lib: Add option for specifying the mountpoint for the erofs image

Otherwise the random tmpdir will be encoded in the mount options. We
want to use this in ostree so we can find the deploy dir from the
root (overlay) mount.

Signed-off-by: Alexander Larsson <[email protected]>

libcomposefs/lcfs-mount.c

@@ -483,6 +483,7 @@ static int lcfs_mount_erofs_ovl(struct lcfs_mount_state_s *state,
 	uint32_t image_flags;
 	char imagemountbuf[] = "/tmp/.composefs.XXXXXX";
 	char *imagemount;
+	bool created_tmpdir = false;
 	char loopname[PATH_MAX];
 	int res, errsv;
 	int lowerdir_alt = 0;
@@ -506,11 +507,16 @@ static int lcfs_mount_erofs_ovl(struct lcfs_mount_state_s *state,
 	if (loopfd < 0)
 		return loopfd;
 
-	imagemount = mkdtemp(imagemountbuf);
-	if (imagemount == NULL) {
-		errsv = errno;
-		close(loopfd);
-		return -errsv;
+	if (options->image_mountdir) {
+		imagemount = (char *)options->image_mountdir;
+	} else {
+		imagemount = mkdtemp(imagemountbuf);
+		if (imagemount == NULL) {
+			errsv = errno;
+			close(loopfd);
+			return -errsv;
+		}
+		created_tmpdir = true;
 	}
 
 	res = lcfs_mount_erofs(loopname, imagemount, image_flags, state);
@@ -582,7 +588,9 @@ static int lcfs_mount_erofs_ovl(struct lcfs_mount_state_s *state,
 	free(overlay_options);
 
 	umount2(imagemount, MNT_DETACH);
-	rmdir(imagemount);
+	if (created_tmpdir) {
+		rmdir(imagemount);
+	}
 
 	return res;
 }
@@ -621,12 +629,16 @@ static int lcfs_mount_cfs(struct lcfs_mount_state_s *state,
 	needs_overlay = options->upperdir != NULL;
 
 	if (needs_overlay) {
-		imagemount = mkdtemp(imagemountbuf);
-		if (imagemount == NULL) {
-			res = -errno;
-			goto fail;
+		if (options->image_mountdir) {
+			imagemount = options->image_mountdir;
+		} else {
+			imagemount = mkdtemp(imagemountbuf);
+			if (imagemount == NULL) {
+				res = -errno;
+				goto fail;
+			}
+			created_tmpdir = true;
 		}
-		created_tmpdir = true;
 	} else {
 		imagemount = state->mountpoint;
 	}
@@ -684,11 +696,13 @@ static int lcfs_mount_cfs(struct lcfs_mount_state_s *state,
 
 fail:
 
-	if (created_tmpdir) {
+	if (needs_overlay) {
 		if (mounted_cfs) {
 			umount2(imagemount, MNT_DETACH);
 		}
-		rmdir(imagemount);
+		if (created_tmpdir) {
+			rmdir(imagemount);
+		}
 	}
 	free(cfsimg);
 	free(basedir);

libcomposefs/lcfs-mount.h

@@ -50,6 +50,7 @@ struct lcfs_mount_options_s {
 	const char *expected_digest;
 	uint32_t flags;
 	int idmap_fd; /* userns fd */
+	const char *image_mountdir; /* Temporary location to mount images if needed */
 
 	uint32_t reserved[4];
 	void *reserved2[4];