libmount: fix mnt_table_is_fs_mounted() for NFS bind mounts.

When you bind-mount a subdirectory of a local filesystem, the
path to that subdirectory appears as the fourth field in mountinfo.

For nfs mounts, the fourth field is always "/", and the subdirectory
part is appended to the "special" (aka "device") field.  This is
consistent with historical NFS usage which always includes a path in
the fs_spec field.

libmount needs to know about this when "mount -a" checks to see if
a filesystem is already mounted.

Without this fix, fstab lines like:

 server::/path /dir nfs defaults 0 0
 /dir/subdir /mnt/test none bind 0 0

result in a new mount at /mnt/test every time "mount -a" is run.

[kzak@redhat.com: - use strappend() rather than asprintf()]

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Karel Zak <kzak@redhat.com>

diff --git a/libmount/src/tab.c b/libmount/src/tab.c
index 968057e429f52ba52b907cfa83fd7d636b4807b7..eb61dd33e87d134c71f4ce02eb65e04f4f5e64a9 100644 (file)
--- a/libmount/src/tab.c
+++ b/libmount/src/tab.c
@@ -1542,6 +1542,7 @@ int mnt_table_is_fs_mounted(struct libmnt_table *tb, struct libmnt_fs *fstab_fs)
        struct libmnt_fs *fs;
 
        char *root = NULL;
+       char *src2 = NULL;
        const char *src = NULL, *tgt = NULL;
        char *xtgt = NULL;
        int rc = 0;
@@ -1566,8 +1567,17 @@ int mnt_table_is_fs_mounted(struct libmnt_table *tb, struct libmnt_fs *fstab_fs)
                        flags = MS_BIND;
 
                rootfs = mnt_table_get_fs_root(tb, fstab_fs, flags, &root);
-               if (rootfs)
+               if (rootfs) {
+                       const char *fstype = mnt_fs_get_fstype(rootfs);
+
                        src = mnt_fs_get_srcpath(rootfs);
+                       if (fstype && strncmp(fstype, "nfs", 3) == 0 && root) {
+                               /* NFS stores the root at the end of the source */
+                               src = src2 = strappend(src, root);
+                               free(root);
+                               root = NULL;
+                       }
+               }
        }
 
        if (!src)
@@ -1667,6 +1677,7 @@ done:
        free(root);
 
        DBG(TAB, ul_debugobj(tb, "mnt_table_is_fs_mounted: %s [rc=%d]", src, rc));
+       free(src2);
        return rc;
 }