When passing -S 0 to qemu-img convert, the target image is supposed to
be fully allocated. Right now, this is not the case if the source image
contains areas which bdrv_get_block_status() reports as being zero.
This patch introduces a new ImgConvertBlockStatus named BLK_ZERO_DATA
which is set by convert_iteration_sectors() if an area is detected to be
zero and min_sparse is 0. Simply using BLK_DATA is not optimal, because
knowing an area to be zero allows us to memset() the buffer to be
written directly rather than having to use blk_read().
Other than that, BLK_ZERO_DATA is handled exactly like BLK_DATA.
This patch changes the reference output for iotest 122; contrary to what
it assumed, -S 0 really should allocate everything in the output, not
just areas that are filled with zeros (as opposed to being zeroed).
Signed-off-by: Max Reitz <mre...@redhat.com>
---
qemu-img.c | 37 ++++++++++++++++++++++++-------------
tests/qemu-iotests/122.out | 6 ++----
2 files changed, 26 insertions(+), 17 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index fb9ab1f..809ea3b 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1232,6 +1232,10 @@ enum ImgConvertBlockStatus {
BLK_DATA,
BLK_ZERO,
BLK_BACKING_FILE,
+
+ /* Will return zeros when read but must be written as data (i.e. is set for
+ * zeroed areas with min_sparse == 0) */
+ BLK_ZERO_DATA,
};
typedef struct ImgConvertState {
@@ -1282,7 +1286,13 @@ static int convert_iteration_sectors(ImgConvertState *s,
int64_t sector_num)
}
if (ret & BDRV_BLOCK_ZERO) {
- s->status = BLK_ZERO;
+ if (s->min_sparse) {
+ s->status = BLK_ZERO;
+ } else {
+ /* If min_sparse is 0, this area must be written to the target
+ * image as data */
+ s->status = BLK_ZERO_DATA;
+ }
} else if (ret & BDRV_BLOCK_DATA) {
s->status = BLK_DATA;
} else if (!s->target_has_backing) {
@@ -1300,7 +1310,7 @@ static int convert_iteration_sectors(ImgConvertState *s,
int64_t sector_num)
}
n = MIN(n, s->sector_next_status - sector_num);
- if (s->status == BLK_DATA) {
+ if (s->status == BLK_DATA || s->status == BLK_ZERO_DATA) {
n = MIN(n, s->buf_sectors);
}
@@ -1325,10 +1335,6 @@ static int convert_read(ImgConvertState *s, int64_t
sector_num, int nb_sectors,
int n;
int ret;
- if (s->status == BLK_ZERO || s->status == BLK_BACKING_FILE) {
- return 0;
- }
-
assert(nb_sectors <= s->buf_sectors);
while (nb_sectors > 0) {
BlockBackend *blk;
@@ -1372,6 +1378,7 @@ static int convert_write(ImgConvertState *s, int64_t
sector_num, int nb_sectors,
break;
case BLK_DATA:
+ case BLK_ZERO_DATA:
/* We must always write compressed clusters as a whole, so don't
* try to find zeroed parts in the buffer. We can only save the
* write if the buffer is completely zeroed and we're allowed to
@@ -1466,7 +1473,7 @@ static int convert_do_copy(ImgConvertState *s)
ret = n;
goto fail;
}
- if (s->status == BLK_DATA) {
+ if (s->status == BLK_DATA || s->status == BLK_ZERO_DATA) {
s->allocated_sectors += n;
}
sector_num += n;
@@ -1486,17 +1493,21 @@ static int convert_do_copy(ImgConvertState *s)
ret = n;
goto fail;
}
- if (s->status == BLK_DATA) {
+ if (s->status == BLK_DATA || s->status == BLK_ZERO_DATA) {
allocated_done += n;
qemu_progress_print(100.0 * allocated_done / s->allocated_sectors,
0);
}
- ret = convert_read(s, sector_num, n, buf);
- if (ret < 0) {
- error_report("error while reading sector %" PRId64
- ": %s", sector_num, strerror(-ret));
- goto fail;
+ if (s->status == BLK_DATA) {
+ ret = convert_read(s, sector_num, n, buf);
+ if (ret < 0) {
+ error_report("error while reading sector %" PRId64
+ ": %s", sector_num, strerror(-ret));
+ goto fail;
+ }
+ } else if (s->status == BLK_ZERO_DATA) {
+ memset(buf, 0, n * BDRV_SECTOR_SIZE);
}
ret = convert_write(s, sector_num, n, buf);
diff --git a/tests/qemu-iotests/122.out b/tests/qemu-iotests/122.out
index 0068e96..98814de 100644
--- a/tests/qemu-iotests/122.out
+++ b/tests/qemu-iotests/122.out
@@ -112,16 +112,14 @@ read 3145728/3145728 bytes at offset 0
3 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
read 63963136/63963136 bytes at offset 3145728
61 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 6291456, "depth": 0, "zero": false, "data": true,
"offset": 327680},
-{ "start": 6291456, "length": 60817408, "depth": 0, "zero": true, "data":
false}]
+[{ "start": 0, "length": 67108864, "depth": 0, "zero": false, "data": true,
"offset": 327680}]
convert -c -S 0:
read 3145728/3145728 bytes at offset 0
3 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
read 63963136/63963136 bytes at offset 3145728
61 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-[{ "start": 0, "length": 6291456, "depth": 0, "zero": false, "data": true},
-{ "start": 6291456, "length": 60817408, "depth": 0, "zero": true, "data":
false}]
+[{ "start": 0, "length": 67108864, "depth": 0, "zero": false, "data": true}]
Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
wrote 33554432/33554432 bytes at offset 0
32 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
--
2.7.1
