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[lvm-devel] LVM2 ./WHATS_NEW lib/activate/dev_manager.c li ...



CVSROOT:	/cvs/lvm2
Module name:	LVM2
Changes by:	jbrassow sourceware org	2011-08-18 19:38:27

Modified files:
	.              : WHATS_NEW 
	lib/activate   : dev_manager.c 
	lib/metadata   : metadata-exported.h raid_manip.c 
	libdm          : libdevmapper.h libdm-deptree.c 
	man            : lvconvert.8.in 
	tools          : args.h commands.h lvconvert.c 

Log message:
	Add the ability to split an image from the mirror and track changes.
	
	~> lvconvert --splitmirrors 1 --trackchanges vg/lv
	The '--trackchanges' option allows a user the ability to use an image of
	a RAID1 array for the purposes of temporary read-only access.  The image
	can be merged back into the array at a later time and only the blocks that
	have changed in the array since the split will be resync'ed.  This
	operation can be thought of as a partial split.  The image is never completely
	extracted from the array, in that the array reserves the position the device
	occupied and tracks the differences between the array and the split image via
	a bitmap.  The image itself is rendered read-only and the name (<LV>_rimage_*)
	cannot be changed.  The user can complete the split (permanently splitting the
	image from the array) by re-issuing the 'lvconvert' command without the
	'--trackchanges' argument and specifying the '--name' argument.
	~> lvconvert --splitmirrors 1 --name my_split vg/lv
	Merging the tracked image back into the array is done with the '--merge'
	option (included in a follow-on patch).
	~> lvconvert --merge vg/lv_rimage_<n>
	
	The internal mechanics of this are relatively simple.  The 'raid' device-
	mapper target allows for the specification of an empty slot in an array
	via '- -'.  This is what will be used if a partial activation of an array
	is ever required.  (It would also be possible to use 'error' targets in
	place of the '- -'.)  If a RAID image is found to be both read-only and
	visible, then it is considered separate from the array and '- -' is used
	to hold it's position in the array.  So, all that needs to be done to
	temporarily split an image from the array /and/ cause the kernel target's
	bitmap to track (aka "mark") changes made is to make the specified image
	visible and read-only.  To merge the device back into the array, the image
	needs to be returned to the read/write state of the top-level LV and made
	invisible.

Patches:
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/WHATS_NEW.diff?cvsroot=lvm2&r1=1.2076&r2=1.2077
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/lib/activate/dev_manager.c.diff?cvsroot=lvm2&r1=1.229&r2=1.230
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/lib/metadata/metadata-exported.h.diff?cvsroot=lvm2&r1=1.199&r2=1.200
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/lib/metadata/raid_manip.c.diff?cvsroot=lvm2&r1=1.6&r2=1.7
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/libdm/libdevmapper.h.diff?cvsroot=lvm2&r1=1.141&r2=1.142
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/libdm/libdm-deptree.c.diff?cvsroot=lvm2&r1=1.104&r2=1.105
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/man/lvconvert.8.in.diff?cvsroot=lvm2&r1=1.19&r2=1.20
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/tools/args.h.diff?cvsroot=lvm2&r1=1.82&r2=1.83
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/tools/commands.h.diff?cvsroot=lvm2&r1=1.160&r2=1.161
http://sourceware.org/cgi-bin/cvsweb.cgi/LVM2/tools/lvconvert.c.diff?cvsroot=lvm2&r1=1.169&r2=1.170

