blktap2: a completely rewritten blktap implementation

Benefits to blktap2 over the old version of blktap:

* Isolation from xenstore - Blktap devices are now created directly on
   the linux dom0 command line, rather than being spawned in response
   to XenStore events.  This is handy for debugging, makes blktap
   generally easier to work with, and is a step toward a generic
   user-level block device implementation that is not Xen-specific.

* Improved tapdisk infrastructure: simpler request forwarding, new
   request scheduler, request merging, more efficient use of AIO.

* Improved tapdisk error handling and memory management.  No
   allocations on the block data path, IO retry logic to protect
   guests
   transient block device failures.  This has been tested and is known
   to work on weird environments such as NFS soft mounts.

* Pause and snapshot of live virtual disks (see xmsnap script).

* VHD support.  The VHD code in this release has been rigorously
   tested, and represents a very mature implementation of the VHD
   image
   format.

* No more duplication of mechanism with blkback.  The blktap kernel
   module has changed dramatically from the original blktap.  Blkback
   is now always used to talk to Xen guests, blktap just presents a
   Linux gendisk that blkback can export.  This is done while
   preserving the zero-copy data path from domU to physical device.

These patches deprecate the old blktap code, which can hopefully be
removed from the tree completely at some point in the future.

Signed-off-by: Jake Wires <jake.wires@citrix.com>
Signed-off-by: Dutch Meyer <dmeyer@cs.ubc.ca>

