[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [PULL 20/35] qemu-img: Change compare_sectors() to be byte-
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 20/35] qemu-img: Change compare_sectors() to be byte-based |
Date: |
Thu, 26 Oct 2017 15:17:26 +0200 |
From: Eric Blake <address@hidden>
In the continuing quest to make more things byte-based, change
compare_sectors(), renaming it to compare_buffers() in the
process. Note that one caller (qemu-img compare) only cares
about the first difference, while the other (qemu-img rebase)
cares about how many consecutive sectors have the same
equal/different status; however, this patch does not bother to
micro-optimize the compare case to avoid the comparisons of
sectors beyond the first mismatch. Both callers are always
passing valid buffers in, so the initial check for buffer size
can be turned into an assertion.
Signed-off-by: Eric Blake <address@hidden>
Reviewed-by: John Snow <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
qemu-img.c | 55 +++++++++++++++++++++++++++----------------------------
1 file changed, 27 insertions(+), 28 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index 66d595be3d..c6b6263853 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1156,31 +1156,28 @@ 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 both
- * buffers matches, non-zero otherwise.
+ * Compares two buffers sector by sector. Returns 0 if the first
+ * sector of each buffer matches, non-zero otherwise.
*
- * pnum is set to the number of sectors (including and immediately following
- * the first one) that are known to have the same comparison result
+ * pnum is set to the sector-aligned size of the buffer prefix that
+ * has the same matching status as the first sector.
*/
-static int compare_sectors(const uint8_t *buf1, const uint8_t *buf2, int n,
- int *pnum)
+static int compare_buffers(const uint8_t *buf1, const uint8_t *buf2,
+ int64_t bytes, int64_t *pnum)
{
bool res;
- int i;
+ int64_t i = MIN(bytes, BDRV_SECTOR_SIZE);
- if (n <= 0) {
- *pnum = 0;
- return 0;
- }
+ assert(bytes > 0);
- res = !!memcmp(buf1, buf2, 512);
- for(i = 1; i < n; i++) {
- buf1 += 512;
- buf2 += 512;
+ res = !!memcmp(buf1, buf2, i);
+ while (i < bytes) {
+ int64_t len = MIN(bytes - i, BDRV_SECTOR_SIZE);
- if (!!memcmp(buf1, buf2, 512) != res) {
+ if (!!memcmp(buf1 + i, buf2 + i, len) != res) {
break;
}
+ i += len;
}
*pnum = i;
@@ -1255,7 +1252,7 @@ static int img_compare(int argc, char **argv)
int64_t total_sectors;
int64_t sector_num = 0;
int64_t nb_sectors;
- int c, pnum;
+ int c;
uint64_t progress_base;
bool image_opts = false;
bool force_share = false;
@@ -1439,6 +1436,8 @@ static int img_compare(int argc, char **argv)
/* nothing to do */
} else if (allocated1 == allocated2) {
if (allocated1) {
+ int64_t pnum;
+
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);
@@ -1458,11 +1457,11 @@ static int img_compare(int argc, char **argv)
ret = 4;
goto out;
}
- ret = compare_sectors(buf1, buf2, nb_sectors, &pnum);
- if (ret || pnum != nb_sectors) {
+ ret = compare_buffers(buf1, buf2,
+ nb_sectors * BDRV_SECTOR_SIZE, &pnum);
+ if (ret || pnum != nb_sectors * BDRV_SECTOR_SIZE) {
qprintf(quiet, "Content mismatch at offset %" PRId64 "!\n",
- sectors_to_bytes(
- ret ? sector_num : sector_num + pnum));
+ sectors_to_bytes(sector_num) + (ret ? 0 : pnum));
ret = 1;
goto out;
}
@@ -3354,16 +3353,16 @@ static int img_rebase(int argc, char **argv)
/* If they differ, we need to write to the COW file */
uint64_t written = 0;
- while (written < n) {
- int pnum;
+ while (written < n * BDRV_SECTOR_SIZE) {
+ int64_t pnum;
- if (compare_sectors(buf_old + written * 512,
- buf_new + written * 512, n - written, &pnum))
+ if (compare_buffers(buf_old + written,
+ buf_new + written,
+ n * BDRV_SECTOR_SIZE - written, &pnum))
{
ret = blk_pwrite(blk,
- (sector + written) << BDRV_SECTOR_BITS,
- buf_old + written * 512,
- pnum << BDRV_SECTOR_BITS, 0);
+ (sector << BDRV_SECTOR_BITS) + written,
+ buf_old + written, pnum, 0);
if (ret < 0) {
error_report("Error while writing to COW image: %s",
strerror(-ret));
--
2.13.6
- [Qemu-devel] [PULL 13/35] block: Switch bdrv_co_get_block_status_above() to byte-based, (continued)
- [Qemu-devel] [PULL 13/35] block: Switch bdrv_co_get_block_status_above() to byte-based, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 16/35] qemu-img: Speed up compare on pre-allocated larger file, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 14/35] block: Convert bdrv_get_block_status_above() to bytes, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 18/35] qemu-img: Drop redundant error message in compare, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 17/35] qemu-img: Add find_nonzero(), Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 19/35] qemu-img: Change check_empty_sectors() to byte-based, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 22/35] qemu-img: Change img_compare() to be byte-based, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 24/35] block: Reduce bdrv_aligned_preadv() rounding, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 25/35] qcow2: Reduce is_zero() rounding, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 21/35] qemu-img: Change img_rebase() to be byte-based, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 20/35] qemu-img: Change compare_sectors() to be byte-based,
Kevin Wolf <=
- [Qemu-devel] [PULL 23/35] block: Align block status requests, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 26/35] qemu-io: Relax 'alloc' now that block-status doesn't assert, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 28/35] qcow2: Use BDRV_SECTOR_BITS instead of its literal value, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 27/35] qemu-img.1: Image invalidation on qemu-img commit, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 30/35] iotests: Pull _filter_actual_image_size from 67/87, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 29/35] iotests: Add test for dataplane mirroring, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 31/35] iotests: Filter actual image size in 184 and 191, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 32/35] qcow2: Emit errp when truncating the image tail, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 33/35] qcow2: Fix unaligned preallocated truncation, Kevin Wolf, 2017/10/26
- [Qemu-devel] [PULL 34/35] qcow2: Always execute preallocate() in a coroutine, Kevin Wolf, 2017/10/26