Finally... Import the latest open-source ZFS version - (SPA) 28.

Few new things available from now on:

- Data deduplication.
- Triple parity RAIDZ (RAIDZ3).
- zfs diff.
- zpool split.
- Snapshot holds.
- zpool import -F. Allows to rewind corrupted pool to earlier
  transaction group.
- Possibility to import pool in read-only mode.

MFC after:	1 month

1 files changed, 832 insertions, 0 deletions

diff --git a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_diff.c b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_diff.c
new file mode 100644
index 0000000..ae84285
--- /dev/null
+++ b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_diff.c
@@ -0,0 +1,832 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
+ */
+
+/*
+ * zfs diff support
+ */
+#include <ctype.h>
+#include <errno.h>
+#include <libintl.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stddef.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <sys/zfs_ioctl.h>
+#include <libzfs.h>
+#include "libzfs_impl.h"
+
+#define	ZDIFF_SNAPDIR		"/.zfs/snapshot/"
+#define	ZDIFF_SHARESDIR 	"/.zfs/shares/"
+#define	ZDIFF_PREFIX		"zfs-diff-%d"
+
+#define	ZDIFF_ADDED	'+'
+#define	ZDIFF_MODIFIED	'M'
+#define	ZDIFF_REMOVED	'-'
+#define	ZDIFF_RENAMED	'R'
+
+static boolean_t
+do_name_cmp(const char *fpath, const char *tpath)
+{
+	char *fname, *tname;
+	fname = strrchr(fpath, '/') + 1;
+	tname = strrchr(tpath, '/') + 1;
+	return (strcmp(fname, tname) == 0);
+}
+
+typedef struct differ_info {
+	zfs_handle_t *zhp;
+	char *fromsnap;
+	char *frommnt;
+	char *tosnap;
+	char *tomnt;
+	char *ds;
+	char *dsmnt;
+	char *tmpsnap;
+	char errbuf[1024];
+	boolean_t isclone;
+	boolean_t scripted;
+	boolean_t classify;
+	boolean_t timestamped;
+	uint64_t shares;
+	int zerr;
+	int cleanupfd;
+	int outputfd;
+	int datafd;
+} differ_info_t;
+
+/*
+ * Given a {dsname, object id}, get the object path
+ */
+static int
+get_stats_for_obj(differ_info_t *di, const char *dsname, uint64_t obj,
+    char *pn, int maxlen, zfs_stat_t *sb)
+{
+	zfs_cmd_t zc = { 0 };
+	int error;
+
+	(void) strlcpy(zc.zc_name, dsname, sizeof (zc.zc_name));
+	zc.zc_obj = obj;
+
+	errno = 0;
+	error = ioctl(di->zhp->zfs_hdl->libzfs_fd, ZFS_IOC_OBJ_TO_STATS, &zc);
+	di->zerr = errno;
+
+	/* we can get stats even if we failed to get a path */
+	(void) memcpy(sb, &zc.zc_stat, sizeof (zfs_stat_t));
+	if (error == 0) {
+		ASSERT(di->zerr == 0);
+		(void) strlcpy(pn, zc.zc_value, maxlen);
+		return (0);
+	}
+
+	if (di->zerr == EPERM) {
+		(void) snprintf(di->errbuf, sizeof (di->errbuf),
+		    dgettext(TEXT_DOMAIN,
+		    "The sys_config privilege or diff delegated permission "
+		    "is needed\nto discover path names"));
+		return (-1);
+	} else {
+		(void) snprintf(di->errbuf, sizeof (di->errbuf),
+		    dgettext(TEXT_DOMAIN,
+		    "Unable to determine path or stats for "
+		    "object %lld in %s"), obj, dsname);
+		return (-1);
+	}
+}
+
+/*
+ * stream_bytes
+ *
+ * Prints a file name out a character at a time.  If the character is
+ * not in the range of what we consider "printable" ASCII, display it
+ * as an escaped 3-digit octal value.  ASCII values less than a space
+ * are all control characters and we declare the upper end as the
+ * DELete character.  This also is the last 7-bit ASCII character.
+ * We choose to treat all 8-bit ASCII as not printable for this
+ * application.
