[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 "module.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 = (void *)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((void *)s->cow_bitmap_addr, s->cow_bitmap_size);
    close(s->fd);
}

static int cow_create(const char *filename, QEMUOptionParameter *options)
{
    int fd, cow_fd;
    struct cow_header_v2 cow_header;
    struct stat st;
    int64_t image_sectors = 0;
    const char *image_filename = NULL;

    /* Read out options */
    while (options && options->name) {
        if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
            image_sectors = options->value.n / 512;
        } else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
            image_filename = options->value.s;
        }
        options++;
    }

    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;
    qemu_fdatasync(s->fd);
}

static QEMUOptionParameter cow_create_options[] = {
    {
        .name = BLOCK_OPT_SIZE,
        .type = OPT_SIZE,
        .help = "Virtual disk size"
    },
    {
        .name = BLOCK_OPT_BACKING_FILE,
        .type = OPT_STRING,
        .help = "File name of a base image"
    },
    { NULL }
};

static BlockDriver bdrv_cow = {
    .format_name	= "cow",
    .instance_size	= sizeof(BDRVCowState),
    .bdrv_probe		= cow_probe,
    .bdrv_open		= cow_open,
    .bdrv_read		= cow_read,
    .bdrv_write		= cow_write,
    .bdrv_close		= cow_close,
    .bdrv_create	= cow_create,
    .bdrv_flush		= cow_flush,
    .bdrv_is_allocated	= cow_is_allocated,

    .create_options = cow_create_options,
};

