[qemu.git] / block-cow.c

/*
 * Block driver for the COW format
 *
 * Copyright (c) 2004 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#ifndef _WIN32
#include "qemu-common.h"
#include "block_int.h"
#include <sys/mman.h>

/**************************************************************/
/* COW block driver using file system holes */

/* user mode linux compatible COW file */
#define COW_MAGIC 0x4f4f4f4d  /* MOOO */
#define COW_VERSION 2

struct cow_header_v2 {
    uint32_t magic;
    uint32_t version;
    char backing_file[1024];
    int32_t mtime;
    uint64_t size;
    uint32_t sectorsize;
};

typedef struct BDRVCowState {
    int fd;
    uint8_t *cow_bitmap; /* if non NULL, COW mappings are used first */
    uint8_t *cow_bitmap_addr; /* mmap address of cow_bitmap */
    int cow_bitmap_size;
    int64_t cow_sectors_offset;
} BDRVCowState;

static int cow_probe(const uint8_t *buf, int buf_size, const char *filename)
{
    const struct cow_header_v2 *cow_header = (const void *)buf;

    if (buf_size >= sizeof(struct cow_header_v2) &&
        be32_to_cpu(cow_header->magic) == COW_MAGIC &&
        be32_to_cpu(cow_header->version) == COW_VERSION)
        return 100;
    else
        return 0;
}

static int cow_open(BlockDriverState *bs, const char *filename, int flags)
{
    BDRVCowState *s = bs->opaque;
    int fd;
    struct cow_header_v2 cow_header;
    int64_t size;

    fd = open(filename, O_RDWR | O_BINARY | O_LARGEFILE);
    if (fd < 0) {
        fd = open(filename, O_RDONLY | O_BINARY | O_LARGEFILE);
        if (fd < 0)
            return -1;
    }
    s->fd = fd;
    /* see if it is a cow image */
    if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
        goto fail;
    }

    if (be32_to_cpu(cow_header.magic) != COW_MAGIC ||
        be32_to_cpu(cow_header.version) != COW_VERSION) {
        goto fail;
    }

    /* cow image found */
    size = be64_to_cpu(cow_header.size);
    bs->total_sectors = size / 512;

    pstrcpy(bs->backing_file, sizeof(bs->backing_file),
            cow_header.backing_file);

    /* mmap the bitmap */
    s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
    s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
                              s->cow_bitmap_size,
                              PROT_READ | PROT_WRITE,
                              MAP_SHARED, s->fd, 0);
    if (s->cow_bitmap_addr == MAP_FAILED)
        goto fail;
    s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
    s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
    return 0;
 fail:
    close(fd);
    return -1;
}

static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
{
    bitmap[bitnum / 8] |= (1 << (bitnum%8));
}

static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
{
    return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
}


/* Return true if first block has been changed (ie. current version is
 * in COW file).  Set the number of continuous blocks for which that
 * is true. */
static inline int is_changed(uint8_t *bitmap,
                             int64_t sector_num, int nb_sectors,
                             int *num_same)
{
    int changed;

    if (!bitmap || nb_sectors == 0) {
	*num_same = nb_sectors;
	return 0;
    }

    changed = is_bit_set(bitmap, sector_num);
    for (*num_same = 1; *num_same < nb_sectors; (*num_same)++) {
	if (is_bit_set(bitmap, sector_num + *num_same) != changed)
	    break;
    }

    return changed;
}

static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
                            int nb_sectors, int *pnum)
{
    BDRVCowState *s = bs->opaque;
    return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
}

static int cow_read(BlockDriverState *bs, int64_t sector_num,
                    uint8_t *buf, int nb_sectors)
{
    BDRVCowState *s = bs->opaque;
    int ret, n;

    while (nb_sectors > 0) {
        if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
            lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
            ret = read(s->fd, buf, n * 512);
            if (ret != n * 512)
                return -1;
        } else {
            if (bs->backing_hd) {
                /* read from the base image */
                ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
                if (ret < 0)
                    return -1;
            } else {
            memset(buf, 0, n * 512);
        }
        }
        nb_sectors -= n;
        sector_num += n;
        buf += n * 512;
    }
    return 0;
}

