btrfs-progs/cmds-send.c

/*
 * Copyright (C) 2012 Alexander Block.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#define _GNU_SOURCE

#include "kerncompat.h"

#include <unistd.h>
#include <stdint.h>
#include <dirent.h>
#include <fcntl.h>
#include <pthread.h>
#include <math.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <libgen.h>
#include <mntent.h>

#include <uuid/uuid.h>

#include "ctree.h"
#include "ioctl.h"
#include "commands.h"
#include "list.h"

#include "send.h"
#include "send-utils.h"

static int g_verbose = 0;

struct btrfs_send {
	int send_fd;
	int dump_fd;
	int mnt_fd;

	u64 *clone_sources;
	u64 clone_sources_count;

	char *root_path;
	struct subvol_uuid_search sus;
};

int find_mount_root(const char *path, char **mount_root)
{
	FILE *mnttab;
	int fd;
	struct mntent *ent;
	int len;
	int longest_matchlen = 0;
	char *longest_match = NULL;

	fd = open(path, O_RDONLY | O_NOATIME);
	if (fd < 0)
		return -errno;
	close(fd);

	mnttab = fopen("/etc/mtab", "r");
	while ((ent = getmntent(mnttab))) {
		len = strlen(ent->mnt_dir);
		if (strncmp(ent->mnt_dir, path, len) == 0) {
			/* match found */
			if (longest_matchlen < len) {
				free(longest_match);
				longest_matchlen = len;
				longest_match = strdup(ent->mnt_dir);
			}
		}
	}

	*mount_root = realpath(longest_match, NULL);
	free(longest_match);

	return 0;
}

static int get_root_id(struct btrfs_send *s, const char *path, u64 *root_id)
{
	struct subvol_info *si;

	si = subvol_uuid_search(&s->sus, 0, NULL, 0, path,
			subvol_search_by_path);
	if (!si)
		return -ENOENT;
	*root_id = si->root_id;
	return 0;
}

static struct subvol_info *get_parent(struct btrfs_send *s, u64 root_id)
{
	struct subvol_info *si;

	si = subvol_uuid_search(&s->sus, root_id, NULL, 0, NULL,
			subvol_search_by_root_id);
	if (!si)
		return NULL;

	si = subvol_uuid_search(&s->sus, 0, si->parent_uuid, 0, NULL,
			subvol_search_by_uuid);
	if (!si)
		return NULL;
	return si;
}

static int find_good_parent(struct btrfs_send *s, u64 root_id, u64 *found)
{
	int ret;
	struct subvol_info *parent;
	struct subvol_info *parent2;
	struct subvol_info *best_parent = NULL;
	__s64 tmp;
	u64 best_diff = (u64)-1;
	int i;

	parent = get_parent(s, root_id);
	if (!parent) {
		ret = -ENOENT;
		goto out;
	}

	for (i = 0; i < s->clone_sources_count; i++) {
		if (s->clone_sources[i] == parent->root_id) {
			best_parent = parent;
			goto out_found;
		}
	}

	for (i = 0; i < s->clone_sources_count; i++) {
		parent2 = get_parent(s, s->clone_sources[i]);
		if (parent2 != parent)
			continue;

		parent2 = subvol_uuid_search(&s->sus, s->clone_sources[i], NULL,
				0, NULL, subvol_search_by_root_id);

		tmp = parent2->ctransid - parent->ctransid;
		if (tmp < 0)
			tmp *= -1;
		if (tmp < best_diff) {
			best_parent = parent;
			best_diff = tmp;
		}
	}

	if (!best_parent) {
		ret = -ENOENT;
		goto out;
	}

out_found:
	*found = best_parent->root_id;
	ret = 0;

out:
	return ret;
}

static void add_clone_source(struct btrfs_send *s, u64 root_id)
{
	s->clone_sources = realloc(s->clone_sources,
		sizeof(*s->clone_sources) * (s->clone_sources_count + 1));
	s->clone_sources[s->clone_sources_count++] = root_id;
}

static int write_buf(int fd, const void *buf, int size)
{
	int ret;
	int pos = 0;

	while (pos < size) {
		ret = write(fd, (char*)buf + pos, size - pos);
		if (ret < 0) {
			ret = -errno;
			fprintf(stderr, "ERROR: failed to dump stream. %s",
					strerror(-ret));
			goto out;
		}
		if (!ret) {
			ret = -EIO;
			fprintf(stderr, "ERROR: failed to dump stream. %s",
					strerror(-ret));
			goto out;
		}
		pos += ret;
	}
	ret = 0;

