From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58790) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e7i3J-0000a5-DD for qemu-devel@nongnu.org; Thu, 26 Oct 2017 09:18:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e7i3G-00022m-3s for qemu-devel@nongnu.org; Thu, 26 Oct 2017 09:18:29 -0400 From: Kevin Wolf Date: Thu, 26 Oct 2017 15:17:21 +0200 Message-Id: <20171026131741.5059-16-kwolf@redhat.com> In-Reply-To: <20171026131741.5059-1-kwolf@redhat.com> References: <20171026131741.5059-1-kwolf@redhat.com> Subject: [Qemu-devel] [PULL 15/35] qemu-img: Simplify logic in img_compare() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, qemu-devel@nongnu.org From: Eric Blake As long as we are querying the status for a chunk smaller than the known image size, we are guaranteed that a successful return will have set pnum to a non-zero size (pnum is zero only for queries beyond the end of the file). Use that to slightly simplify the calculation of the current chunk size being compared. Likewise, we don't have to shrink the amount of data operated on until we know we have to read the file, and therefore have to fit in the bounds of our buffer. Also, note that 'total_sectors_over' is equivalent to 'progress_base'. With these changes in place, sectors_to_process() is now dead code, and can be removed. Signed-off-by: Eric Blake Signed-off-by: Kevin Wolf --- qemu-img.c | 38 +++++++++++--------------------------- 1 file changed, 11 insertions(+), 27 deletions(-) diff --git a/qemu-img.c b/qemu-img.c index 78c820e487..cfa28d41d5 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -1172,11 +1172,6 @@ static int64_t sectors_to_bytes(int64_t sectors) return sectors << BDRV_SECTOR_BITS; } -static int64_t sectors_to_process(int64_t total, int64_t from) -{ - return MIN(total - from, IO_BUF_SIZE >> BDRV_SECTOR_BITS); -} - /* * Check if passed sectors are empty (not allocated or contain only 0 bytes) * @@ -1373,13 +1368,9 @@ static int img_compare(int argc, char **argv) goto out; } - for (;;) { + while (sector_num < total_sectors) { int status1, status2; - nb_sectors = sectors_to_process(total_sectors, sector_num); - if (nb_sectors <= 0) { - break; - } status1 = bdrv_block_status_above(bs1, NULL, sector_num * BDRV_SECTOR_SIZE, (total_sectors1 - sector_num) * @@ -1406,12 +1397,9 @@ static int img_compare(int argc, char **argv) /* TODO: Relax this once comparison is byte-based, and we no longer * have to worry about sector alignment */ assert(QEMU_IS_ALIGNED(pnum1 | pnum2, BDRV_SECTOR_SIZE)); - if (pnum1) { - nb_sectors = MIN(nb_sectors, pnum1 >> BDRV_SECTOR_BITS); - } - if (pnum2) { - nb_sectors = MIN(nb_sectors, pnum2 >> BDRV_SECTOR_BITS); - } + + assert(pnum1 && pnum2); + nb_sectors = MIN(pnum1, pnum2) >> BDRV_SECTOR_BITS; if (strict) { if (status1 != status2) { @@ -1423,9 +1411,10 @@ static int img_compare(int argc, char **argv) } } if ((status1 & BDRV_BLOCK_ZERO) && (status2 & BDRV_BLOCK_ZERO)) { - nb_sectors = DIV_ROUND_UP(MIN(pnum1, pnum2), BDRV_SECTOR_SIZE); + /* nothing to do */ } else if (allocated1 == allocated2) { if (allocated1) { + nb_sectors = MIN(nb_sectors, IO_BUF_SIZE >> BDRV_SECTOR_BITS); ret = blk_pread(blk1, sector_num << BDRV_SECTOR_BITS, buf1, nb_sectors << BDRV_SECTOR_BITS); if (ret < 0) { @@ -1454,7 +1443,7 @@ static int img_compare(int argc, char **argv) } } } else { - + nb_sectors = MIN(nb_sectors, IO_BUF_SIZE >> BDRV_SECTOR_BITS); if (allocated1) { ret = check_empty_sectors(blk1, sector_num, nb_sectors, filename1, buf1, quiet); @@ -1477,30 +1466,24 @@ static int img_compare(int argc, char **argv) if (total_sectors1 != total_sectors2) { BlockBackend *blk_over; - int64_t total_sectors_over; const char *filename_over; qprintf(quiet, "Warning: Image size mismatch!\n"); if (total_sectors1 > total_sectors2) { - total_sectors_over = total_sectors1; blk_over = blk1; filename_over = filename1; } else { - total_sectors_over = total_sectors2; blk_over = blk2; filename_over = filename2; } - for (;;) { + while (sector_num < progress_base) { int64_t count; - nb_sectors = sectors_to_process(total_sectors_over, sector_num); - if (nb_sectors <= 0) { - break; - } ret = bdrv_is_allocated_above(blk_bs(blk_over), NULL, sector_num * BDRV_SECTOR_SIZE, - nb_sectors * BDRV_SECTOR_SIZE, + (progress_base - sector_num) * + BDRV_SECTOR_SIZE, &count); if (ret < 0) { ret = 3; @@ -1514,6 +1497,7 @@ static int img_compare(int argc, char **argv) assert(QEMU_IS_ALIGNED(count, BDRV_SECTOR_SIZE)); nb_sectors = count >> BDRV_SECTOR_BITS; if (ret) { + nb_sectors = MIN(nb_sectors, IO_BUF_SIZE >> BDRV_SECTOR_BITS); ret = check_empty_sectors(blk_over, sector_num, nb_sectors, filename_over, buf1, quiet); if (ret) { -- 2.13.6