btrfs-progs: scrub userland implementation

Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
Signed-off-by: Hugo Mills <hugo@carfax.org.uk>

1 files changed, 1666 insertions, 0 deletions

diff --git a/scrub.c b/scrub.c
new file mode 100644
index 00000000..9dca5f62
--- /dev/null
+++ b/scrub.c
@@ -0,0 +1,1666 @@
+/*
+ * Copyright (C) 2011 STRATO.  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.
+ */
+
+#include <sys/ioctl.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <poll.h>
+#include <sys/file.h>
+#include <uuid/uuid.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <ctype.h>
+#include <signal.h>
+#include <stdarg.h>
+
+#include "ctree.h"
+#include "ioctl.h"
+#include "btrfs_cmds.h"
+#include "utils.h"
+#include "volumes.h"
+#include "disk-io.h"
+
+#define SCRUB_DATA_FILE "/var/lib/btrfs/scrub.status"
+#define SCRUB_PROGRESS_SOCKET_PATH "/var/lib/btrfs/scrub.progress"
+#define SCRUB_FILE_VERSION_PREFIX "scrub status"
+#define SCRUB_FILE_VERSION "1"
+
+struct scrub_stats {
+	time_t t_start;
+	time_t t_resumed;
+	u64 duration;
+	u64 finished;
+	u64 canceled;
+};
+
+struct scrub_progress {
+	struct btrfs_ioctl_scrub_args scrub_args;
+	int fd;
+	int ret;
+	int skip;
+	struct scrub_stats stats;
+	struct scrub_file_record *resumed;
+	int ioctl_errno;
+	pthread_mutex_t progress_mutex;
+};
+
+struct scrub_file_record {
+	u8 fsid[BTRFS_FSID_SIZE];
+	u64 devid;
+	struct scrub_stats stats;
+	struct btrfs_scrub_progress p;
+};
+
+struct scrub_progress_cycle {
+	int fdmnt;
+	int prg_fd;
+	int do_record;
+	struct btrfs_ioctl_fs_info_args *fi;
+	struct scrub_progress *progress;
+	struct scrub_progress *shared_progress;
+	pthread_mutex_t *write_mutex;
+};
+
+struct scrub_fs_stat {
+	struct btrfs_scrub_progress p;
+	struct scrub_stats s;
+	int i;
+};
+
+static void print_scrub_full(struct btrfs_scrub_progress *sp)
+{
+	printf("\tdata_extents_scrubbed: %lld\n", sp->data_extents_scrubbed);
+	printf("\ttree_extents_scrubbed: %lld\n", sp->tree_extents_scrubbed);
+	printf("\tdata_bytes_scrubbed: %lld\n", sp->data_bytes_scrubbed);
+	printf("\ttree_bytes_scrubbed: %lld\n", sp->tree_bytes_scrubbed);
+	printf("\tread_errors: %lld\n", sp->read_errors);
+	printf("\tcsum_errors: %lld\n", sp->csum_errors);
+	printf("\tverify_errors: %lld\n", sp->verify_errors);
+	printf("\tno_csum: %lld\n", sp->no_csum);
+	printf("\tcsum_discards: %lld\n", sp->csum_discards);
+	printf("\tsuper_errors: %lld\n", sp->super_errors);
+	printf("\tmalloc_errors: %lld\n", sp->malloc_errors);
+	printf("\tuncorrectable_errors: %lld\n", sp->uncorrectable_errors);
+	printf("\tunverified_errors: %lld\n", sp->unverified_errors);
+	printf("\tcorrected_errors: %lld\n", sp->corrected_errors);
+	printf("\tlast_physical: %lld\n", sp->last_physical);
+}
+
+#define ERR(test, ...) do {			\
+	if (test)				\
+		fprintf(stderr, __VA_ARGS__);	\
+} while (0)
+
+#define PRINT_SCRUB_ERROR(test, desc) do {	\
+	if (test)				\
+		printf(" %s=%llu", desc, test);	\
+} while (0)
+
+static void print_scrub_summary(struct btrfs_scrub_progress *p)
+{
+	u64 err_cnt;
+	u64 err_cnt2;
+	char *bytes;
+
+	err_cnt = p->read_errors +
+			p->csum_errors +
+			p->verify_errors +
+			p->super_errors;
+
+	err_cnt2 = p->corrected_errors + p->uncorrectable_errors;
+
+	if (p->malloc_errors)
+		printf("*** WARNING: memory allocation failed while scrubbing. "
+		       "results may be inaccurate\n");
+	bytes = pretty_sizes(p->data_bytes_scrubbed + p->tree_bytes_scrubbed);
+	printf("\ttotal bytes scrubbed: %s with %llu errors\n", bytes,
+		max(err_cnt, err_cnt2));
+	free(bytes);
+	if (err_cnt || err_cnt2) {
+		printf("\terror details:");
+		PRINT_SCRUB_ERROR(p->read_errors, "read");
+		PRINT_SCRUB_ERROR(p->super_errors, "super");
+		PRINT_SCRUB_ERROR(p->verify_errors, "verify");
+		PRINT_SCRUB_ERROR(p->csum_errors, "csum");
+		printf("\n");
+		printf("\tcorrected errors: %llu, uncorrectable errors: %llu, "
+			"unverified errors: %llu\n", p->corrected_errors,
+			p->uncorrectable_errors, p->unverified_errors);
+	}
+}
+
+#define _SCRUB_FS_STAT(p, name, fs_stat) do {	\
+	fs_stat->p.name += p->name;		\
+} while (0)
+
+#define _SCRUB_FS_STAT_MIN(ss, name, fs_stat)	\
+do {						\
+	if (fs_stat->s.name > ss->name) {	\
+		fs_stat->s.name = ss->name;	\
+	}					\
+} while (0)
+
+#define _SCRUB_FS_STAT_ZMIN(ss, name, fs_stat)			\
+do {								\
+	if (!fs_stat->s.name || fs_stat->s.name > ss->name) {	\
+		fs_stat->s.name = ss->name;			\
+	}							\
+} while (0)
+
+#define _SCRUB_FS_STAT_ZMAX(ss, name, fs_stat)				\
+do {									\
+	if (!(fs_stat)->s.name || (fs_stat)->s.name < (ss)->name) {	\
+		(fs_stat)->s.name = (ss)->name;				\
+	}								\
+} while (0)
+
+static void add_to_fs_stat(struct btrfs_scrub_progress *p,
+				struct scrub_stats *ss,
+				struct scrub_fs_stat *fs_stat)
+{
+	_SCRUB_FS_STAT(p, data_extents_scrubbed, fs_stat);
+	_SCRUB_FS_STAT(p, tree_extents_scrubbed, fs_stat);
+	_SCRUB_FS_STAT(p, data_bytes_scrubbed, fs_stat);
+	_SCRUB_FS_STAT(p, tree_bytes_scrubbed, fs_stat);
+	_SCRUB_FS_STAT(p, read_errors, fs_stat);
+	_SCRUB_FS_STAT(p, csum_errors, fs_stat);
+	_SCRUB_FS_STAT(p, verify_errors, fs_stat);
+	_SCRUB_FS_STAT(p, no_csum, fs_stat);
+	_SCRUB_FS_STAT(p, csum_discards, fs_stat);
+	_SCRUB_FS_STAT(p, super_errors, fs_stat);
+	_SCRUB_FS_STAT(p, malloc_errors, fs_stat);
+	_SCRUB_FS_STAT(p, uncorrectable_errors, fs_stat);