--- LVM2/WHATS_NEW	2011/08/18 19:34:18	1.2076
+++ LVM2/WHATS_NEW	2011/08/18 19:38:26	1.2077
@@ -1,5 +1,6 @@
 Version 2.02.88 - 
 ==================================
+  Add --trackchanges support to --splitmirrors option for RAID1
   Add --splitmirrors support for RAID1 (1 image only)
   When down-converting RAID1, don't activate sub-lvs between suspend/resume
   Add -V as short form of --virtualsize in lvcreate.
--- LVM2/lib/activate/dev_manager.c	2011/08/11 19:38:00	1.229
+++ LVM2/lib/activate/dev_manager.c	2011/08/18 19:38:26	1.230
@@ -1226,17 +1226,39 @@
 			if (!dm_tree_node_add_target_area(node, dev_name(seg_dev(seg, s)), NULL,
 				    (seg_pv(seg, s)->pe_start + (extent_size * seg_pe(seg, s)))))
 				return_0;
-		} else if (seg_type(seg, s) == AREA_LV) {
-			if (seg_is_raid(seg)) {
-				dlid = build_dm_uuid(dm->mem,
-						     seg_metalv(seg, s)->lvid.s,
-						     NULL);
-				if (!dlid)
-					return_0;
-				if (!dm_tree_node_add_target_area(node, NULL, dlid,
-								  extent_size * seg_metale(seg, s)))
+		} else if (seg_is_raid(seg)) {
+			/*
+			 * RAID can handle unassigned areas.  It simple puts
+			 * '- -' in for the metadata/data device pair.  This
+			 * is a valid way to indicate to the RAID target that
+			 * the device is missing.
+			 *
+			 * If an image is marked as VISIBLE_LV and !LVM_WRITE,
+			 * it means the device has temporarily been extracted
+			 * from the array.  It may come back at a future date,
+			 * so the bitmap must track differences.  Again, '- -'
+			 * is used in the CTR table.
+			 */
+			if ((seg_type(seg, s) == AREA_UNASSIGNED) ||
+			    ((seg_lv(seg, s)->status & VISIBLE_LV) &&
+			     !(seg_lv(seg, s)->status & LVM_WRITE))) {
+				/* One each for metadata area and data area */
+				if (!dm_tree_node_add_null_area(node, 0) ||
+				    !dm_tree_node_add_null_area(node, 0))
 					return_0;
+				continue;
 			}
+			if (!(dlid = build_dm_uuid(dm->mem, seg_metalv(seg, s)->lvid.s, NULL)))
+				return_0;
+			if (!dm_tree_node_add_target_area(node, NULL, dlid, extent_size * seg_metale(seg, s)))
+				return_0;
+
+			if (!(dlid = build_dm_uuid(dm->mem, seg_lv(seg, s)->lvid.s, NULL)))
+				return_0;
+			if (!dm_tree_node_add_target_area(node, NULL, dlid, extent_size * seg_le(seg, s)))
+				return_0;
+		} else if (seg_type(seg, s) == AREA_LV) {
+
 			if (!(dlid = build_dm_uuid(dm->mem, seg_lv(seg, s)->lvid.s, NULL)))
 				return_0;
 			if (!dm_tree_node_add_target_area(node, NULL, dlid, extent_size * seg_le(seg, s)))
--- LVM2/lib/metadata/metadata-exported.h	2011/08/18 19:34:18	1.199
+++ LVM2/lib/metadata/metadata-exported.h	2011/08/18 19:38:27	1.200
@@ -744,6 +744,8 @@
 			       uint32_t new_count, struct dm_list *pvs);
 int lv_raid_split(struct logical_volume *lv, const char *split_name,
 		  uint32_t new_count, struct dm_list *splittable_pvs);
+int lv_raid_split_and_track(struct logical_volume *lv,
+			    struct dm_list *splittable_pvs);
 
 /* --  metadata/raid_manip.c */
 
--- LVM2/lib/metadata/raid_manip.c	2011/08/18 19:34:18	1.6
+++ LVM2/lib/metadata/raid_manip.c	2011/08/18 19:38:27	1.7
@@ -34,6 +34,22 @@
 	return seg->area_count;
 }
 
+static int _activate_sublv_preserving_excl(struct logical_volume *top_lv,
+					   struct logical_volume *sub_lv)
+{
+	struct cmd_context *cmd = top_lv->vg->cmd;
+
+	/* If top RAID was EX, use EX */
+	if (lv_is_active_exclusive_locally(top_lv)) {
+		if (!activate_lv_excl(cmd, sub_lv))
+			return_0;
+	} else {
+		if (!activate_lv(cmd, sub_lv))
+			return_0;
+	}
+	return 1;
+}
+
 /*
  * lv_is_on_pv
  * @lv:
@@ -623,3 +639,83 @@
 
