444 lines
12 KiB
C
444 lines
12 KiB
C
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/*
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* Copyright (C) 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
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* Licensed under the GPL
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*/
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/*
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* _XOPEN_SOURCE is needed for pread, but we define _GNU_SOURCE, which defines
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* that.
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*/
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#include <unistd.h>
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#include <errno.h>
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#include <string.h>
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#include <arpa/inet.h>
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#include <endian.h>
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#include "cow.h"
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#include "cow_sys.h"
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#define PATH_LEN_V1 256
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typedef __u32 time32_t;
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struct cow_header_v1 {
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__s32 magic;
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__s32 version;
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char backing_file[PATH_LEN_V1];
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time32_t mtime;
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__u64 size;
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__s32 sectorsize;
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} __attribute__((packed));
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/*
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* Define PATH_LEN_V3 as the usual value of MAXPATHLEN, just hard-code it in
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* case other systems have different values for MAXPATHLEN.
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*
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* The same must hold for V2 - we want file format compatibility, not anything
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* else.
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*/
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#define PATH_LEN_V3 4096
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#define PATH_LEN_V2 PATH_LEN_V3
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struct cow_header_v2 {
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__u32 magic;
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__u32 version;
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char backing_file[PATH_LEN_V2];
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time32_t mtime;
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__u64 size;
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__s32 sectorsize;
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} __attribute__((packed));
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/*
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* Changes from V2 -
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* PATH_LEN_V3 as described above
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* Explicitly specify field bit lengths for systems with different
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* lengths for the usual C types. Not sure whether char or
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* time_t should be changed, this can be changed later without
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* breaking compatibility
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* Add alignment field so that different alignments can be used for the
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* bitmap and data
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* Add cow_format field to allow for the possibility of different ways
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* of specifying the COW blocks. For now, the only value is 0,
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* for the traditional COW bitmap.
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* Move the backing_file field to the end of the header. This allows
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* for the possibility of expanding it into the padding required
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* by the bitmap alignment.
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* The bitmap and data portions of the file will be aligned as specified
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* by the alignment field. This is to allow COW files to be
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* put on devices with restrictions on access alignments, such as
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* /dev/raw, with a 512 byte alignment restriction. This also
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* allows the data to be more aligned more strictly than on
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* sector boundaries. This is needed for ubd-mmap, which needs
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* the data to be page aligned.
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* Fixed (finally!) the rounding bug
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*/
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/*
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* Until Dec2005, __attribute__((packed)) was left out from the below
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* definition, leading on 64-bit systems to 4 bytes of padding after mtime, to
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* align size to 8-byte alignment. This shifted all fields above (no padding
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* was present on 32-bit, no other padding was added).
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*
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* However, this _can be detected_: it means that cow_format (always 0 until
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* now) is shifted onto the first 4 bytes of backing_file, where it is otherwise
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* impossible to find 4 zeros. -bb */
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struct cow_header_v3 {
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__u32 magic;
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__u32 version;
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__u32 mtime;
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__u64 size;
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__u32 sectorsize;
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__u32 alignment;
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__u32 cow_format;
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char backing_file[PATH_LEN_V3];
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} __attribute__((packed));
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/* This is the broken layout used by some 64-bit binaries. */
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struct cow_header_v3_broken {
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__u32 magic;
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__u32 version;
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__s64 mtime;
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__u64 size;
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__u32 sectorsize;
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__u32 alignment;
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__u32 cow_format;
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char backing_file[PATH_LEN_V3];
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};
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/* COW format definitions - for now, we have only the usual COW bitmap */
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#define COW_BITMAP 0
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union cow_header {
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struct cow_header_v1 v1;
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struct cow_header_v2 v2;
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struct cow_header_v3 v3;
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struct cow_header_v3_broken v3_b;
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};
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#define COW_MAGIC 0x4f4f4f4d /* MOOO */
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#define COW_VERSION 3
