From:   Anand Jain <anand.jain@oracle.com>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     linux-btrfs@vger.kernel.org, Anand Jain <anand.jain@oracle.com>,
        Su Yue <l@damenly.su>, David Sterba <dsterba@suse.com>
Subject: [PATCH stable-5.15.y 3/4] btrfs: update latest_dev when we create a sprout device
Date:   Thu, 16 Dec 2021 21:04:12 +0800
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Commit b7cb29e666fe79dda5dbe5f57fb7c92413bf161c upstream.

When we add a device to the seed filesystem (sprouting) it is a new
filesystem (and fsid) on the device added. Update the latest_dev so
that /proc/self/mounts shows the correct device.

Example:

  $ btrfstune -S1 /dev/vg/seed
  $ mount /dev/vg/seed /btrfs
  mount: /btrfs: WARNING: device write-protected, mounted read-only.

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-seed /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

  $ btrfs dev add -f /dev/vg/new /btrfs

Before:

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-seed /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

After:

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-new /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

Tested-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/volumes.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4afa050384d9..b996ea0dc78b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2634,6 +2634,8 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 			btrfs_abort_transaction(trans, ret);
 			goto error_trans;
 		}
+		btrfs_assign_next_active_device(fs_info->fs_devices->latest_dev,
+						device);
 	}
 
 	device->fs_devices = fs_devices;
-- 
2.33.1