Archipelago » qemu

/*

 * QEMU System Emulator block driver

 *

 * Copyright (c) 2003 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.

 */

#include "qemu-common.h"

#include "console.h"

#include "block_int.h"

#ifdef _BSD

#include <sys/types.h>

#include <sys/stat.h>

#include <sys/ioctl.h>

#include <sys/queue.h>

#include <sys/disk.h>

#endif

#define SECTOR_BITS 9

#define SECTOR_SIZE (1 << SECTOR_BITS)

typedef struct BlockDriverAIOCBSync {

    BlockDriverAIOCB common;

    QEMUBH *bh;

    int ret;

} BlockDriverAIOCBSync;

static BlockDriverAIOCB *bdrv_aio_read_em(BlockDriverState *bs,

        int64_t sector_num, uint8_t *buf, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque);

static BlockDriverAIOCB *bdrv_aio_write_em(BlockDriverState *bs,

        int64_t sector_num, const uint8_t *buf, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque);

static void bdrv_aio_cancel_em(BlockDriverAIOCB *acb);

static int bdrv_read_em(BlockDriverState *bs, int64_t sector_num,

                        uint8_t *buf, int nb_sectors);

static int bdrv_write_em(BlockDriverState *bs, int64_t sector_num,

                         const uint8_t *buf, int nb_sectors);

BlockDriverState *bdrv_first;

static BlockDriver *first_drv;

int path_is_absolute(const char *path)

{

    const char *p;

#ifdef _WIN32

    /* specific case for names like: "\\.\d:" */

    if (*path == '/' || *path == '\\')

        return 1;

#endif

    p = strchr(path, ':');

    if (p)

        p++;

    else

        p = path;

#ifdef _WIN32

    return (*p == '/' || *p == '\\');

#else

    return (*p == '/');

#endif

}

/* if filename is absolute, just copy it to dest. Otherwise, build a

   path to it by considering it is relative to base_path. URL are

   supported. */

void path_combine(char *dest, int dest_size,

                  const char *base_path,

                  const char *filename)

{

    const char *p, *p1;

    int len;

    if (dest_size <= 0)

        return;

    if (path_is_absolute(filename)) {

        pstrcpy(dest, dest_size, filename);

    } else {

        p = strchr(base_path, ':');

        if (p)

            p++;

        else

            p = base_path;

        p1 = strrchr(base_path, '/');

#ifdef _WIN32

        {

            const char *p2;

            p2 = strrchr(base_path, '\\');

            if (!p1 || p2 > p1)

                p1 = p2;

        }

#endif

        if (p1)

            p1++;

        else

            p1 = base_path;

        if (p1 > p)

            p = p1;

        len = p - base_path;

        if (len > dest_size - 1)

            len = dest_size - 1;

        memcpy(dest, base_path, len);

        dest[len] = '\0';

        pstrcat(dest, dest_size, filename);

    }

}

static void bdrv_register(BlockDriver *bdrv)

{

    if (!bdrv->bdrv_aio_read) {

        /* add AIO emulation layer */

        bdrv->bdrv_aio_read = bdrv_aio_read_em;

        bdrv->bdrv_aio_write = bdrv_aio_write_em;

        bdrv->bdrv_aio_cancel = bdrv_aio_cancel_em;

        bdrv->aiocb_size = sizeof(BlockDriverAIOCBSync);

    } else if (!bdrv->bdrv_read && !bdrv->bdrv_pread) {

        /* add synchronous IO emulation layer */

        bdrv->bdrv_read = bdrv_read_em;

        bdrv->bdrv_write = bdrv_write_em;

    }

    bdrv->next = first_drv;

    first_drv = bdrv;

}

/* create a new block device (by default it is empty) */

BlockDriverState *bdrv_new(const char *device_name)

{

    BlockDriverState **pbs, *bs;

    bs = qemu_mallocz(sizeof(BlockDriverState));

    if(!bs)

        return NULL;

    pstrcpy(bs->device_name, sizeof(bs->device_name), device_name);

    if (device_name[0] != '\0') {

        /* insert at the end */

        pbs = &bdrv_first;

        while (*pbs != NULL)

            pbs = &(*pbs)->next;

        *pbs = bs;

    }

    return bs;

}

BlockDriver *bdrv_find_format(const char *format_name)