 	return 1;
 }
+
+/*
+ * lv_raid_split_and_track
+ * @lv
+ * @splittable_pvs
+ *
+ * Only allows a single image to be split while tracking.  The image
+ * never actually leaves the mirror.  It is simply made visible.  This
+ * action triggers two things: 1) users are able to access the (data) image
+ * and 2) lower layers replace images marked with a visible flag with
+ * error targets.
+ *
+ * Returns: 1 on success, 0 on error
+ */
+int lv_raid_split_and_track(struct logical_volume *lv,
+			    struct dm_list *splittable_pvs)
+{
+	int s;
+	struct lv_segment *seg = first_seg(lv);
+
+	if (!seg_is_mirrored(seg)) {
+		log_error("Unable to split images from non-mirrored RAID");
+		return 0;
+	}
+
+	if (!raid_in_sync(lv)) {
+		log_error("Unable to split image from %s/%s while not in-sync",
+			  lv->vg->name, lv->name);
+		return 0;
+	}
+
+	for (s = seg->area_count - 1; s >= 0; s--) {
+		if (!lv_is_on_pvs(seg_lv(seg, s), splittable_pvs))
+			continue;
+		lv_set_visible(seg_lv(seg, s));
+		seg_lv(seg, s)->status &= ~LVM_WRITE;
+		break;
+	}
+
+	if (s >= seg->area_count) {
+		log_error("Unable to find image to satisfy request");
+		return 0;
+	}
+
+	if (!vg_write(lv->vg)) {
+		log_error("Failed to write changes to %s in %s",
+			  lv->name, lv->vg->name);
+		return 0;
+	}
+
+	if (!suspend_lv(lv->vg->cmd, lv)) {
+		log_error("Failed to suspend %s/%s before committing changes",
+			  lv->vg->name, lv->name);
+		return 0;
+	}
+
+	if (!vg_commit(lv->vg)) {
+		log_error("Failed to commit changes to %s in %s",
+			  lv->name, lv->vg->name);
+		return 0;
+	}
+
+	log_print("%s split from %s for read-only purposes.",
+		  seg_lv(seg, s)->name, lv->name);
+
+	/* Resume original LV */
+	if (!resume_lv(lv->vg->cmd, lv)) {
+		log_error("Failed to resume %s/%s after committing changes",
+			  lv->vg->name, lv->name);
+		return 0;
+	}
+
+	/* Activate the split (and tracking) LV */
+	if (!_activate_sublv_preserving_excl(lv, seg_lv(seg, s)))
+		return 0;
+
+	log_print("Use 'lvconvert --merge %s/%s' to merge back into %s",
+		  lv->vg->name, seg_lv(seg, s)->name, lv->name);
+	return 1;
+}
--- LVM2/libdm/libdevmapper.h	2011/08/11 17:29:04	1.141
+++ LVM2/libdm/libdevmapper.h	2011/08/18 19:38:27	1.142
@@ -516,6 +516,7 @@
 				    const char *dev_name,
 				    const char *dlid,
 				    uint64_t offset);
+int dm_tree_node_add_null_area(struct dm_tree_node *node, uint64_t offset);
 
 /*
  * Set readahead (in sectors) after loading the node.
--- LVM2/libdm/libdm-deptree.c	2011/08/11 19:17:10	1.104
+++ LVM2/libdm/libdm-deptree.c	2011/08/18 19:38:27	1.105
@@ -1484,11 +1484,11 @@
 	unsigned log_parm_count;
 
 	dm_list_iterate_items(area, &seg->areas) {
-		if (!_build_dev_string(devbuf, sizeof(devbuf), area->dev_node))
-			return_0;
-
 		switch (seg->type) {
 		case SEG_REPLICATOR_DEV:
+			if (!_build_dev_string(devbuf, sizeof(devbuf), area->dev_node))
+				return_0;
+
 			EMIT_PARAMS(*pos, " %d 1 %s", area->rsite_index, devbuf);
 			if (first_time)
 				EMIT_PARAMS(*pos, " nolog 0");
@@ -1530,9 +1530,19 @@
 		case SEG_RAID6_ZR:
 		case SEG_RAID6_NR:
 		case SEG_RAID6_NC:
+			if (!area->dev_node) {
+				EMIT_PARAMS(*pos, " -");
+				break;
+			}
+			if (!_build_dev_string(devbuf, sizeof(devbuf), area->dev_node))
+				return_0;
+
 			EMIT_PARAMS(*pos, " %s", devbuf);
 			break;
 		default:
+			if (!_build_dev_string(devbuf, sizeof(devbuf), area->dev_node))
+				return_0;
+
 			EMIT_PARAMS(*pos, "%s%s %" PRIu64, first_time ? "" : " ",
 				    devbuf, area->offset);
 		}
@@ -2571,7 +2581,7 @@
 		if (!_link_tree_nodes(node, dev_node))
 			return_0;
 	} else {
-        	if (stat(dev_name, &info) < 0) {
+		if (stat(dev_name, &info) < 0) {
 			log_error("Device %s not found.", dev_name);
 			return 0;
 		}
@@ -2600,6 +2610,18 @@
 	return 1;
 }
 
+int dm_tree_node_add_null_area(struct dm_tree_node *node, uint64_t offset)
+{
+	struct load_segment *seg;
+
+	seg = dm_list_item(dm_list_last(&node->props.segs), struct load_segment);
+
+	if (!_add_area(node, seg, NULL, offset))
+		return_0;
+
+	return 1;
+}
+
 void dm_tree_set_cookie(struct dm_tree_node *node, uint32_t cookie)
 {
 	node->dtree->cookie = cookie;
--- LVM2/man/lvconvert.8.in	2011/01/04 21:41:35	1.19
+++ LVM2/man/lvconvert.8.in	2011/08/18 19:38:27	1.20
@@ -17,7 +17,7 @@
 
 .br
 .B lvconvert
-\-\-splitmirrors Images \-\-name SplitLogicalVolumeName
+\-\-splitmirrors Images [\-\-name SplitLogicalVolumeName] [\-\-trackchanges]
 .br
 MirrorLogicalVolume[Path] [SplittablePhysicalVolume[Path][:PE[-PE]]...]
 .br
@@ -114,7 +114,8 @@
 .I \-\-splitmirrors Images
 The number of redundant Images of a mirror to be split off and used
 to form a new logical volume.  A name must be supplied for the
-newly-split-off logical volume using the \-\-name argument.
+newly-split-off logical volume using the \-\-name argument, unless
+the \-\-trackchanges argument is given.
 
