110  * image, then, once the inactive image has completed the hash chain
112  * atomically switched, making the formerly-inactive image authoritative.
113  * After the image switch, the update code then updates the formerly-active
114  * image's hash chains to match the active image's hash chains.
118  * inactive image's hash chains with the active image's chains.  Note that
119  * the atomic image switch serves as the "commit point" for the operation:
329 	uchar_t		image;
341 	 * our active image's hash chains correct and only swap to the
342 	 * alternate image when the other image is completely safe to use.
357 	image = header.dnh_image;
384 				if (read_hashhead(fd, &recid, hash, image)
389 				if (recid == rec.rec_next[image])
391 				recid = rec.rec_next[image];
403 				recid = header.dnh_cidhash[hash][image];
406 				if (recid == rec.rec_next[image])
408 				recid = rec.rec_next[image];
412 				recid = header.dnh_cidhash[hash][image];
437 		if (rec.rec_prev[image] == DN_NOREC)
573 	uchar_t		image;
588 	 * Get the active image.
590 	retval = getabyte(fd, offsetof(dn_header_t, dnh_image), &image);
601 	if (rec.rec_prev[image] != DN_NOREC)
607 	 * image's hash record id pointers so that the record will
608 	 * atomically become in-use when we switch to the alternate image.
610 	if (read_hashhead(fd, &recid_head, hash, image) == -1)
615 	rec.rec_prev[!image] = DN_HASHHEAD;
616 	rec.rec_next[!image] = recid_head;
622 	if (rec.rec_next[!image] != DN_NOREC) {
623 		if (read_rec(fd, &rec_next, rec.rec_next[!image]) == -1)
644 	 * Update the alternate image's on-disk hash pointers.  We need to
645 	 * do this before we switch to the alternate image so we cannot
646 	 * abort with an inconsistent active image.
648 	if (rec.rec_next[!image] != DN_NOREC) {
649 		rec_next.rec_prev[!image] = recid;
650 		if (write_rec(fd, &rec_next, rec.rec_next[!image]) == -1)
653 	if (write_hashhead(fd, recid, hash, !image) == -1)
657 	 * Activate the alternate image.  This is our commit point -- if we
660 	image = !image;
661 	retval = setabyte(fd, offsetof(dn_header_t, dnh_image), image);
668 	rec.rec_prev[!image] = rec.rec_prev[image];
669 	rec.rec_next[!image] = rec.rec_next[image];
673 	if (rec.rec_next[!image] != DN_NOREC) {
674 		rec_next.rec_prev[!image] = recid;
675 		if (write_rec(fd, &rec_next, rec.rec_next[!image]) == -1)
678 	if (write_hashhead(fd, recid, hash, !image) == -1)
698 	uchar_t		image;
711 	 * Get the active image.
713 	retval = getabyte(fd, offsetof(dn_header_t, dnh_image), &image);
726 	if (rec.rec_prev[image] == DN_NOREC)
742 	if (rec.rec_next[image] != DN_NOREC) {
743 		if (read_rec(fd, &rec_next, rec.rec_next[image]) == -1)
747 	if (rec.rec_prev[image] != DN_HASHHEAD) {
748 		if (read_rec(fd, &rec_prev, rec.rec_prev[image]) == -1)
753 	 * Before we update the alternate image's on-disk hash pointers,
762 	 * Update the alternate image's on-disk hash pointers.  We need to
763 	 * do this before we switch to the alternate image so we do not
764 	 * abort with an inconsistent active image.  Also reset the
765 	 * record's alternate image record id pointers, so that the old
766 	 * record will not be in-use when we switch to the alternate image.
768 	if (rec.rec_next[image] != DN_NOREC) {
769 		rec_next.rec_prev[!image] = rec.rec_prev[image];
770 		if (write_rec(fd, &rec_next, rec.rec_next[image]) == -1)
774 	if (rec.rec_prev[image] != DN_HASHHEAD) {
775 		rec_prev.rec_next[!image] = rec.rec_next[image];
776 		if (write_rec(fd, &rec_prev, rec.rec_prev[image]) == -1)
779 		if (write_hashhead(fd, rec.rec_next[image], hash, !image) == -1)
783 	rec.rec_next[!image] = DN_NOREC;
784 	rec.rec_prev[!image] = DN_NOREC;
789 	 * Activate the alternate image.  This is our commit point -- if we
792 	image = !image;
793 	retval = setabyte(fd, offsetof(dn_header_t, dnh_image), image);
800 	if (rec.rec_next[!image] != DN_NOREC) {
801 		rec_next.rec_prev[!image] = rec.rec_prev[!image];
802 		if (write_rec(fd, &rec_next, rec.rec_next[!image]) == -1)
806 	if (rec.rec_prev[!image] != DN_HASHHEAD) {
807 		rec_prev.rec_next[!image] = rec.rec_next[!image];
808 		if (write_rec(fd, &rec_prev, rec.rec_prev[!image]) == -1)
811 		if (write_hashhead(fd, rec.rec_next[!image], hash, !image)
816 	rec.rec_next[!image] = DN_NOREC;
817 	rec.rec_prev[!image] = DN_NOREC;
833 	uchar_t		image;
846 	 * Get the active image
848 	retval = getabyte(fd, offsetof(dn_header_t, dnh_image), &image);
861 	if (rec.rec_prev[image] == DN_NOREC)
876 		if (new_rec.rec_prev[image] != DN_NOREC)
890 	 * in either case, only update the alternate image pointers, so
892 	 * alternate image.