{

    BlockDriver *drv1;

    for(drv1 = first_drv; drv1 != NULL; drv1 = drv1->next) {

        if (!strcmp(drv1->format_name, format_name))

            return drv1;

    }

    return NULL;

}

int bdrv_create(BlockDriver *drv,

                const char *filename, int64_t size_in_sectors,

                const char *backing_file, int flags)

{

    if (!drv->bdrv_create)

        return -ENOTSUP;

    return drv->bdrv_create(filename, size_in_sectors, backing_file, flags);

}

#ifdef _WIN32

void get_tmp_filename(char *filename, int size)

{

    char temp_dir[MAX_PATH];

    GetTempPath(MAX_PATH, temp_dir);

    GetTempFileName(temp_dir, "qem", 0, filename);

}

#else

void get_tmp_filename(char *filename, int size)

{

    int fd;

    const char *tmpdir;

    /* XXX: race condition possible */

    tmpdir = getenv("TMPDIR");

    if (!tmpdir)

        tmpdir = "/tmp";

    snprintf(filename, size, "%s/vl.XXXXXX", tmpdir);

    fd = mkstemp(filename);

    close(fd);

}

#endif

#ifdef _WIN32

static int is_windows_drive_prefix(const char *filename)

{

    return (((filename[0] >= 'a' && filename[0] <= 'z') ||

             (filename[0] >= 'A' && filename[0] <= 'Z')) &&

            filename[1] == ':');

}

static int is_windows_drive(const char *filename)

{

    if (is_windows_drive_prefix(filename) &&

        filename[2] == '\0')

        return 1;

    if (strstart(filename, "\\\\.\\", NULL) ||

        strstart(filename, "//./", NULL))

        return 1;

    return 0;

}

#endif

static BlockDriver *find_protocol(const char *filename)

{

    BlockDriver *drv1;

    char protocol[128];

    int len;

    const char *p;

#ifdef _WIN32

    if (is_windows_drive(filename) ||

        is_windows_drive_prefix(filename))

        return &bdrv_raw;

#endif

    p = strchr(filename, ':');

    if (!p)

        return &bdrv_raw;

    len = p - filename;

    if (len > sizeof(protocol) - 1)

        len = sizeof(protocol) - 1;

    memcpy(protocol, filename, len);

    protocol[len] = '\0';

    for(drv1 = first_drv; drv1 != NULL; drv1 = drv1->next) {

        if (drv1->protocol_name &&

            !strcmp(drv1->protocol_name, protocol))

            return drv1;

    }

    return NULL;

}

/* XXX: force raw format if block or character device ? It would

   simplify the BSD case */

static BlockDriver *find_image_format(const char *filename)

{

    int ret, score, score_max;

    BlockDriver *drv1, *drv;

    uint8_t buf[2048];

    BlockDriverState *bs;

    /* detect host devices. By convention, /dev/cdrom[N] is always

       recognized as a host CDROM */

    if (strstart(filename, "/dev/cdrom", NULL))

        return &bdrv_host_device;

#ifdef _WIN32

    if (is_windows_drive(filename))

        return &bdrv_host_device;

#else

    {

        struct stat st;

        if (stat(filename, &st) >= 0 &&

            (S_ISCHR(st.st_mode) || S_ISBLK(st.st_mode))) {

            return &bdrv_host_device;

        }

    }

#endif

    drv = find_protocol(filename);

    /* no need to test disk image formats for vvfat */

    if (drv == &bdrv_vvfat)

        return drv;

    ret = bdrv_file_open(&bs, filename, BDRV_O_RDONLY);

    if (ret < 0)

        return NULL;

    ret = bdrv_pread(bs, 0, buf, sizeof(buf));

    bdrv_delete(bs);

    if (ret < 0) {

        return NULL;

    }

    score_max = 0;

    for(drv1 = first_drv; drv1 != NULL; drv1 = drv1->next) {

        if (drv1->bdrv_probe) {

            score = drv1->bdrv_probe(buf, ret, filename);

            if (score > score_max) {

                score_max = score;

                drv = drv1;

            }

        }

    }

    return drv;

}

int bdrv_file_open(BlockDriverState **pbs, const char *filename, int flags)

