Commit 93c65b47 authored by Anthony Liguori's avatar Anthony Liguori
Browse files

Add host_device support to qemu-img. (Nolan Leake) 



This patch allows the use a host_device as the destination for "qemu-img
convert".

I added a ->bdrv_create function host_device.  It merely verifies that
the device exists and is large enough.

A check is needed in the qemu-img convert loop to ensure that we write
out all 0 sectors to the host_device.  Otherwise they end up with stale
garbage where all zero sectors were expected.

I also made the check against bdrv_is_allocated enabled for everything
_except_ host devices, since there is no point in making the block
backend write a bunch of zeros just so that we can memcmp them
immediately afterwards.  Host devices can't benefit from this because
there is no way to differentiate between a sector being unallocated
because it was never written, or because it was written with all zeros
and then made a trip through qemu-img convert.

Finally, there is an unrelated fix for a typo in the error message
printed if the destination device does not support ->bdrv_create.

Signed-off-by: Nolan Leake <nolan <at> sigbus.net>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6978 c046a42c-6fe2-441c-8c8c-71466251a162
parent f8de1660

block-raw-posix.c

+36 −0
Original line number Diff line number Diff line
@@ -1378,11 +1378,47 @@ static BlockDriverAIOCB *raw_aio_ioctl(BlockDriverState *bs, 
}

#endif /* !linux && !FreeBSD */



#if defined(__linux__) || defined(__FreeBSD__)

static int hdev_create(const char *filename, int64_t total_size,

                       const char *backing_file, int flags)

{

    int fd;

    int ret = 0;

    struct stat stat_buf;



    if (flags || backing_file)

        return -ENOTSUP;



    fd = open(filename, O_WRONLY | O_BINARY);

    if (fd < 0)

        return -EIO;



    if (fstat(fd, &stat_buf) < 0)

        ret = -EIO;

    else if (!S_ISBLK(stat_buf.st_mode))

        ret = -EIO;

    else if (lseek(fd, 0, SEEK_END) < total_size * 512)

        ret = -ENOSPC;



    close(fd);

    return ret;

}



#else  /* !(linux || freebsd) */



static int hdev_create(const char *filename, int64_t total_size,

                       const char *backing_file, int flags)

{

    return -ENOTSUP;

}

#endif



BlockDriver bdrv_host_device = {

    .format_name	= "host_device",

    .instance_size	= sizeof(BDRVRawState),

    .bdrv_open		= hdev_open,

    .bdrv_close		= raw_close,

    .bdrv_create        = hdev_create,

    .bdrv_flush		= raw_flush,



#ifdef CONFIG_AIO

qemu-img.c

+19 −15
Original line number Diff line number Diff line
@@ -493,7 +493,7 @@ static int img_convert(int argc, char **argv) 
    ret = bdrv_create(drv, out_filename, total_sectors, out_baseimg, flags);

    if (ret < 0) {

        if (ret == -ENOTSUP) {

            error("Formatting not supported for file format '%s'", fmt);

            error("Formatting not supported for file format '%s'", out_fmt);

        } else {

            error("Error while formatting '%s'", out_filename);

        }
@@ -592,18 +592,17 @@ static int img_convert(int argc, char **argv) 
            if (n > bs_offset + bs_sectors - sector_num)

                n = bs_offset + bs_sectors - sector_num;



            /* If the output image is being created as a copy on write image,

               assume that sectors which are unallocated in the input image

               are present in both the output's and input's base images (no

               need to copy them). */

            if (out_baseimg) {

               if (!bdrv_is_allocated(bs[bs_i], sector_num - bs_offset, n, &n1)) {

            if (drv != &bdrv_host_device) {

                if (!bdrv_is_allocated(bs[bs_i], sector_num - bs_offset,

                                       n, &n1)) {

                    sector_num += n1;

                    continue;

                }

                /* The next 'n1' sectors are allocated in the input image. Copy

                   only those as they may be followed by unallocated sectors. */

                n = n1;

            } else {

                n1 = n;

            }



            if (bdrv_read(bs[bs_i], sector_num - bs_offset, buf, n) < 0)
@@ -615,8 +614,13 @@ static int img_convert(int argc, char **argv) 
            while (n > 0) {

                /* If the output image is being created as a copy on write image,

                   copy all sectors even the ones containing only NUL bytes,

                   because they may differ from the sectors in the base image. */

                if (out_baseimg || is_allocated_sectors(buf1, n, &n1)) {

                   because they may differ from the sectors in the base image.



                   If the output is to a host device, we also write out

                   sectors that are entirely 0, since whatever data was

                   already there is garbage, not 0s. */

                if (drv == &bdrv_host_device || out_baseimg ||

                    is_allocated_sectors(buf1, n, &n1)) {

                    if (bdrv_write(out_bs, sector_num, buf1, n1) < 0)

                        error("error while writing");

                }