mount: Move btrfs checks into callback

Introduce fstype->sb_equal and move btrfs-specific checks
into it.

travis-ci: success for mount: Sanitize sb comparison code
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/filesystems.c

@@ -590,6 +590,40 @@ static int cgroup_parse(struct mount_info *pm)
 	return 0;
 }
 
+static bool btrfs_sb_equal(struct mount_info *a, struct mount_info *b)
+{
+	/* There is a btrfs bug where it doesn't emit subvol= correctly when
+	 * files are bind mounted, so let's ignore it for now.
+	 * https://marc.info/?l=linux-btrfs&m=145857372803614&w=2
+	 */
+
+	char *posa = strstr(a->options, "subvol="), *posb = strstr(b->options, "subvol=");
+	bool equal;
+
+	if (!posa || !posb) {
+		pr_err("invalid btrfs options, no subvol argument");
+		return false;
+	}
+
+	*posa = *posb = 0;
+	equal = !strcmp(a->options, b->options);
+	*posa = *posb = 's';
+
+	if (!equal)
+		return false;
+
+	posa = strchr(posa, ',');
+	posb = strchr(posb, ',');
+
+	if ((posa && !posb) || (!posa && posb))
+		return false;
+
+	if (posa && strcmp(posa, posb))
+		return false;
+
+	return true;
+}
+
 static int dump_empty_fs(struct mount_info *pm)
 {
 	int fd, ret = -1;
@@ -658,6 +692,7 @@ static struct fstype fstypes[] = {
 	}, {
 		.name = "btrfs",
 		.code = FSTYPE__UNSUPPORTED,
+		.sb_equal = btrfs_sb_equal,
 	}, {
 		.name = "pstore",
 		.dump = dump_empty_fs,

criu/include/filesystems.h

@@ -14,6 +14,7 @@ struct fstype {
 	int (*dump)(struct mount_info *pm);
 	int (*restore)(struct mount_info *pm);
 	int (*parse)(struct mount_info *pm);
+	bool (*sb_equal)(struct mount_info *a, struct mount_info *b);
 	mount_fn_t mount;
 };
 

criu/mount.c

@@ -300,38 +300,11 @@ static bool mounts_sb_equal(struct mount_info *a, struct mount_info *b)
 	if (strcmp(a->source, b->source) != 0)
 		return false;
 
-	/* There is a btrfs bug where it doesn't emit subvol= correctly when
-	 * files are bind mounted, so let's ignore it for now.
-	 * https://marc.info/?l=linux-btrfs&m=145857372803614&w=2
-	 */
-	if (!strcmp(a->fstype->name, "btrfs")) {
-		char *posa = strstr(a->options, "subvol="), *posb = strstr(b->options, "subvol=");
-		bool equal;
-
-		if (!posa || !posb) {
-			pr_err("invalid btrfs options, no subvol argument");
-			return false;
-		}
-
-		*posa = *posb = 0;
-		equal = !strcmp(a->options, b->options);
-		*posa = *posb = 's';
-
-		if (!equal)
-			return false;
+	if (a->fstype->sb_equal) /* :) */
+		return b->fstype->sb_equal(a, b);
 
-		posa = strchr(posa, ',');
-		posb = strchr(posb, ',');
-
-		if ((posa && !posb) || (!posa && posb))
-			return false;
-
-		if (posa && strcmp(posa, posb))
-			return false;
-	} else {
 	if (strcmp(a->options, b->options))
 		return false;
-	}
 
 	if (a->fstype->code == FSTYPE__CGROUP &&
 	    a->private && b->private &&