2 files changed, 387 insertions, 0 deletions

diff --git a/tools/blktap2/lvm/Makefile b/tools/blktap2/lvm/Makefile
new file mode 100644
index 0000000000..3a726d7c8b
--- /dev/null
+++ b/tools/blktap2/lvm/Makefile
@@ -0,0 +1,38 @@
+XEN_ROOT = ../../../
+BLKTAP_ROOT := ../
+include $(XEN_ROOT)/tools/Rules.mk
+
+ifeq ($(LVM_UTIL_TEST),y)
+TEST              := lvm-util
+endif
+
+CFLAGS            += -Werror
+CFLAGS            += -Wno-unused
+CFLAGS            += -I../include
+CFLAGS            += -D_GNU_SOURCE
+
+ifeq ($(CONFIG_X86_64),y)
+CFLAGS            += -fPIC
+endif
+
+# Get gcc to generate the dependencies for us.
+CFLAGS            += -Wp,-MD,.$(@F).d
+DEPS               = .*.d
+
+LVM-OBJS          := lvm-util.o
+
+all: build
+
+build: $(TEST) $(LVM-OBJS)
+
+install: all
+
+lvm-util: lvm-util.o
+	$(CC) $(CFLAGS) -DLVM_UTIL -o lvm-util lvm-util.c
+
+clean:
+	rm -rf *.o *~ $(DEPS) $(IBIN)
+
+.PHONY: all build clean install lvm-util
+
+-include $(DEPS)
diff --git a/tools/blktap2/lvm/lvm-util.c b/tools/blktap2/lvm/lvm-util.c
new file mode 100644
index 0000000000..b456e0438b
--- /dev/null
+++ b/tools/blktap2/lvm/lvm-util.c
@@ -0,0 +1,349 @@
+/* 
+ * Copyright (c) 2008, XenSource Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *     * Redistributions of source code must retain the above copyright
+ *       notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above copyright
+ *       notice, this list of conditions and the following disclaimer in the
+ *       documentation and/or other materials provided with the distribution.
+ *     * Neither the name of XenSource Inc. nor the names of its contributors
+ *       may be used to endorse or promote products derived from this software
+ *       without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
+ * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "lvm-util.h"
+
+#define _NAME "%255s"
+static char line[1024];
+
+static inline int
+lvm_read_line(FILE *scan)
+{
+	memset(line, 0, sizeof(line));
+	return (fscanf(scan, "%1023[^\n]", line) != 1);
+}
+
+static inline int
+lvm_next_line(FILE *scan)
+{
+	return (fscanf(scan, "%1023[\n]", line) != 1);
+}
+
+static int
+lvm_copy_name(char *dst, const char *src, size_t size)
+{
+	if (strnlen(src, size) == size)
+		return -ENAMETOOLONG;
+
+	strcpy(dst, src);
+	return 0;
+}
+
+static int
+lvm_parse_pv(struct vg *vg, const char *name, int pvs, uint64_t start)
+{
+	int i, err;
+	struct pv *pv;
+
+	pv = NULL;
+
+	if (!vg->pvs) {
+		vg->pvs = calloc(pvs, sizeof(struct pv));
+		if (!vg->pvs)
+			return -ENOMEM;
+	}
+
+	for (i = 0; i < pvs; i++) {
+		pv = vg->pvs + i;
+
+		if (!pv->name[0])
+			break;
+
+		if (!strcmp(pv->name, name))
+			return -EEXIST;
+	}
+
+	if (!pv)
+		return -ENOENT;
+
+	if (i == pvs)
+		return -ENOMEM;
+
+	err = lvm_copy_name(pv->name, name, sizeof(pv->name) - 1);
+	if (err)
+		return err;
+
+	pv->start = start;
+	return 0;
+}
+
+static int
+lvm_open_vg(const char *vgname, struct vg *vg)
+{
+	FILE *scan;
+	int i, err, pvs, lvs;
+	char *cmd, pvname[256];
+	uint64_t size, pv_start;
+
+	memset(vg, 0, sizeof(*vg));
+
+	err = asprintf(&cmd, "/usr/sbin/vgs %s --noheadings --nosuffix --units=b "
+		       "--options=vg_name,vg_extent_size,lv_count,pv_count,"
+		       "pv_name,pe_start --unbuffered 2> /dev/null", vgname);
+	if (err == -1)
+		return -ENOMEM;
+
+	errno = 0;
+	scan  = popen(cmd, "r");
+	if (!scan) {
+		err = (errno ? -errno : ENOMEM);
+		goto out;
+	}
+
+	for (;;) {
+		if (lvm_read_line(scan))
+			break;
+
+		err = -EINVAL;
+                if (sscanf(line, _NAME" %"SCNu64" %d %d "_NAME" %"SCNu64,
+			   vg->name, &size, &lvs, &pvs, pvname, &pv_start) != 6)
+			goto out;
+
+		if (strcmp(vg->name, vgname))
+			goto out;
+
+		err = lvm_parse_pv(vg, pvname, pvs, pv_start);
+		if (err)
+			goto out;
+
+		if (lvm_next_line(scan))
+			break;
+	}
+
+	err = -EINVAL;
+	if (strcmp(vg->name, vgname))