out:
	return ret;
}

static void *dump_thread(void *arg_)
{
	int ret;
	struct btrfs_send *s = (struct btrfs_send*)arg_;
	char buf[4096];
	int readed;

	while (1) {
		readed = read(s->send_fd, buf, sizeof(buf));
		if (readed < 0) {
			ret = -errno;
			fprintf(stderr, "ERROR: failed to read stream from "
					"kernel. %s\n", strerror(-ret));
			goto out;
		}
		if (!readed) {
			ret = 0;
			goto out;
		}
		ret = write_buf(s->dump_fd, buf, readed);
		if (ret < 0)
			goto out;
	}

out:
	if (ret < 0) {
		exit(-ret);
	}

	return ERR_PTR(ret);
}

static int do_send(struct btrfs_send *send, u64 root_id, u64 parent_root_id)
{
	int ret;
	pthread_t t_read;
	pthread_attr_t t_attr;
	struct btrfs_ioctl_send_args io_send;
	struct subvol_info *si;
	void *t_err = NULL;
	int subvol_fd = -1;
	int pipefd[2];

	si = subvol_uuid_search(&send->sus, root_id, NULL, 0, NULL,
			subvol_search_by_root_id);
	if (!si) {
		ret = -ENOENT;
		fprintf(stderr, "ERROR: could not find subvol info for %llu",
				root_id);
		goto out;
	}

	subvol_fd = openat(send->mnt_fd, si->path, O_RDONLY | O_NOATIME);
	if (subvol_fd < 0) {
		ret = -errno;
		fprintf(stderr, "ERROR: open %s failed. %s\n", si->path,
				strerror(-ret));
		goto out;
	}

	ret = pthread_attr_init(&t_attr);

	ret = pipe(pipefd);
	if (ret < 0) {
		ret = -errno;
		fprintf(stderr, "ERROR: pipe failed. %s\n", strerror(-ret));
		goto out;
	}

	memset(&io_send, 0, sizeof(io_send));
	io_send.send_fd = pipefd[1];
	send->send_fd = pipefd[0];

	if (!ret)
		ret = pthread_create(&t_read, &t_attr, dump_thread,
					send);
	if (ret) {
		ret = -ret;
		fprintf(stderr, "ERROR: thread setup failed: %s\n",
			strerror(-ret));
		goto out;
	}

	io_send.clone_sources = (__u64*)send->clone_sources;
	io_send.clone_sources_count = send->clone_sources_count;
	io_send.parent_root = parent_root_id;
	ret = ioctl(subvol_fd, BTRFS_IOC_SEND, &io_send);
	if (ret) {
		ret = -errno;
		fprintf(stderr, "ERROR: send ioctl failed with %d: %s\n", ret,
			strerror(-ret));
		goto out;
	}
	if (g_verbose > 0)
		fprintf(stderr, "BTRFS_IOC_SEND returned %d\n", ret);

	if (g_verbose > 0)
		fprintf(stderr, "joining genl thread\n");

	close(pipefd[1]);
	pipefd[1] = 0;

	ret = pthread_join(t_read, &t_err);
	if (ret) {
		ret = -ret;
		fprintf(stderr, "ERROR: pthread_join failed: %s\n",
			strerror(-ret));
		goto out;
	}
	if (t_err) {
		ret = (long int)t_err;
		fprintf(stderr, "ERROR: failed to process send stream, ret=%ld "
			"(%s)\n", (long int)t_err, strerror(-ret));
		goto out;
	}

	pthread_attr_destroy(&t_attr);

	ret = 0;

out:
	if (subvol_fd != -1)
		close(subvol_fd);
	if (pipefd[0])
		close(pipefd[0]);
	if (pipefd[1])
		close(pipefd[1]);
	return ret;
}

static const char *get_subvol_name(struct btrfs_send *s, const char *full_path)
{
	int len = strlen(s->root_path);
	if (!len)
		return full_path;
	if (s->root_path[len - 1] != '/')
		len += 1;

	return full_path + len;
}

static int init_root_path(struct btrfs_send *s, const char *subvol)
{
	int ret = 0;

	if (s->root_path)
		goto out;

	ret = find_mount_root(subvol, &s->root_path);
	if (ret < 0) {
		ret = -EINVAL;
		fprintf(stderr, "ERROR: failed to determine mount point "
				"for %s\n", subvol);
		goto out;
	}

	s->mnt_fd = open(s->root_path, O_RDONLY | O_NOATIME);
	if (s->mnt_fd < 0) {
		ret = -errno;
		fprintf(stderr, "ERROR: can't open '%s': %s\n", s->root_path,
			strerror(-ret));
		goto out;
	}

	ret = subvol_uuid_search_init(s->mnt_fd, &s->sus);
	if (ret < 0) {
		fprintf(stderr, "ERROR: failed to initialize subvol search. "
				"%s\n", strerror(-ret));
		goto out;
	}

out:
	return ret;

