On 27/04/11 22:02, Brad Campbell wrote:
On 27/04/11 21:56, Kevin Wolf wrote:
When you don't have a backing file, leaving an cluster unallocated means
that it's zero. When you have a backing file, it could be anything. So
if qemu-img convert wanted to save this space, it would have to read
from the backing file and leave the cluster unallocated if it reads as
zero.
This is something that qemu-img doesn't do today.
This passes cursory testing, but I'm just wondering if this is along the
right lines?
diff --git a/qemu-img.c b/qemu-img.c
index d9c2c12..ab4c70c 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1,4 +1,4 @@
-/*
+ /*
* QEMU disk image utility
*
* Copyright (c) 2003-2008 Fabrice Bellard
@@ -571,11 +571,12 @@ static int img_convert(int argc, char **argv)
int progress = 0;
const char *fmt, *out_fmt, *out_baseimg, *out_filename;
BlockDriver *drv, *proto_drv;
- BlockDriverState **bs = NULL, *out_bs = NULL;
+ BlockDriverState **bs = NULL, *out_bs = NULL, *out_bf = NULL;
int64_t total_sectors, nb_sectors, sector_num, bs_offset;
uint64_t bs_sectors;
uint8_t * buf = NULL;
const uint8_t *buf1;
+ uint8_t * buf3 = NULL;
BlockDriverInfo bdi;
QEMUOptionParameter *param = NULL, *create_options = NULL;
QEMUOptionParameter *out_baseimg_param;
@@ -719,6 +720,12 @@ static int img_convert(int argc, char **argv)
out_baseimg_param = get_option_parameter(param,
BLOCK_OPT_BACKING_FILE);
if (out_baseimg_param) {
out_baseimg = out_baseimg_param->value.s;
+ out_bf = bdrv_new_open(out_baseimg, NULL, BDRV_O_FLAGS);
+ if (!out_bf) {
+ error_report("Could not open backing file '%s'", out_baseimg);
+ ret = -1;
+ goto out;
+ }
}
/* Check if compression is supported */
@@ -767,6 +774,9 @@ static int img_convert(int argc, char **argv)
bs_offset = 0;
bdrv_get_geometry(bs[0], &bs_sectors);
buf = qemu_malloc(IO_BUF_SIZE);
+ if (out_baseimg) {
+ buf3 = qemu_malloc(IO_BUF_SIZE);
+ }
if (compress) {
ret = bdrv_get_info(out_bs, &bdi);
@@ -889,9 +899,17 @@ static int img_convert(int argc, char **argv)
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 (bdrv_read(bs[bs_i], sector_num - bs_offset,
buf, n) < 0) {
+ error_report("error while reading input file");
+ goto out;
+ }
+ if (bdrv_read(out_bf, sector_num - bs_offset, buf3,
n) < 0) {
+ error_report("error while reading backing file");
+ goto out;
+ }
+ if (!compare_sectors(buf, buf3, n, &n1)) {
sector_num += n1;
+ // printf("Skipping %u sectors\n",n1);
continue;
}
/* The next 'n1' sectors are allocated in the
input image. Copy
@@ -939,9 +957,16 @@ out:
free_option_parameters(create_options);
free_option_parameters(param);
qemu_free(buf);
+ if (buf3) {
+ qemu_free(buf3);
+ }
if (out_bs) {
bdrv_delete(out_bs);
}
+ if (out_bf) {
+ bdrv_delete(out_bf);
+ }
+
if (bs) {
for (bs_i = 0; bs_i < bs_n; bs_i++) {
if (bs[bs_i]) {
