358 lines
9.6 KiB
C
358 lines
9.6 KiB
C
/*
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* Block driver for the COW format
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*
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* Copyright (c) 2004 Fabrice Bellard
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#include "qemu-common.h"
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#include "block/block_int.h"
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#include "qemu/module.h"
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/**************************************************************/
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/* COW block driver using file system holes */
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/* user mode linux compatible COW file */
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#define COW_MAGIC 0x4f4f4f4d /* MOOO */
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#define COW_VERSION 2
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struct cow_header_v2 {
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uint32_t magic;
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uint32_t version;
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char backing_file[1024];
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int32_t mtime;
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uint64_t size;
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uint32_t sectorsize;
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};
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typedef struct BDRVCowState {
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CoMutex lock;
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int64_t cow_sectors_offset;
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} BDRVCowState;
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static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
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{
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const struct cow_header_v2 *cow_header = (const void *)buf;
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if (buf_size >= sizeof(struct cow_header_v2) &&
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be32_to_cpu(cow_header->magic) == COW_MAGIC &&
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be32_to_cpu(cow_header->version) == COW_VERSION)
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return 100;
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else
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return 0;
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}
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static int cow_open(BlockDriverState *bs, QDict *options, int flags)
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{
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BDRVCowState *s = bs->opaque;
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struct cow_header_v2 cow_header;
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int bitmap_size;
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int64_t size;
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int ret;
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/* see if it is a cow image */
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ret = bdrv_pread(bs->file, 0, &cow_header, sizeof(cow_header));
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if (ret < 0) {
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goto fail;
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}
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if (be32_to_cpu(cow_header.magic) != COW_MAGIC) {
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ret = -EMEDIUMTYPE;
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goto fail;
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}
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if (be32_to_cpu(cow_header.version) != COW_VERSION) {
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char version[64];
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snprintf(version, sizeof(version),
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"COW version %d", cow_header.version);
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qerror_report(QERR_UNKNOWN_BLOCK_FORMAT_FEATURE,
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bs->device_name, "cow", version);
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ret = -ENOTSUP;
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goto fail;
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}
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/* cow image found */
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size = be64_to_cpu(cow_header.size);
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bs->total_sectors = size / 512;
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pstrcpy(bs->backing_file, sizeof(bs->backing_file),
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cow_header.backing_file);
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bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
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s->cow_sectors_offset = (bitmap_size + 511) & ~511;
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qemu_co_mutex_init(&s->lock);
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return 0;
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fail:
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return ret;
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}
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/*
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* XXX(hch): right now these functions are extremely inefficient.
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* We should just read the whole bitmap we'll need in one go instead.
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*/
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static inline int cow_set_bit(BlockDriverState *bs, int64_t bitnum)
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{
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uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
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uint8_t bitmap;
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int ret;
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ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
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if (ret < 0) {
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return ret;
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}
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bitmap |= (1 << (bitnum % 8));
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ret = bdrv_pwrite_sync(bs->file, offset, &bitmap, sizeof(bitmap));
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if (ret < 0) {
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return ret;
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}
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return 0;
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}
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static inline int is_bit_set(BlockDriverState *bs, int64_t bitnum)
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{
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uint64_t offset = sizeof(struct cow_header_v2) + bitnum / 8;
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uint8_t bitmap;
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int ret;
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ret = bdrv_pread(bs->file, offset, &bitmap, sizeof(bitmap));
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if (ret < 0) {
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return ret;
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}
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return !!(bitmap & (1 << (bitnum % 8)));
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}
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/* Return true if first block has been changed (ie. current version is
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* in COW file). Set the number of continuous blocks for which that
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* is true. */
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static int coroutine_fn cow_co_is_allocated(BlockDriverState *bs,
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int64_t sector_num, int nb_sectors, int *num_same)
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{
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int changed;
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if (nb_sectors == 0) {
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*num_same = nb_sectors;
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return 0;
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}
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changed = is_bit_set(bs, sector_num);
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if (changed < 0) {
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return 0; /* XXX: how to return I/O errors? */
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}
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for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
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if (is_bit_set(bs, sector_num + *num_same) != changed)
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break;
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}
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return changed;
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}
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static int cow_update_bitmap(BlockDriverState *bs, int64_t sector_num,
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int nb_sectors)
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{
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int error = 0;
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int i;
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for (i = 0; i < nb_sectors; i++) {
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error = cow_set_bit(bs, sector_num + i);
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if (error) {
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break;
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}
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}
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return error;
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}
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static int coroutine_fn cow_read(BlockDriverState *bs, int64_t sector_num,
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uint8_t *buf, int nb_sectors)
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{
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BDRVCowState *s = bs->opaque;
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int ret, n;
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while (nb_sectors > 0) {