+ */
+static void
+stream_bytes(FILE *fp, const char *string)
+{
+	while (*string) {
+		if (*string > ' ' && *string != '\\' && *string < '\177')
+			(void) fprintf(fp, "%c", *string++);
+		else
+			(void) fprintf(fp, "\\%03o", *string++);
+	}
+}
+
+static void
+print_what(FILE *fp, mode_t what)
+{
+	char symbol;
+
+	switch (what & S_IFMT) {
+	case S_IFBLK:
+		symbol = 'B';
+		break;
+	case S_IFCHR:
+		symbol = 'C';
+		break;
+	case S_IFDIR:
+		symbol = '/';
+		break;
+#ifdef S_IFDOOR
+	case S_IFDOOR:
+		symbol = '>';
+		break;
+#endif
+	case S_IFIFO:
+		symbol = '|';
+		break;
+	case S_IFLNK:
+		symbol = '@';
+		break;
+#ifdef S_IFPORT
+	case S_IFPORT:
+		symbol = 'P';
+		break;
+#endif
+	case S_IFSOCK:
+		symbol = '=';
+		break;
+	case S_IFREG:
+		symbol = 'F';
+		break;
+	default:
+		symbol = '?';
+		break;
+	}
+	(void) fprintf(fp, "%c", symbol);
+}
+
+static void
+print_cmn(FILE *fp, differ_info_t *di, const char *file)
+{
+	stream_bytes(fp, di->dsmnt);
+	stream_bytes(fp, file);
+}
+
+static void
+print_rename(FILE *fp, differ_info_t *di, const char *old, const char *new,
+    zfs_stat_t *isb)
+{
+	if (di->timestamped)
+		(void) fprintf(fp, "%10lld.%09lld\t",
+		    (longlong_t)isb->zs_ctime[0],
+		    (longlong_t)isb->zs_ctime[1]);
+	(void) fprintf(fp, "%c\t", ZDIFF_RENAMED);
+	if (di->classify) {
+		print_what(fp, isb->zs_mode);
+		(void) fprintf(fp, "\t");
+	}
+	print_cmn(fp, di, old);
+	if (di->scripted)
+		(void) fprintf(fp, "\t");
+	else
+		(void) fprintf(fp, " -> ");
+	print_cmn(fp, di, new);
+	(void) fprintf(fp, "\n");
+}
+
+static void
+print_link_change(FILE *fp, differ_info_t *di, int delta, const char *file,
+    zfs_stat_t *isb)
+{
+	if (di->timestamped)
+		(void) fprintf(fp, "%10lld.%09lld\t",
+		    (longlong_t)isb->zs_ctime[0],
+		    (longlong_t)isb->zs_ctime[1]);
+	(void) fprintf(fp, "%c\t", ZDIFF_MODIFIED);
+	if (di->classify) {
+		print_what(fp, isb->zs_mode);
+		(void) fprintf(fp, "\t");
+	}
+	print_cmn(fp, di, file);
+	(void) fprintf(fp, "\t(%+d)", delta);
+	(void) fprintf(fp, "\n");
+}
+
+static void
+print_file(FILE *fp, differ_info_t *di, char type, const char *file,
+    zfs_stat_t *isb)
+{
+	if (di->timestamped)
+		(void) fprintf(fp, "%10lld.%09lld\t",
+		    (longlong_t)isb->zs_ctime[0],
+		    (longlong_t)isb->zs_ctime[1]);
+	(void) fprintf(fp, "%c\t", type);
+	if (di->classify) {
+		print_what(fp, isb->zs_mode);
+		(void) fprintf(fp, "\t");
+	}
+	print_cmn(fp, di, file);
+	(void) fprintf(fp, "\n");
+}
+
+static int
+write_inuse_diffs_one(FILE *fp, differ_info_t *di, uint64_t dobj)
+{
+	struct zfs_stat fsb, tsb;
+	boolean_t same_name;
+	mode_t fmode, tmode;
+	char fobjname[MAXPATHLEN], tobjname[MAXPATHLEN];
+	int fobjerr, tobjerr;
+	int change;
+
+	if (dobj == di->shares)
+		return (0);
+
+	/*
+	 * Check the from and to snapshots for info on the object. If
+	 * we get ENOENT, then the object just didn't exist in that
+	 * snapshot.  If we get ENOTSUP, then we tried to get
+	 * info on a non-ZPL object, which we don't care about anyway.
