btrfs-progs: add small tool to set the received-uuid of exisiting subvolumes

pkgs/tools/filesystems/btrfsprogs/btrfs-set-received-uuid.c

@@ -0,0 +1,109 @@
+/*
+btrfs receive currently mandates that incremental receives can only be performed on a parent subvolume
+that was also received. This means you cannot apply it to (snapshotted) subvolumes you still have on disk, 
+as they were not received themselves.
+
+This small utility allows you to set the received_uuid of a subvolume, tricking btrfs receive into using it.
+
+found on btrfs mailing list
+read the discussion here: http://comments.gmane.org/gmane.comp.file-systems.btrfs/21922
+*/
+
+#define _GNU_SOURCE
+
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <string.h>
+#include <uuid/uuid.h>
+#include <sys/ioctl.h>
+
+#include "ctree.h"
+#include "ioctl.h"
+#include "send-utils.h"
+
+#define CLEAR(var) memset(&var, 0, sizeof(var))
+
+
+int main(int argc, char **argv) {
+	int ret, fd;
+	struct subvol_uuid_search sus;
+	struct btrfs_ioctl_received_subvol_args rs_args;
+	struct subvol_info *si;
+	char uuidbuf[37], parent_uuidbuf[37], received_uuidbuf[37];
+
+
+	if (argc != 3 && argc != 4) {
+		printf("usage: btrfs-set-received-uuid btrfs-mountpoint src-subvolume-path-relative-to-mountpoint [dest-absolute-subvolume-path]\n");
+		exit(1);
+	}
+
+	printf("opening srcmnt %s\n", argv[1]);
+	fd = open(argv[1], O_RDONLY | O_NOATIME);
+	if (fd < 0) {
+		printf("failed to open srcmnt %s! %s\n", argv[1], strerror(errno));
+		exit(2);
+	}
+
+	puts("initializing sub search");
+	CLEAR(sus);
+	ret = subvol_uuid_search_init(fd, &sus);
+	if (ret < 0) {
+		printf("failed to initialize sub search! %s\n", strerror(-ret));
+		exit(3);
+	}
+	
+	printf("searching srcsub %s\n", argv[2]);
+	si = subvol_uuid_search(&sus, 0, NULL, 0, argv[2], subvol_search_by_path);
+	if (!si) {
+		puts("srcsub not found!");
+		exit(4);
+	}
+
+	uuid_unparse(si->uuid,                   uuidbuf);
+	uuid_unparse(si->parent_uuid,     parent_uuidbuf);
+	uuid_unparse(si->received_uuid, received_uuidbuf);
+
+	printf("\nsrcsub found:\n"
+	       "         uuid=%s\n"
+	       "  parent_uuid=%s\n"
+	       "received_uuid=%s\n"
+	       "ctransid=%Lu otransid=%Lu stransid=%Lu rtransid=%Lu\n\n",
+	       uuidbuf, parent_uuidbuf, received_uuidbuf,
+	       (unsigned long long)(si->ctransid),
+	       (unsigned long long)(si->otransid),
+	       (unsigned long long)(si->stransid),
+	       (unsigned long long)(si->rtransid));
+
+	if (argc == 3)
+		goto done;
+
+	printf("opening dst subvol %s\n", argv[3]);
+	fd = open(argv[3], O_RDONLY | O_NOATIME);
+	if (fd < 0) {
+		printf("failed to open dst subvol %s. %s\n", argv[3], strerror(errno));
+		exit(5);
+	}
+
+	printf("\nhere we go with BTRFS_IOC_SET_RECEIVED_SUBVOL:\n"
+	       "dstsub.received_uuid = srcsub.uuid == %s\n"
+	       "dstsub.stransid = srcsub.ctransid == %Lu\n\n",
+	       uuidbuf, (unsigned long long)(si->ctransid));
+
+	CLEAR(rs_args);
+	memcpy(rs_args.uuid, si->uuid, BTRFS_UUID_SIZE);
+	rs_args.stransid = si->ctransid;
+
+	ret = ioctl(fd, BTRFS_IOC_SET_RECEIVED_SUBVOL, &rs_args);
+	if (ret < 0) {
+		printf("BTRFS_IOC_SET_RECEIVED_SUBVOL failed: %s", strerror(-ret));
+		exit(6);
+	}
+
+done:
+	printf("done.\n");
+	exit(0);
+}

pkgs/tools/filesystems/btrfsprogs/default.nix

@@ -20,6 +20,18 @@ stdenv.mkDerivation {
 
   buildInputs = [ zlib libuuid acl attr e2fsprogs ];
 
+  postPatch = ''
+    cp ${./btrfs-set-received-uuid.c} btrfs-set-received-uuid.c
+  '';
+
+  postBuild = ''
+    gcc -O2 -luuid -o btrfs-set-received-uuid send-utils.o rbtree.o btrfs-list.o btrfs-set-received-uuid.c
+  '';
+
+  postInstall = ''
+    cp btrfs-set-received-uuid $out/bin
+  '';
+
   makeFlags = "prefix=$(out)";
 
   meta = {