[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 "vl.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 (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)
{
    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);
    
#if 0
    if (cow_header.backing_file[0] != '\0') {
        if (stat(cow_header.backing_file, &st) != 0) {
            fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
            goto fail;
        }
        if (st.st_mtime != be32_to_cpu(cow_header.mtime)) {
            fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
            goto fail;
            }
        fd = open(cow_header.backing_file, O_RDONLY | O_LARGEFILE);
        if (fd < 0)
            goto fail;
        bs->fd = fd;
    }
#endif
    /* 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 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 {
            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++)
        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 | O_LARGEFILE, 
              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) {
        fd = open(image_filename, O_RDONLY | O_BINARY);
        if (fd < 0) {
            close(cow_fd);
            return -1;
        }
        if (fstat(fd, &st) != 0) {
            close(fd);
            return -1;
        }
        close(fd);
        cow_header.mtime = cpu_to_be32(st.st_mtime);
        realpath(image_filename, cow_header.backing_file);
    }
    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;
}

BlockDriver bdrv_cow = {
    "cow",
    sizeof(BDRVCowState),
    cow_probe,
    cow_open,
    cow_read,
    cow_write,
    cow_close,
    cow_create,
    cow_is_allocated,
};
#endif
Commit	Line	Data
ea2384d3 FB	1	/*
	2	* Block driver for the COW format
	3	*
	4	* Copyright (c) 2004 Fabrice Bellard
	5	*
	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
	25	#include "vl.h"
	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
	57	if (be32_to_cpu(cow_header->magic) == COW_MAGIC &&
	58	be32_to_cpu(cow_header->version) == COW_VERSION)
	59	return 100;
	60	else
	61	return 0;
	62	}
	63
	64	static int cow_open(BlockDriverState bs, const char filename)
65	{
66	BDRVCowState *s = bs->opaque;
67	int fd;
68	struct cow_header_v2 cow_header;
69	int64_t size;
70
71	fd = open(filename, O_RDWR \| O_BINARY \| O_LARGEFILE);
72	if (fd < 0) {
73	fd = open(filename, O_RDONLY \| O_BINARY \| O_LARGEFILE);
74	if (fd < 0)
75	return -1;
76	}
77	s->fd = fd;
78	/* see if it is a cow image */
79	if (read(fd, &cow_header, sizeof(cow_header)) != sizeof(cow_header)) {
80	goto fail;
81	}
82
83	if (be32_to_cpu(cow_header.magic) != COW_MAGIC \|\|
84	be32_to_cpu(cow_header.version) != COW_VERSION) {
85	goto fail;
86	}
87
88	/* cow image found */
89	size = be64_to_cpu(cow_header.size);
90	bs->total_sectors = size / 512;
91
92	pstrcpy(bs->backing_file, sizeof(bs->backing_file),
93	cow_header.backing_file);
94
95	#if 0
96	if (cow_header.backing_file[0] != '\0') {
97	if (stat(cow_header.backing_file, &st) != 0) {
98	fprintf(stderr, "%s: could not find original disk image '%s'\n", filename, cow_header.backing_file);
99	goto fail;
100	}
101	if (st.st_mtime != be32_to_cpu(cow_header.mtime)) {
102	fprintf(stderr, "%s: original raw disk image '%s' does not match saved timestamp\n", filename, cow_header.backing_file);
103	goto fail;
104	}
105	fd = open(cow_header.backing_file, O_RDONLY \| O_LARGEFILE);
106	if (fd < 0)
107	goto fail;
108	bs->fd = fd;
109	}
110	#endif
111	/* mmap the bitmap */
112	s->cow_bitmap_size = ((bs->total_sectors + 7) >> 3) + sizeof(cow_header);
113	s->cow_bitmap_addr = mmap(get_mmap_addr(s->cow_bitmap_size),
114	s->cow_bitmap_size,
115	PROT_READ \| PROT_WRITE,
116	MAP_SHARED, s->fd, 0);
117	if (s->cow_bitmap_addr == MAP_FAILED)
118	goto fail;
119	s->cow_bitmap = s->cow_bitmap_addr + sizeof(cow_header);