static int cow_write(BlockDriverState *bs, int64_t sector_num,
                     const uint8_t *buf, int nb_sectors)
{
    BDRVCowState *s = bs->opaque;
    int ret, i;

    lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
    ret = write(s->fd, buf, nb_sectors * 512);
    if (ret != nb_sectors * 512)
        return -1;
    for (i = 0; i < nb_sectors; i++)
        cow_set_bit(s->cow_bitmap, sector_num + i);
    return 0;
}

static void cow_close(BlockDriverState *bs)
{
    BDRVCowState *s = bs->opaque;
    munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
    close(s->fd);
}

static int cow_create(const char *filename, int64_t image_sectors,
                      const char *image_filename, int flags)
{
    int fd, cow_fd;
    struct cow_header_v2 cow_header;
    struct stat st;

    if (flags)
        return -ENOTSUP;

    cow_fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY,
              0644);
    if (cow_fd < 0)
        return -1;
    memset(&cow_header, 0, sizeof(cow_header));
    cow_header.magic = cpu_to_be32(COW_MAGIC);
    cow_header.version = cpu_to_be32(COW_VERSION);
    if (image_filename) {
        /* Note: if no file, we put a dummy mtime */
        cow_header.mtime = cpu_to_be32(0);

        fd = open(image_filename, O_RDONLY | O_BINARY);
        if (fd < 0) {
            close(cow_fd);
            goto mtime_fail;
        }
        if (fstat(fd, &st) != 0) {
            close(fd);
            goto mtime_fail;
        }
        close(fd);
        cow_header.mtime = cpu_to_be32(st.st_mtime);
    mtime_fail:
        pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
                image_filename);
    }
    cow_header.sectorsize = cpu_to_be32(512);
    cow_header.size = cpu_to_be64(image_sectors * 512);
    write(cow_fd, &cow_header, sizeof(cow_header));
    /* resize to include at least all the bitmap */
    ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
    close(cow_fd);
    return 0;
}

static void cow_flush(BlockDriverState *bs)
{
    BDRVCowState *s = bs->opaque;
    fsync(s->fd);
}