+	_SCRUB_FS_STAT(p, corrected_errors, fs_stat);
+	_SCRUB_FS_STAT(p, last_physical, fs_stat);
+	_SCRUB_FS_STAT_ZMIN(ss, t_start, fs_stat);
+	_SCRUB_FS_STAT_ZMIN(ss, t_resumed, fs_stat);
+	_SCRUB_FS_STAT_ZMAX(ss, duration, fs_stat);
+	_SCRUB_FS_STAT_ZMAX(ss, canceled, fs_stat);
+	_SCRUB_FS_STAT_MIN(ss, finished, fs_stat);
+}
+
+static void init_fs_stat(struct scrub_fs_stat *fs_stat)
+{
+	memset(fs_stat, 0, sizeof(*fs_stat));
+	fs_stat->s.finished = 1;
+}
+
+static void _print_scrub_ss(struct scrub_stats *ss)
+{
+	char t[4096];
+	struct tm tm;
+
+	if (!ss || !ss->t_start) {
+		printf("\tno stats available\n");
+		return;
+	}
+	if (ss->t_resumed) {
+		localtime_r(&ss->t_resumed, &tm);
+		strftime(t, sizeof(t), "%c", &tm);
+		t[sizeof(t) - 1] = '\0';
+		printf("\tscrub resumed at %s", t);
+	} else {
+		localtime_r(&ss->t_start, &tm);
+		strftime(t, sizeof(t), "%c", &tm);
+		t[sizeof(t) - 1] = '\0';
+		printf("\tscrub started at %s", t);
+	}
+	if (ss->finished && !ss->canceled) {
+		printf(" and finished after %llu seconds\n",
+		       ss->duration);
+	} else if (ss->canceled) {
+		printf(" and was aborted after %llu seconds\n",
+		       ss->duration);
+	} else {
+		printf(", running for %llu seconds\n", ss->duration);
+	}
+}
+
+static void print_scrub_dev(struct btrfs_ioctl_dev_info_args *di,
+				struct btrfs_scrub_progress *p, int raw,
+				const char *append, struct scrub_stats *ss)
+{
+	printf("scrub device %s (id %llu) %s\n", di->path, di->devid,
+	       append ? append : "");
+
+	_print_scrub_ss(ss);
+
+	if (p) {
+		if (raw)
+			print_scrub_full(p);
+		else
+			print_scrub_summary(p);
+	}
+}
+
+static void print_fs_stat(struct scrub_fs_stat *fs_stat, int raw)
+{
+	_print_scrub_ss(&fs_stat->s);
+
+	if (raw)
+		print_scrub_full(&fs_stat->p);
+	else
+		print_scrub_summary(&fs_stat->p);
+}
+
+static void free_history(struct scrub_file_record **last_scrubs)
+{
+	struct scrub_file_record **l = last_scrubs;
+	if (!l)
+		return;
+	while (*l)
+		free(*l++);
+	free(last_scrubs);
+}
+
+/*
+ * cancels a running scrub and makes the master process record the current
+ * progress status before exiting.
+ */
+static int cancel_fd = -1;
+static void scrub_sigint_record_progress(int signal)
+{
+	ioctl(cancel_fd, BTRFS_IOC_SCRUB_CANCEL, NULL);
+}
+
+static int scrub_handle_sigint_parent(void)
+{
+	struct sigaction sa = {
+		.sa_handler = SIG_IGN,
+		.sa_flags = SA_RESTART,
+	};
+
+	return sigaction(SIGINT, &sa, NULL);
+}
+
+static int scrub_handle_sigint_child(int fd)
+{
+	struct sigaction sa = {
+		.sa_handler = fd == -1 ? SIG_DFL : scrub_sigint_record_progress,
+	};
+
+	cancel_fd = fd;
+	return sigaction(SIGINT, &sa, NULL);
+}
+
+static int scrub_datafile(const char *fn_base, const char *fn_local,
+				const char *fn_tmp, char *datafile, int size)
+{
+	int ret;
+	int end = size - 2;
+
+	datafile[end + 1] = '\0';
+	strncpy(datafile, fn_base, end);
+	ret = strlen(datafile);
+
+	if (ret + 1 > end)
+		return -EOVERFLOW;
+
+	datafile[ret] = '.';
+	strncpy(datafile + ret + 1, fn_local, end - ret - 1);
+	ret = strlen(datafile);
+
+	if (ret + 1 > end)
+		return -EOVERFLOW;
+
+	if (fn_tmp) {
+		datafile[ret] = '_';
+		strncpy(datafile + ret + 1, fn_tmp, end - ret - 1);
+		ret = strlen(datafile);
+
+		if (ret > end)
+			return -EOVERFLOW;
+	}
+
+	return 0;
+}
+
+static int scrub_open_file(const char *datafile, int m)
+{
+	int fd;
+	int ret;
+
+	fd = open(datafile, m, 0600);
+	if (fd < 0)
+		return -errno;
+
+	ret = flock(fd, LOCK_EX|LOCK_NB);
+	if (ret) {
+		ret = errno;
+		close(fd);
+		return -ret;
+	}
+
+	return fd;
+}
+
+static int scrub_open_file_r(const char *fn_base, const char *fn_local)
+{
+	int ret;
+	char datafile[BTRFS_PATH_NAME_MAX + 1];
+	ret = scrub_datafile(fn_base, fn_local, NULL,
+				datafile, sizeof(datafile));
+	if (ret < 0)
+		return ret;
+	return scrub_open_file(datafile, O_RDONLY);
+}
+
+static int scrub_open_file_w(const char *fn_base, const char *fn_local,
+				const char *tmp)
+{
+	int ret;
+	char datafile[BTRFS_PATH_NAME_MAX + 1];
+	ret = scrub_datafile(fn_base, fn_local, tmp,
+				datafile, sizeof(datafile));
+	if (ret < 0)
+		return ret;
+	return scrub_open_file(datafile, O_WRONLY|O_CREAT);
+}
+
+static int scrub_rename_file(const char *fn_base, const char *fn_local,
+				const char *tmp)
+{
+	int ret;
+	char datafile_old[BTRFS_PATH_NAME_MAX + 1];
+	char datafile_new[BTRFS_PATH_NAME_MAX + 1];
+	ret = scrub_datafile(fn_base, fn_local, tmp,
+				datafile_old, sizeof(datafile_old));
+	if (ret < 0)
+		return ret;
+	ret = scrub_datafile(fn_base, fn_local, NULL,
+				datafile_new, sizeof(datafile_new));
+	if (ret < 0)
+		return ret;
+	ret = rename(datafile_old, datafile_new);
+	return ret ? -errno : 0;
+}
+
+#define _SCRUB_KVREAD(ret, i, name, avail, l, dest) if (ret == 0) {	  \
+	ret = scrub_kvread(i, sizeof(#name), avail, l, #name, dest.name); \
+}
+
+/*
+ * returns 0 if the key did not match (nothing was read)
+ *         1 if the key did match (success)
+ *        -1 if the key did match and an error occured
+ */
+static int scrub_kvread(int *i, int len, int avail, const char *buf,
+			const char *key, u64 *dest)
+{
+	int j;
+
+	if (*i + len + 1 < avail && strncmp(&buf[*i], key, len - 1) == 0) {
+		*i += len - 1;
+		if (buf[*i] != ':')
+			return -1;
+		*i += 1;
+		for (j = 0; isdigit(buf[*i + j]) && *i + j < avail; ++j)
+			;
+		if (*i + j >= avail)
+			return -1;
