From 97ec9117c346239fc5b0f6d1973111e8ca370087 Mon Sep 17 00:00:00 2001 From: Fam Zheng Date: Fri, 8 Sep 2017 17:44:57 +0800 Subject: [PATCH] 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 Signed-off-by: Kevin Wolf --- block/file-posix.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/block/file-posix.c b/block/file-posix.c index ab12a2b591..36ee89e940 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; } -- 2.11.4.GIT