People get surprised when, after "qemu-img create -f raw /dev/sdX", they
still see qcow2 with "qemu-img info", if previously the bdev had a qcow2
header. While this is natural because raw doesn't need to write any
magic bytes during creation, hdev_create is free to clear out the first
sector to make sure the stale qcow2 header doesn't cause such confusion.
Signed-off-by: Fam Zheng <famz@redhat.com>
---
v3: Don't do anything if there were errors. [Kevin]
v2: Use stack allocated buffer. [Eric]
Fix return value.
(Keep qemu_write_full instead of switching to qemu_pwritev because
the former handles short writes.)
Fix typo "qemu-img". [Changlong]
---
block/file-posix.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/block/file-posix.c b/block/file-posix.c
index 6acbd56238..72ecfbb0e0 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2700,6 +2700,16 @@ static int hdev_create(const char *filename, QemuOpts *opts,
ret = -ENOSPC;
}
+ if (!ret && total_size) {
+ uint8_t buf[BDRV_SECTOR_SIZE] = { 0 };
+ int64_t zero_size = MIN(BDRV_SECTOR_SIZE, total_size);
+ if (lseek(fd, 0, SEEK_SET) == -1) {
+ ret = -errno;
+ } else {
+ ret = qemu_write_full(fd, buf, zero_size);
+ ret = ret == zero_size ? 0 : -errno;
+ }
+ }
qemu_close(fd);
return ret;
}
--
2.13.5