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#define DIV_ROUND(x, len) (((x) + (len) - 1) / (len))
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#define ROUND_UP(x, align) DIV_ROUND(x, align) * (align)
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void cow_sizes(int version, __u64 size, int sectorsize, int align,
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int bitmap_offset, unsigned long *bitmap_len_out,
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int *data_offset_out)
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{
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if (version < 3) {
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*bitmap_len_out = (size + sectorsize - 1) / (8 * sectorsize);
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*data_offset_out = bitmap_offset + *bitmap_len_out;
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*data_offset_out = (*data_offset_out + sectorsize - 1) /
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sectorsize;
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*data_offset_out *= sectorsize;
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}
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else {
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*bitmap_len_out = DIV_ROUND(size, sectorsize);
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*bitmap_len_out = DIV_ROUND(*bitmap_len_out, 8);
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*data_offset_out = bitmap_offset + *bitmap_len_out;
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*data_offset_out = ROUND_UP(*data_offset_out, align);
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}
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}
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static int absolutize(char *to, int size, char *from)
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{
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char save_cwd[256], *slash;
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int remaining;
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if (getcwd(save_cwd, sizeof(save_cwd)) == NULL) {
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cow_printf("absolutize : unable to get cwd - errno = %d\n",
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errno);
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return -1;
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}
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slash = strrchr(from, '/');
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if (slash != NULL) {
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*slash = '\0';
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if (chdir(from)) {
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*slash = '/';
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cow_printf("absolutize : Can't cd to '%s' - "
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"errno = %d\n", from, errno);
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return -1;
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}
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*slash = '/';
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if (getcwd(to, size) == NULL) {
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cow_printf("absolutize : unable to get cwd of '%s' - "
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"errno = %d\n", from, errno);
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return -1;
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}
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remaining = size - strlen(to);
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if (strlen(slash) + 1 > remaining) {
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cow_printf("absolutize : unable to fit '%s' into %d "
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"chars\n", from, size);
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return -1;
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}
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strcat(to, slash);
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}
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else {
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if (strlen(save_cwd) + 1 + strlen(from) + 1 > size) {
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cow_printf("absolutize : unable to fit '%s' into %d "
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"chars\n", from, size);
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return -1;
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}
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strcpy(to, save_cwd);
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strcat(to, "/");
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strcat(to, from);
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}
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if (chdir(save_cwd)) {
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cow_printf("absolutize : Can't cd to '%s' - "
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"errno = %d\n", save_cwd, errno);
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return -1;
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}
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return 0;
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}
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int write_cow_header(char *cow_file, int fd, char *backing_file,
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int sectorsize, int alignment, unsigned long long *size)
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{
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struct cow_header_v3 *header;
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unsigned long modtime;
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int err;
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err = cow_seek_file(fd, 0);
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if (err < 0) {
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cow_printf("write_cow_header - lseek failed, err = %d\n", -err);
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goto out;
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}
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err = -ENOMEM;
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header = cow_malloc(sizeof(*header));
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if (header == NULL) {
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cow_printf("write_cow_header - failed to allocate COW V3 "
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"header\n");
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goto out;
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}
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header->magic = htobe32(COW_MAGIC);
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header->version = htobe32(COW_VERSION);
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err = -EINVAL;
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if (strlen(backing_file) > sizeof(header->backing_file) - 1) {
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/* Below, %zd is for a size_t value */
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cow_printf("Backing file name \"%s\" is too long - names are "
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"limited to %zd characters\n", backing_file,
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sizeof(header->backing_file) - 1);
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goto out_free;
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}
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if (absolutize(header->backing_file, sizeof(header->backing_file),
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backing_file))
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goto out_free;
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err = os_file_modtime(header->backing_file, &modtime);
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if (err < 0) {
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cow_printf("write_cow_header - backing file '%s' mtime "
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"request failed, err = %d\n", header->backing_file,
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-err);
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goto out_free;
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}
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err = cow_file_size(header->backing_file, size);
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if (err < 0) {
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cow_printf("write_cow_header - couldn't get size of "
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"backing file '%s', err = %d\n",
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header->backing_file, -err);