+		*dest = atoll(&buf[*i]);
+		*i += j;
+		return 1;
+	}
+
+	return 0;
+}
+
+#define _SCRUB_INVALID do {						\
+	if (report_errors)						\
+		fprintf(stderr, "WARNING: invalid data in line %d pos "	\
+			"%d state %d (near \"%.*s\") at %s:%d\n",	\
+			lineno, i, state, 20 > avail ? avail : 20,	\
+			l + i,	__FILE__, __LINE__);			\
+	goto skip;							\
+} while (0)
+
+static struct scrub_file_record **scrub_read_file(int fd, int report_errors)
+{
+	int avail = 0;
+	int old_avail = 0;
+	char l[16 * 1024];
+	int state = 0;
+	int curr = -1;
+	int i = 0;
+	int j;
+	int ret;
+	int eof = 0;
+	int lineno = 0;
+	u64 version;
+	char empty_uuid[BTRFS_FSID_SIZE] = {0};
+	struct scrub_file_record **p = NULL;
+
+	if (fd < 0)
+		return ERR_PTR(-EINVAL);
+
+again:
+	old_avail = avail - i;
+	BUG_ON(old_avail < 0);
+	if (old_avail)
+		memmove(l, l + i, old_avail);
+	avail = read(fd, l + old_avail, sizeof(l) - old_avail);
+	if (avail == 0)
+		eof = 1;
+	if (avail == 0 && old_avail == 0) {
+		if (curr >= 0 &&
+		    memcmp(p[curr]->fsid, empty_uuid, BTRFS_FSID_SIZE) == 0) {
+			p[curr] = NULL;
+		} else if (curr == -1) {
+			p = ERR_PTR(-ENODATA);
+		}
+		return p;
+	}
+	if (avail == -1)
+		return ERR_PTR(-errno);
+	avail += old_avail;
+
+	i = 0;
+	while (i < avail) {
+		switch (state) {
+		case 0: /* start of file */
+			ret = scrub_kvread(&i,
+				sizeof(SCRUB_FILE_VERSION_PREFIX), avail, l,
+				SCRUB_FILE_VERSION_PREFIX, &version);
+			if (ret != 1)
+				_SCRUB_INVALID;
+			if (version != atoll(SCRUB_FILE_VERSION))
+				return ERR_PTR(-ENOTSUP);
+			state = 6;
+			continue;
+		case 1: /* start of line, alloc */
+			/*
+			 * this state makes sure we have a complete line in
+			 * further processing, so we don't need wrap-tracking
+			 * everywhere.
+			 */
+			if (!eof && !memchr(l + i, '\n', avail - i))
+				goto again;
+			++lineno;
+			if (curr > -1 && memcmp(p[curr]->fsid, empty_uuid,
+						BTRFS_FSID_SIZE) == 0) {
+				state = 2;
+				continue;
+			}
+			++curr;
+			p = realloc(p, (curr + 2) * sizeof(*p));
+			if (p)
+				p[curr] = malloc(sizeof(**p));
+			if (!p || !p[curr])
+				return ERR_PTR(-errno);
+			memset(p[curr], 0, sizeof(**p));
+			p[curr + 1] = NULL;
+			++state;
+			/* fall through */
+		case 2: /* start of line, skip space */
+			while (isspace(l[i]) && i < avail) {
+				if (l[i] == '\n')
+					++lineno;
+				++i;
+			}
+			if (i >= avail ||
+			    (!eof && !memchr(l + i, '\n', avail - i)))
+				goto again;
+			++state;
+			/* fall through */
+		case 3: /* read fsid */
+			if (i == avail)
+				continue;
+			for (j = 0; l[i + j] != ':' && i + j < avail; ++j)
+				;
+			if (i + j + 1 >= avail)
+				_SCRUB_INVALID;
+			if (j != 36)
+				_SCRUB_INVALID;
+			l[i + j] = '\0';
+			ret = uuid_parse(l + i, p[curr]->fsid);
+			if (ret)
+				_SCRUB_INVALID;
+			i += j + 1;
+			++state;
+			/* fall through */
+		case 4: /* read dev id */
+			for (j = 0; isdigit(l[i + j]) && i+j < avail; ++j)
+				;
+			if (j == 0 || i + j + 1 >= avail)
+				_SCRUB_INVALID;
+			p[curr]->devid = atoll(&l[i]);
+			i += j + 1;
+			++state;
+			/* fall through */
+		case 5: /* read key/value pair */
+			ret = 0;
+			_SCRUB_KVREAD(ret, &i, data_extents_scrubbed, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, data_extents_scrubbed, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, tree_extents_scrubbed, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, data_bytes_scrubbed, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, tree_bytes_scrubbed, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, read_errors, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, csum_errors, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, verify_errors, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, no_csum, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, csum_discards, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, super_errors, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, malloc_errors, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, uncorrectable_errors, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, corrected_errors, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, last_physical, avail, l,
+					&p[curr]->p);
+			_SCRUB_KVREAD(ret, &i, finished, avail, l,
+					&p[curr]->stats);
+			_SCRUB_KVREAD(ret, &i, t_start, avail, l,
+					(u64 *)&p[curr]->stats);
+			_SCRUB_KVREAD(ret, &i, t_resumed, avail, l,
+					(u64 *)&p[curr]->stats);
+			_SCRUB_KVREAD(ret, &i, duration, avail, l,
+					(u64 *)&p[curr]->stats);
+			_SCRUB_KVREAD(ret, &i, canceled, avail, l,
+					&p[curr]->stats);
+			if (ret != 1)
+				_SCRUB_INVALID;
+			++state;
+			/* fall through */
+		case 6: /* after number */
+			if (l[i] == '|')
+				state = 5;
+			else if (l[i] == '\n')
+				state = 1;
+			else
+				_SCRUB_INVALID;
+			++i;
+			continue;
+		case 99: /* skip rest of line */
+skip:
+			state = 99;
+			do {
+				++i;
+				if (l[i - 1] == '\n') {
+					state = 1;
+					break;
+				}
+			} while (i < avail);
+			continue;
+		}
+		BUG();
+	}
+	goto again;
+}
+
+static int scrub_write_buf(int fd, const void *data, int len)
+{
+	int ret;
+	ret = write(fd, data, len);
+	return ret - len;
+}
+
+static int scrub_writev(int fd, char *buf, int max, const char *fmt, ...)
+				__attribute__ ((format (printf, 4, 5)));
+static int scrub_writev(int fd, char *buf, int max, const char *fmt, ...)
