On 7.10.19 г. 12:45 ч., Anand Jain wrote:
> Following test case explains it all, even though the degraded mount is
> successful the btrfs-progs fails to report the missing device.
>
> mkfs.btrfs -fq -draid1 -mraid1 /dev/sdc /dev/sdd && \
> wipefs -a /dev/sdd && mount -o degraded /dev/sdc /btrfs && \
> btrfs fi show -m /btrfs
>
> Label: none uuid: 2b3b8d92-572b-4d37-b4ee-046d3a538495
> Total devices 2 FS bytes used 128.00KiB
> devid 1 size 1.09TiB used 2.01GiB path /dev/sdc
> devid 2 size 1.09TiB used 2.01GiB path /dev/sdd
>
> This is because btrfs-progs does it fundamentally wrong way that
> it deduces the missing device status in the user land instead of
> refuting from the kernel.
>
> At the same time in the kernel when we know that there is device
> with non-btrfs magic, then remove that device from the list so
> that btrfs-progs or someother userland utility won't be confused.
>
> Signed-off-by: Anand Jain <anand.j...@oracle.com>
> ---
> fs/btrfs/disk-io.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 326d5281ad93..e05856432456 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -3417,7 +3417,7 @@ int btrfs_read_dev_one_super(struct block_device *bdev,
> int copy_num,
> if (btrfs_super_bytenr(super) != bytenr ||
> btrfs_super_magic(super) != BTRFS_MAGIC) {
> brelse(bh);
> - return -EINVAL;
> + return -EUCLEAN;
This is really non-obvious and you are propagating the special-meaning
of EUCLEAN waaaaaaaay beyond btrfs_open_one_device. In fact what this
patch does is make the following call chain return EUCLAN:
btrfs_open_one_device <-- finally removing the device in this function
btrfs_get_bdev_and_sb <-- propagating it to here
btrfs_read_dev_super
btrfs_read_dev_one_super <-- you return the EUCLEAN
And your commit log doesn't mention anything about that. EUCLEAN
warrants a comment in this case since it changes behavior in
higher-level layers.
> }
>
> *bh_ret = bh;
>
