[PATCH 2/2] btrfs-progs: optimize not to scan repeated fsid mount points

[Anand Jain <anand.jain@oracle.com>]

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>
---
 cmds-filesystem.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index 793df0e..e2049cc 100644
--- 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)
-- 
2.4.1