+	 */
+	fobjerr = get_stats_for_obj(di, di->fromsnap, dobj, fobjname,
+	    MAXPATHLEN, &fsb);
+	if (fobjerr && di->zerr != ENOENT && di->zerr != ENOTSUP)
+		return (-1);
+
+	tobjerr = get_stats_for_obj(di, di->tosnap, dobj, tobjname,
+	    MAXPATHLEN, &tsb);
+	if (tobjerr && di->zerr != ENOENT && di->zerr != ENOTSUP)
+		return (-1);
+
+	/*
+	 * Unallocated object sharing the same meta dnode block
+	 */
+	if (fobjerr && tobjerr) {
+		ASSERT(di->zerr == ENOENT || di->zerr == ENOTSUP);
+		di->zerr = 0;
+		return (0);
+	}
+
+	di->zerr = 0; /* negate get_stats_for_obj() from side that failed */
+	fmode = fsb.zs_mode & S_IFMT;
+	tmode = tsb.zs_mode & S_IFMT;
+	if (fmode == S_IFDIR || tmode == S_IFDIR || fsb.zs_links == 0 ||
+	    tsb.zs_links == 0)
+		change = 0;
+	else
+		change = tsb.zs_links - fsb.zs_links;
+
+	if (fobjerr) {
+		if (change) {
+			print_link_change(fp, di, change, tobjname, &tsb);
+			return (0);
+		}
+		print_file(fp, di, ZDIFF_ADDED, tobjname, &tsb);
+		return (0);
+	} else if (tobjerr) {
+		if (change) {
+			print_link_change(fp, di, change, fobjname, &fsb);
+			return (0);
+		}
+		print_file(fp, di, ZDIFF_REMOVED, fobjname, &fsb);
+		return (0);
+	}
+
+	if (fmode != tmode && fsb.zs_gen == tsb.zs_gen)
+		tsb.zs_gen++;	/* Force a generational difference */
+	same_name = do_name_cmp(fobjname, tobjname);
+
+	/* Simple modification or no change */
+	if (fsb.zs_gen == tsb.zs_gen) {
+		/* No apparent changes.  Could we assert !this?  */
+		if (fsb.zs_ctime[0] == tsb.zs_ctime[0] &&
+		    fsb.zs_ctime[1] == tsb.zs_ctime[1])
+			return (0);
+		if (change) {
+			print_link_change(fp, di, change,
+			    change > 0 ? fobjname : tobjname, &tsb);
+		} else if (same_name) {
+			print_file(fp, di, ZDIFF_MODIFIED, fobjname, &tsb);
+		} else {
+			print_rename(fp, di, fobjname, tobjname, &tsb);
+		}
+		return (0);
+	} else {
+		/* file re-created or object re-used */
+		print_file(fp, di, ZDIFF_REMOVED, fobjname, &fsb);
+		print_file(fp, di, ZDIFF_ADDED, tobjname, &tsb);
+		return (0);
+	}
+}
+
+static int
+write_inuse_diffs(FILE *fp, differ_info_t *di, dmu_diff_record_t *dr)
+{
+	uint64_t o;
+	int err;
+
+	for (o = dr->ddr_first; o <= dr->ddr_last; o++) {
+		if (err = write_inuse_diffs_one(fp, di, o))
+			return (err);
+	}
+	return (0);
+}
+
+static int
+describe_free(FILE *fp, differ_info_t *di, uint64_t object, char *namebuf,
+    int maxlen)
+{
+	struct zfs_stat sb;
+
+	if (get_stats_for_obj(di, di->fromsnap, object, namebuf,
+	    maxlen, &sb) != 0) {
+		/* Let it slide, if in the delete queue on from side */
+		if (di->zerr == ENOENT && sb.zs_links == 0) {
+			di->zerr = 0;
+			return (0);
+		}
+		return (-1);
+	}
+
+	print_file(fp, di, ZDIFF_REMOVED, namebuf, &sb);
+	return (0);
+}
+
+static int
+write_free_diffs(FILE *fp, differ_info_t *di, dmu_diff_record_t *dr)
+{
+	zfs_cmd_t zc = { 0 };
+	libzfs_handle_t *lhdl = di->zhp->zfs_hdl;
