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

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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: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6978 c046a42c-6fe2-441c-8c8c-71466251a162
This commit is contained in:
aliguori 2009-04-05 17:40:43 +00:00
parent f8de16605c
commit 93c65b47a6
2 changed files with 55 additions and 15 deletions
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36
block-raw-posix.c
View File

@ -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

34
qemu-img.c
View File

@ -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)) {
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;
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");
}