{

    BlockDriverState *bs;

    int ret;

    bs = bdrv_new("");

    if (!bs)

        return -ENOMEM;

    ret = bdrv_open2(bs, filename, flags | BDRV_O_FILE, NULL);

    if (ret < 0) {

        bdrv_delete(bs);

        return ret;

    }

    *pbs = bs;

    return 0;

}

int bdrv_open(BlockDriverState *bs, const char *filename, int flags)

{

    return bdrv_open2(bs, filename, flags, NULL);

}

int bdrv_open2(BlockDriverState *bs, const char *filename, int flags,

               BlockDriver *drv)

{

    int ret, open_flags;

    char tmp_filename[PATH_MAX];

    char backing_filename[PATH_MAX];

    bs->read_only = 0;

    bs->is_temporary = 0;

    bs->encrypted = 0;

    if (flags & BDRV_O_SNAPSHOT) {

        BlockDriverState *bs1;

        int64_t total_size;

        int is_protocol = 0;

        /* if snapshot, we create a temporary backing file and open it

           instead of opening 'filename' directly */

        /* if there is a backing file, use it */

        bs1 = bdrv_new("");

        if (!bs1) {

            return -ENOMEM;

        }

        if (bdrv_open(bs1, filename, 0) < 0) {

            bdrv_delete(bs1);

            return -1;

        }

        total_size = bdrv_getlength(bs1) >> SECTOR_BITS;

        if (bs1->drv && bs1->drv->protocol_name)

            is_protocol = 1;

        bdrv_delete(bs1);

        get_tmp_filename(tmp_filename, sizeof(tmp_filename));

        /* Real path is meaningless for protocols */

        if (is_protocol)

            snprintf(backing_filename, sizeof(backing_filename),

                     "%s", filename);

        else

            realpath(filename, backing_filename);

        if (bdrv_create(&bdrv_qcow2, tmp_filename,

                        total_size, backing_filename, 0) < 0) {

            return -1;

        }

        filename = tmp_filename;

        bs->is_temporary = 1;

    }

    pstrcpy(bs->filename, sizeof(bs->filename), filename);

    if (flags & BDRV_O_FILE) {

        drv = find_protocol(filename);

        if (!drv)

            return -ENOENT;

    } else {

        if (!drv) {

            drv = find_image_format(filename);

            if (!drv)

                return -1;

        }

    }

    bs->drv = drv;

    bs->opaque = qemu_mallocz(drv->instance_size);

    if (bs->opaque == NULL && drv->instance_size > 0)

        return -1;

    /* Note: for compatibility, we open disk image files as RDWR, and

       RDONLY as fallback */

    if (!(flags & BDRV_O_FILE))

        open_flags = BDRV_O_RDWR | (flags & BDRV_O_CACHE_MASK);

    else

        open_flags = flags & ~(BDRV_O_FILE | BDRV_O_SNAPSHOT);

    ret = drv->bdrv_open(bs, filename, open_flags);

    if ((ret == -EACCES || ret == -EPERM) && !(flags & BDRV_O_FILE)) {

        ret = drv->bdrv_open(bs, filename, open_flags & ~BDRV_O_RDWR);

        bs->read_only = 1;

    }

    if (ret < 0) {

        qemu_free(bs->opaque);

        bs->opaque = NULL;

        bs->drv = NULL;

        return ret;

    }

    if (drv->bdrv_getlength) {

        bs->total_sectors = bdrv_getlength(bs) >> SECTOR_BITS;

    }

#ifndef _WIN32

    if (bs->is_temporary) {

        unlink(filename);

    }

#endif

    if (bs->backing_file[0] != '\0') {

        /* if there is a backing file, use it */

        bs->backing_hd = bdrv_new("");

        if (!bs->backing_hd) {

        fail:

            bdrv_close(bs);

            return -ENOMEM;

        }

        path_combine(backing_filename, sizeof(backing_filename),

                     filename, bs->backing_file);

        if (bdrv_open(bs->backing_hd, backing_filename, open_flags) < 0)

            goto fail;

    }

    /* call the change callback */

    bs->media_changed = 1;

    if (bs->change_cb)

        bs->change_cb(bs->change_opaque);

    return 0;

}

void bdrv_close(BlockDriverState *bs)

{

    if (bs->drv) {

        if (bs->backing_hd)

            bdrv_delete(bs->backing_hd);

        bs->drv->bdrv_close(bs);

        qemu_free(bs->opaque);

