| Message ID | 20230919165804.439110-5-andrey.drobyshev@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | qemu-img: rebase: add compression support | expand |
Am 19.09.2023 um 18:58 hat Andrey Drobyshev geschrieben: > 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> > --- > qemu-img.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/qemu-img.c b/qemu-img.c > index 4dc91505bf..0f67b021f7 100644 > --- a/qemu-img.c > +++ b/qemu-img.c > @@ -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) uint64_t might be too large, depending on the platform. memcmp() takes size_t, so in theory we can get truncation. I assume that we won't see a problem in practice because you'll never pass that large values, but I'd prefer making chsize size_t here. Kevin
diff --git a/qemu-img.c b/qemu-img.c index 4dc91505bf..0f67b021f7 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -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)); @@ -3878,7 +3884,7 @@ 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);