+{
+	int ret;
+	va_list args;
+
+	va_start(args, fmt);
+	ret = vsnprintf(buf, max, fmt, args);
+	va_end(args);
+	if (ret >= max)
+		return ret - max;
+	return scrub_write_buf(fd, buf, ret);
+}
+
+#define _SCRUB_SUM(dest, data, name) dest->scrub_args.progress.name =	\
+			data->resumed->p.name + data->scrub_args.progress.name
+
+static struct scrub_progress *scrub_resumed_stats(struct scrub_progress *data,
+						  struct scrub_progress *dest)
+{
+	if (!data->resumed || data->skip)
+		return data;
+
+	_SCRUB_SUM(dest, data, data_extents_scrubbed);
+	_SCRUB_SUM(dest, data, tree_extents_scrubbed);
+	_SCRUB_SUM(dest, data, data_bytes_scrubbed);
+	_SCRUB_SUM(dest, data, tree_bytes_scrubbed);
+	_SCRUB_SUM(dest, data, read_errors);
+	_SCRUB_SUM(dest, data, csum_errors);
+	_SCRUB_SUM(dest, data, verify_errors);
+	_SCRUB_SUM(dest, data, no_csum);
+	_SCRUB_SUM(dest, data, csum_discards);
+	_SCRUB_SUM(dest, data, super_errors);
+	_SCRUB_SUM(dest, data, malloc_errors);
+	_SCRUB_SUM(dest, data, uncorrectable_errors);
+	_SCRUB_SUM(dest, data, corrected_errors);
+	_SCRUB_SUM(dest, data, last_physical);
+	dest->stats.canceled = data->stats.canceled;
+	dest->stats.finished = data->stats.finished;
+	dest->stats.t_resumed = data->stats.t_start;
+	dest->stats.t_start = data->resumed->stats.t_start;
+	dest->stats.duration = data->resumed->stats.duration +
+							data->stats.duration;
+	dest->scrub_args.devid = data->scrub_args.devid;
+	return dest;
+}
+
+#define _SCRUB_KVWRITE(fd, buf, name, use)		\
+	scrub_kvwrite(fd, buf, sizeof(buf), #name,	\
+			use->scrub_args.progress.name)
+
+#define _SCRUB_KVWRITE_STATS(fd, buf, name, use)	\
+	scrub_kvwrite(fd, buf, sizeof(buf), #name,	\
+			use->stats.name)
+
+static int scrub_kvwrite(int fd, char *buf, int max, const char *key, u64 val)
+{
+	return scrub_writev(fd, buf, max, "|%s:%lld", key, val);
+}
+
+static int scrub_write_file(int fd, const char *fsid,
+				struct scrub_progress *data, int n)
+{
+	int ret = 0;
+	int i;
+	char buf[1024];
+	struct scrub_progress local;
+	struct scrub_progress *use;
+
+	if (n < 1)
+		return -EINVAL;
+
+	/* each -1 is to subtract one \0 byte, the + 2 is for ':' and '\n' */
+	ret = scrub_write_buf(fd, SCRUB_FILE_VERSION_PREFIX ":"
+				SCRUB_FILE_VERSION "\n",
+				(sizeof(SCRUB_FILE_VERSION_PREFIX) - 1) +
+				(sizeof(SCRUB_FILE_VERSION) - 1) + 2);
+	if (ret)
+		return -EOVERFLOW;
+
+	for (i = 0; i < n; ++i) {
+		use = scrub_resumed_stats(&data[i], &local);
+		if (scrub_write_buf(fd, fsid, strlen(fsid)) ||
+		    scrub_write_buf(fd, ":", 1) ||
+		    scrub_writev(fd, buf, sizeof(buf), "%lld",
+					use->scrub_args.devid) ||
+		    scrub_write_buf(fd, buf, ret) ||
+		    _SCRUB_KVWRITE(fd, buf, data_extents_scrubbed, use) ||
+		    _SCRUB_KVWRITE(fd, buf, tree_extents_scrubbed, use) ||
+		    _SCRUB_KVWRITE(fd, buf, data_bytes_scrubbed, use) ||
+		    _SCRUB_KVWRITE(fd, buf, tree_bytes_scrubbed, use) ||
+		    _SCRUB_KVWRITE(fd, buf, read_errors, use) ||
+		    _SCRUB_KVWRITE(fd, buf, csum_errors, use) ||
+		    _SCRUB_KVWRITE(fd, buf, verify_errors, use) ||
+		    _SCRUB_KVWRITE(fd, buf, no_csum, use) ||
+		    _SCRUB_KVWRITE(fd, buf, csum_discards, use) ||
+		    _SCRUB_KVWRITE(fd, buf, super_errors, use) ||
+		    _SCRUB_KVWRITE(fd, buf, malloc_errors, use) ||
+		    _SCRUB_KVWRITE(fd, buf, uncorrectable_errors, use) ||
+		    _SCRUB_KVWRITE(fd, buf, corrected_errors, use) ||
+		    _SCRUB_KVWRITE(fd, buf, last_physical, use) ||
+		    _SCRUB_KVWRITE_STATS(fd, buf, t_start, use) ||
+		    _SCRUB_KVWRITE_STATS(fd, buf, t_resumed, use) ||
+		    _SCRUB_KVWRITE_STATS(fd, buf, duration, use) ||
+		    _SCRUB_KVWRITE_STATS(fd, buf, canceled, use) ||
+		    _SCRUB_KVWRITE_STATS(fd, buf, finished, use) ||
+		    scrub_write_buf(fd, "\n", 1)) {
+			return -EOVERFLOW;
+		}
+	}
+
+	return 0;
+}
+
+static int scrub_write_progress(pthread_mutex_t *m, const char *fsid,
+				struct scrub_progress *data, int n)
+{
+	int ret;
+	int err;
+	int fd = 0;
+	int old;
+
+	ret = pthread_mutex_lock(m);
+	if (ret) {
+		err = -errno;
+		goto out;
+	}
+
+	ret = pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &old);
+	if (ret) {
+		err = -ret;
+		goto out;
+	}
+
+	fd = scrub_open_file_w(SCRUB_DATA_FILE, fsid, "tmp");
+	if (fd < 0) {
+		err = fd;
+		goto out;
+	}
+	err = scrub_write_file(fd, fsid, data, n);
+	if (err)
+		goto out;
+	err = scrub_rename_file(SCRUB_DATA_FILE, fsid, "tmp");
+	if (err)
+		goto out;
+
+out:
+	if (fd > 0) {
+		ret = close(fd);
+		if (ret)
+			err = -errno;
+	}
+
+	ret = pthread_mutex_unlock(m);
+	if (ret && !err)
+		err = -ret;
+
+	ret = pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &old);
+	if (ret && !err)
+		err = -ret;
+
+	return err;
+}
+
+static void *scrub_one_dev(void *ctx)
+{
+	struct scrub_progress *sp = ctx;
+	int ret;
+	struct timeval tv;
+
+	sp->stats.canceled = 0;
+	sp->stats.duration = 0;
+	sp->stats.finished = 0;
+
+	ret = ioctl(sp->fd, BTRFS_IOC_SCRUB, &sp->scrub_args);
+	gettimeofday(&tv, NULL);
+	sp->ret = ret;
+	sp->stats.duration = tv.tv_sec - sp->stats.t_start;
+	sp->stats.canceled = !!ret;
+	sp->ioctl_errno = errno;
+	ret = pthread_mutex_lock(&sp->progress_mutex);
+	if (ret)
+		return ERR_PTR(-ret);
+	sp->stats.finished = 1;
+	ret = pthread_mutex_unlock(&sp->progress_mutex);
+	if (ret)
+		return ERR_PTR(-ret);
+
+	return NULL;
+}
+
+static void *progress_one_dev(void *ctx)
+{
+	struct scrub_progress *sp = ctx;
