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;
}
*bh_ret = bh;
--
1.8.3.1