+	char fobjname[MAXPATHLEN];
+
+	(void) strlcpy(zc.zc_name, di->fromsnap, sizeof (zc.zc_name));
+	zc.zc_obj = dr->ddr_first - 1;
+
+	ASSERT(di->zerr == 0);
+
+	while (zc.zc_obj < dr->ddr_last) {
+		int err;
+
+		err = ioctl(lhdl->libzfs_fd, ZFS_IOC_NEXT_OBJ, &zc);
+		if (err == 0) {
+			if (zc.zc_obj == di->shares) {
+				zc.zc_obj++;
+				continue;
+			}
+			if (zc.zc_obj > dr->ddr_last) {
+				break;
+			}
+			err = describe_free(fp, di, zc.zc_obj, fobjname,
+			    MAXPATHLEN);
+			if (err)
+				break;
+		} else if (errno == ESRCH) {
+			break;
+		} else {
+			(void) snprintf(di->errbuf, sizeof (di->errbuf),
+			    dgettext(TEXT_DOMAIN,
+			    "next allocated object (> %lld) find failure"),
+			    zc.zc_obj);
+			di->zerr = errno;
+			break;
+		}
+	}
+	if (di->zerr)
+		return (-1);
+	return (0);
+}
+
+static void *
+differ(void *arg)
+{
+	differ_info_t *di = arg;
+	dmu_diff_record_t dr;
+	FILE *ofp;
+	int err = 0;
+
+	if ((ofp = fdopen(di->outputfd, "w")) == NULL) {
+		di->zerr = errno;
+		(void) strerror_r(errno, di->errbuf, sizeof (di->errbuf));
+		(void) close(di->datafd);
+		return ((void *)-1);
+	}
+
+	for (;;) {
+		char *cp = (char *)&dr;
+		int len = sizeof (dr);
+		int rv;
+
+		do {
+			rv = read(di->datafd, cp, len);
+			cp += rv;
+			len -= rv;
+		} while (len > 0 && rv > 0);
+
+		if (rv < 0 || (rv == 0 && len != sizeof (dr))) {
+			di->zerr = EPIPE;
+			break;
+		} else if (rv == 0) {
+			/* end of file at a natural breaking point */
+			break;
+		}
+
+		switch (dr.ddr_type) {
+		case DDR_FREE:
+			err = write_free_diffs(ofp, di, &dr);
+			break;
+		case DDR_INUSE:
+			err = write_inuse_diffs(ofp, di, &dr);
+			break;
+		default:
+			di->zerr = EPIPE;
+			break;
+		}
+
+		if (err || di->zerr)
+			break;
+	}
+
+	(void) fclose(ofp);
+	(void) close(di->datafd);
+	if (err)
+		return ((void *)-1);
+	if (di->zerr) {
+		ASSERT(di->zerr == EINVAL);
+		(void) snprintf(di->errbuf, sizeof (di->errbuf),
+		    dgettext(TEXT_DOMAIN,
+		    "Internal error: bad data from diff IOCTL"));
+		return ((void *)-1);
+	}
+	return ((void *)0);
+}
+
+static int
+find_shares_object(differ_info_t *di)
+{
+	char fullpath[MAXPATHLEN];
+	struct stat64 sb = { 0 };
+
+	(void) strlcpy(fullpath, di->dsmnt, MAXPATHLEN);
+	(void) strlcat(fullpath, ZDIFF_SHARESDIR, MAXPATHLEN);
+
+	if (stat64(fullpath, &sb) != 0) {
+#ifdef sun
+		(void) snprintf(di->errbuf, sizeof (di->errbuf),
+		    dgettext(TEXT_DOMAIN, "Cannot stat %s"), fullpath);
+		return (zfs_error(di->zhp->zfs_hdl, EZFS_DIFF, di->errbuf));
+#else
+		return (0);
+#endif
+	}
+
+	di->shares = (uint64_t)sb.st_ino;
+	return (0);
+}
+
+static int
+make_temp_snapshot(differ_info_t *di)
+{
+	libzfs_handle_t *hdl = di->zhp->zfs_hdl;
+	zfs_cmd_t zc = { 0 };
+
+	(void) snprintf(zc.zc_value, sizeof (zc.zc_value),
+	    ZDIFF_PREFIX, getpid());
+	(void) strlcpy(zc.zc_name, di->ds, sizeof (zc.zc_name));
