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qemu-img: add chunk size parameter to compare_buffers()

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Add @chsize param to the function which, if non-zero, would represent
the chunk size to be used for comparison.  If it's zero, then
BDRV_SECTOR_SIZE is used as default chunk size, which is the previous
behaviour.

In particular, we're going to use this param in img_rebase() to make the
write requests aligned to a predefined alignment value.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Hanna Czenczek <hreitz@redhat.com>
Message-ID: <20230919165804.439110-5-andrey.drobyshev@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Andrey Drobyshev 2023-09-19 19:58:00 +03:00 committed by Kevin Wolf
parent ce8b8f9fe7
commit c20c8ae700
1 changed files with 15 additions and 9 deletions
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24
qemu-img.c
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@ -1274,23 +1274,29 @@ static int is_allocated_sectors_min(const uint8_t *buf, int n, int *pnum,
}
/*
* Compares two buffers sector by sector. Returns 0 if the first
* sector of each buffer matches, non-zero otherwise.
* Compares two buffers chunk by chunk, where @chsize is the chunk size.
* If @chsize is 0, default chunk size of BDRV_SECTOR_SIZE is used.
* Returns 0 if the first chunk of each buffer matches, non-zero otherwise.
*
* pnum is set to the sector-aligned size of the buffer prefix that
* has the same matching status as the first sector.
* @pnum is set to the size of the buffer prefix aligned to @chsize that
* has the same matching status as the first chunk.
*/
static int compare_buffers(const uint8_t *buf1, const uint8_t *buf2,
int64_t bytes, int64_t *pnum)
int64_t bytes, uint64_t chsize, int64_t *pnum)
{
bool res;
int64_t i = MIN(bytes, BDRV_SECTOR_SIZE);
int64_t i;
assert(bytes > 0);
if (!chsize) {
chsize = BDRV_SECTOR_SIZE;
}
i = MIN(bytes, chsize);
res = !!memcmp(buf1, buf2, i);
while (i < bytes) {
int64_t len = MIN(bytes - i, BDRV_SECTOR_SIZE);
int64_t len = MIN(bytes - i, chsize);
if (!!memcmp(buf1 + i, buf2 + i, len) != res) {
break;
@ -1559,7 +1565,7 @@ static int img_compare(int argc, char **argv)
ret = 4;
goto out;
}
ret = compare_buffers(buf1, buf2, chunk, &pnum);
ret = compare_buffers(buf1, buf2, chunk, 0, &pnum);
if (ret || pnum != chunk) {
qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n",
offset + (ret ? 0 : pnum));
@ -3887,7 +3893,7 @@ static int img_rebase(int argc, char **argv)
int64_t pnum;
if (compare_buffers(buf_old + written, buf_new + written,
n - written, &pnum))
n - written, 0, &pnum))
{
if (buf_old_is_zero) {
ret = blk_pwrite_zeroes(blk, offset + written, pnum, 0);