On 2016/06/17 1:38, Chandan Rajendra wrote:
> stripesize should ideally be set to the value of sectorsize. However
> previous versions of btrfs-progs/mkfs.btrfs had set stripesize to a
> value of 4096. On machines with PAGE_SIZE other than 4096, This could
> lead to the following scenario,
>
> - /dev/loop0, /dev/loop1 and /dev/loop2 are mounted as a single
> filesystem. The filesystem was created by an older version of mkfs.btrfs
> which set stripesize to 4k.
> - losetup -a
> /dev/loop0: [0030]:19477 (/root/disk-imgs/file-0.img)
> /dev/loop1: [0030]:16577 (/root/disk-imgs/file-1.img)
> /dev/loop2: [64770]:3423229 (/root/disk-imgs/file-2.img)
> - /etc/mtab lists only /dev/loop0
> - losetup /dev/loop4 /root/disk-imgs/file-1.img
> The new mkfs.btrfs invoked as 'mkfs.btrfs -f /dev/loop4' succeeds even
> though /dev/loop1 has already been mounted and has
> /root/disk-imgs/file-1.img as its backing file.
>
> The above behaviour occurs because check_super() function returns an
> error code (due to stripesize not being set to 4096) and hence
> check_mounted_where() function treats /dev/loop1 as a disk containing a
> filesystem other than Btrfs.
>
> Hence as a workaround this commit allows 4096 as a valid stripesize.
>
> Signed-off-by: Chandan Rajendra <chan...@linux.vnet.ibm.com>
> ---
> disk-io.c | 4 +++-
> mkfs.c | 1 +
> 2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/disk-io.c b/disk-io.c
> index 77eb0a6..1ac7631 100644
> --- a/disk-io.c
> +++ b/disk-io.c
> @@ -1476,7 +1476,9 @@ static int check_super(struct btrfs_super_block *sb)
> error("invalid bytes_used %llu", btrfs_super_bytes_used(sb));
> goto error_out;
> }
> - if (btrfs_super_stripesize(sb) != 4096) {
> +
> + if ((btrfs_super_stripesize(sb) != 4096)
Just one trivial comment. Tab was converted to some spaces.
Thanks,
Satoru
> + && (btrfs_super_stripesize(sb) != btrfs_super_sectorsize(sb))) {
> error("invalid stripesize %u", btrfs_super_stripesize(sb));
> goto error_out;
> }
> diff --git a/mkfs.c b/mkfs.c
> index a3a3c14..697bdc2 100644
> --- a/mkfs.c
> +++ b/mkfs.c
> @@ -1482,6 +1482,7 @@ int main(int argc, char **argv)
> }
>
> sectorsize = max(sectorsize, (u32)sysconf(_SC_PAGESIZE));
> + stripesize = sectorsize;
> saved_optind = optind;
> dev_cnt = argc - optind;
> if (dev_cnt == 0)
>
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