+
+	sp->ret = ioctl(sp->fd, BTRFS_IOC_SCRUB_PROGRESS, &sp->scrub_args);
+	sp->ioctl_errno = errno;
+
+	return NULL;
+}
+
+static void *scrub_progress_cycle(void *ctx)
+{
+	int ret;
+	int old;
+	int i;
+	char fsid[37];
+	struct scrub_progress *sp;
+	struct scrub_progress *sp_last;
+	struct scrub_progress *sp_shared;
+	struct timeval tv;
+	struct scrub_progress_cycle *spc = ctx;
+	int ndev = spc->fi->num_devices;
+	int this = 1;
+	int last = 0;
+	int peer_fd = -1;
+	struct pollfd accept_poll_fd = {
+		.fd = spc->prg_fd,
+		.events = POLLIN,
+		.revents = 0,
+	};
+	struct pollfd write_poll_fd = {
+		.events = POLLOUT,
+		.revents = 0,
+	};
+	struct sockaddr_un peer;
+	socklen_t peer_size = sizeof(peer);
+
+	ret = pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &old);
+	if (ret)
+		return ERR_PTR(-ret);
+
+	uuid_unparse(spc->fi->fsid, fsid);
+
+	for (i = 0; i < ndev; ++i) {
+		sp = &spc->progress[i];
+		sp_last = &spc->progress[i + ndev];
+		sp_shared = &spc->shared_progress[i];
+		sp->scrub_args.devid = sp_last->scrub_args.devid =
+						sp_shared->scrub_args.devid;
+		sp->fd = sp_last->fd = spc->fdmnt;
+		sp->stats.t_start = sp_last->stats.t_start =
+						sp_shared->stats.t_start;
+		sp->resumed = sp_last->resumed = sp_shared->resumed;
+		sp->skip = sp_last->skip = sp_shared->skip;
+		sp->stats.finished = sp_last->stats.finished =
+						sp_shared->stats.finished;
+	}
+
+	while (1) {
+		ret = poll(&accept_poll_fd, 1, 5 * 1000);
+		if (ret == -1)
+			return ERR_PTR(-errno);
+		if (ret)
+			peer_fd = accept(spc->prg_fd, (struct sockaddr *)&peer,
+					 &peer_size);
+		gettimeofday(&tv, NULL);
+		this = (this + 1)%2;
+		last = (last + 1)%2;
+		for (i = 0; i < ndev; ++i) {
+			sp = &spc->progress[this * ndev + i];
+			sp_last = &spc->progress[last * ndev + i];
+			sp_shared = &spc->shared_progress[i];
+			if (sp->stats.finished)
+				continue;
+			progress_one_dev(sp);
+			sp->stats.duration = tv.tv_sec - sp->stats.t_start;
+			if (!sp->ret)
+				continue;
+			if (sp->ioctl_errno != ENOTCONN &&
+			    sp->ioctl_errno != ENODEV)
+				return ERR_PTR(-sp->ioctl_errno);
+			/*
+			 * scrub finished or device removed, check the
+			 * finished flag. if unset, just use the last
+			 * result we got for the current write and go
+			 * on. flag should be set on next cycle, then.
+			 */
+			ret = pthread_mutex_lock(&sp_shared->progress_mutex);
+			if (ret)
+				return ERR_PTR(-ret);
+			if (!sp_shared->stats.finished) {
+				ret = pthread_mutex_unlock(
+						&sp_shared->progress_mutex);
+				if (ret)
+					return ERR_PTR(-ret);
+				memcpy(sp, sp_last, sizeof(*sp));
+				continue;
+			}
+			ret = pthread_mutex_unlock(&sp_shared->progress_mutex);
+			if (ret)
+				return ERR_PTR(-ret);
+			memcpy(sp, sp_shared, sizeof(*sp));
+			memcpy(sp_last, sp_shared, sizeof(*sp));
+		}
+		if (peer_fd != -1) {
+			write_poll_fd.fd = peer_fd;
+			ret = poll(&write_poll_fd, 1, 0);
+			if (ret == -1)
+				return ERR_PTR(-errno);
+			if (ret) {
+				ret = scrub_write_file(
+					peer_fd, fsid,
+					&spc->progress[this * ndev], ndev);
+				if (ret)
+					return ERR_PTR(ret);
+			}
+			close(peer_fd);
+			peer_fd = -1;
+		}
+		if (!spc->do_record)
+			continue;
+		ret = scrub_write_progress(spc->write_mutex, fsid,
+					   &spc->progress[this * ndev], ndev);
+		if (ret)
+			return ERR_PTR(ret);
+	}
+}
+
+static struct scrub_file_record *last_dev_scrub(
+		struct scrub_file_record *const *const past_scrubs, u64 devid)
+{
+	int i;
+
+	if (!past_scrubs || IS_ERR(past_scrubs))
+		return NULL;
+
+	for (i = 0; past_scrubs[i]; ++i)
+		if (past_scrubs[i]->devid == devid)
+			return past_scrubs[i];
+
+	return NULL;
+}
+
+static int scrub_device_info(int fd, u64 devid,
+			     struct btrfs_ioctl_dev_info_args *di_args)
+{
+	int ret;
+
+	di_args->devid = devid;
+	memset(&di_args->uuid, '\0', sizeof(di_args->uuid));
+
+	ret = ioctl(fd, BTRFS_IOC_DEV_INFO, di_args);
+	return ret ? -errno : 0;
+}
+
+static int scrub_fs_info(int fd, char *path,
+				struct btrfs_ioctl_fs_info_args *fi_args,
+				struct btrfs_ioctl_dev_info_args **di_ret)
+{
+	int ret = 0;
+	int ndevs = 0;
+	int i = 1;
+	struct btrfs_fs_devices *fs_devices_mnt = NULL;
+	struct btrfs_ioctl_dev_info_args *di_args;
+	char mp[BTRFS_PATH_NAME_MAX + 1];
+
+	memset(fi_args, 0, sizeof(*fi_args));
+
+	ret = ioctl(fd, BTRFS_IOC_FS_INFO, fi_args);
+	if (ret && errno == EINVAL) {
+		/* path is no mounted btrfs. try if it's a device */
+		ret = check_mounted_where(fd, path, mp, sizeof(mp),
+						&fs_devices_mnt);
+		if (!ret)
+			return -EINVAL;
+		if (ret < 0)
+			return ret;
+		fi_args->num_devices = 1;
+		fi_args->max_id = fs_devices_mnt->latest_devid;
+		i = fs_devices_mnt->latest_devid;
+		memcpy(fi_args->fsid, fs_devices_mnt->fsid, BTRFS_FSID_SIZE);
+		close(fd);
+		fd = open_file_or_dir(mp);
+		if (fd < 0)
+			return -errno;
+	} else if (ret) {
+		return -errno;
+	}
+
+	if (!fi_args->num_devices)
+		return 0;
+
+	di_args = *di_ret = malloc(fi_args->num_devices * sizeof(*di_args));
+	if (!di_args)
+		return -errno;
+
+	for (; i <= fi_args->max_id; ++i) {
+		BUG_ON(ndevs >= fi_args->num_devices);
+		ret = scrub_device_info(fd, i, &di_args[ndevs]);
+		if (ret == -ENODEV)
+			continue;
+		if (ret)
+			return ret;
+		++ndevs;
+	}
+
+	BUG_ON(ndevs == 0);
+
+	return 0;
+}
+
+int mkdir_p(char *path)
+{
+	int i;
+	int ret;
+
+	for (i = 1; i < strlen(path); ++i) {