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goto out_free;
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}
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header->mtime = htobe32(modtime);
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header->size = htobe64(*size);
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header->sectorsize = htobe32(sectorsize);
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header->alignment = htobe32(alignment);
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header->cow_format = COW_BITMAP;
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err = cow_write_file(fd, header, sizeof(*header));
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if (err != sizeof(*header)) {
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cow_printf("write_cow_header - write of header to "
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"new COW file '%s' failed, err = %d\n", cow_file,
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-err);
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goto out_free;
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}
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err = 0;
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out_free:
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cow_free(header);
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out:
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return err;
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}
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int file_reader(__u64 offset, char *buf, int len, void *arg)
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{
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int fd = *((int *) arg);
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return pread(fd, buf, len, offset);
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}
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/* XXX Need to sanity-check the values read from the header */
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int read_cow_header(int (*reader)(__u64, char *, int, void *), void *arg,
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__u32 *version_out, char **backing_file_out,
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time_t *mtime_out, unsigned long long *size_out,
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int *sectorsize_out, __u32 *align_out,
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int *bitmap_offset_out)
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{
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union cow_header *header;
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char *file;
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int err, n;
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unsigned long version, magic;
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header = cow_malloc(sizeof(*header));
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if (header == NULL) {
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cow_printf("read_cow_header - Failed to allocate header\n");
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return -ENOMEM;
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}
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err = -EINVAL;
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n = (*reader)(0, (char *) header, sizeof(*header), arg);
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if (n < offsetof(typeof(header->v1), backing_file)) {
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cow_printf("read_cow_header - short header\n");
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goto out;
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}
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magic = header->v1.magic;
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if (magic == COW_MAGIC)
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version = header->v1.version;
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else if (magic == be32toh(COW_MAGIC))
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version = be32toh(header->v1.version);
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/* No error printed because the non-COW case comes through here */
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else goto out;
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*version_out = version;
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if (version == 1) {
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if (n < sizeof(header->v1)) {
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cow_printf("read_cow_header - failed to read V1 "
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"header\n");
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goto out;
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}
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*mtime_out = header->v1.mtime;
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*size_out = header->v1.size;
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*sectorsize_out = header->v1.sectorsize;
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*bitmap_offset_out = sizeof(header->v1);
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*align_out = *sectorsize_out;
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file = header->v1.backing_file;
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}
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else if (version == 2) {
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if (n < sizeof(header->v2)) {
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cow_printf("read_cow_header - failed to read V2 "
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"header\n");
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goto out;
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}
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*mtime_out = be32toh(header->v2.mtime);
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*size_out = be64toh(header->v2.size);
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*sectorsize_out = be32toh(header->v2.sectorsize);
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*bitmap_offset_out = sizeof(header->v2);
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*align_out = *sectorsize_out;
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file = header->v2.backing_file;
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}
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/* This is very subtle - see above at union cow_header definition */
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else if (version == 3 && (*((int*)header->v3.backing_file) != 0)) {
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if (n < sizeof(header->v3)) {
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cow_printf("read_cow_header - failed to read V3 "
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"header\n");
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goto out;
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}
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*mtime_out = be32toh(header->v3.mtime);
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*size_out = be64toh(header->v3.size);
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*sectorsize_out = be32toh(header->v3.sectorsize);
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*align_out = be32toh(header->v3.alignment);
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if (*align_out == 0) {
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cow_printf("read_cow_header - invalid COW header, "
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"align == 0\n");
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}
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*bitmap_offset_out = ROUND_UP(sizeof(header->v3), *align_out);
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file = header->v3.backing_file;
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}
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else if (version == 3) {
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cow_printf("read_cow_header - broken V3 file with"
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" 64-bit layout - recovering content.\n");
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if (n < sizeof(header->v3_b)) {
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cow_printf("read_cow_header - failed to read V3 "
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"header\n");
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goto out;
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}
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|
||
|
|
/*
|
||
|
|
* this was used until Dec2005 - 64bits are needed to represent
|
||
|
|
* 2038+. I.e. we can safely do this truncating cast.