#ifdef _WIN32

        if (bs->is_temporary) {

            unlink(bs->filename);

        }

#endif

        bs->opaque = NULL;

        bs->drv = NULL;

        /* call the change callback */

        bs->media_changed = 1;

        if (bs->change_cb)

            bs->change_cb(bs->change_opaque);

    }

}

void bdrv_delete(BlockDriverState *bs)

{

    BlockDriverState **pbs;

    pbs = &bdrv_first;

    while (*pbs != bs && *pbs != NULL)

        pbs = &(*pbs)->next;

    if (*pbs == bs)

        *pbs = bs->next;

    bdrv_close(bs);

    qemu_free(bs);

}

/* commit COW file into the raw image */

int bdrv_commit(BlockDriverState *bs)

{

    BlockDriver *drv = bs->drv;

    int64_t i, total_sectors;

    int n, j;

    unsigned char sector[512];

    if (!drv)

        return -ENOMEDIUM;

    if (bs->read_only) {

        return -EACCES;

    }

    if (!bs->backing_hd) {

        return -ENOTSUP;

    }

    total_sectors = bdrv_getlength(bs) >> SECTOR_BITS;

    for (i = 0; i < total_sectors;) {

        if (drv->bdrv_is_allocated(bs, i, 65536, &n)) {

            for(j = 0; j < n; j++) {

                if (bdrv_read(bs, i, sector, 1) != 0) {

                    return -EIO;

                }

                if (bdrv_write(bs->backing_hd, i, sector, 1) != 0) {

                    return -EIO;

                }

                i++;

            }

        } else {

            i += n;

        }

    }

    if (drv->bdrv_make_empty)

        return drv->bdrv_make_empty(bs);

    return 0;

}

/* return < 0 if error. See bdrv_write() for the return codes */

int bdrv_read(BlockDriverState *bs, int64_t sector_num,

              uint8_t *buf, int nb_sectors)

{

    BlockDriver *drv = bs->drv;

    if (!drv)

        return -ENOMEDIUM;

    if (drv->bdrv_pread) {

        int ret, len;

        len = nb_sectors * 512;

        ret = drv->bdrv_pread(bs, sector_num * 512, buf, len);

        if (ret < 0)

            return ret;

        else if (ret != len)

            return -EINVAL;

        else {

            bs->rd_bytes += (unsigned) len;

            bs->rd_ops ++;

            return 0;

        }

    } else {

        return drv->bdrv_read(bs, sector_num, buf, nb_sectors);

    }

}

/* Return < 0 if error. Important errors are:

  -EIO         generic I/O error (may happen for all errors)

  -ENOMEDIUM   No media inserted.

  -EINVAL      Invalid sector number or nb_sectors

  -EACCES      Trying to write a read-only device

*/

int bdrv_write(BlockDriverState *bs, int64_t sector_num,

               const uint8_t *buf, int nb_sectors)

{

    BlockDriver *drv = bs->drv;

    if (!bs->drv)

        return -ENOMEDIUM;

    if (bs->read_only)

        return -EACCES;

    if (drv->bdrv_pwrite) {

        int ret, len;

        len = nb_sectors * 512;

        ret = drv->bdrv_pwrite(bs, sector_num * 512, buf, len);

        if (ret < 0)

            return ret;

        else if (ret != len)

            return -EIO;

        else {

            bs->wr_bytes += (unsigned) len;

            bs->wr_ops ++;

            return 0;

        }

    } else {

        return drv->bdrv_write(bs, sector_num, buf, nb_sectors);

    }

}

static int bdrv_pread_em(BlockDriverState *bs, int64_t offset,

                         uint8_t *buf, int count1)

{

    uint8_t tmp_buf[SECTOR_SIZE];

    int len, nb_sectors, count;

    int64_t sector_num;

    count = count1;

    /* first read to align to sector start */

    len = (SECTOR_SIZE - offset) & (SECTOR_SIZE - 1);

    if (len > count)

        len = count;

    sector_num = offset >> SECTOR_BITS;

    if (len > 0) {

        if (bdrv_read(bs, sector_num, tmp_buf, 1) < 0)

            return -EIO;

        memcpy(buf, tmp_buf + (offset & (SECTOR_SIZE - 1)), len);

        count -= len;

        if (count == 0)

            return count1;

        sector_num++;

        buf += len;