+		if (path[i] != '/')
+			continue;
+		path[i] = '\0';
+		ret = mkdir(path, 0777);
+		if (ret && errno != EEXIST)
+			return 1;
+		path[i] = '/';
+	}
+
+	return 0;
+}
+
+static int scrub_start(int argc, char **argv, int resume)
+{
+	int fdmnt;
+	int prg_fd = -1;
+	int fdres = -1;
+	int ret;
+	pid_t pid;
+	int c;
+	int i;
+	int err = 0;
+	int e_uncorrectable = 0;
+	int e_correctable = 0;
+	int print_raw = 0;
+	char *path;
+	int do_background = 1;
+	int do_wait = 0;
+	int do_print = 0;
+	int do_quiet = 0;
+	int do_record = 1;
+	int readonly = 0;
+	int do_stats_per_dev = 0;
+	int n_start = 0;
+	int n_skip = 0;
+	int n_resume = 0;
+	struct btrfs_ioctl_fs_info_args fi_args;
+	struct btrfs_ioctl_dev_info_args *di_args = NULL;
+	struct scrub_progress *sp = NULL;
+	struct scrub_fs_stat fs_stat;
+	struct timeval tv;
+	struct sockaddr_un addr = {
+		.sun_family = AF_UNIX,
+	};
+	pthread_t *t_devs = NULL;
+	pthread_t t_prog;
+	pthread_attr_t t_attr;
+	struct scrub_file_record **past_scrubs = NULL;
+	struct scrub_file_record *last_scrub = NULL;
+	char *datafile = strdup(SCRUB_DATA_FILE);
+	char fsid[37];
+	char sock_path[BTRFS_PATH_NAME_MAX + 1] = "";
+	struct scrub_progress_cycle spc;
+	pthread_mutex_t spc_write_mutex = PTHREAD_MUTEX_INITIALIZER;
+	void *terr;
+	u64 devid;
+
+	optind = 1;
+	while ((c = getopt(argc, argv, "BdqrR")) != -1) {
+		switch (c) {
+		case 'B':
+			do_background = 0;
+			do_wait = 1;
+			do_print = 1;
+			break;
+		case 'd':
+			do_stats_per_dev = 1;
+			break;
+		case 'q':
+			do_quiet = 1;
+			break;
+		case 'r':
+			readonly = 1;
+			break;
+		case 'R':
+			print_raw = 1;
+			break;
+		case '?':
+		default:
+			fprintf(stderr, "ERROR: scrub args invalid.\n"
+					" -B  do not background\n"
+					" -d  stats per device (-B only)\n"
+					" -q  quiet\n"
+					" -r  read only mode\n");
+			return 1;
+		}
+	}
+
+	/* try to catch most error cases before forking */
+
+	if (optind + 1 != argc) {
+		fprintf(stderr, "ERROR: scrub start needs path as last "
+			"argument\n");
+		return 1;
+	}
+
+	spc.progress = NULL;
+	if (do_quiet && do_print)
+		do_print = 0;
+
+	if (mkdir_p(datafile)) {
+		ERR(!do_quiet, "WARNING: cannot create scrub data "
+			       "file, mkdir %s failed: %s. Status recording "
+			       "disabled\n", datafile, strerror(errno));
+		do_record = 0;
+	}
+	free(datafile);
+
+	path = argv[optind];
+
+	fdmnt = open_file_or_dir(path);
+	if (fdmnt < 0) {
+		ERR(!do_quiet, "ERROR: can't access '%s'\n", path);
+		return 12;
+	}
+
+	ret = scrub_fs_info(fdmnt, path, &fi_args, &di_args);
+	if (ret) {
+		ERR(!do_quiet, "ERROR: getting dev info for scrub failed: "
+		    "%s\n", strerror(-ret));
+		err = 1;
+		goto out;
+	}
+	if (!fi_args.num_devices) {
+		ERR(!do_quiet, "ERROR: no devices found\n");
+		err = 1;
+		goto out;
+	}
+
+	uuid_unparse(fi_args.fsid, fsid);
+	fdres = scrub_open_file_r(SCRUB_DATA_FILE, fsid);
+	if (fdres < 0 && fdres != -ENOENT) {
+		ERR(!do_quiet, "WARNING: failed to open status file: "
+		    "%s\n", strerror(-fdres));
+	} else if (fdres >= 0) {
+		past_scrubs = scrub_read_file(fdres, !do_quiet);
+		if (IS_ERR(past_scrubs))
+			ERR(!do_quiet, "WARNING: failed to read status file: "
+			    "%s\n", strerror(-PTR_ERR(past_scrubs)));
+		close(fdres);
+	}
+
+	t_devs = malloc(fi_args.num_devices * sizeof(*t_devs));
+	sp = calloc(fi_args.num_devices, sizeof(*sp));
+	spc.progress = calloc(fi_args.num_devices * 2, sizeof(*spc.progress));
+
+	if (!t_devs || !sp || !spc.progress) {
+		ERR(!do_quiet, "ERROR: scrub failed: %s", strerror(errno));
+		err = 1;
+		goto out;
+	}
+
+	ret = pthread_attr_init(&t_attr);
+	if (ret) {
+		ERR(!do_quiet, "ERROR: pthread_attr_init failed: %s\n",
+		    strerror(ret));
+		err = 1;
+		goto out;
+	}
+
+	for (i = 0; i < fi_args.num_devices; ++i) {
+		devid = di_args[i].devid;
+		ret = pthread_mutex_init(&sp[i].progress_mutex, NULL);
+		if (ret) {
+			ERR(!do_quiet, "ERROR: pthread_mutex_init failed: "
+			    "%s\n", strerror(ret));
+			err = 1;
+			goto out;
+		}
+		last_scrub = last_dev_scrub(past_scrubs, devid);
+		sp[i].scrub_args.devid = devid;
+		sp[i].fd = fdmnt;
+		if (resume && last_scrub && (last_scrub->stats.canceled ||
+					     !last_scrub->stats.finished)) {
+			++n_resume;
+			sp[i].scrub_args.start = last_scrub->p.last_physical;
+			sp[i].resumed = last_scrub;
+		} else if (resume) {
+			++n_skip;
+			sp[i].skip = 1;
+			sp[i].resumed = last_scrub;
+			continue;
+		} else {
+			++n_start;
+			sp[i].scrub_args.start = 0ll;
+			sp[i].resumed = NULL;
+		}
+		sp[i].skip = 0;
+		sp[i].scrub_args.end = (u64)-1ll;
+		sp[i].scrub_args.flags = readonly ? BTRFS_SCRUB_READONLY : 0;
+	}
+
+	if (!n_start && !n_resume) {
+		if (!do_quiet)
+			printf("scrub: nothing to resume for %s, fsid %s\n",
+			       path, fsid);
+		err = 0;
+		goto out;
+	}
+
+	ret = prg_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	while (ret != -1) {
+		ret = scrub_datafile(SCRUB_PROGRESS_SOCKET_PATH, fsid, NULL,
+					sock_path, sizeof(sock_path));
+		/* ignore EOVERFLOW, try using a shorter path for the socket */
+		addr.sun_path[sizeof(addr.sun_path) - 1] = '\0';
+		strncpy(addr.sun_path, sock_path, sizeof(addr.sun_path) - 1);
+		ret = bind(prg_fd, (struct sockaddr *)&addr, sizeof(addr));
+		if (ret != -1 || errno != EADDRINUSE)
+			break;
+		/*
+		 * bind failed with EADDRINUSE. so let's see if anyone answers
+		 * when we make a call to the socket ...