static void bdrv_cow_init(void)
{
    bdrv_register(&bdrv_cow);
}

block_init(bdrv_cow_init);
#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	26	#include "block_int.h"
5efa9d5a	27	#include "module.h"
ea2384d3 FB	28	#include <sys/mman.h>
	29
	30	/**************************************************************/
	31	/* COW block driver using file system holes */
	32
	33	/* user mode linux compatible COW file */
	34	#define COW_MAGIC 0x4f4f4f4d /* MOOO */
	35	#define COW_VERSION 2
	36
	37	struct cow_header_v2 {
	38	uint32_t magic;
	39	uint32_t version;
	40	char backing_file[1024];
	41	int32_t mtime;
	42	uint64_t size;
	43	uint32_t sectorsize;
	44	};
	45
	46	typedef struct BDRVCowState {
	47	int fd;
	48	uint8_t cow_bitmap; / if non NULL, COW mappings are used first */
	49	uint8_t cow_bitmap_addr; / mmap address of cow_bitmap */
	50	int cow_bitmap_size;
	51	int64_t cow_sectors_offset;
	52	} BDRVCowState;
	53
	54	static int cow_probe(const uint8_t buf, int buf_size, const char filename)
	55	{
	56	const struct cow_header_v2 cow_header = (const void )buf;
	57
712e7874 FB	58	if (buf_size >= sizeof(struct cow_header_v2) &&
712e7874 FB	59	be32_to_cpu(cow_header->magic) == COW_MAGIC &&
5fafdf24	60	be32_to_cpu(cow_header->version) == COW_VERSION)
ea2384d3 FB	61	return 100;
	62	else
	63	return 0;
	64	}
	65
83f64091	66	static int cow_open(BlockDriverState bs, const char filename, int flags)
ea2384d3 FB	67	{
	68	BDRVCowState *s = bs->opaque;
	69	int fd;
	70	struct cow_header_v2 cow_header;
	71	int64_t size;
	72
	73	fd = open(filename, O_RDWR \| O_BINARY \| O_LARGEFILE);
	74	if (fd < 0) {
	75	fd = open(filename, O_RDONLY \| O_BINARY \| O_LARGEFILE);
	76	if (fd < 0)
	77	return -1;
	78	}
	79	s->fd = fd;
	80	/* see if it is a cow image */
	81	if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
	82	goto fail;
	83	}
	84
	85	if (be32_to_cpu(cow_header.magic) != COW_MAGIC \|\|
	86	be32_to_cpu(cow_header.version) != COW_VERSION) {
	87	goto fail;
	88	}
3b46e624	89
ea2384d3 FB	90	/* cow image found */
	91	size = be64_to_cpu(cow_header.size);
	92	bs->total_sectors = size / 512;
	93
5fafdf24	94	pstrcpy(bs->backing_file, sizeof(bs->backing_file),
ea2384d3	95	cow_header.backing_file);
3b46e624	96
ea2384d3 FB	97	/* mmap the bitmap */
ea2384d3 FB	98	s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
3f4cb3d3 BS	99	s->cow_bitmap_addr = (void *)mmap(get_mmap_addr(s->cow_bitmap_size),
	100	s->cow_bitmap_size,
	101	PROT_READ \| PROT_WRITE,
	102	MAP_SHARED, s->fd, 0);
ea2384d3 FB	103	if (s->cow_bitmap_addr == MAP_FAILED)
	104	goto fail;
	105	s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
	106	s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
	107	return 0;
	108	fail:
	109	close(fd);
	110	return -1;
	111	}
	112
2b03a7a5	113	static inline void cow_set_bit(uint8_t *bitmap, int64_t bitnum)
ea2384d3 FB	114	{
	115	bitmap[bitnum / 8] \|= (1 << (bitnum%8));
	116	}
	117
	118	static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
	119	{
	120	return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
	121	}
	122
	123
	124	/* Return true if first block has been changed (ie. current version is
	125	* in COW file). Set the number of continuous blocks for which that
	126	* is true. */
	127	static inline int is_changed(uint8_t *bitmap,
	128	int64_t sector_num, int nb_sectors,
	129	int *num_same)
	130	{
	131	int changed;
	132
	133	if (!bitmap \|\| nb_sectors == 0) {
	134	*num_same = nb_sectors;
	135	return 0;
	136	}
	137
	138	changed = is_bit_set(bitmap, sector_num);
	139	for (num_same = 1; num_same < nb_sectors; (*num_same)++) {
	140	if (is_bit_set(bitmap, sector_num + *num_same) != changed)
	141	break;
	142	}
	143
	144	return changed;
	145	}
	146
5fafdf24	147	static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
ea2384d3 FB	148	int nb_sectors, int *pnum)
	149	{
	150	BDRVCowState *s = bs->opaque;
	151	return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
	152	}
	153
5fafdf24	154	static int cow_read(BlockDriverState *bs, int64_t sector_num,
ea2384d3 FB	155	uint8_t *buf, int nb_sectors)
	156	{
	157	BDRVCowState *s = bs->opaque;
	158	int ret, n;
3b46e624	159
ea2384d3 FB	160	while (nb_sectors > 0) {
ea2384d3 FB	161	if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