    }

    /* read the sectors "in place" */

    nb_sectors = count >> SECTOR_BITS;

    if (nb_sectors > 0) {

        if (bdrv_read(bs, sector_num, buf, nb_sectors) < 0)

            return -EIO;

        sector_num += nb_sectors;

        len = nb_sectors << SECTOR_BITS;

        buf += len;

        count -= len;

    }

    /* add data from the last sector */

    if (count > 0) {

        if (bdrv_read(bs, sector_num, tmp_buf, 1) < 0)

            return -EIO;

        memcpy(buf, tmp_buf, count);

    }

    return count1;

}

static int bdrv_pwrite_em(BlockDriverState *bs, int64_t offset,

                          const uint8_t *buf, int count1)

{

    uint8_t tmp_buf[SECTOR_SIZE];

    int len, nb_sectors, count;

    int64_t sector_num;

    count = count1;

    /* first write to align to sector start */

    len = (SECTOR_SIZE - offset) & (SECTOR_SIZE - 1);

    if (len > count)

        len = count;

    sector_num = offset >> SECTOR_BITS;

    if (len > 0) {

        if (bdrv_read(bs, sector_num, tmp_buf, 1) < 0)

            return -EIO;

        memcpy(tmp_buf + (offset & (SECTOR_SIZE - 1)), buf, len);

        if (bdrv_write(bs, sector_num, tmp_buf, 1) < 0)

            return -EIO;

        count -= len;

        if (count == 0)

            return count1;

        sector_num++;

        buf += len;

    }

    /* write the sectors "in place" */

    nb_sectors = count >> SECTOR_BITS;

    if (nb_sectors > 0) {

        if (bdrv_write(bs, sector_num, buf, nb_sectors) < 0)

            return -EIO;

        sector_num += nb_sectors;

        len = nb_sectors << SECTOR_BITS;

        buf += len;

        count -= len;

    }

    /* add data from the last sector */

    if (count > 0) {

        if (bdrv_read(bs, sector_num, tmp_buf, 1) < 0)

            return -EIO;

        memcpy(tmp_buf, buf, count);

        if (bdrv_write(bs, sector_num, tmp_buf, 1) < 0)

            return -EIO;

    }

    return count1;

}

/**

 * Read with byte offsets (needed only for file protocols)

 */

int bdrv_pread(BlockDriverState *bs, int64_t offset,

               void *buf1, int count1)

{

    BlockDriver *drv = bs->drv;

    if (!drv)

        return -ENOMEDIUM;

    if (!drv->bdrv_pread)

        return bdrv_pread_em(bs, offset, buf1, count1);

    return drv->bdrv_pread(bs, offset, buf1, count1);

}

/**

 * Write with byte offsets (needed only for file protocols)

 */

int bdrv_pwrite(BlockDriverState *bs, int64_t offset,

                const void *buf1, int count1)

{

    BlockDriver *drv = bs->drv;

    if (!drv)

        return -ENOMEDIUM;

    if (!drv->bdrv_pwrite)

        return bdrv_pwrite_em(bs, offset, buf1, count1);

    return drv->bdrv_pwrite(bs, offset, buf1, count1);

}

/**

 * Truncate file to 'offset' bytes (needed only for file protocols)

 */

int bdrv_truncate(BlockDriverState *bs, int64_t offset)

{

    BlockDriver *drv = bs->drv;

    if (!drv)

        return -ENOMEDIUM;

    if (!drv->bdrv_truncate)

        return -ENOTSUP;

    return drv->bdrv_truncate(bs, offset);

}

/**

 * Length of a file in bytes. Return < 0 if error or unknown.

