is supported - self.block_is_mapped(0) - def __del__(self): """The class destructor which just closes the image file.""" if self._f_image_needs_close: @@ -165,6 +128,240 @@ class FilemapFiemap: self._f_image_needs_close = True + def block_is_mapped(self, block): # pylint: disable=W0613,R0201 + """ + This method has has to be implemented by child classes. It returns + 'True' if block number 'block' of the image file is mapped and 'False' + otherwise. + """ + + raise Error("the method is not implemented") + + def block_is_unmapped(self, block): # pylint: disable=W0613,R0201 + """ + This method has has to be implemented by child classes. It returns + 'True' if block number 'block' of the image file is not mapped (hole) + and 'False' otherwise. + """ + + raise Error("the method is not implemented") + + def get_mapped_ranges(self, start, count): # pylint: disable=W0613,R0201 + """ + This method has has to be implemented by child classes. This is 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'. + """ + + raise Error("the method is not implemented") + + def get_unmapped_ranges(self, start, count): # pylint: disable=W0613,R0201 + """ + This method has has to be implemented by child classes. Just like + 'get_mapped_ranges()', but yields unmapped block ranges instead + (holes). + """ + + raise Error("the method is not implemented") + + +# The 'SEEK_HOLE' and 'SEEK_DATA' options of the file seek system call +_SEEK_DATA = 3 +_SEEK_HOLE = 4 + +def _lseek(file_obj, offset, whence): + """This is a helper function which invokes 'os.lseek' for file object + 'file_obj' and with specified 'offset' and 'whence'. The 'whence' + argument is supposed to be either '_SEEK_DATA' or '_SEEK_HOLE'. When + there is no more data or hole starting from 'offset', this function + returns '-1'. Otherwise the data or hole position is returned.""" + + try: + return os.lseek(file_obj.fileno(), offset, whence) + except OSError as err: + # The 'lseek' system call returns the ENXIO if there is no data or + # hole starting from the specified offset. + if err.errno == os.errno.ENXIO: + return -1 + elif err.errno == os.errno.EINVAL: + raise ErrorNotSupp("the kernel or file-system does not support " + "\"SEEK_HOLE\" and \"SEEK_DATA\"") + else: + raise + +class FilemapSeek(_FilemapBase): + """ + This class uses the 'SEEK_HOLE' and 'SEEK_DATA' to find file block mapping. + Unfortunately, the current implementation requires the caller to have write + access to the image file. + """ + + def __init__(self, image, log=None): + """Refer the '_FilemapBase' class for the documentation.""" + + # Call the base class constructor first + _FilemapBase.__init__(self, image, log) + self._log.debug("FilemapSeek: initializing") + + self._probe_seek_hole() + + def _probe_seek_hole(self): + """ + Check whether the system implements 'SEEK_HOLE' and 'SEEK_DATA'. + Unfortunately, there seems to be no clean way for detecting this, + because often the system just fakes them by just assuming that all + files are fully mapped, so 'SEEK_HOLE' always returns EOF and + 'SEEK_DATA' always returns the requested offset. + + I could not invent a better way of detecting the fake 'SEEK_HOLE' + implementation than just to create a temporary file in the same + directory where the image file resides. It would be nice to change this + to something better. + """ + + directory = os.path.dirname(self._image_path) + + try: + tmp_obj = tempfile.TemporaryFile("w+", dir=directory) + except IOError as err: + raise ErrorNotSupp("cannot create a temporary in \"%s\": %s" + % (directory, err)) + + try: + os.ftruncate(tmp_obj.fileno(), self.block_size) + except OSError as err: + raise ErrorNotSupp("cannot truncate temporary file in \"%s\": %s" + % (directory, err)) + + offs = _lseek(tmp_obj, 0, _SEEK_HOLE) + if offs != 0: + # We are dealing with the stub 'SEEK_HOLE' implementation which + # always returns EOF. + self._log.debug("lseek(0, SEEK_HOLE) returned %d" % offs) + raise ErrorNotSupp("the file-system does not support " + "\"SEEK_HOLE\" and \"SEEK_DATA\" but only " + "provides a stub implementation") + + tmp_obj.close() + + def block_is_mapped(self, block): + """Refer the '_FilemapBase' class for the