}

static int is_subvol_ro(struct btrfs_send *s, char *subvol)
{
	int ret;
	u64 flags;
	int fd = -1;

	fd = openat(s->mnt_fd, subvol, O_RDONLY | O_NOATIME);
	if (fd < 0) {
		ret = -errno;
		fprintf(stderr, "ERROR: failed to open %s. %s\n",
				subvol, strerror(-ret));
		goto out;
	}

	ret = ioctl(fd, BTRFS_IOC_SUBVOL_GETFLAGS, &flags);
	if (ret < 0) {
		ret = -errno;
		fprintf(stderr, "ERROR: failed to get flags for subvolume. "
				"%s\n", strerror(-ret));
		goto out;
	}

	if (flags & BTRFS_SUBVOL_RDONLY)
		ret = 1;
	else
		ret = 0;

out:
	if (fd != -1)
		close(fd);

	return ret;
}

int cmd_send_start(int argc, char **argv)
{
	char *subvol = NULL;
	int c;
	int ret;
	char *outname = NULL;
	struct btrfs_send send;
	u32 i;
	char *mount_root = NULL;
	char *snapshot_parent = NULL;
	u64 root_id;
	u64 parent_root_id = 0;
	int full_send = 1;

	memset(&send, 0, sizeof(send));
	send.dump_fd = fileno(stdout);

	if (isatty(send.dump_fd)) {
		fprintf(stderr, "ERROR: not dumping send stream into a terminal, redirect it into a file\n");
		return 1;
	}

	while ((c = getopt(argc, argv, "vc:f:i:p:")) != -1) {
		switch (c) {
		case 'v':
			g_verbose++;
			break;
		case 'c':
			subvol = realpath(optarg, NULL);
			if (!subvol) {
				ret = -errno;
				fprintf(stderr, "ERROR: realpath %s failed. "
						"%s\n", optarg, strerror(-ret));
				goto out;
			}

			ret = init_root_path(&send, subvol);
			if (ret < 0)
				goto out;

			ret = get_root_id(&send, get_subvol_name(&send, subvol),
					&root_id);
			if (ret < 0) {
				fprintf(stderr, "ERROR: could not resolve "
						"root_id for %s\n", subvol);
				goto out;
			}
			add_clone_source(&send, root_id);
			free(subvol);
			full_send = 0;
			break;
		case 'f':
			outname = optarg;
			break;
		case 'p':
			if (snapshot_parent) {
				fprintf(stderr, "ERROR: you cannot have more than one parent (-p)\n");
				return 1;
			}
			snapshot_parent = realpath(optarg, NULL);
			if (!snapshot_parent) {
				ret = -errno;
				fprintf(stderr, "ERROR: realpath %s failed. "
						"%s\n", optarg, strerror(-ret));
				goto out;
			}
			full_send = 0;
			break;
		case 'i':
			fprintf(stderr,
				"ERROR: -i was removed, use -c instead\n");
			return 1;
		case '?':
		default:
			fprintf(stderr, "ERROR: send args invalid.\n");
			return 1;
		}
	}

	if (optind == argc) {
		fprintf(stderr, "ERROR: send needs path to snapshot\n");
		return 1;
	}

	if (outname != NULL) {
		send.dump_fd = creat(outname, 0600);
		if (send.dump_fd == -1) {
			ret = -errno;
			fprintf(stderr, "ERROR: can't create '%s': %s\n",
					outname, strerror(-ret));
			goto out;
		}
	}

