File util-linux-libmount-cifs-is_mounted.patch of Package util-linux

To: util-linux <util-linux@vger.kernel.org>
From: Stanislav Brabec <sbrabec@suse.cz>
Subject: [PATCH] libmount: Skip root comparison for cifs in
 mnt_table_is_fs_mounted()
Date: Mon, 1 Aug 2016 18:25:01 +0200

In mountinfo of cifs filesystem, root is filled with a relative path to the root
of the exported volume. There is no reasonable way to compare it without making
a network look-up.

This causes false negative result in some cases.

Skipping root comparison in mnt_table_is_fs_mounted() makes things better,
however it still does not cover all possible setups.

How to reproduce:
1) Create and export a cifs volume (with guest allowed).
2) Make a subdirectory in this volume.
3) Mount this subdirectory using fstab:
   //server/volume/subdir /mnt cifs guest 0 0
4) Call mount -a twice.
   Depending on a system running, you either get:
     mount error(16): Device or resource busy
     Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)
   or you get a volume mounted twice.

Signed-off-by: Stanislav Brabec <sbrabec@suse.cz>
---
 libmount/src/tab.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index 155c65e..aa9185a 100644
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -1562,7 +1562,10 @@ int mnt_table_is_fs_mounted(struct libmnt_table *tb, struct libmnt_fs *fstab_fs)
 #endif
 		}
 
-		if (root) {
+		/* For cifs, root contains a relative path to the exported volume,
+		 * i. e. something we cannot compare.
+		 */
+		if (root && strcmp(mnt_fs_get_fstype(fs), "cifs")) {
 			const char *r = mnt_fs_get_root(fs);
 			if (!r || strcmp(r, root) != 0)
 				continue;
-- 
2.9.2