BlockDriver bdrv_cow = {
    "cow",
    sizeof(BDRVCowState),
    cow_probe,
    cow_open,
    cow_read,
    cow_write,
    cow_close,
    cow_create,
    cow_flush,
    cow_is_allocated,
};
#endif
Commit	Line	Data
ea2384d3 FB	1	/*
ea2384d3 FB	2	* Block driver for the COW format
5fafdf24	3	*
ea2384d3	4	* Copyright (c) 2004 Fabrice Bellard
5fafdf24	5	*
ea2384d3 FB	6	* Permission is hereby granted, free of charge, to any person obtaining a copy
	7	* of this software and associated documentation files (the "Software"), to deal
	8	* in the Software without restriction, including without limitation the rights
	9	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	10	* copies of the Software, and to permit persons to whom the Software is
	11	* furnished to do so, subject to the following conditions:
	12	*
	13	* The above copyright notice and this permission notice shall be included in
	14	* all copies or substantial portions of the Software.
	15	*
	16	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	17	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	18	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	19	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	20	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	21	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	22	* THE SOFTWARE.
	23	*/
	24	#ifndef _WIN32
faf07963	25	#include "qemu-common.h"
ea2384d3 FB	26	#include "block_int.h"
	27	#include <sys/mman.h>
	28
	29	/**************************************************************/
	30	/* COW block driver using file system holes */
	31
	32	/* user mode linux compatible COW file */
	33	#define COW_MAGIC 0x4f4f4f4d /* MOOO */
	34	#define COW_VERSION 2
	35
	36	struct cow_header_v2 {
	37	uint32_t magic;
	38	uint32_t version;
	39	char backing_file[1024];
	40	int32_t mtime;
	41	uint64_t size;
	42	uint32_t sectorsize;
	43	};
	44
	45	typedef struct BDRVCowState {
	46	int fd;
	47	uint8_t cow_bitmap; / if non NULL, COW mappings are used first */
	48	uint8_t cow_bitmap_addr; / mmap address of cow_bitmap */
	49	int cow_bitmap_size;
	50	int64_t cow_sectors_offset;
	51	} BDRVCowState;
	52
	53	static int cow_probe(const uint8_t buf, int buf_size, const char filename)
	54	{
	55	const struct cow_header_v2 cow_header = (const void )buf;
	56
712e7874 FB	57	if (buf_size >= sizeof(struct cow_header_v2) &&
712e7874 FB	58	be32_to_cpu(cow_header->magic) == COW_MAGIC &&
5fafdf24	59	be32_to_cpu(cow_header->version) == COW_VERSION)
ea2384d3 FB	60	return 100;
	61	else
	62	return 0;
	63	}
	64
83f64091	65	static int cow_open(BlockDriverState bs, const char filename, int flags)
ea2384d3 FB	66	{
	67	BDRVCowState *s = bs->opaque;
	68	int fd;
	69	struct cow_header_v2 cow_header;
	70	int64_t size;
	71
	72	fd = open(filename, O_RDWR \| O_BINARY \| O_LARGEFILE);
	73	if (fd < 0) {
	74	fd = open(filename, O_RDONLY \| O_BINARY \| O_LARGEFILE);
	75	if (fd < 0)
	76	return -1;
	77	}
	78	s->fd = fd;
	79	/* see if it is a cow image */
	80	if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
	81	goto fail;
	82	}
	83
	84	if (be32_to_cpu(cow_header.magic) != COW_MAGIC \|\|
	85	be32_to_cpu(cow_header.version) != COW_VERSION) {
	86	goto fail;
	87	}
3b46e624	88
ea2384d3 FB	89	/* cow image found */
	90	size = be64_to_cpu(cow_header.size);
	91	bs->total_sectors = size / 512;
	92
5fafdf24	93	pstrcpy(bs->backing_file, sizeof(bs->backing_file),
ea2384d3	94	cow_header.backing_file);
3b46e624	95
ea2384d3 FB	96	/* mmap the bitmap */
ea2384d3 FB	97	s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
5fafdf24 TS	98	s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
5fafdf24 TS	99	s->cow_bitmap_size,
ea2384d3 FB	100	PROT_READ \| PROT_WRITE,
	101	MAP_SHARED, s->fd, 0);
	102	if (s->cow_bitmap_addr == MAP_FAILED)
	103	goto fail;
	104	s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
	105	s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
	106	return 0;
	107	fail:
	108	close(fd);
	109	return -1;
	110	}
	111
2b03a7a5	112	static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
ea2384d3 FB	113	{
	114	bitmap[bitnum / 8] \|= (1 << (bitnum%8));
	115	}
	116
	117	static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
	118	{
	119	return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
	120	}
	121
	122