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if (bdrv_co_is_allocated(bs, sector_num, nb_sectors, &n)) {
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ret = bdrv_pread(bs->file,
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s->cow_sectors_offset + sector_num * 512,
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buf, n * 512);
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if (ret < 0) {
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return ret;
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}
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} else {
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if (bs->backing_hd) {
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/* read from the base image */
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ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
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if (ret < 0) {
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return ret;
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}
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} else {
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memset(buf, 0, n * 512);
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}
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}
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nb_sectors -= n;
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sector_num += n;
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buf += n * 512;
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}
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return 0;
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}
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static coroutine_fn int cow_co_read(BlockDriverState *bs, int64_t sector_num,
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uint8_t *buf, int nb_sectors)
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{
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int ret;
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BDRVCowState *s = bs->opaque;
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qemu_co_mutex_lock(&s->lock);
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ret = cow_read(bs, sector_num, buf, nb_sectors);
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qemu_co_mutex_unlock(&s->lock);
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return ret;
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}
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static int cow_write(BlockDriverState *bs, int64_t sector_num,
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const uint8_t *buf, int nb_sectors)
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{
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BDRVCowState *s = bs->opaque;
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int ret;
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ret = bdrv_pwrite(bs->file, s->cow_sectors_offset + sector_num * 512,
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buf, nb_sectors * 512);
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if (ret < 0) {
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return ret;
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}
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return cow_update_bitmap(bs, sector_num, nb_sectors);
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}
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static coroutine_fn int cow_co_write(BlockDriverState *bs, int64_t sector_num,
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const uint8_t *buf, int nb_sectors)
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{
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int ret;
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BDRVCowState *s = bs->opaque;
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qemu_co_mutex_lock(&s->lock);
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ret = cow_write(bs, sector_num, buf, nb_sectors);
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qemu_co_mutex_unlock(&s->lock);
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return ret;
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}
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static void cow_close(BlockDriverState *bs)
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{
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}
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static int cow_create(const char *filename, QEMUOptionParameter *options)
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{
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struct cow_header_v2 cow_header;
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struct stat st;
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int64_t image_sectors = 0;
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const char *image_filename = NULL;
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int ret;
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BlockDriverState *cow_bs;
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/* Read out options */
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while (options && options->name) {
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if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
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image_sectors = options->value.n / 512;
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} else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
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image_filename = options->value.s;
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}
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options++;
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}
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ret = bdrv_create_file(filename, options);
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if (ret < 0) {
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return ret;
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}
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ret = bdrv_file_open(&cow_bs, filename, NULL, BDRV_O_RDWR);
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if (ret < 0) {
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return ret;
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}
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memset(&cow_header, 0, sizeof(cow_header));
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cow_header.magic = cpu_to_be32(COW_MAGIC);
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cow_header.version = cpu_to_be32(COW_VERSION);
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if (image_filename) {
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/* Note: if no file, we put a dummy mtime */
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cow_header.mtime = cpu_to_be32(0);
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if (stat(image_filename, &st) != 0) {
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goto mtime_fail;
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}
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cow_header.mtime = cpu_to_be32(st.st_mtime);
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mtime_fail:
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pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
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image_filename);
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}
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cow_header.sectorsize = cpu_to_be32(512);
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cow_header.size = cpu_to_be64(image_sectors * 512);
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ret = bdrv_pwrite(cow_bs, 0, &cow_header, sizeof(cow_header));
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if (ret < 0) {
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goto exit;
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}
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/* resize to include at least all the bitmap */
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ret = bdrv_truncate(cow_bs,
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sizeof(cow_header) + ((image_sectors + 7) >> 3));
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if (ret < 0) {
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goto exit;
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}
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exit:
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bdrv_delete(cow_bs);
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return ret;
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}
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static QEMUOptionParameter cow_create_options[] = {
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{
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.name = BLOCK_OPT_SIZE,
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.type = OPT_SIZE,
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.help = "Virtual disk size"
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},
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{
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.name = BLOCK_OPT_BACKING_FILE,
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.type = OPT_STRING,
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.help = "File name of a base image"
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},
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{ NULL }
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};
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static BlockDriver bdrv_cow = {
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.format_name = "cow",
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.instance_size = sizeof(BDRVCowState),
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.bdrv_probe = cow_probe,
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.bdrv_open = cow_open,
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.bdrv_close = cow_close,
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.bdrv_create = cow_create,
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.bdrv_has_zero_init = bdrv_has_zero_init_1,
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.bdrv_read = cow_co_read,
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.bdrv_write = cow_co_write,
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.bdrv_co_is_allocated = cow_co_is_allocated,
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.create_options = cow_create_options,
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};
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static void bdrv_cow_init(void)
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{
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bdrv_register(&bdrv_cow);
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}
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block_init(bdrv_cow_init);
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