On 2018/7/17 8:20 PM, shenghui wrote:
>
> When run make-bcache with --wipe-bcache on a bcache device,
> write_sb() would fall through to blkid probe before write cache_sb.
> If libblkid is not up-to-date, e.g version provided by Linux distribution,
> it will not recognize bcache magic, and will complain
> "
> Device XX already has a non-bcache superblock, remove it using wipefs and wipefs -a
> "
> even if it's a bcache device. This should be avoided.
>
>
> Test steps before the change:
> ---------
> 1) ./make-bcache -C /dev/sda8
> 2) ./make-bcache -B --wipe-bcache /dev/sda8
> Device /dev/sda8 already has a non-bcache superblock, remove it using wipefs and wipefs -a
>
>
> Test steps after the change:
> ---------
> 1) ./make-bcache -C /dev/sda8
> 2) ./make-bcache -B --wipe-bcache /dev/sda8
> UUID: c43ac77e-1821-4445-9d44-217676662a97
> Set UUID: 398f284e-dbf2-4d53-b602-3c2b8de31b0c
> version: 1
> block_size: 1
> data_offset: 16
> 3) mkfs.xfs -f /dev/sda8
> 4) ./make-bcache -C --wipe-bcache /dev/sda8
> Device /dev/sda8 already has a non-bcache superblock, remove it using wipefs and wipefs -a
> 5) wipefs -a /dev/sda8
> /dev/sda8: 4 bytes were erased at offset 0x00000000 (xfs): 58 46 53 42
> 6) ./make-bcache -C /dev/sda8
> UUID: 398413e6-27f3-48f6-bbad-07a1f8550e25
> Set UUID: 347612c8-c2e8-4794-bfd5-9d039a0bd139
> version: 0
> nbuckets: 102998
> block_size: 1
> bucket_size: 1024
> nr_in_set: 1
> nr_this_dev: 0
> first_bucket: 1
>
>
> Signed-off-by: Shenghui Wang <shhuiw@xxxxxxxxxxx>
It looks good to me.
Reviewed-by: Coly Li <colyli@xxxxxxx>
Thanks.
Coly Li
> ---
> make-bcache.c | 38 ++++++++++++++++++++------------------
> 1 file changed, 20 insertions(+), 18 deletions(-)
>
> diff --git a/make-bcache.c b/make-bcache.c
> index c626eae..a9c9f2d 100644
> --- a/make-bcache.c
> +++ b/make-bcache.c
> @@ -186,24 +186,26 @@ static void write_sb(char *dev, unsigned block_size, unsigned bucket_size,
> if (pread(fd, &sb, sizeof(sb), SB_START) != sizeof(sb))
> exit(EXIT_FAILURE);
>
> - if (!memcmp(sb.magic, bcache_magic, 16) && !wipe_bcache) {
> - fprintf(stderr, "Already a bcache device on %s, "
> - "overwrite with --wipe-bcache\n", dev);
> - exit(EXIT_FAILURE);
> - }
> -
> - if (!(pr = blkid_new_probe()))
> - exit(EXIT_FAILURE);
> - if (blkid_probe_set_device(pr, fd, 0, 0))
> - exit(EXIT_FAILURE);
> - /* enable ptable probing; superblock probing is enabled by default */
> - if (blkid_probe_enable_partitions(pr, true))
> - exit(EXIT_FAILURE);
> - if (!blkid_do_probe(pr)) {
> - /* XXX wipefs doesn't know how to remove partition tables */
> - fprintf(stderr, "Device %s already has a non-bcache superblock, "
> - "remove it using wipefs and wipefs -a\n", dev);
> - exit(EXIT_FAILURE);
> + if (!memcmp(sb.magic, bcache_magic, 16)) {
> + if (!wipe_bcache) {
> + fprintf(stderr, "Already a bcache device on %s, "
> + "overwrite with --wipe-bcache\n", dev);
> + exit(EXIT_FAILURE);
> + }
> + } else {
> + if (!(pr = blkid_new_probe()))
> + exit(EXIT_FAILURE);
> + if (blkid_probe_set_device(pr, fd, 0, 0))
> + exit(EXIT_FAILURE);
> + /* enable ptable probing; superblock probing is enabled by default */
> + if (blkid_probe_enable_partitions(pr, true))
> + exit(EXIT_FAILURE);
> + if (!blkid_do_probe(pr)) {
> + /* XXX wipefs doesn't know how to remove partition tables */
> + fprintf(stderr, "Device %s already has a non-bcache superblock, "
> + "remove it using wipefs and wipefs -a\n", dev);
> + exit(EXIT_FAILURE);
> + }
> }
>
> memset(&sb, 0, sizeof(struct cache_sb));
>
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