+	zc.zc_cleanup_fd = di->cleanupfd;
+
+	if (ioctl(hdl->libzfs_fd, ZFS_IOC_TMP_SNAPSHOT, &zc) != 0) {
+		int err = errno;
+		if (err == EPERM) {
+			(void) snprintf(di->errbuf, sizeof (di->errbuf),
+			    dgettext(TEXT_DOMAIN, "The diff delegated "
+			    "permission is needed in order\nto create a "
+			    "just-in-time snapshot for diffing\n"));
+			return (zfs_error(hdl, EZFS_DIFF, di->errbuf));
+		} else {
+			(void) snprintf(di->errbuf, sizeof (di->errbuf),
+			    dgettext(TEXT_DOMAIN, "Cannot create just-in-time "
+			    "snapshot of '%s'"), zc.zc_name);
+			return (zfs_standard_error(hdl, err, di->errbuf));
+		}
+	}
+
+	di->tmpsnap = zfs_strdup(hdl, zc.zc_value);
+	di->tosnap = zfs_asprintf(hdl, "%s@%s", di->ds, di->tmpsnap);
+	return (0);
+}
+
+static void
+teardown_differ_info(differ_info_t *di)
+{
+	free(di->ds);
+	free(di->dsmnt);
+	free(di->fromsnap);
+	free(di->frommnt);
+	free(di->tosnap);
+	free(di->tmpsnap);
+	free(di->tomnt);
+	(void) close(di->cleanupfd);
+}
+
+static int
+get_snapshot_names(differ_info_t *di, const char *fromsnap,
+    const char *tosnap)
+{
+	libzfs_handle_t *hdl = di->zhp->zfs_hdl;
+	char *atptrf = NULL;
+	char *atptrt = NULL;
+	int fdslen, fsnlen;
+	int tdslen, tsnlen;
+
+	/*
+	 * Can accept
+	 *    dataset@snap1
+	 *    dataset@snap1 dataset@snap2
+	 *    dataset@snap1 @snap2
+	 *    dataset@snap1 dataset
+	 *    @snap1 dataset@snap2
+	 */
+	if (tosnap == NULL) {
+		/* only a from snapshot given, must be valid */
+		(void) snprintf(di->errbuf, sizeof (di->errbuf),
+		    dgettext(TEXT_DOMAIN,
+		    "Badly formed snapshot name %s"), fromsnap);
+
+		if (!zfs_validate_name(hdl, fromsnap, ZFS_TYPE_SNAPSHOT,
+		    B_FALSE)) {
+			return (zfs_error(hdl, EZFS_INVALIDNAME,
+			    di->errbuf));
+		}
+
+		atptrf = strchr(fromsnap, '@');
+		ASSERT(atptrf != NULL);
+		fdslen = atptrf - fromsnap;
+
+		di->fromsnap = zfs_strdup(hdl, fromsnap);
+		di->ds = zfs_strdup(hdl, fromsnap);
+		di->ds[fdslen] = '\0';
+
+		/* the to snap will be a just-in-time snap of the head */
+		return (make_temp_snapshot(di));
+	}
+
+	(void) snprintf(di->errbuf, sizeof (di->errbuf),
+	    dgettext(TEXT_DOMAIN,
+	    "Unable to determine which snapshots to compare"));
+
+	atptrf = strchr(fromsnap, '@');
+	atptrt = strchr(tosnap, '@');
+	fdslen = atptrf ? atptrf - fromsnap : strlen(fromsnap);
+	tdslen = atptrt ? atptrt - tosnap : strlen(tosnap);
+	fsnlen = strlen(fromsnap) - fdslen;	/* includes @ sign */
+	tsnlen = strlen(tosnap) - tdslen;	/* includes @ sign */
+
+	if (fsnlen <= 1 || tsnlen == 1 || (fdslen == 0 && tdslen == 0) ||
+	    (fsnlen == 0 && tsnlen == 0)) {
+		return (zfs_error(hdl, EZFS_INVALIDNAME, di->errbuf));
+	} else if ((fdslen > 0 && tdslen > 0) &&
+	    ((tdslen != fdslen || strncmp(fromsnap, tosnap, fdslen) != 0))) {
+		/*
+		 * not the same dataset name, might be okay if
+		 * tosnap is a clone of a fromsnap descendant.