 */

int64_t bdrv_getlength(BlockDriverState *bs)

{

    BlockDriver *drv = bs->drv;

    if (!drv)

        return -ENOMEDIUM;

    if (!drv->bdrv_getlength) {

        /* legacy mode */

        return bs->total_sectors * SECTOR_SIZE;

    }

    return drv->bdrv_getlength(bs);

}

/* return 0 as number of sectors if no device present or error */

void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr)

{

    int64_t length;

    length = bdrv_getlength(bs);

    if (length < 0)

        length = 0;

    else

        length = length >> SECTOR_BITS;

    *nb_sectors_ptr = length;

}

void bdrv_set_geometry_hint(BlockDriverState *bs,

                            int cyls, int heads, int secs)

{

    bs->cyls = cyls;

    bs->heads = heads;

    bs->secs = secs;

}

void bdrv_set_type_hint(BlockDriverState *bs, int type)

{

    bs->type = type;

    bs->removable = ((type == BDRV_TYPE_CDROM ||

                      type == BDRV_TYPE_FLOPPY));

}

void bdrv_set_translation_hint(BlockDriverState *bs, int translation)

{

    bs->translation = translation;

}

void bdrv_get_geometry_hint(BlockDriverState *bs,

                            int *pcyls, int *pheads, int *psecs)

{

    *pcyls = bs->cyls;

    *pheads = bs->heads;

    *psecs = bs->secs;

}

int bdrv_get_type_hint(BlockDriverState *bs)

{

    return bs->type;

}

int bdrv_get_translation_hint(BlockDriverState *bs)

{

    return bs->translation;

}

int bdrv_is_removable(BlockDriverState *bs)

{

    return bs->removable;

}

int bdrv_is_read_only(BlockDriverState *bs)

{

    return bs->read_only;

}

int bdrv_is_sg(BlockDriverState *bs)

{

    return bs->sg;

}

/* XXX: no longer used */

void bdrv_set_change_cb(BlockDriverState *bs,

                        void (*change_cb)(void *opaque), void *opaque)

{

    bs->change_cb = change_cb;

    bs->change_opaque = opaque;

}

int bdrv_is_encrypted(BlockDriverState *bs)

{

    if (bs->backing_hd && bs->backing_hd->encrypted)

        return 1;

    return bs->encrypted;

}

int bdrv_set_key(BlockDriverState *bs, const char *key)

{

    int ret;

    if (bs->backing_hd && bs->backing_hd->encrypted) {

        ret = bdrv_set_key(bs->backing_hd, key);

        if (ret < 0)

            return ret;

        if (!bs->encrypted)

            return 0;

    }

    if (!bs->encrypted || !bs->drv || !bs->drv->bdrv_set_key)

        return -1;

    return bs->drv->bdrv_set_key(bs, key);

}

void bdrv_get_format(BlockDriverState *bs, char *buf, int buf_size)

{

    if (!bs->drv) {

        buf[0] = '\0';

    } else {

        pstrcpy(buf, buf_size, bs->drv->format_name);

    }

}

void bdrv_iterate_format(void (*it)(void *opaque, const char *name),

                         void *opaque)

{

    BlockDriver *drv;

    for (drv = first_drv; drv != NULL; drv = drv->next) {

        it(opaque, drv->format_name);

    }

}

BlockDriverState *bdrv_find(const char *name)

{

    BlockDriverState *bs;

    for (bs = bdrv_first; bs != NULL; bs = bs->next) {

        if (!strcmp(name, bs->device_name))

            return bs;

    }

    return NULL;

}

void bdrv_iterate(void (*it)(void *opaque, const char *name), void *opaque)

{

    BlockDriverState *bs;

    for (bs = bdrv_first; bs != NULL; bs = bs->next) {

        it(opaque, bs->device_name);

    }

}

const char *bdrv_get_device_name(BlockDriverState *bs)

{

    return bs->device_name;

}

void bdrv_flush(BlockDriverState *bs)

{

    if (bs->drv->bdrv_flush)

        bs->drv->bdrv_flush(bs);

    if (bs->backing_hd)

        bdrv_flush(bs->backing_hd);

}

void bdrv_flush_all(void)

{

    BlockDriverState *bs;

    for (bs = bdrv_first; bs != NULL; bs = bs->next)

        if (bs->drv && !bdrv_is_read_only(bs) && 

            (!bdrv_is_removable(bs) || bdrv_is_inserted(bs)))

            bdrv_flush(bs);

}

/*

 * Returns true iff the specified sector is present in the disk image. Drivers

 * not implementing the functionality are assumed to not support backing files,

 * hence all their sectors are reported as allocated.

 *

 * 'pnum' is set to the number of sectors (including and immediately following

 * the specified sector) that are known to be in the same

 * allocated/unallocated state.

 *

 * 'nb_sectors' is the max value 'pnum' should be set to.

 */

int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,