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authorFam Zheng <famz@redhat.com>2017-09-08 17:44:57 +0800
committerKevin Wolf <kwolf@redhat.com>2017-09-26 14:46:23 +0200
commit97ec9117c346239fc5b0f6d1973111e8ca370087 (patch)
treef07754e7dfde0bda52d770b7e5f214ab163fb169
parenta16efd53406bc8d89f87253ab10290f8d1b145a7 (diff)
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file-posix: Clear out first sector in hdev_create
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> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
-rw-r--r--block/file-posix.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/block/file-posix.c b/block/file-posix.c
index ab12a2b..36ee89e 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2730,6 +2730,16 @@ 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;
}