|
||
|
|
*
|
||
|
|
* Additionally, we must use be32toh() instead of be64toh(), since
|
||
|
|
* the program used to use the former (tested - I got mtime
|
||
|
|
* mismatch "0 vs whatever").
|
||
|
|
*
|
||
|
|
* Ever heard about bug-to-bug-compatibility ? ;-) */
|
||
|
|
*mtime_out = (time32_t) be32toh(header->v3_b.mtime);
|
||
|
|
|
||
|
|
*size_out = be64toh(header->v3_b.size);
|
||
|
|
*sectorsize_out = be32toh(header->v3_b.sectorsize);
|
||
|
|
*align_out = be32toh(header->v3_b.alignment);
|
||
|
|
if (*align_out == 0) {
|
||
|
|
cow_printf("read_cow_header - invalid COW header, "
|
||
|
|
"align == 0\n");
|
||
|
|
}
|
||
|
|
*bitmap_offset_out = ROUND_UP(sizeof(header->v3_b), *align_out);
|
||
|
|
file = header->v3_b.backing_file;
|
||
|
|
}
|
||
|
|
else {
|
||
|
|
cow_printf("read_cow_header - invalid COW version\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
err = -ENOMEM;
|
||
|
|
*backing_file_out = cow_strdup(file);
|
||
|
|
if (*backing_file_out == NULL) {
|
||
|
|
cow_printf("read_cow_header - failed to allocate backing "
|
||
|
|
"file\n");
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
err = 0;
|
||
|
|
out:
|
||
|
|
cow_free(header);
|
||
|
|
return err;
|
||
|
|
}
|
||
|
|
|
||
|
|
int init_cow_file(int fd, char *cow_file, char *backing_file, int sectorsize,
|
||
|
|
int alignment, int *bitmap_offset_out,
|
||
|
|
unsigned long *bitmap_len_out, int *data_offset_out)
|
||
|
|
{
|
||
|
|
unsigned long long size, offset;
|
||
|
|
char zero = 0;
|
||
|
|
int err;
|
||
|
|
|
||
|
|
err = write_cow_header(cow_file, fd, backing_file, sectorsize,
|
||
|
|
alignment, &size);
|
||
|
|
if (err)
|
||
|
|
goto out;
|
||
|
|
|
||
|
|
*bitmap_offset_out = ROUND_UP(sizeof(struct cow_header_v3), alignment);
|
||
|
|
cow_sizes(COW_VERSION, size, sectorsize, alignment, *bitmap_offset_out,
|
||
|
|
bitmap_len_out, data_offset_out);
|
||
|
|
|
||
|
|
offset = *data_offset_out + size - sizeof(zero);
|
||
|
|
err = cow_seek_file(fd, offset);
|
||
|
|
if (err < 0) {
|
||
|
|
cow_printf("cow bitmap lseek failed : err = %d\n", -err);
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*
|
||
|
|
* does not really matter how much we write it is just to set EOF
|
||
|
|
* this also sets the entire COW bitmap
|
||
|
|
* to zero without having to allocate it
|
||
|
|
*/
|
||
|
|
err = cow_write_file(fd, &zero, sizeof(zero));
|
||
|
|
if (err != sizeof(zero)) {
|
||
|
|
cow_printf("Write of bitmap to new COW file '%s' failed, "
|
||
|
|
"err = %d\n", cow_file, -err);
|
||
|
|
if (err >= 0)
|
||
|
|
err = -EINVAL;
|
||
|
|
goto out;
|
||
|
|
}
|
||
|
|
|
||
|
|
return 0;
|
||
|
|
out:
|
||
|
|
return err;
|
||
|
|
}
|