bdev: "detect" loop file

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/bdev/bdev.c

@@ -854,12 +854,16 @@ static const struct bdev_type *get_bdev_by_name(const char *name)
 	return NULL;
 }
 
-static const struct bdev_type *bdev_query(struct lxc_conf *conf, const char *src)
+static const struct bdev_type *bdev_query(struct lxc_conf *conf,
+					  const char *src)
 {
 	size_t i;
 
-	if (conf->rootfs.bdev_type)
+	if (conf->rootfs.bdev_type) {
+		DEBUG("config file specified rootfs type \"%s\"",
+		      conf->rootfs.bdev_type);
 		return get_bdev_by_name(conf->rootfs.bdev_type);
+	}
 
 	for (i = 0; i < numbdevs; i++) {
 		int r;
@@ -870,6 +874,9 @@ static const struct bdev_type *bdev_query(struct lxc_conf *conf, const char *src
 
 	if (i == numbdevs)
 		return NULL;
+
+	DEBUG("detected rootfs type \"%s\"", bdevs[i].name);
+
 	return &bdevs[i];
 }
 

src/lxc/bdev/lxcloop.c

@@ -28,6 +28,7 @@
 #include <string.h>
 #include <unistd.h>
 #include <linux/loop.h>
+#include <sys/stat.h>
 #include <sys/types.h>
 
 #include "bdev.h"
@@ -157,22 +158,39 @@ int loop_destroy(struct bdev *orig)
 
 int loop_detect(const char *path)
 {
+	int ret;
+	struct stat s;
+
 	if (strncmp(path, "loop:", 5) == 0)
 		return 1;
+
+	ret = stat(path, &s);
+	if (ret < 0)
+		return 0;
+
+	if (__S_ISTYPE(s.st_mode, S_IFREG))
+		return 1;
+
 	return 0;
 }
 
 int loop_mount(struct bdev *bdev)
 {
 	int ret, loopfd;
 	char loname[MAXPATHLEN];
+	char *src = bdev->src;
 
 	if (strcmp(bdev->type, "loop"))
 		return -22;
+
 	if (!bdev->src || !bdev->dest)
 		return -22;
 
-	loopfd = lxc_prepare_loop_dev(bdev->src + 5, loname, LO_FLAGS_AUTOCLEAR);
+	/* skip prefix */
+	if (!strncmp(bdev->src, "loop:", 5))
+		src += 5;
+
+	loopfd = lxc_prepare_loop_dev(src, loname, LO_FLAGS_AUTOCLEAR);
 	if (loopfd < 0)
 		return -1;
 	DEBUG("prepared loop device \"%s\"", loname);