mnt: Use ns_mountpoint to open a mount point

open_mountpoint helper is called when mount namespace are
already restored so we have to use local paths.

This is a continuation to patch a082f27 -- we keep mount
point id in fsnotify, thus we should use the namespace's
path for open.

https://jira.sw.ru/browse/PSBM-39957

Signed-off-by: Andrew Vagin <[email protected]>
Signed-off-by: Cyrill Gorcunov <[email protected]>
Signed-off-by: Pavel Emelyanov <[email protected]>

Author: avagin

fsnotify.c

@@ -536,9 +536,9 @@ static int restore_one_fanotify(int fd, struct fsnotify_mark_info *mark)
 
 		mntns_root = mntns_get_root_fd(m->nsid);
 
-		target = openat(mntns_root, m->mountpoint, O_PATH);
+		target = openat(mntns_root, m->ns_mountpoint, O_PATH);
 		if (target == -1) {
-			pr_perror("Unable to open %s", m->mountpoint);
+			pr_perror("Unable to open %s", m->ns_mountpoint);
 			goto err;
 		}
 

mount.c

@@ -1017,23 +1017,23 @@ static int __open_mountpoint(struct mount_info *pm, int mnt_fd)
 		if (mntns_root < 0)
 			return -1;
 
-		mnt_fd = openat(mntns_root, pm->mountpoint, O_RDONLY);
+		mnt_fd = openat(mntns_root, pm->ns_mountpoint, O_RDONLY);
 		if (mnt_fd < 0) {
-			pr_perror("Can't open %s", pm->mountpoint);
+			pr_perror("Can't open %s", pm->ns_mountpoint);
 			return -1;
 		}
 	}
 
 	ret = fstat(mnt_fd, &st);
 	if (ret < 0) {
-		pr_perror("fstat(%s) failed", pm->mountpoint);
+		pr_perror("fstat(%s) failed", pm->ns_mountpoint);
 		goto err;
 	}
 
-	dev = phys_stat_resolve_dev(pm->nsid, st.st_dev, pm->mountpoint + 1);
+	dev = phys_stat_resolve_dev(pm->nsid, st.st_dev, pm->ns_mountpoint + 1);
 	if (dev != pm->s_dev) {
 		pr_err("The file system %#x (%#x) %s %s is inaccessible\n",
-				pm->s_dev, (int)dev, pm->fstype->name, pm->mountpoint);
+		       pm->s_dev, (int)dev, pm->fstype->name, pm->ns_mountpoint);
 		goto err;
 	}
 

proc_parse.c

@@ -1026,6 +1026,7 @@ static int parse_mountinfo_ent(char *str, struct mount_info *new, char **fsname)
 	new->mountpoint = xmalloc(PATH_MAX);
 	if (new->mountpoint == NULL)
 		goto err;
+	new->ns_mountpoint = new->mountpoint;
 
 	new->mountpoint[0] = '.';
 	ret = sscanf(str, "%i %i %u:%u %ms %s %ms %n",