Commit 97ec9117 authored by Fam Zheng's avatar Fam Zheng Committed by Kevin Wolf
Browse files

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: default avatarFam Zheng <famz@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent a16efd53

block/file-posix.c

+10 −0
Original line number Diff line number Diff line
@@ -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;

}