898 		new_rec.rec_prev[!image] = rec.rec_prev[image];
899 		new_rec.rec_next[!image] = rec.rec_next[image];
901 		if (read_hashhead(fd, &recid_head, new_hash, image) == -1)
904 		new_rec.rec_prev[!image] = DN_HASHHEAD;
905 		new_rec.rec_next[!image] = recid_head;
931 	 * alternate image for now so that we can recover upon failure.
934 		if (rec.rec_next[image] != DN_NOREC) {
935 			if (read_rec(fd, &rec_next, rec.rec_next[image]) == -1)
938 		if (rec.rec_prev[image] != DN_HASHHEAD) {
939 			if (read_rec(fd, &rec_prev, rec.rec_prev[image]) == -1)
944 			rec_next.rec_prev[!image] = rec.rec_prev[!image];
945 			rec_prev.rec_next[!image] = rec.rec_next[!image];
947 			rec_next.rec_prev[!image] = new_recid;
948 			rec_prev.rec_next[!image] = new_recid;
951 		if (rec.rec_next[image] != DN_NOREC) {
952 			if (write_rec(fd, &rec_next, rec.rec_next[image]) == -1)
955 		if (rec.rec_prev[image] != DN_HASHHEAD) {
956 			if (write_rec(fd, &rec_prev, rec.rec_prev[image]) == -1)
959 			if (write_hashhead(fd, rec_prev.rec_next[!image], hash,
960 			    !image) == -1)
965 		 * If our hash is changing, update the alternate image
972 				rec_head.rec_prev[!image] = new_recid;
976 			if (write_hashhead(fd, new_recid, new_hash, !image)
983 		 * alternate image record id pointers, so that the old
985 		 * alternate image.
988 			rec.rec_prev[!image] = DN_NOREC;
989 			rec.rec_next[!image] = DN_NOREC;
997 	 * the image that will be active when we're done.  This piece of
1000 	 * failed before or after activating the alternate image (below).
1001 	 * If we failed before activating the alternate image, then the
1004 	 * after making the alternate image active but before we completed
1011 		    !image);
1017 	 * Activate the alternate image.  This is our commit point -- if we
1020 	image = !image;
1021 	retval = setabyte(fd, offsetof(dn_header_t, dnh_image), image);
1043 	new_rec.rec_prev[!image] = new_rec.rec_prev[image];
1044 	new_rec.rec_next[!image] = new_rec.rec_next[image];
1049 		if (rec.rec_next[image] != DN_NOREC) {
1050 			rec_next.rec_prev[!image] = rec.rec_prev[image];
1051 			if (write_rec(fd, &rec_next, rec.rec_next[image]) == -1)
1054 		if (rec.rec_prev[image] != DN_HASHHEAD) {
1055 			rec_prev.rec_next[!image] = rec.rec_next[image];
1056 			if (write_rec(fd, &rec_prev, rec.rec_prev[image]) == -1)
1059 			if (write_hashhead(fd, rec.rec_next[image], hash,
1060 			    !image) == -1)
1065 		 * If our hash changed, update the alternate image record
1070 				rec_head.rec_prev[!image] =
1071 				    rec_head.rec_prev[image];
1075 			if (write_hashhead(fd, new_recid, new_hash, !image)
1085 			rec.rec_prev[!image] = DN_NOREC;
1086 			rec.rec_next[!image] = DN_NOREC;
1189 	uchar_t		image, dirty;
1212 	 * If `dnh_tempimage' matches the current working image, then we
1231 	image = header.dnh_image;
1233 		header.dnh_cidhash[hash][!image] =
1234 		    header.dnh_cidhash[hash][image];
1252 		if (rec.rec_next[image] != rec.rec_next[!image] ||
1253 		    rec.rec_prev[image] != rec.rec_prev[!image]) {
1256 			rec.rec_prev[!image] = rec.rec_prev[image];
1257 			rec.rec_next[!image] = rec.rec_next[image];
1426  * into `recid_headp', using image `image'.  Returns 0 on success, -1 on
1430 read_hashhead(int fd, dn_recid_t *recid_headp, uint16_t cidhash, uchar_t image)
1433 	    offsetof(dn_header_t, dnh_cidhash[cidhash][image])) == -1)
1442  * from `recid_head', using image `image'.  Returns 0 on success, -1 on
1446 write_hashhead(int fd, dn_recid_t recid_head, uint16_t cidhash, uchar_t image)
1450 	    offsetof(dn_header_t, dnh_cidhash[cidhash][image])));

Indexes created Tue Jul 24 14:28:13 CEST 2018