+		 */
+		char origin[ZFS_MAXNAMELEN];
+		zprop_source_t src;
+		zfs_handle_t *zhp;
+
+		di->ds = zfs_alloc(di->zhp->zfs_hdl, tdslen + 1);
+		(void) strncpy(di->ds, tosnap, tdslen);
+		di->ds[tdslen] = '\0';
+
+		zhp = zfs_open(hdl, di->ds, ZFS_TYPE_FILESYSTEM);
+		while (zhp != NULL) {
+			(void) zfs_prop_get(zhp, ZFS_PROP_ORIGIN,
+			    origin, sizeof (origin), &src, NULL, 0, B_FALSE);
+
+			if (strncmp(origin, fromsnap, fsnlen) == 0)
+				break;
+
+			(void) zfs_close(zhp);
+			zhp = zfs_open(hdl, origin, ZFS_TYPE_FILESYSTEM);
+		}
+
+		if (zhp == NULL) {
+			(void) snprintf(di->errbuf, sizeof (di->errbuf),
+			    dgettext(TEXT_DOMAIN,
+			    "Not an earlier snapshot from the same fs"));
+			return (zfs_error(hdl, EZFS_INVALIDNAME, di->errbuf));
+		} else {
+			(void) zfs_close(zhp);
+		}
+
+		di->isclone = B_TRUE;
+		di->fromsnap = zfs_strdup(hdl, fromsnap);
+		if (tsnlen) {
+			di->tosnap = zfs_strdup(hdl, tosnap);
+		} else {
+			return (make_temp_snapshot(di));
+		}
+	} else {
+		int dslen = fdslen ? fdslen : tdslen;
+
+		di->ds = zfs_alloc(hdl, dslen + 1);
+		(void) strncpy(di->ds, fdslen ? fromsnap : tosnap, dslen);
+		di->ds[dslen] = '\0';
+
+		di->fromsnap = zfs_asprintf(hdl, "%s%s", di->ds, atptrf);
+		if (tsnlen) {
+			di->tosnap = zfs_asprintf(hdl, "%s%s", di->ds, atptrt);
+		} else {
+			return (make_temp_snapshot(di));
+		}
+	}
+	return (0);
+}
+
+static int
+get_mountpoint(differ_info_t *di, char *dsnm, char **mntpt)
+{
+	boolean_t mounted;
+
+	mounted = is_mounted(di->zhp->zfs_hdl, dsnm, mntpt);
+	if (mounted == B_FALSE) {
+		(void) snprintf(di->errbuf, sizeof (di->errbuf),
+		    dgettext(TEXT_DOMAIN,
+		    "Cannot diff an unmounted snapshot"));
+		return (zfs_error(di->zhp->zfs_hdl, EZFS_BADTYPE, di->errbuf));
+	}
+
+	/* Avoid a double slash at the beginning of root-mounted datasets */
+	if (**mntpt == '/' && *(*mntpt + 1) == '\0')
+		**mntpt = '\0';
+	return (0);
+}
+
+static int
+get_mountpoints(differ_info_t *di)
+{
+	char *strptr;
+	char *frommntpt;
+
+	/*
+	 * first get the mountpoint for the parent dataset
+	 */
+	if (get_mountpoint(di, di->ds, &di->dsmnt) != 0)
+		return (-1);
+
+	strptr = strchr(di->tosnap, '@');
+	ASSERT3P(strptr, !=, NULL);
+	di->tomnt = zfs_asprintf(di->zhp->zfs_hdl, "%s%s%s", di->dsmnt,
+	    ZDIFF_SNAPDIR, ++strptr);
+
+	strptr = strchr(di->fromsnap, '@');
+	ASSERT3P(strptr, !=, NULL);
+
+	frommntpt = di->dsmnt;
+	if (di->isclone) {
+		char *mntpt;
+		int err;
+
+		*strptr = '\0';
+		err = get_mountpoint(di, di->fromsnap, &mntpt);
+		*strptr = '@';
+		if (err != 0)
+			return (-1);
+		frommntpt = mntpt;
+	}
+
+	di->frommnt = zfs_asprintf(di->zhp->zfs_hdl, "%s%s%s", frommntpt,
+	    ZDIFF_SNAPDIR, ++strptr);
+
+	if (di->isclone)
+		free(frommntpt);
+
+	return (0);
+}
+
+static int
+setup_differ_info(zfs_handle_t *zhp, const char *fromsnap,
