Skip to content

Commit

Permalink
qemu-img: add support for skipping zeroes in input during convert
Browse files Browse the repository at this point in the history 
we currently do not check if a sector is allocated during convert.
This means if a sector is unallocated that we allocate a bounce
buffer of zeroes, find out its zero later and do not write it
in the best case. In the worst case this can lead to reading
blocks from a raw device (like iSCSI) altough we could easily
know via get_block_status that they are zero and simply skip them.

This patch also fixes the progress output not being at 100% after
a successful conversion.

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
  • Loading branch information
@plieven @stefanhaRH
plieven authored and stefanhaRH committed Dec 5, 2013
1 parent 4323fdc commit 13c28af
Showing 1 changed file with 42 additions and 38 deletions.
80 changes: 42 additions & 38 deletions qemu-img.c
View file
Expand Up @@ -1130,13 +1130,15 @@ static int img_compare(int argc, char **argv)

static int img_convert(int argc, char **argv)
{
int c, ret = 0, n, n1, bs_n, bs_i, compress, cluster_size,
int c, n, n1, bs_n, bs_i, compress, cluster_size,
cluster_sectors, skip_create;
int64_t ret = 0;
int progress = 0, flags;
const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
BlockDriver *drv, *proto_drv;
BlockDriverState **bs = NULL, *out_bs = NULL;
int64_t total_sectors, nb_sectors, sector_num, bs_offset;
int64_t total_sectors, nb_sectors, sector_num, bs_offset,
sector_num_next_status = 0;
uint64_t bs_sectors;
uint8_t * buf = NULL;
const uint8_t *buf1;
Expand All @@ -1145,7 +1147,6 @@ static int img_convert(int argc, char **argv)
QEMUOptionParameter *out_baseimg_param;
char *options = NULL;
const char *snapshot_name = NULL;
float local_progress = 0;
int min_sparse = 8; /* Need at least 4k of zeros for sparse detection */
bool quiet = false;
Error *local_err = NULL;
Expand Down Expand Up @@ -1430,10 +1431,6 @@ static int img_convert(int argc, char **argv)
sector_num = 0;

nb_sectors = total_sectors;
if (nb_sectors != 0) {
local_progress = (float)100 /
(nb_sectors / MIN(nb_sectors, cluster_sectors));
}

for(;;) {
int64_t bs_num;
Expand Down Expand Up @@ -1491,7 +1488,7 @@ static int img_convert(int argc, char **argv)
}
}
sector_num += n;
qemu_progress_print(local_progress, 100);
qemu_progress_print(100.0 * sector_num / total_sectors, 0);
}
/* signal EOF to align */
bdrv_write_compressed(out_bs, 0, NULL, 0);
Expand All @@ -1508,21 +1505,13 @@ static int img_convert(int argc, char **argv)

sector_num = 0; // total number of sectors converted so far
nb_sectors = total_sectors - sector_num;
if (nb_sectors != 0) {
local_progress = (float)100 /
(nb_sectors / MIN(nb_sectors, IO_BUF_SIZE / 512));
}

for(;;) {
nb_sectors = total_sectors - sector_num;
if (nb_sectors <= 0) {
ret = 0;
break;
}
if (nb_sectors >= (IO_BUF_SIZE / 512)) {
n = (IO_BUF_SIZE / 512);
} else {
n = nb_sectors;
}

while (sector_num - bs_offset >= bs_sectors) {
bs_i ++;
Expand All @@ -1534,34 +1523,46 @@ static int img_convert(int argc, char **argv)
sector_num, bs_i, bs_offset, bs_sectors); */
}

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) {
ret = bdrv_is_allocated(bs[bs_i], sector_num - bs_offset,
n, &n1);
if ((out_baseimg || has_zero_init) &&
sector_num >= sector_num_next_status) {
n = nb_sectors > INT_MAX ? INT_MAX : nb_sectors;
ret = bdrv_get_block_status(bs[bs_i], sector_num - bs_offset,
n, &n1);
if (ret < 0) {
error_report("error while reading metadata for sector "
"%" PRId64 ": %s",
sector_num - bs_offset, strerror(-ret));
error_report("error while reading block status of sector %"
PRId64 ": %s", sector_num - bs_offset,
strerror(-ret));
goto out;
}
if (!ret) {
/* If the output image is zero initialized, we are not working
* on a shared base and the input is zero we can skip the next
* n1 sectors */
if (has_zero_init && !out_baseimg && (ret & BDRV_BLOCK_ZERO)) {
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 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 (!(ret & BDRV_BLOCK_DATA)) {
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. */
nb_sectors = n1;
}
/* avoid redundant callouts to get_block_status */
sector_num_next_status = sector_num + n1;
}

n = MIN(nb_sectors, IO_BUF_SIZE / 512);
n = MIN(n, bs_sectors - (sector_num - bs_offset));
n1 = n;

ret = bdrv_read(bs[bs_i], sector_num - bs_offset, buf, n);
if (ret < 0) {
error_report("error while reading sector %" PRId64 ": %s",
Expand All @@ -1586,10 +1587,13 @@ static int img_convert(int argc, char **argv)
n -= n1;
buf1 += n1 * 512;
}
qemu_progress_print(local_progress, 100);
qemu_progress_print(100.0 * sector_num / total_sectors, 0);
}
}
out:
if (!ret) {
qemu_progress_print(100, 0);
}
qemu_progress_end();
free_option_parameters(create_options);
free_option_parameters(param);
Expand Down

0 comments on commit 13c28af

Please sign in to comment.