 .TP
 .I \-n Name
@@ -122,6 +123,15 @@
 a mirror logical volume.
 .br
 
+.TP
+.I \-\-trackchanges
+This argument is used along with \-\-splitmirrors when the intention
+is to use the split-off image temporarily in a read-only fashion.  Splitting
+off an image in this way allows it to be merged back into the mirror later
+- only resynchronizing those portions of the image that have changed since
+the split occurred.  This option is only available to the "raid1" segment
+type.
+.br
 
 .TP
 .I \-s, \-\-snapshot
--- LVM2/tools/args.h	2011/08/17 15:15:37	1.82
+++ LVM2/tools/args.h	2011/08/18 19:38:27	1.83
@@ -54,6 +54,7 @@
 arg(corelog_ARG, '\0', "corelog", NULL, 0)
 arg(mirrorlog_ARG, '\0', "mirrorlog", string_arg, 0)
 arg(splitmirrors_ARG, '\0', "splitmirrors", int_arg, 0)
+arg(trackchanges_ARG, '\0', "trackchanges", NULL, 0)
 arg(repair_ARG, '\0', "repair", NULL, 0)
 arg(use_policies_ARG, '\0', "use-policies", NULL, 0)
 arg(monitor_ARG, '\0', "monitor", yes_no_arg, 0)
--- LVM2/tools/commands.h	2011/08/17 15:15:37	1.160
+++ LVM2/tools/commands.h	2011/08/18 19:38:27	1.161
@@ -114,6 +114,7 @@
    "\tLogicalVolume[Path] [PhysicalVolume[Path]...]\n\n"
 
    "lvconvert "
+   "[--splitmirrors Images --trackchanges]\n"
    "[--splitmirrors Images --name SplitLogicalVolumeName]\n"
    "\tLogicalVolume[Path] [SplittablePhysicalVolume[Path]...]\n\n"
 
@@ -139,7 +140,7 @@
 
    alloc_ARG, background_ARG, chunksize_ARG, corelog_ARG, interval_ARG,
    merge_ARG, mirrorlog_ARG, mirrors_ARG, name_ARG, noudevsync_ARG,
-   regionsize_ARG, repair_ARG, snapshot_ARG, splitmirrors_ARG,
+   regionsize_ARG, repair_ARG, snapshot_ARG, splitmirrors_ARG, trackchanges_ARG,
    stripes_long_ARG, stripesize_ARG, test_ARG,
    use_policies_ARG, yes_ARG, force_ARG, zero_ARG)
 
--- LVM2/tools/lvconvert.c	2011/08/18 19:34:18	1.169
+++ LVM2/tools/lvconvert.c	2011/08/18 19:38:27	1.170
@@ -158,13 +158,15 @@
 	 * discarding it.
 	 */
 	if (arg_count(cmd, splitmirrors_ARG)) {
-		if (!arg_count(cmd, name_ARG)) {
+		if (!arg_count(cmd, name_ARG) &&
+		    !arg_count(cmd, trackchanges_ARG)) {
 			log_error("Please name the new logical volume using '--name'");
 			return 0;
 		}
 
 		lp->lv_split_name = arg_value(cmd, name_ARG);
-		if (!apply_lvname_restrictions(lp->lv_split_name))
+		if (lp->lv_split_name &&
+		    !apply_lvname_restrictions(lp->lv_split_name))
 			return_0;
 
 		lp->keep_mimages = 1;
@@ -1146,6 +1148,11 @@
 
 		/* Reduce number of mirrors */
 		if (lp->keep_mimages) {
+			if (arg_count(cmd, trackchanges_ARG)) {
+				log_error("--trackchanges is not available "
+					  "to 'mirror' segment type");
+				return 0;
+			}
 			if (!lv_split_mirror_images(lv, lp->lv_split_name,
 						    nmc, operable_pvs))
 				return 0;
@@ -1417,7 +1424,9 @@
 			return 0;
 		}
 
-		if (arg_count(cmd, splitmirrors_ARG))
+		if (arg_count(cmd, trackchanges_ARG))
+			return lv_raid_split_and_track(lv, lp->pvh);
+		else if (arg_count(cmd, splitmirrors_ARG))
 			return lv_raid_split(lv, lp->lv_split_name,
 					     image_count, lp->pvh);
 		else


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