+    const char *tosnap, differ_info_t *di)
+{
+	di->zhp = zhp;
+
+	di->cleanupfd = open(ZFS_DEV, O_RDWR|O_EXCL);
+	VERIFY(di->cleanupfd >= 0);
+
+	if (get_snapshot_names(di, fromsnap, tosnap) != 0)
+		return (-1);
+
+	if (get_mountpoints(di) != 0)
+		return (-1);
+
+	if (find_shares_object(di) != 0)
+		return (-1);
+
+	return (0);
+}
+
+int
+zfs_show_diffs(zfs_handle_t *zhp, int outfd, const char *fromsnap,
+    const char *tosnap, int flags)
+{
+	zfs_cmd_t zc = { 0 };
+	char errbuf[1024];
+	differ_info_t di = { 0 };
+	pthread_t tid;
+	int pipefd[2];
+	int iocerr;
+
+	(void) snprintf(errbuf, sizeof (errbuf),
+	    dgettext(TEXT_DOMAIN, "zfs diff failed"));
+
+	if (setup_differ_info(zhp, fromsnap, tosnap, &di)) {
+		teardown_differ_info(&di);
+		return (-1);
+	}
+
+	if (pipe(pipefd)) {
+		zfs_error_aux(zhp->zfs_hdl, strerror(errno));
+		teardown_differ_info(&di);
+		return (zfs_error(zhp->zfs_hdl, EZFS_PIPEFAILED, errbuf));
+	}
+
+	di.scripted = (flags & ZFS_DIFF_PARSEABLE);
+	di.classify = (flags & ZFS_DIFF_CLASSIFY);
+	di.timestamped = (flags & ZFS_DIFF_TIMESTAMP);
+
+	di.outputfd = outfd;
+	di.datafd = pipefd[0];
+
+	if (pthread_create(&tid, NULL, differ, &di)) {
+		zfs_error_aux(zhp->zfs_hdl, strerror(errno));
+		(void) close(pipefd[0]);
+		(void) close(pipefd[1]);
+		teardown_differ_info(&di);
+		return (zfs_error(zhp->zfs_hdl,
+		    EZFS_THREADCREATEFAILED, errbuf));
+	}
+
+	/* do the ioctl() */
+	(void) strlcpy(zc.zc_value, di.fromsnap, strlen(di.fromsnap) + 1);
+	(void) strlcpy(zc.zc_name, di.tosnap, strlen(di.tosnap) + 1);
+	zc.zc_cookie = pipefd[1];
+
+	iocerr = ioctl(zhp->zfs_hdl->libzfs_fd, ZFS_IOC_DIFF, &zc);
+	if (iocerr != 0) {
+		(void) snprintf(errbuf, sizeof (errbuf),
+		    dgettext(TEXT_DOMAIN, "Unable to obtain diffs"));
+		if (errno == EPERM) {
+			zfs_error_aux(zhp->zfs_hdl, dgettext(TEXT_DOMAIN,
+			    "\n   The sys_mount privilege or diff delegated "
+			    "permission is needed\n   to execute the "
+			    "diff ioctl"));
+		} else if (errno == EXDEV) {
+			zfs_error_aux(zhp->zfs_hdl, dgettext(TEXT_DOMAIN,
+			    "\n   Not an earlier snapshot from the same fs"));
+		} else if (errno != EPIPE || di.zerr == 0) {
+			zfs_error_aux(zhp->zfs_hdl, strerror(errno));
+		}
+		(void) close(pipefd[1]);
+		(void) pthread_cancel(tid);
+		(void) pthread_join(tid, NULL);
+		teardown_differ_info(&di);
+		if (di.zerr != 0 && di.zerr != EPIPE) {
+			zfs_error_aux(zhp->zfs_hdl, strerror(di.zerr));
+			return (zfs_error(zhp->zfs_hdl, EZFS_DIFF, di.errbuf));
+		} else {
+			return (zfs_error(zhp->zfs_hdl, EZFS_DIFFDATA, errbuf));
+		}
+	}
+
+	(void) close(pipefd[1]);
+	(void) pthread_join(tid, NULL);
+
+	if (di.zerr != 0) {
+		zfs_error_aux(zhp->zfs_hdl, strerror(di.zerr));
+		return (zfs_error(zhp->zfs_hdl, EZFS_DIFF, di.errbuf));
+	}
+	teardown_differ_info(&di);
+	return (0);
+}