From: Anand Jain <anand.jain@oracle.com>
To: linux-btrfs@vger.kernel.org
Cc: josef@toxicpanda.com
Subject: [PATCH RFC 2/2] btrfs: fix replace of seed device
Date: Fri, 21 Aug 2020 21:15:22 +0800 [thread overview]
Message-ID: <eb6040708e4f351ae668726862e3f112f64d8ab9.1598012410.git.anand.jain@oracle.com> (raw)
In-Reply-To: <2c7ca821f53d71d6c1a4e1f1c969c1d8e686021a.1598012410.git.anand.jain@oracle.com>
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 -fq /dev/sda
btrfstune -S1 /dev/sda
mount /dev/sda /btrfs
btrfs dev add /dev/sdb /btrfs
umount /btrfs; btrfs dev scan --forget
mount -o device=/dev/sda /dev/sdb /btrfs
btrfs rep 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 dev 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 in 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 dev scan --forget
mount -o device=/dev/sda /dev/sdb /btrfs
Fix in this patch:
Make 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.
As in the below changes.
Another possible fix:
If we want to keep the ability to replace for seed-device, then we could
update the fsid of the replace-target blocks. And after replacement, you
have seed device but with sprout fsid. But then I don't know what is the
point and if there is any such use case.
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
To test this patch you need the patch 1/2.
Tested with fstests group volume
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 1d09bd3101e2..1aff10337b90 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -225,7 +225,7 @@ 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;
}
--
2.25.1
next prev parent reply other threads:[~2020-08-21 13:17 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 13:15 [PATCH RFC] btrfs/163: replace sprout instead of seed Anand Jain
2020-08-30 14:41 ` [PATCH] fstests: " Anand Jain
2020-08-21 13:15 ` [PATCH 1/2] btrfs: initialize sysfs devid and device link for seed device Anand Jain
2020-08-21 13:15 ` Anand Jain [this message]
2020-08-21 14:38 ` [PATCH RFC 2/2] btrfs: fix replace of " Josef Bacik
2020-08-23 15:05 ` Anand Jain
2020-08-21 14:36 ` [PATCH 1/2] btrfs: initialize sysfs devid and device link for " Josef Bacik
2020-08-23 13:05 ` Anand Jain
2020-08-29 11:44 ` Anand Jain
2020-08-30 14:40 Anand Jain
2020-08-30 14:40 ` Anand Jain
2020-08-31 1:38 ` [PATCH 0/11] btrfs: seed fix null ptr, use only main device_list_mutex, and cleanups Anand Jain
2020-08-30 14:40 ` [PATCH 01/11] btrfs: initialize sysfs devid and device link for seed device Anand Jain
2020-08-31 9:07 ` Nikolay Borisov
2020-08-31 12:00 ` Anand Jain
2020-08-31 16:21 ` Josef Bacik
2020-09-01 16:16 ` Anand Jain
2020-08-30 14:40 ` [PATCH 02/11] btrfs: refactor btrfs_sysfs_add_devices_dir Anand Jain
2020-08-30 14:40 ` [PATCH 03/11] btrfs: refactor btrfs_sysfs_remove_devices_dir Anand Jain
2020-08-31 8:58 ` Nikolay Borisov
2020-08-31 9:12 ` Anand Jain
2020-08-30 14:40 ` [PATCH 04/11] btrfs: reada: use sprout device_list_mutex Anand Jain
2020-08-31 8:54 ` Nikolay Borisov
2020-08-31 16:08 ` Josef Bacik
2020-09-01 9:02 ` Anand Jain
2020-08-30 14:41 ` [PATCH 05/11] btrfs: btrfs_init_devices_late: " Anand Jain
2020-08-31 8:37 ` Nikolay Borisov
2020-09-01 8:54 ` Anand Jain
2020-08-30 14:41 ` [PATCH 06/11] btrfs: open code list_head pointer in btrfs_init_dev_replace_tgtdev Anand Jain
2020-08-31 8:38 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 07/11] btrfs: cleanup btrfs_remove_chunk Anand Jain
2020-08-31 8:43 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 08/11] btrfs: cleanup btrfs_assign_next_active_device() Anand Jain
2020-08-31 8:44 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 09/11] btrfs: cleanup unnecessary goto in open_seed_device Anand Jain
2020-08-31 8:44 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 10/11] btrfs: btrfs_dev_replace_update_device_in_mapping_tree drop file global declare Anand Jain
2020-08-31 8:46 ` Nikolay Borisov
2020-08-30 14:41 ` [PATCH 11/11] btrfs: fix replace of seed device Anand Jain
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