120	s->cow_sectors_offset = (s->cow_bitmap_size + 511) & ~511;
121	return 0;
122	fail:
123	close(fd);
124	return -1;
125	}
126
127	static inline void set_bit(uint8_t *bitmap, int64_t bitnum)
128	{
129	bitmap[bitnum / 8] \|= (1 << (bitnum%8));
130	}
131
132	static inline int is_bit_set(const uint8_t *bitmap, int64_t bitnum)
133	{
134	return !!(bitmap[bitnum / 8] & (1 << (bitnum%8)));
135	}
136
137
138	/* Return true if first block has been changed (ie. current version is
139	* in COW file). Set the number of continuous blocks for which that
140	* is true. */
141	static inline int is_changed(uint8_t *bitmap,
142	int64_t sector_num, int nb_sectors,
143	int *num_same)
144	{
145	int changed;
146
147	if (!bitmap \|\| nb_sectors == 0) {
148	*num_same = nb_sectors;
149	return 0;
150	}
151
152	changed = is_bit_set(bitmap, sector_num);
153	for (num_same = 1; num_same < nb_sectors; (*num_same)++) {
154	if (is_bit_set(bitmap, sector_num + *num_same) != changed)
155	break;
156	}
157
158	return changed;
159	}
160
161	static int cow_is_allocated(BlockDriverState *bs, int64_t sector_num,
162	int nb_sectors, int *pnum)
163	{
164	BDRVCowState *s = bs->opaque;
165	return is_changed(s->cow_bitmap, sector_num, nb_sectors, pnum);
166	}
167
168	static int cow_read(BlockDriverState *bs, int64_t sector_num,
169	uint8_t *buf, int nb_sectors)
170	{
171	BDRVCowState *s = bs->opaque;
172	int ret, n;
173
174	while (nb_sectors > 0) {
175	if (is_changed(s->cow_bitmap, sector_num, nb_sectors, &n)) {
d5249393	176	lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3 FB	177	ret = read(s->fd, buf, n * 512);
	178	if (ret != n * 512)
	179	return -1;
	180	} else {
	181	memset(buf, 0, n * 512);
	182	}
	183	nb_sectors -= n;
	184	sector_num += n;
	185	buf += n * 512;
	186	}
	187	return 0;
	188	}
	189
	190	static int cow_write(BlockDriverState *bs, int64_t sector_num,
	191	const uint8_t *buf, int nb_sectors)
	192	{
	193	BDRVCowState *s = bs->opaque;
	194	int ret, i;
	195
d5249393	196	lseek(s->fd, s->cow_sectors_offset + sector_num * 512, SEEK_SET);
ea2384d3 FB	197	ret = write(s->fd, buf, nb_sectors * 512);
	198	if (ret != nb_sectors * 512)
	199	return -1;
	200	for (i = 0; i < nb_sectors; i++)
	201	set_bit(s->cow_bitmap, sector_num + i);
	202	return 0;
	203	}
	204
e2731add	205	static void cow_close(BlockDriverState *bs)
ea2384d3 FB	206	{
	207	BDRVCowState *s = bs->opaque;
	208	munmap(s->cow_bitmap_addr, s->cow_bitmap_size);
	209	close(s->fd);
	210	}
	211
	212	static int cow_create(const char *filename, int64_t image_sectors,
	213	const char *image_filename, int flags)
	214	{
	215	int fd, cow_fd;
	216	struct cow_header_v2 cow_header;
	217	struct stat st;
	218
	219	if (flags)
	220	return -ENOTSUP;
	221
	222	cow_fd = open(filename, O_WRONLY \| O_CREAT \| O_TRUNC \| O_BINARY \| O_LARGEFILE,
	223	0644);
	224	if (cow_fd < 0)
	225	return -1;
	226	memset(&cow_header, 0, sizeof(cow_header));
	227	cow_header.magic = cpu_to_be32(COW_MAGIC);
	228	cow_header.version = cpu_to_be32(COW_VERSION);
	229	if (image_filename) {
	230	fd = open(image_filename, O_RDONLY \| O_BINARY);
	231	if (fd < 0) {
	232	close(cow_fd);
	233	return -1;
	234	}
	235	if (fstat(fd, &st) != 0) {
	236	close(fd);
	237	return -1;
	238	}
	239	close(fd);
	240	cow_header.mtime = cpu_to_be32(st.st_mtime);
	241	realpath(image_filename, cow_header.backing_file);
	242	}
	243	cow_header.sectorsize = cpu_to_be32(512);
	244	cow_header.size = cpu_to_be64(image_sectors * 512);
	245	write(cow_fd, &cow_header, sizeof(cow_header));
	246	/* resize to include at least all the bitmap */
	247	ftruncate(cow_fd, sizeof(cow_header) + ((image_sectors + 7) >> 3));
	248	close(cow_fd);
	249	return 0;
	250	}
	251
	252	BlockDriver bdrv_cow = {
	253	"cow",
	254	sizeof(BDRVCowState),
	255	cow_probe,
	256	cow_open,
	257	cow_read,
	258	cow_write,
	259	cow_close,
	260	cow_create,
	261	cow_is_allocated,
	262	};
	263	#endif