Delete snapshot links in Windows

cmdline/mingw.c

@@ -2445,7 +2445,20 @@ static int windows_rebuild_link(const struct fssnapshot_struct* fss, const char*
 	return 0;
 }
 
-int fssnapshot(const char* dir, struct fssnapshot_struct* fss)
+static int windows_delete_link(const struct fssnapshot_struct* fss, const char* name)
+{
+	char link_path[PATH_MAX];
+
+	pathcpy(link_path, sizeof(link_path), fss->snapshot_dir);
+	pathcat(link_path, sizeof(link_path), name);
+
+	/* remove link if present */
+	windows_rmdir(link_path);
+
+	return 0;
+}
+
+int fssnapshot_mount(const char* dir, struct fssnapshot_struct* fss)
 {
 	wchar_t conv_buf_vol[CONV_MAX];
 	char conv_buf_root[CONV_MAX];
@@ -2537,6 +2550,7 @@ int fssnapshot_stat(struct fssnapshot_struct* fss, const char* name, struct stat
 
 	pathcpy(link_path, sizeof(link_path), fss->snapshot_dir);
 	pathcat(link_path, sizeof(link_path), name);
+	pathcat(link_path, sizeof(link_path), SNAPSHOT_GUID); /* we check the GUID as it's the one that matter */
 
 	/* use lstat because we want to check the link */
 	if (windows_lstat(link_path, st) != 0)
@@ -2600,6 +2614,9 @@ int fssnapshot_create(const struct fssnapshot_struct* fss, const char* name)
 	pathcpy(link_path, sizeof(link_path), fss->snapshot_dir);
 	pathcat(link_path, sizeof(link_path), name);
 
+	/* remove potential stale link */
+	windows_rmdir(link_path);
+
 	int ret = windows_symlink_directory(target_path, link_path);
 	if (ret != 0) {
 		log_error(errno, "Error creating symlink '%s'. %s.\n", link_path, strerror(errno));
@@ -2629,7 +2646,6 @@ bail_and_delete:
 
 int fssnapshot_delete(const struct fssnapshot_struct* fss, const char* name)
 {
-	char link_path[PATH_MAX];
 	char guid[PATH_MAX];
 	char cmd[PS_CMD_MAX];
 	char guid_link[PATH_MAX];
@@ -2638,16 +2654,13 @@ int fssnapshot_delete(const struct fssnapshot_struct* fss, const char* name)
 	pathcat(guid_link, sizeof(guid_link), name);
 	pathcat(guid_link, sizeof(guid_link), SNAPSHOT_GUID);
 
-	pathcpy(link_path, sizeof(link_path), fss->snapshot_dir);
-	pathcat(link_path, sizeof(link_path), name);
-
 	if (windows_read_guid(guid_link, guid, sizeof(guid)) != 0)
 		return -1;
 
 	/* if the GUID link is gone, assume everything is gone */
 	if (guid[0] == 0) {
 		/* remove as not valid anymore */
-		windows_rmdir(link_path);
+		windows_delete_link(fss, name);
 		return 0;
 	}
 
@@ -2657,12 +2670,12 @@ int fssnapshot_delete(const struct fssnapshot_struct* fss, const char* name)
 	if (ret != 0) {
 		log_error(errno, "Error destroy the snapshot from GUID '%s'. %s.\n", guid, strerror(errno));
 		/* remove as not valid anymore */
-		windows_rmdir(link_path);
+		windows_delete_link(fss, name);
 		return -1;
 	}
 
 	/* remove live symlink if present */
-	windows_rmdir(link_path);
+	windows_delete_link(fss, name);
 
 	/* remove persistent GUID symlink */
 	if (windows_rmdir(guid_link) != 0) {
@@ -2675,16 +2688,9 @@ int fssnapshot_delete(const struct fssnapshot_struct* fss, const char* name)
 
 int fssnapshot_rename(const struct fssnapshot_struct* fss, const char* old_name, const char* new_name)
 {
-	char old_link[PATH_MAX];
-	char new_link[PATH_MAX];
 	char old_guid[PATH_MAX];
 	char new_guid[PATH_MAX];
 
-	pathcpy(old_link, sizeof(old_link), fss->snapshot_dir);
-	pathcat(old_link, sizeof(old_link), old_name);
-	pathcpy(new_link, sizeof(new_link), fss->snapshot_dir);
-	pathcat(new_link, sizeof(new_link), new_name);
-
 	pathcpy(old_guid, sizeof(old_guid), fss->snapshot_dir);
 	pathcat(old_guid, sizeof(old_guid), old_name);
 	pathcat(old_guid, sizeof(old_guid), SNAPSHOT_GUID);
@@ -2692,21 +2698,33 @@ int fssnapshot_rename(const struct fssnapshot_struct* fss, const char* old_name,
 	pathcat(new_guid, sizeof(new_guid), new_name);
 	pathcat(new_guid, sizeof(new_guid), SNAPSHOT_GUID);
 
-	if (windows_rename(old_link, new_link) != 0) {
-		log_error(errno, "Error renaming  '%s' to '%s'. %s.\n", old_link, new_link, strerror(errno));
-		return -1;
-	}
-
 	if (windows_rename(old_guid, new_guid) != 0) {
 		log_error(errno, "Error renaming  '%s' to '%s'. %s.\n", old_guid, new_guid, strerror(errno));
-		/* try to restore */
-		windows_rename(new_link, old_link);
 		return -1;
 	}
 
+	/* the rename is the latest operation, and then we don't care about the links, we just remove both */
+	windows_delete_link(fss, old_name);
+	windows_delete_link(fss, new_name);
+
 	return 0;
 }
 