	/* use first send subvol to determine mount_root */
	subvol = argv[optind];

	subvol = realpath(argv[optind], NULL);
	if (!subvol) {
		ret = -errno;
		fprintf(stderr, "ERROR: unable to resolve %s\n", argv[optind]);
		goto out;
	}

	ret = init_root_path(&send, subvol);
	if (ret < 0)
		goto out;

	if (snapshot_parent != NULL) {
		ret = get_root_id(&send,
				get_subvol_name(&send, snapshot_parent),
				&parent_root_id);
		if (ret < 0) {
			fprintf(stderr, "ERROR: could not resolve root_id "
					"for %s\n", snapshot_parent);
			goto out;
		}

		add_clone_source(&send, parent_root_id);
	}

	for (i = optind; i < argc; i++) {
		subvol = realpath(argv[i], NULL);
		if (!subvol) {
			ret = -errno;
			fprintf(stderr, "ERROR: unable to resolve %s\n", argv[i]);
			goto out;
		}

		ret = find_mount_root(subvol, &mount_root);
		if (ret < 0) {
			fprintf(stderr, "ERROR: find_mount_root failed on %s: "
					"%s\n", subvol,
				strerror(-ret));
			goto out;
		}
		if (strcmp(send.root_path, mount_root) != 0) {
			ret = -EINVAL;
			fprintf(stderr, "ERROR: all subvols must be from the "
					"same fs.\n");
			goto out;
		}
		free(mount_root);

		ret = is_subvol_ro(&send, subvol);
		if (ret < 0)
			goto out;
		if (!ret) {
			ret = -EINVAL;
			fprintf(stderr, "ERROR: %s is not read-only.\n",
					subvol);
			goto out;
		}
		free(subvol);
	}

	for (i = optind; i < argc; i++) {
		subvol = argv[i];

		fprintf(stderr, "At subvol %s\n", subvol);

		subvol = realpath(subvol, NULL);
		if (!subvol) {
			ret = -errno;
			fprintf(stderr, "ERROR: realpath %s failed. "
					"%s\n", argv[i], strerror(-ret));
			goto out;
		}

		ret = get_root_id(&send, get_subvol_name(&send, subvol),
				&root_id);
		if (ret < 0) {
			fprintf(stderr, "ERROR: could not resolve root_id "
					"for %s\n", subvol);
			goto out;
		}

		if (!full_send && !parent_root_id) {
			ret = find_good_parent(&send, root_id, &parent_root_id);
			if (ret < 0) {
				fprintf(stderr, "ERROR: parent determination failed for %lld\n",
					root_id);
				goto out;
			}
		}

		ret = is_subvol_ro(&send, subvol);
		if (ret < 0)
			goto out;
		if (!ret) {
			ret = -EINVAL;
			fprintf(stderr, "ERROR: %s is not read-only.\n",
					subvol);
			goto out;
		}

		ret = do_send(&send, root_id, parent_root_id);
		if (ret < 0)
			goto out;

		/* done with this subvol, so add it to the clone sources */
		add_clone_source(&send, root_id);

		parent_root_id = 0;
		full_send = 0;
		free(subvol);
	}

	ret = 0;

out:
	if (send.mnt_fd >= 0)
		close(send.mnt_fd);
	return ret;
}

static const char * const send_cmd_group_usage[] = {
	"btrfs send <command> <args>",
	NULL
};

static const char * const cmd_send_usage[] = {
	"btrfs send [-v] [-p <parent>] [-c <clone-src>] <subvol>",
	"Send the subvolume to stdout.",
	"Sends the subvolume specified by <subvol> to stdout.",
	"By default, this will send the whole subvolume. To do an incremental",
	"send, use '-p <parent>'. If you want to allow btrfs to clone from",
	"any additional local snapshots, use -c <clone-src> (multiple times",
	"where applicable). You must not specify clone sources unless you",
	"guarantee that these snapshots are exactly in the same state on both",
	"sides, the sender and the receiver. It is allowed to omit the",
	"'-p <parent>' option when '-c <clone-src>' options are given, in",
	"which case 'btrfs send' will determine a suitable parent among the",
	"clone sources itself.",
	"\n",
	"-v               Enable verbose debug output. Each occurrency of",
	"                 this option increases the verbose level more.",
	"-p <parent>      Send an incremental stream from <parent> to",
	"                 <subvol>.",
	"-c <clone-src>   Use this snapshot as a clone source for an ",
	"                 incremental send (multiple allowed)",
	"-f <outfile>     Output is normally written to stdout. To write to",
	"                 a file, use this option. An alternative would be to",
	"                 use pipes.",
	NULL
};

const struct cmd_group send_cmd_group = {
	send_cmd_group_usage, NULL, {
		{ "send", cmd_send_start, cmd_send_usage, NULL, 0 },
		{ 0, 0, 0, 0, 0 },
        },
};

int cmd_send(int argc, char **argv)
{
	return cmd_send_start(argc, argv);
}