pvck: new dump option to extract metadata

The new command 'pvck --dump metadata PV' will extract
the current version of VG metadata from a PV for testing
and debugging.  --dump metadata_area extracts the entire
text metadata area.

lib/format_text/format-text.c

@@ -2602,3 +2602,221 @@ bad:
 
 	return NULL;
 }
+
+static char *_read_metadata_text(struct cmd_context *cmd, struct device *dev,
+				 uint64_t area_start, uint64_t area_size,
+				 uint32_t *len, uint64_t *disk_offset)
+{
+	struct mda_header *mh;
+	struct raw_locn *rlocn_slot0;
+	uint64_t text_offset, text_size;
+	char *area_buf;
+	char *text_buf;
+
+	/*
+	 * Read the entire metadata area, including mda_header and entire
+	 * circular buffer.
+	 */
+	if (!(area_buf = malloc(area_size)))
+		return_NULL;
+
+	if (!dev_read_bytes(dev, area_start, area_size, area_buf)) {
+		log_error("Failed to read device %s at %llu size %llu",
+			  dev_name(dev),
+			  (unsigned long long)area_start,
+			  (unsigned long long)area_size);
+		return NULL;
+	}
+
+	mh = (struct mda_header *)area_buf;
+	_xlate_mdah(mh);
+
+	rlocn_slot0 = &mh->raw_locns[0];
+	text_offset = rlocn_slot0->offset;
+	text_size = rlocn_slot0->size;
+
+	/*
+	 * Copy and return the current metadata text out of the metadata area.
+	 */
+
+	if (!(text_buf = malloc(text_size)))
+		return_NULL;
+
+	memcpy(text_buf, area_buf + text_offset, text_size);
+
+	if (len)
+		*len = (uint32_t)text_size;
+	if (disk_offset)
+		*disk_offset = area_start + text_offset;
+
+	free(area_buf);
+
+	return text_buf;
+}
+
+int dump_metadata_text(struct cmd_context *cmd,
+		       const char *vgname,
+		       const char *vgid,
+		       struct device *dev,
+		       struct metadata_area *mda,
+		       const char *tofile)
+{
+	char *textbuf;
+	struct format_instance *fid;
+	struct format_instance_ctx fic;
+	struct mda_context *mdac;
+	struct volume_group *vg;
+	unsigned use_previous_vg = 0;
+	uint32_t textlen = 0;
+	uint32_t textcrc;
+	uint64_t text_disk_offset;
+	int ret = 0;
+
+	/*
+	 * Set up overhead/abstractions for reading a given vgname
+	 * (fmt/fid/fic/vgid).
+	 */
+
+	fic.type = FMT_INSTANCE_MDAS | FMT_INSTANCE_AUX_MDAS;
+	fic.context.vg_ref.vg_name = vgname;
+	fic.context.vg_ref.vg_id = vgid;
+
+	if (!(fid = _text_create_text_instance(cmd->fmt, &fic))) {
+		log_error("Failed to create format instance");
+		return 0;
+	}
+
+	mdac = mda->metadata_locn;
+
+	/*
+	 * Read the VG metadata from the device as a raw chunk of original text.
+	 */
+	textbuf = _read_metadata_text(cmd, dev,
+				      mdac->area.start, mdac->area.size,
+				      &textlen, &text_disk_offset);
+	if (!textbuf || !textlen) {
+		log_error("No metadata text found on %s", dev_name(dev));
+		_text_destroy_instance(fid);
+		return 0;
+	}
+
+	textcrc = calc_crc(INITIAL_CRC, (uint8_t *)textbuf, textlen);
+
+	/*
+	 * Read the same VG metadata, but imported/parsed into a vg struct
+	 * format so we know it's valid/parsable, and can look at values in it.
+	 */
+	if (!(vg = _vg_read_raw(fid, vgname, mda, NULL, &use_previous_vg))) {
+		log_warn("WARNING: parse error for metadata on %s.", dev_name(dev));
+		_text_destroy_instance(fid);
+	}
+
+	log_print("Metadata for %s from %s at %llu size %u with seqno %u checksum 0x%x.",
+		  vgname, dev_name(dev),
+		  (unsigned long long)text_disk_offset, textlen,
+		  vg ? vg->seqno : 0, textcrc);
+
+	if (!tofile) {
+		log_print("---");
+		printf("%s\n", textbuf);
+		log_print("---");
+	} else {
+		FILE *fp;
+		if (!(fp = fopen(tofile, "wx"))) {
+			log_error("Failed to create file %s", tofile);
+			goto out;
+		}
+
+		fprintf(fp, "%s", textbuf);
+
+		if (fflush(fp))
+			stack;
+		if (fclose(fp))
+			stack;
+	}
+
+	if (vg)
+		release_vg(vg);
+
+	free(textbuf);
+	ret = 1;
+out:
+	return ret;
+}
+
+static char *_read_metadata_area(struct cmd_context *cmd, struct device *dev,
+				 uint64_t area_start, uint64_t area_size)
+{
+	char *area_buf;
+
+	/*
+	 * Read the entire metadata area, including mda_header and entire
+	 * circular buffer.
+	 */
+	if (!(area_buf = malloc(area_size)))
+		return_NULL;
+
+	if (!dev_read_bytes(dev, area_start, area_size, area_buf)) {
+		log_error("Failed to read device %s at %llu size %llu",
+			  dev_name(dev),
+			  (unsigned long long)area_start,
+			  (unsigned long long)area_size);
+		return NULL;
+	}
+
+	return area_buf;
+}
+
+int dump_metadata_area(struct cmd_context *cmd,
+		       const char *vgname,
+		       const char *vgid,
+		       struct device *dev,
+		       struct metadata_area *mda,
+		       const char *tofile)
+{
+	char *areabuf;
+	char *textbuf;
+	struct mda_context *mdac;
+	int ret = 0;
+
+	mdac = mda->metadata_locn;
+
+	areabuf = _read_metadata_area(cmd, dev,
+				      mdac->area.start, mdac->area.size);
+	if (!areabuf) {
+		log_error("No metadata area found on %s", dev_name(dev));
+		return 0;
+	}
+
+	log_print("Metadata buffer for %s from %s in area at %llu size %llu offset 512.",
+		  vgname, dev_name(dev),
+		  (unsigned long long)mdac->area.start,
+		  (unsigned long long)mdac->area.size);
+
+	/* text starts after mda_header which uses 512 bytes */
+	textbuf = areabuf + 512;
+
+	if (!tofile) {
+		/* N.B. this will often include unprintable data */
+		log_print("---");
+		fwrite(textbuf, mdac->area.size - 512, 1, stdout);
+		log_print("---");
+	} else {
+		FILE *fp;
+		if (!(fp = fopen(tofile, "wx"))) {
+			log_error("Failed to create file %s", tofile);
+			goto out;
+		}
+
+		fwrite(textbuf, mdac->area.size - 512, 1, fp);
+
+		if (fflush(fp))
+			stack;
+		if (fclose(fp))
+			stack;
+	}
+	ret = 1;
+out:
+	free(areabuf);
+	return ret;
+}