d5249393	162	lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3	163	ret = read(s->fd, buf, n * 512);
5fafdf24	164	if (ret != n * 512)
ea2384d3 FB	165	return -1;
ea2384d3 FB	166	} else {
83f64091 FB	167	if (bs->backing_hd) {
	168	/* read from the base image */
	169	ret = bdrv_read(bs->backing_hd, sector_num, buf, n);
	170	if (ret < 0)
	171	return -1;
	172	} else {
ea2384d3 FB	173	memset(buf, 0, n * 512);
ea2384d3 FB	174	}
83f64091	175	}
ea2384d3 FB	176	nb_sectors -= n;
	177	sector_num += n;
	178	buf += n * 512;
	179	}
	180	return 0;
	181	}
	182
5fafdf24	183	static int cow_write(BlockDriverState *bs, int64_t sector_num,
ea2384d3 FB	184	const uint8_t *buf, int nb_sectors)
	185	{
	186	BDRVCowState *s = bs->opaque;
	187	int ret, i;
3b46e624	188
d5249393	189	lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3	190	ret = write(s->fd, buf, nb_sectors * 512);
5fafdf24	191	if (ret != nb_sectors * 512)
ea2384d3 FB	192	return -1;
ea2384d3 FB	193	for (i = 0; i < nb_sectors; i++)
2b03a7a5	194	cow_set_bit(s->cow_bitmap, sector_num + i);
ea2384d3 FB	195	return 0;
	196	}
	197
e2731add	198	static void cow_close(BlockDriverState *bs)
ea2384d3 FB	199	{
ea2384d3 FB	200	BDRVCowState *s = bs->opaque;
3f4cb3d3	201	munmap((void *)s->cow_bitmap_addr, s->cow_bitmap_size);
ea2384d3 FB	202	close(s->fd);
	203	}
	204
0e7e1989	205	static int cow_create(const char filename, QEMUOptionParameter options)
ea2384d3 FB	206	{
	207	int fd, cow_fd;
	208	struct cow_header_v2 cow_header;
	209	struct stat st;
0e7e1989 KW	210	int64_t image_sectors = 0;
	211	const char *image_filename = NULL;
	212
	213	/* Read out options */
	214	while (options && options->name) {
	215	if (!strcmp(options->name, BLOCK_OPT_SIZE)) {
	216	image_sectors = options->value.n / 512;
	217	} else if (!strcmp(options->name, BLOCK_OPT_BACKING_FILE)) {
	218	image_filename = options->value.s;
	219	}
	220	options++;
	221	}
ea2384d3	222
5fafdf24	223	cow_fd = open(filename, O_WRONLY \| O_CREAT \| O_TRUNC \| O_BINARY,
ea2384d3 FB	224	0644);
	225	if (cow_fd < 0)
	226	return -1;
	227	memset(&cow_header, 0, sizeof(cow_header));
	228	cow_header.magic = cpu_to_be32(COW_MAGIC);
	229	cow_header.version = cpu_to_be32(COW_VERSION);
	230	if (image_filename) {
83f64091 FB	231	/* Note: if no file, we put a dummy mtime */
	232	cow_header.mtime = cpu_to_be32(0);
	233
ea2384d3 FB	234	fd = open(image_filename, O_RDONLY \| O_BINARY);
	235	if (fd < 0) {
	236	close(cow_fd);
83f64091	237	goto mtime_fail;
ea2384d3 FB	238	}
	239	if (fstat(fd, &st) != 0) {
	240	close(fd);
83f64091	241	goto mtime_fail;
ea2384d3 FB	242	}
	243	close(fd);
	244	cow_header.mtime = cpu_to_be32(st.st_mtime);
83f64091 FB	245	mtime_fail:
	246	pstrcpy(cow_header.backing_file, sizeof(cow_header.backing_file),
	247	image_filename);
ea2384d3 FB	248	}
	249	cow_header.sectorsize = cpu_to_be32(512);
	250	cow_header.size = cpu_to_be64(image_sectors * 512);
	251	write(cow_fd, &cow_header, sizeof(cow_header));
	252	/* resize to include at least all the bitmap */
	253	ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
	254	close(cow_fd);
	255	return 0;
	256	}
	257
7a6cba61 PB	258	static void cow_flush(BlockDriverState *bs)
	259	{
	260	BDRVCowState *s = bs->opaque;
6f1953c4	261	qemu_fdatasync(s->fd);
7a6cba61 PB	262	}
7a6cba61 PB	263
0e7e1989	264	static QEMUOptionParameter cow_create_options[] = {
db08adf5 KW	265	{
	266	.name = BLOCK_OPT_SIZE,
	267	.type = OPT_SIZE,
	268	.help = "Virtual disk size"
	269	},
	270	{
	271	.name = BLOCK_OPT_BACKING_FILE,
	272	.type = OPT_STRING,
	273	.help = "File name of a base image"
	274	},
0e7e1989 KW	275	{ NULL }
	276	};
	277
5efa9d5a	278	static BlockDriver bdrv_cow = {
e60f469c AJ	279	.format_name = "cow",
	280	.instance_size = sizeof(BDRVCowState),
	281	.bdrv_probe = cow_probe,
	282	.bdrv_open = cow_open,
	283	.bdrv_read = cow_read,
	284	.bdrv_write = cow_write,
	285	.bdrv_close = cow_close,
	286	.bdrv_create = cow_create,
	287	.bdrv_flush = cow_flush,
	288	.bdrv_is_allocated = cow_is_allocated,
0e7e1989 KW	289
0e7e1989 KW	290	.create_options = cow_create_options,
ea2384d3	291	};
5efa9d5a AL	292
	293	static void bdrv_cow_init(void)
	294	{
	295	bdrv_register(&bdrv_cow);
	296	}
	297
	298	block_init(bdrv_cow_init);
ea2384d3	299	#endif