btrfs-progs: optimize not to scan repeated fsid mount points

fsid can be mounted multiple times, with different subvolid.
And we don't have to scan a mount point if we already have
that in the scanned list.

And thus nicely avoids the following warning with multiple
subvol mounts on older kernel like 2.6.32 where
BTRFS_IOC_GET_FSLABEL ioctl does not exist.

./btrfs fi show -m
Label: none  uuid: 31845933-611e-422d-ae6f-386e57ad81aa
	Total devices 2 FS bytes used 172.00KiB
	devid    1 size 3.00GiB used 642.38MiB path /dev/sdd
	devid    2 size 3.00GiB used 622.38MiB path /dev/sde

warning, device 2 is missing
warning devid 2 not found already
warning, device 2 is missing
warning devid 2 not found already

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index 02def40..3663734 100644 (file)
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -468,6 +468,10 @@ static int btrfs_scan_kernel(void *search, unsigned unit_mode)
                        goto out;
                }
 
+               /* skip all fs already shown as mounted fs */
+               if (is_seen_fsid(fs_info_arg.fsid))
+                       continue;
+
                ret = get_label_mounted(mnt->mnt_dir, label);
                /* provide backward kernel compatibility */
                if (ret == -ENOTTY)