documentation.""" + offs = _lseek(self._f_image, block * self.block_size, _SEEK_DATA) + if offs == -1: + result = False + else: + result = (offs // self.block_size == block) + + self._log.debug("FilemapSeek: block_is_mapped(%d) returns %s" + % (block, result)) + return result + + def block_is_unmapped(self, block): + """Refer the '_FilemapBase' class for the documentation.""" + return not self.block_is_mapped(block) + + def _get_ranges(self, start, count, whence1, whence2): + """ + This function implements 'get_mapped_ranges()' and + 'get_unmapped_ranges()' depending on what is passed in the 'whence1' + and 'whence2' arguments. + """ + + assert whence1 != whence2 + end = start * self.block_size + limit = end + count * self.block_size + + while True: + start = _lseek(self._f_image, end, whence1) + if start == -1 or start >= limit or start == self.image_size: + break + + end = _lseek(self._f_image, start, whence2) + if end == -1 or end == self.image_size: + end = self.blocks_cnt * self.block_size + if end > limit: + end = limit + + start_blk = start // self.block_size + end_blk = end // self.block_size - 1 + self._log.debug("FilemapSeek: yielding range (%d, %d)" + % (start_blk, end_blk)) + yield (start_blk, end_blk) + + def get_mapped_ranges(self, start, count): + """Refer the '_FilemapBase' class for the documentation.""" + self._log.debug("FilemapSeek: get_mapped_ranges(%d, %d(%d))" + % (start, count, start + count - 1)) + return self._get_ranges(start, count, _SEEK_DATA, _SEEK_HOLE) + + def get_unmapped_ranges(self, start, count): + """Refer the '_FilemapBase' class for the documentation.""" + self._log.debug("FilemapSeek: get_unmapped_ranges(%d, %d(%d))" + % (start, count, start + count - 1)) + return self._get_ranges(start, count, _SEEK_HOLE, _SEEK_DATA) + + +# Below goes the FIEMAP ioctl implementation, which 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. + +# 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 +# This FIEMAP ioctl flag which instructs the kernel to sync the file before +# reading the block map +_FIEMAP_FLAG_SYNC = 0x00000001 +# 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. +_FIEMAP_BUFFER_SIZE = 256 * 1024 + +class FilemapFiemap(_FilemapBase): + """ + This class provides API to the FIEMAP ioctl. Namely, it allows to iterate + over all mapped blocks and over all holes. + + This class synchronizes the image file every time it invokes the FIEMAP + ioctl in order to work-around early FIEMAP implementation kernel bugs. + """ + + def __init__(self, image, log=None): + """ + Initialize a class instance. The 'image' argument is full the file + object to operate on. + """ + + # Call the base class constructor first + _FilemapBase.__init__(self, image, log) + self._log.debug("FilemapFiemap: initializing") + + self._buf_size = _FIEMAP_BUFFER_SIZE + + # Calculate how many 'struct fiemap_extent' elements fit the buffer + self._buf_size -= _FIEMAP_SIZE + self._fiemap_extent_cnt = self._buf_size // _FIEMAP_EXTENT_SIZE + assert self._fiemap_extent_cnt > 0 + 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) + + # Check if the FIEMAP ioctl is supported + self.block_is_mapped(0) + def _invoke_fiemap(self, block, count): """ Invoke the FIEMAP ioctl for 'count' blocks of the file starting from @@ -318,10 +515,24 @@ class FilemapFiemap: % (hole_first, start + count - 1)) yield (hole_first, start + count - 1) +def filemap(image, log=None): + """ + Create and return an instance of a Filemap class - 'FilemapFiemap' or + 'FilemapSeek', depending on what the system we run on supports. If the + FIEMAP ioctl is supported, an instance of the 'FilemapFiemap' class is + returned. Otherwise, if 'SEEK_HOLE' is supported an instance of the + 'FilemapSeek' class is returned. If none of these are supported, the + function generates an 'Error' type exception. + """ + + try: + return FilemapFiemap(image, log) + except ErrorNotSupp: + return FilemapSeek(image, log) def sparse_copy(src_fname, dst_fname, offset=0, skip=0): """Efficiently copy sparse file to or into another file.""" - fmap = FilemapFiemap(src_fname) + fmap = filemap(src_fname) try: dst_file = open(dst_fname, 'r+b') except IOError: -- cgit v1.2.3-54-g00ecf