+		 */
+		ret = connect(prg_fd, (struct sockaddr *)&addr, sizeof(addr));
+		if (!ret || errno != ECONNREFUSED) {
+			/* ... yes, so scrub must be running. error out */
+			fprintf(stderr, "ERROR: scrub already running\n");
+			close(prg_fd);
+			goto out;
+		}
+		/*
+		 * ... no, this means someone left us alone with an unused
+		 * socket in the file system. remove it and try again.
+		 */
+		ret = unlink(sock_path);
+	}
+	if (ret != -1)
+		ret = listen(prg_fd, 100);
+	if (ret == -1) {
+		ERR(!do_quiet, "WARNING: failed to open the progress status "
+		    "socket at %s: %s. Progress cannot be queried\n",
+		    sock_path[0] ? sock_path : SCRUB_PROGRESS_SOCKET_PATH,
+		    strerror(errno));
+		if (prg_fd != -1) {
+			close(prg_fd);
+			prg_fd = -1;
+			if (sock_path[0])
+				unlink(sock_path);
+		}
+	}
+
+	if (do_record) {
+		/* write all-zero progress file for a start */
+		ret = scrub_write_progress(&spc_write_mutex, fsid, sp,
+					   fi_args.num_devices);
+		if (ret) {
+			ERR(!do_quiet, "WARNING: failed to write the progress "
+			    "status file: %s. Status recording disabled\n",
+			    strerror(-ret));
+			do_record = 0;
+		}
+	}
+
+	if (do_background) {
+		pid = fork();
+		if (pid == -1) {
+			ERR(!do_quiet, "ERROR: cannot scrub, fork failed: "
+					"%s\n", strerror(errno));
+			err = 1;
+			goto out;
+		}
+
+		if (pid) {
+			int stat;
+			scrub_handle_sigint_parent();
+			if (!do_quiet)
+				printf("scrub %s on %s, fsid %s (pid=%d)\n",
+				       n_start ? "started" : "resumed",
+				       path, fsid, pid);
+			if (!do_wait) {
+				err = 0;
+				goto out;
+			}
+			ret = wait(&stat);
+			if (ret != pid) {
+				ERR(!do_quiet, "ERROR: wait failed: (ret=%d) "
+				    "%s\n", ret, strerror(errno));
+				err = 1;
+				goto out;
+			}
+			if (!WIFEXITED(stat) || WEXITSTATUS(stat)) {
+				ERR(!do_quiet, "ERROR: scrub process failed\n");
+				err = WIFEXITED(stat) ? WEXITSTATUS(stat) : -1;
+				goto out;
+			}
+			err = 0;
+			goto out;
+		}
+	}
+
+	scrub_handle_sigint_child(fdmnt);
+
+	for (i = 0; i < fi_args.num_devices; ++i) {
+		if (sp[i].skip) {
+			sp[i].scrub_args.progress = sp[i].resumed->p;
+			sp[i].stats = sp[i].resumed->stats;
+			sp[i].ret = 0;
+			sp[i].stats.finished = 1;
+			continue;
+		}
+		devid = di_args[i].devid;
+		gettimeofday(&tv, NULL);
+		sp[i].stats.t_start = tv.tv_sec;
+		ret = pthread_create(&t_devs[i], &t_attr,
+					scrub_one_dev, &sp[i]);
+		if (ret) {
+			if (do_print)
+				fprintf(stderr, "ERROR: creating "
+					"scrub_one_dev[%llu] thread failed: "
+					"%s\n", devid, strerror(ret));
+			err = 1;
+			goto out;
+		}
+	}
+
+	spc.fdmnt = fdmnt;
+	spc.prg_fd = prg_fd;
+	spc.do_record = do_record;
+	spc.write_mutex = &spc_write_mutex;
+	spc.shared_progress = sp;
+	spc.fi = &fi_args;
+	ret = pthread_create(&t_prog, &t_attr, scrub_progress_cycle, &spc);
+	if (ret) {
+		if (do_print)
+			fprintf(stderr, "ERROR: creating progress thread "
+				"failed: %s\n", strerror(ret));
+		err = 1;
+		goto out;
+	}
+
+	err = 0;
+	for (i = 0; i < fi_args.num_devices; ++i) {
+		if (sp[i].skip)
+			continue;
+		devid = di_args[i].devid;
+		ret = pthread_join(t_devs[i], NULL);
+		if (ret) {
+			if (do_print)
+				fprintf(stderr, "ERROR: pthread_join failed "
+					"for scrub_one_dev[%llu]: %s\n", devid,
+					strerror(ret));
+			++err;
+			continue;
+		}
+		if (sp[i].ret && sp[i].ioctl_errno == ENODEV) {
+			if (do_print)
+				fprintf(stderr, "WARNING: device %lld not "
+					"present\n", devid);
+			continue;
+		}
+		if (sp[i].ret && sp[i].ioctl_errno == ECANCELED) {
+			++err;
+		} else if (sp[i].ret) {
+			if (do_print)
+				fprintf(stderr, "ERROR: scrubbing %s failed "
+					"for device id %lld (%s)\n", path,
+					devid, strerror(sp[i].ioctl_errno));
+			++err;
+			continue;
+		}
+		if (sp[i].scrub_args.progress.uncorrectable_errors > 0)
+			e_uncorrectable++;
+		if (sp[i].scrub_args.progress.corrected_errors > 0
+		    || sp[i].scrub_args.progress.unverified_errors > 0)
+			e_correctable++;
+	}
+
+	if (do_print) {
+		const char *append = "done";
+		if (!do_stats_per_dev)
+			init_fs_stat(&fs_stat);
+		for (i = 0; i < fi_args.num_devices; ++i) {
+			if (do_stats_per_dev) {
+				print_scrub_dev(&di_args[i],
+						&sp[i].scrub_args.progress,
+						print_raw,
+						sp[i].ret ? "canceled" : "done",
+						&sp[i].stats);
+			} else {
+				if (sp[i].ret)
+					append = "canceled";
+				add_to_fs_stat(&sp[i].scrub_args.progress,
+						&sp[i].stats, &fs_stat);
+			}
+		}
+		if (!do_stats_per_dev) {
+			printf("scrub %s for %s\n", append, fsid);
+			print_fs_stat(&fs_stat, print_raw);
+		}
+	}
+
+	ret = pthread_cancel(t_prog);
+	if (!ret)
+		ret = pthread_join(t_prog, &terr);
+	if (do_print && ret) {
+		fprintf(stderr, "ERROR: progress thead handling failed: %s\n",
+			strerror(ret));
+	}
+
+	if (do_print && terr && terr != PTHREAD_CANCELED) {
+		fprintf(stderr, "ERROR: recording progress "
+			"failed: %s\n", strerror(-PTR_ERR(terr)));
+	}
+