+		goto out;
+
+	for (i = 0; i < pvs; i++)
+		if (!vg->pvs[i].name[0])
+			goto out;
+
+	err = -ENOMEM;
+	vg->lvs = calloc(lvs, sizeof(struct lv));
+	if (!vg->lvs)
+		goto out;
+
+	err             = 0;
+	vg->lv_cnt      = lvs;
+	vg->pv_cnt      = pvs;
+	vg->extent_size = size;
+
+out:
+	if (scan)
+		pclose(scan);
+	if (err)
+		lvm_free_vg(vg);
+	free(cmd);
+	return err;
+}
+
+static int
+lvm_parse_lv_devices(struct vg *vg, struct lv_segment *seg, char *devices)
+{
+	int i;
+	uint64_t start, pe_start;
+
+	for (i = 0; i < strlen(devices); i++)
+		if (strchr(",()", devices[i]))
+			devices[i] = ' ';
+
+        if (sscanf(devices, _NAME" %"SCNu64, seg->device, &start) != 2)
+		return -EINVAL;
+
+	pe_start = -1;
+	for (i = 0; i < vg->pv_cnt; i++)
+		if (!strcmp(vg->pvs[i].name, seg->device)) {
+			pe_start = vg->pvs[i].start;
+			break;
+		}
+
+	if (pe_start == -1)
+		return -EINVAL;
+
+	seg->pe_start = (start * vg->extent_size) + pe_start;
+	return 0;
+}
+
+static int
+lvm_scan_lvs(struct vg *vg)
+{
+	char *cmd;
+	FILE *scan;
+	int i, err;
+
+	err = asprintf(&cmd, "/usr/sbin/lvs %s --noheadings --nosuffix --units=b "
+		       "--options=lv_name,lv_size,segtype,seg_count,seg_start,"
+		       "seg_size,devices --unbuffered 2> /dev/null", vg->name);
+	if (err == -1)
+		return -ENOMEM;
+
+	errno = 0;
+	scan  = popen(cmd, "r");
+	if (!scan) {
+		err = (errno ? -errno : -ENOMEM);
+		goto out;
+	}
+
+	for (i = 0;;) {
+		int segs;
+		struct lv *lv;
+		struct lv_segment seg;
+		uint64_t size, seg_start;
+		char type[32], name[256], dev[256], devices[1024];
+
+		if (i >= vg->lv_cnt)
+			break;
+
+		if (lvm_read_line(scan)) {
+			vg->lv_cnt = i;
+			break;
+		}
+
+		err = -EINVAL;
+		lv  = vg->lvs + i;
+
+                if (sscanf(line, _NAME" %"SCNu64" %31s %u %"SCNu64" %"SCNu64" %1023s",
+			   name, &size, type, &segs, &seg_start,
+			   &seg.pe_size, devices) != 7)
+			goto out;
+
+		if (seg_start)
+			goto next;
+
+		if (!strcmp(type, "linear"))
+			seg.type = LVM_SEG_TYPE_LINEAR;
+		else
+			seg.type = LVM_SEG_TYPE_UNKNOWN;
+
+		if (lvm_parse_lv_devices(vg, &seg, devices))
+			goto out;
+
+		i++;
+		lv->size          = size;
+		lv->segments      = segs;
+		lv->first_segment = seg;
+
+		err = lvm_copy_name(lv->name, name, sizeof(lv->name) - 1);
+		if (err)
+			goto out;
+		err = -EINVAL;
+
+	next:
+		if (lvm_next_line(scan))
+			goto out;
+	}
+
+	err = 0;
+
+out:
+	if (scan)
+		pclose(scan);
+	free(cmd);
+	return err;
+}
+
+void
+lvm_free_vg(struct vg *vg)
+{
+	free(vg->lvs);
+	free(vg->pvs);
+	memset(vg, 0, sizeof(*vg));
+}
+
+int
+lvm_scan_vg(const char *vg_name, struct vg *vg)
+{
+	int err;
+
+	memset(vg, 0, sizeof(*vg));
+
+	err = lvm_open_vg(vg_name, vg);
+	if (err)
+		return err;
+
+	err = lvm_scan_lvs(vg);
+	if (err) {
+		lvm_free_vg(vg);
+		return err;
+	}
+
+	return 0;
+}
+
+#ifdef LVM_UTIL
+static int
+usage(void)
+{
+	printf("usage: lvm-util <vgname>\n");
+	exit(EINVAL);
+}
+
+int
+main(int argc, char **argv)
+{
+	int i, err;
+	struct vg vg;
+	struct pv *pv;
+	struct lv *lv;
+	struct lv_segment *seg;
+
+	if (argc != 2)
+		usage();
+
+	err = lvm_scan_vg(argv[1], &vg);
+	if (err) {
+		printf("scan failed: %d\n", err);
+		return (err >= 0 ? err : -err);
+	}
+
+	
+        printf("vg %s: extent_size: %"PRIu64", pvs: %d, lvs: %d\n",
+	       vg.name, vg.extent_size, vg.pv_cnt, vg.lv_cnt);
+
+	for (i = 0; i < vg.pv_cnt; i++) {
+		pv = vg.pvs + i;
+                printf("pv %s: start %"PRIu64"\n", pv->name, pv->start);
+	}
+
+	for (i = 0; i < vg.lv_cnt; i++) {
+		lv  = vg.lvs + i;
+		seg = &lv->first_segment;                
+                printf("lv %s: size: %"PRIu64", segments: %u, type: %u, "
+                       "dev: %s, pe_start: %"PRIu64", pe_size: %"PRIu64"\n",
+		       lv->name, lv->size, lv->segments, seg->type,
+		       seg->device, seg->pe_start, seg->pe_size);
+	}
+
+	lvm_free_vg(&vg);
+	return 0;
+}
+#endif