+void fssnapshot_unmount(const struct fssnapshot_struct* fss)
+{
+	/*
+	 * Remove symlinks on exit to prevent "Dangling Links."
+	 * Since \Device\HarddiskVolumeShadowCopyN paths are reassigned by the kernel
+	 * at boot, a stale link would either point to a non-existent device or,
+	 * worse, a different disk's snapshot.
+	 *
+	 * Deleting the link ensures system hygiene and prevents users from seeing
+	 * "Location not available" errors or incorrect data after a reboot.
+	 */
+	windows_delete_link(fss, SNAPSHOT_PENDING);
+	windows_delete_link(fss, SNAPSHOT_STABLE);
+}
+
 uint64_t os_tick(void)
 {
 	LARGE_INTEGER t;

cmdline/portable.h

@@ -426,7 +426,16 @@ struct fssnapshot_struct {
  * @param fss Output snapshot context
  * @return 0 on success, -1 on failure
  */
-int fssnapshot(const char* dir, struct fssnapshot_struct* fss);
+int fssnapshot_mount(const char* dir, struct fssnapshot_struct* fss);
+
+/**
+ * Unmount the snapshots.
+ *
+ * Required in Windows to remove the temporary symlinks.
+ *
+ * @param fss Snapshot context
+ */
+void fssnapshot_unmount(const struct fssnapshot_struct* fss);
 
 /**
  * Stat the snapshot directory.

cmdline/snapraid.c

@@ -1856,8 +1856,10 @@ int snapraid_main(int argc, char* argv[])
 		ret = state_sync(&state, blockstart, blockcount);
 
 		/* commit the snapshot as stable */
-		if (ret == 0)
+		if (ret == 0) {
 			state_snapshot_commit(&state);
+			state_snapshot_cleanup(&state);
+		}
 	} else if (operation == OPERATION_DRY) {
 		state_read(&state);
 
@@ -1899,6 +1901,10 @@ int snapraid_main(int argc, char* argv[])
 		state_snapshot_read(&state);
 
 		ret = state_scrub(&state, plan100, olderthan);
+
+		if (ret == 0) {
+			state_snapshot_cleanup(&state);
+		}
 	} else if (operation == OPERATION_REWRITE) {
 		state_read(&state);
 
@@ -2023,6 +2029,10 @@ int snapraid_main(int argc, char* argv[])
 			if (opt.gui_rescan_after)
 				state_scan(&state);
 		}
+
+		if (ret == 0) {
+			state_snapshot_cleanup(&state);
+		}
 	} else {
 		/* LCOV_EXCL_START */
 		log_fatal(errno, "Unexpected command '%s'\n", command);

cmdline/state.c

@@ -5834,7 +5834,7 @@ int state_snapshot_new(struct snapraid_state* state)
 		struct snapraid_disk* disk = i->data;
 
 		/* check if it supports snapshot */
-		if (fssnapshot(disk->mount_point, &disk->fss) != 0)
+		if (fssnapshot_mount(disk->mount_point, &disk->fss) != 0)
 			continue;
 
 		size_t root_len = strlen(disk->fss.root_dir);
@@ -5906,7 +5906,7 @@ void state_snapshot_read(struct snapraid_state* state)
 		struct snapraid_disk* disk = i->data;
 
 		/* check if it supports snapshot */
-		if (fssnapshot(disk->mount_point, &disk->fss) != 0)
+		if (fssnapshot_mount(disk->mount_point, &disk->fss) != 0)
 			continue;
 
 		size_t root_len = strlen(disk->fss.root_dir);
@@ -5939,7 +5939,7 @@ void state_snapshot_write(struct snapraid_state* state, tommy_list* filterlist_d
 		struct snapraid_disk* disk = i->data;
 
 		/* check if it supports snapshot */
-		if (fssnapshot(disk->mount_point, &disk->fss) != 0)
+		if (fssnapshot_mount(disk->mount_point, &disk->fss) != 0)
 			continue;
 
 		size_t root_len = strlen(disk->fss.root_dir);
@@ -5979,3 +5979,16 @@ void state_snapshot_write(struct snapraid_state* state, tommy_list* filterlist_d
 	}
 }
 
+void state_snapshot_cleanup(struct snapraid_state* state)
+{
+	for (tommy_node* i = state->disklist; i != 0; i = i->next) {
+		struct snapraid_disk* disk = i->data;
+
+		/* check if it supports snapshot */
+		if (disk->fss.magic == 0)
+			continue;
+
+		fssnapshot_unmount(&disk->fss);
+	}
+}
+

cmdline/state.h

@@ -445,6 +445,13 @@ void state_snapshot_read(struct snapraid_state* state);
  */
 void state_snapshot_write(struct snapraid_state* state, tommy_list* filterlist_disk);
 
+/**
+ * Cleanup snapshots
+ *
+ * Required only in Windows.
+ */
+void state_snapshot_cleanup(struct snapraid_state* state);
+
 /****************************************************************************/
 /* misc */
 

cmdline/unix.c

@@ -2558,7 +2558,7 @@ static int fssnapshot_zfs(const char* dir, uint32_t magic, struct fssnapshot_str
 }
 #endif
 
-int fssnapshot(const char* path, struct fssnapshot_struct* fss)
+int fssnapshot_mount(const char* path, struct fssnapshot_struct* fss)
 {
 #if HAVE_LINUX_DEVICE
 	struct statfs sfs;
@@ -3069,6 +3069,11 @@ int fssnapshot_rename(const struct fssnapshot_struct* fss, const char* old_name,
 #endif
 }
 
+void fssnapshot_unmount(const struct fssnapshot_struct* fss)
+{
+	(void)fss;
+}
+
 uint64_t os_tick(void)
 {
 #if HAVE_MACH_ABSOLUTE_TIME