+	if (do_record) {
+		ret = scrub_write_progress(&spc_write_mutex, fsid, sp,
+					   fi_args.num_devices);
+		if (ret && do_print) {
+			fprintf(stderr, "ERROR: failed to record the result: "
+				"%s\n", strerror(-ret));
+		}
+	}
+
+	scrub_handle_sigint_child(-1);
+
+out:
+	free_history(past_scrubs);
+	free(di_args);
+	free(t_devs);
+	free(sp);
+	free(spc.progress);
+	if (prg_fd > -1) {
+		close(prg_fd);
+		if (sock_path[0])
+			unlink(sock_path);
+	}
+	close(fdmnt);
+
+	if (err)
+		return 1;
+	if (e_correctable)
+		return 7;
+	if (e_uncorrectable)
+		return 8;
+	return 0;
+}
+
+int do_scrub_start(int argc, char **argv)
+{
+	return scrub_start(argc, argv, 0);
+}
+
+int do_scrub_resume(int argc, char **argv)
+{
+	return scrub_start(argc, argv, 1);
+}
+
+int do_scrub_cancel(int argc, char **argv)
+{
+	char *path = argv[1];
+	int ret;
+	int fdmnt;
+	int err;
+	char mp[BTRFS_PATH_NAME_MAX + 1];
+	struct btrfs_fs_devices *fs_devices_mnt = NULL;
+
+	fdmnt = open_file_or_dir(path);
+	if (fdmnt < 0) {
+		fprintf(stderr, "ERROR: scrub cancel failed\n");
+		return 12;
+	}
+
+again:
+	ret = ioctl(fdmnt, BTRFS_IOC_SCRUB_CANCEL, NULL);
+	err = errno;
+	close(fdmnt);
+
+	if (ret && err == EINVAL) {
+		/* path is no mounted btrfs. try if it's a device */
+		ret = check_mounted_where(fdmnt, path, mp, sizeof(mp),
+					  &fs_devices_mnt);
+		close(fdmnt);
+		if (ret) {
+			fdmnt = open_file_or_dir(mp);
+			if (fdmnt >= 0) {
+				path = mp;
+				goto again;
+			}
+		}
+	}
+
+	if (ret) {
+		fprintf(stderr, "ERROR: scrub cancel failed on %s: %s\n", path,
+			err == ENOTCONN ? "not running" : strerror(errno));
+		return 1;
+	}
+
+	printf("scrub cancelled\n");
+
+	return 0;
+}
+
+int do_scrub_status(int argc, char **argv)
+{
+
+	char *path;
+	struct btrfs_ioctl_fs_info_args fi_args;
+	struct btrfs_ioctl_dev_info_args *di_args = NULL;
+	struct scrub_file_record **past_scrubs = NULL;
+	struct scrub_file_record *last_scrub;
+	struct scrub_fs_stat fs_stat;
+	struct sockaddr_un addr = {
+		.sun_family = AF_UNIX,
+	};
+	int ret;
+	int fdmnt;
+	int i;
+	optind = 1;
+	int print_raw = 0;
+	int do_stats_per_dev = 0;
+	char c;
+	char fsid[37];
+	int fdres = -1;
+	int err = 0;
+
+	while ((c = getopt(argc, argv, "dR")) != -1) {
+		switch (c) {
+		case 'd':
+			do_stats_per_dev = 1;
+			break;
+		case 'R':
+			print_raw = 1;
+			break;
+		case '?':
+		default:
+			fprintf(stderr, "ERROR: scrub status args invalid.\n"
+					" -d  stats per device\n");
+			return 1;
+		}
+	}
+
+	if (optind + 1 != argc) {
+		fprintf(stderr, "ERROR: scrub status needs path as last "
+			"argument\n");
+		return 1;
+	}
+
+	path = argv[optind];
+
+	fdmnt = open_file_or_dir(path);
+	if (fdmnt < 0) {
+		fprintf(stderr, "ERROR: can't access to '%s'\n", path);
+		return 12;
+	}
+
+	ret = scrub_fs_info(fdmnt, path, &fi_args, &di_args);
+	if (ret) {
+		fprintf(stderr, "ERROR: getting dev info for scrub failed: "
+				"%s\n", strerror(-ret));
+		err = 1;
+		goto out;
+	}
+	if (!fi_args.num_devices) {
+		fprintf(stderr, "ERROR: no devices found\n");
+		err = 1;
+		goto out;
+	}
+
+	uuid_unparse(fi_args.fsid, fsid);
+
+	fdres = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (fdres == -1) {
+		fprintf(stderr, "ERROR: failed to create socket to "
+			"receive progress information: %s\n",
+			strerror(errno));
+		err = 1;
+		goto out;
+	}
+	scrub_datafile(SCRUB_PROGRESS_SOCKET_PATH, fsid,
+			NULL, addr.sun_path, sizeof(addr.sun_path));
+	/* ignore EOVERFLOW, just use shorter name and hope for the best */
+	addr.sun_path[sizeof(addr.sun_path) - 1] = '\0';
+	ret = connect(fdres, (struct sockaddr *)&addr, sizeof(addr));
+	if (ret == -1) {
+		fdres = scrub_open_file_r(SCRUB_DATA_FILE, fsid);
+		if (fdres < 0 && fdres != -ENOENT) {
+			fprintf(stderr, "WARNING: failed to open status file: "
+				"%s\n", strerror(-fdres));
+			err = 1;
+			goto out;
+		}
+	}
+
+	if (fdres >= 0) {
+		past_scrubs = scrub_read_file(fdres, 1);
+		if (IS_ERR(past_scrubs))
+			fprintf(stderr, "WARNING: failed to read status: %s\n",
+				strerror(-PTR_ERR(past_scrubs)));
+	}
+
+	printf("scrub status for %s\n", fsid);
+
+	if (do_stats_per_dev) {
+		for (i = 0; i < fi_args.num_devices; ++i) {
+			last_scrub = last_dev_scrub(past_scrubs,
+							di_args[i].devid);
+			if (!last_scrub) {
+				print_scrub_dev(&di_args[i], NULL, print_raw,
+						NULL, NULL);
+				continue;
+			}
+			print_scrub_dev(&di_args[i], &last_scrub->p, print_raw,
+					last_scrub->stats.finished ?
+							"history" : "status",
+					&last_scrub->stats);
+		}
+	} else {
+		init_fs_stat(&fs_stat);
+		for (i = 0; i < fi_args.num_devices; ++i) {
+			last_scrub = last_dev_scrub(past_scrubs,
+							di_args[i].devid);
+			if (!last_scrub)
+				continue;
+			add_to_fs_stat(&last_scrub->p, &last_scrub->stats,
+					&fs_stat);
+		}
+		print_fs_stat(&fs_stat, print_raw);
+	}
+
+out:
+	free_history(past_scrubs);
+	free(di_args);
+	close(fdmnt);
+	if (fdres > -1)
+		close(fdres);
+
+	return err;
+}