Add device/md_chunk_alignment to lvm.conf

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.40 - 
 ================================
+  Add device/md_chunk_alignment to lvm.conf.
   Pass struct physical_volume to pe_align and adjust for md chunk size.
   Store sysfs location in struct cmd_context.
   Avoid shuffling remaining mirror images when removing one, retaining primary.

doc/example.conf

@@ -93,6 +93,11 @@ devices {
     # 1 enables; 0 disables.
     md_component_detection = 1
 
+    # By default, if a PV is placed directly upon an md device, LVM2
+    # will align its data blocks with the the chunk_size exposed in sysfs.
+    # 1 enables; 0 disables.
+    md_chunk_alignment = 1
+
     # If, while scanning the system for PVs, LVM2 encounters a device-mapper
     # device that has its I/O suspended, it waits for it to become accessible.
     # Set this to 1 to skip such devices.  This should only be needed

lib/config/defaults.h

@@ -32,6 +32,7 @@
 #define DEFAULT_PROC_DIR "/proc"
 #define DEFAULT_SYSFS_SCAN 1
 #define DEFAULT_MD_COMPONENT_DETECTION 1
+#define DEFAULT_MD_CHUNK_ALIGNMENT 1
 #define DEFAULT_IGNORE_SUSPENDED_DEVICES 1
 
 #define DEFAULT_LOCK_DIR "/var/lock/lvm"

lib/metadata/metadata.c

@@ -27,6 +27,7 @@
 #include "display.h"
 #include "locking.h"
 #include "archiver.h"
+#include "defaults.h"
 
 #include <sys/param.h>
 
@@ -74,7 +75,9 @@ unsigned long pe_align(struct physical_volume *pv)
 	/*
 	 * Align to chunk size of underlying md device if present
 	 */
-	if (pv->dev)
+	if (pv->dev &&
+	    find_config_tree_bool(pv->fmt->cmd, "devices/md_chunk_alignment",
+				  DEFAULT_MD_CHUNK_ALIGNMENT))
 		pv->pe_align = MAX(pv->pe_align,
 				   dev_md_chunk_size(pv->fmt->cmd->sysfs_dir,
 						     pv->dev));