From: Anand Jain anand.jain@oracle.com
[ Upstream commit c6a5d954950c5031444173ad2195efc163afcac9 ]
If you replace a seed device in a sprouted fs, it appears to have successfully replaced the seed device, but if you look closely, it didn't. Here is an example.
$ mkfs.btrfs /dev/sda $ btrfstune -S1 /dev/sda $ mount /dev/sda /btrfs $ btrfs device add /dev/sdb /btrfs $ umount /btrfs $ btrfs device scan --forget $ mount -o device=/dev/sda /dev/sdb /btrfs $ btrfs replace start -f /dev/sda /dev/sdc /btrfs $ echo $? 0
BTRFS info (device sdb): dev_replace from /dev/sda (devid 1) to /dev/sdc started BTRFS info (device sdb): dev_replace from /dev/sda (devid 1) to /dev/sdc finished
$ btrfs fi show Label: none uuid: ab2c88b7-be81-4a7e-9849-c3666e7f9f4f Total devices 2 FS bytes used 256.00KiB devid 1 size 3.00GiB used 520.00MiB path /dev/sdc devid 2 size 3.00GiB used 896.00MiB path /dev/sdb
Label: none uuid: 10bd3202-0415-43af-96a8-d5409f310a7e Total devices 1 FS bytes used 128.00KiB devid 1 size 3.00GiB used 536.00MiB path /dev/sda
So as per the replace start command and kernel log replace was successful. Now let's try to clean mount.
$ umount /btrfs $ btrfs device scan --forget
$ mount -o device=/dev/sdc /dev/sdb /btrfs mount: /btrfs: wrong fs type, bad option, bad superblock on /dev/sdb, missing codepage or helper program, or other error.
[ 636.157517] BTRFS error (device sdc): failed to read chunk tree: -2 [ 636.180177] BTRFS error (device sdc): open_ctree failed
That's because per dev items it is still looking for the original seed device.
$ btrfs inspect-internal dump-tree -d /dev/sdb
item 0 key (DEV_ITEMS DEV_ITEM 1) itemoff 16185 itemsize 98 devid 1 total_bytes 3221225472 bytes_used 545259520 io_align 4096 io_width 4096 sector_size 4096 type 0 generation 6 start_offset 0 dev_group 0 seek_speed 0 bandwidth 0 uuid 59368f50-9af2-4b17-91da-8a783cc418d4 <--- seed uuid fsid 10bd3202-0415-43af-96a8-d5409f310a7e <--- seed fsid item 1 key (DEV_ITEMS DEV_ITEM 2) itemoff 16087 itemsize 98 devid 2 total_bytes 3221225472 bytes_used 939524096 io_align 4096 io_width 4096 sector_size 4096 type 0 generation 0 start_offset 0 dev_group 0 seek_speed 0 bandwidth 0 uuid 56a0a6bc-4630-4998-8daf-3c3030c4256a <- sprout uuid fsid ab2c88b7-be81-4a7e-9849-c3666e7f9f4f <- sprout fsid
But the replaced target has the following uuid+fsid in its superblock which doesn't match with the expected uuid+fsid in its devitem.
$ btrfs in dump-super /dev/sdc | egrep '^generation|dev_item.uuid|dev_item.fsid|devid' generation 20 dev_item.uuid 59368f50-9af2-4b17-91da-8a783cc418d4 dev_item.fsid ab2c88b7-be81-4a7e-9849-c3666e7f9f4f [match] dev_item.devid 1
So if you provide the original seed device the mount shall be successful. Which so long happening in the test case btrfs/163.
$ btrfs device scan --forget $ mount -o device=/dev/sda /dev/sdb /btrfs
Fix in this patch: If a seed is not sprouted then there is no replacement of it, because of its read-only filesystem with a read-only device. Similarly, in the case of a sprouted filesystem, the seed device is still read only. So, mark it as you can't replace a seed device, you can only add a new device and then delete the seed device. If replace is attempted then returns -EINVAL.
Signed-off-by: Anand Jain anand.jain@oracle.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/dev-replace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c index e4a1c6afe35dc..0cb36746060da 100644 --- a/fs/btrfs/dev-replace.c +++ b/fs/btrfs/dev-replace.c @@ -230,7 +230,7 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info, int ret = 0;
*device_out = NULL; - if (fs_info->fs_devices->seeding) { + if (srcdev->fs_devices->seeding) { btrfs_err(fs_info, "the filesystem is a seed filesystem!"); return -EINVAL; }