	123	/* Return true if first block has been changed (ie. current version is
	124	* in COW file). Set the number of continuous blocks for which that
	125	* is true. */
	126	static inline int is_changed(uint8_t *bitmap,
	127	int64_t sector_num, int nb_sectors,
	128	int *num_same)
	129	{
	130	int changed;
	131
	132	if (!bitmap \|\| nb_sectors == 0) {
	133	*num_same = nb_sectors;
	134	return 0;
	135	}
	136
	137	changed = is_bit_set(bitmap, sector_num);
	138	for (num_same = 1; num_same < nb_sectors; (*num_same)++) {
	139	if (is_bit_set(bitmap, sector_num + *num_same) != changed)
	140	break;
	141	}
	142
	143	return changed;
	144	}
	145
5fafdf24	146	static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
ea2384d3 FB	147	int nb_sectors, int *pnum)
	148	{
	149	BDRVCowState *s = bs->opaque;
	150	return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
	151	}
	152
5fafdf24	153	static int cow_read(BlockDriverState *bs, int64_t sector_num,
ea2384d3 FB	154	uint8_t *buf, int nb_sectors)
	155	{
	156	BDRVCowState *s = bs->opaque;
	157	int ret, n;
3b46e624	158
ea2384d3 FB	159	while (nb_sectors > 0) {
ea2384d3 FB	160	if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
d5249393	161	lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3	162	ret = read(s->fd, buf, n * 512);
5fafdf24	163	if (ret != n * 512)
ea2384d3 FB	164	return -1;
ea2384d3 FB	165	} else {
83f64091 FB	166	if (bs->backing_hd) {
	167	/* read from the base image */
	168	ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
	169	if (ret < 0)
	170	return -1;
	171	} else {
ea2384d3 FB	172	memset(buf, 0, n * 512);
ea2384d3 FB	173	}
83f64091	174	}
ea2384d3 FB	175	nb_sectors -= n;
	176	sector_num += n;
	177	buf += n * 512;
	178	}
	179	return 0;
	180	}
	181
5fafdf24	182	static int cow_write(BlockDriverState *bs, int64_t sector_num,
ea2384d3 FB	183	const uint8_t *buf, int nb_sectors)
	184	{
	185	BDRVCowState *s = bs->opaque;
	186	int ret, i;
3b46e624	187
d5249393	188	lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3	189	ret = write(s->fd, buf, nb_sectors * 512);
5fafdf24	190	if (ret != nb_sectors * 512)
ea2384d3 FB	191	return -1;
ea2384d3 FB	192	for (i = 0; i < nb_sectors; i++)
2b03a7a5	193	cow_set_bit(s->cow_bitmap, sector_num + i);
ea2384d3 FB	194	return 0;
	195	}
	196
e2731add	197	static void cow_close(BlockDriverState *bs)
ea2384d3 FB	198	{
	199	BDRVCowState *s = bs->opaque;
	200	munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
	201	close(s->fd);
	202	}
	203
	204	static int cow_create(const char *filename, int64_t image_sectors,
	205	const char *image_filename, int flags)
	206	{
	207	int fd, cow_fd;
	208	struct cow_header_v2 cow_header;
	209	struct stat st;
	210
	211	if (flags)
	212	return -ENOTSUP;
	213
5fafdf24	214	cow_fd = open(filename, O_WRONLY \| O_CREAT \| O_TRUNC \| O_BINARY,
ea2384d3 FB	215	0644);
	216	if (cow_fd < 0)
	217	return -1;
	218	memset(&cow_header, 0, sizeof(cow_header));
	219	cow_header.magic = cpu_to_be32(COW_MAGIC);
	220	cow_header.version = cpu_to_be32(COW_VERSION);
	221	if (image_filename) {
83f64091 FB	222	/* Note: if no file, we put a dummy mtime */
	223	cow_header.mtime = cpu_to_be32(0);
	224
ea2384d3 FB	225	fd = open(image_filename, O_RDONLY \| O_BINARY);
	226	if (fd < 0) {
	227	close(cow_fd);
83f64091	228	goto mtime_fail;
ea2384d3 FB	229	}
	230	if (fstat(fd, &st) != 0) {
	231	close(fd);
83f64091	232	goto mtime_fail;
ea2384d3 FB	233	}
	234	close(fd);
	235	cow_header.mtime = cpu_to_be32(st.st_mtime);
83f64091 FB	236	mtime_fail:
	237	pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
	238	image_filename);
ea2384d3 FB	239	}
	240	cow_header.sectorsize = cpu_to_be32(512);
	241	cow_header.size = cpu_to_be64(image_sectors * 512);
	242	write(cow_fd, &cow_header, sizeof(cow_header));
	243	/* resize to include at least all the bitmap */
	244	ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
	245	close(cow_fd);
	246	return 0;
	247	}
	248
7a6cba61 PB	249	static void cow_flush(BlockDriverState *bs)
	250	{
	251	BDRVCowState *s = bs->opaque;
	252	fsync(s->fd);
	253	}
	254
ea2384d3 FB	255	BlockDriver bdrv_cow = {
	256	"cow",
	257	sizeof(BDRVCowState),
	258	cow_probe,
	259	cow_open,
	260	cow_read,
	261	cow_write,
	262	cow_close,
	263	cow_create,
7a6cba61	264	cow_flush,
ea2384d3 FB	265	cow_is_allocated,
	266	};
	267	#endif