[PATCH] pseries/memory-hotplug: Only update DT once per memory DLPAR request

[Nathan Fontenot]

The updates to powerpc numa and memory hotplug code now use the
in-kernel LMB array instead of the device tree. This change
allows the pseries memory DLPAR code to only update the device
tree once after successfully handling a DLPAR request.

Prior to the in-kernel LMB array, the numa code looked up the
affinity for memory being added in the device tree, the code
now looks this up in the LMB array. This change means the
memory hotplug code can just update the affinity for an LMB
in the LMB array instead of updating the device tree.

This also provides a savings in kernel memory. When updating the
device tree old properties are never free'ed since there is no
usecount on properties. This behavior leads to a new copy of the
property being allocated every time a LMB is added or removed
(i.e. a request to add 100 LMBs creates 100 new copies of the
property). With this update only a single new property is created
when a DLPAR request completes successfully.

Signed-off-by: Nathan Fontenot <nfont at linux.vnet.ibm.com>
---
 arch/powerpc/include/asm/drmem.h                |    5 ++
 arch/powerpc/platforms/pseries/hotplug-memory.c |   55 +++++++----------------
 2 files changed, 21 insertions(+), 39 deletions(-)

diff --git a/arch/powerpc/include/asm/drmem.h b/arch/powerpc/include/asm/drmem.h
index ce242b9ea8c6..7c1d8e74b25d 100644
--- a/arch/powerpc/include/asm/drmem.h
+++ b/arch/powerpc/include/asm/drmem.h
@@ -99,4 +99,9 @@ void __init walk_drmem_lmbs_early(unsigned long node,
 			void (*func)(struct drmem_lmb *, const __be32 **));
 #endif
 
+static inline void invalidate_lmb_associativity_index(struct drmem_lmb *lmb)
+{
+	lmb->aa_index = 0xffffffff;
+}
+
 #endif /* _ASM_POWERPC_LMB_H */
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index c1578f54c626..9a15d39995e5 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -163,7 +163,7 @@ static u32 find_aa_index(struct device_node *dr_node,
 	return aa_index;
 }
 
-static u32 lookup_lmb_associativity_index(struct drmem_lmb *lmb)
+static int update_lmb_associativity_index(struct drmem_lmb *lmb)
 {
 	struct device_node *parent, *lmb_node, *dr_node;
 	struct property *ala_prop;
@@ -203,43 +203,14 @@ static u32 lookup_lmb_associativity_index(struct drmem_lmb *lmb)
 	aa_index = find_aa_index(dr_node, ala_prop, lmb_assoc);
 
 	dlpar_free_cc_nodes(lmb_node);
-	return aa_index;
-}
-
-static int dlpar_add_device_tree_lmb(struct drmem_lmb *lmb)
-{
-	int rc, aa_index;
-
-	lmb->flags |= DRCONF_MEM_ASSIGNED;
 
-	aa_index = lookup_lmb_associativity_index(lmb);
 	if (aa_index < 0) {
-		pr_err("Couldn't find associativity index for drc index %x\n",
-		       lmb->drc_index);
-		return aa_index;
+		pr_err("Could not find LMB associativity\n");
+		return -1;
 	}
 
 	lmb->aa_index = aa_index;
-
-	rtas_hp_event = true;
-	rc = drmem_update_dt();
-	rtas_hp_event = false;
-
-	return rc;
-}
-
-static int dlpar_remove_device_tree_lmb(struct drmem_lmb *lmb)
-{
-	int rc;
-
-	lmb->flags &= ~DRCONF_MEM_ASSIGNED;
-	lmb->aa_index = 0xffffffff;
-
-	rtas_hp_event = true;
-	rc = drmem_update_dt();
-	rtas_hp_event = false;
-
-	return rc;
+	return 0;
 }
 
 static struct memory_block *lmb_to_memblock(struct drmem_lmb *lmb)
@@ -428,7 +399,9 @@ static int dlpar_remove_lmb(struct drmem_lmb *lmb)
 	/* Update memory regions for memory remove */
 	memblock_remove(lmb->base_addr, block_sz);
 
-	dlpar_remove_device_tree_lmb(lmb);
+	invalidate_lmb_associativity_index(lmb);
+	lmb->flags &= ~DRCONF_MEM_ASSIGNED;
+
 	return 0;
 }
 
@@ -688,10 +661,8 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
 	if (lmb->flags & DRCONF_MEM_ASSIGNED)
 		return -EINVAL;
 
-	rc = dlpar_add_device_tree_lmb(lmb);
+	rc = update_lmb_associativity_index(lmb);
 	if (rc) {
-		pr_err("Couldn't update device tree for drc index %x\n",
-		       lmb->drc_index);
 		dlpar_release_drc(lmb->drc_index);
 		return rc;
 	}
@@ -704,14 +675,14 @@ static int dlpar_add_lmb(struct drmem_lmb *lmb)
 	/* Add the memory */
 	rc = add_memory(nid, lmb->base_addr, block_sz);
 	if (rc) {
-		dlpar_remove_device_tree_lmb(lmb);
+		invalidate_lmb_associativity_index(lmb);
 		return rc;
 	}
 
 	rc = dlpar_online_lmb(lmb);
 	if (rc) {
 		remove_memory(nid, lmb->base_addr, block_sz);
-		dlpar_remove_device_tree_lmb(lmb);
+		invalidate_lmb_associativity_index(lmb);
 	} else {
 		lmb->flags |= DRCONF_MEM_ASSIGNED;
 	}
@@ -958,6 +929,12 @@ int dlpar_memory(struct pseries_hp_errorlog *hp_elog)
 		break;
 	}
 
+	if (!rc) {
+		rtas_hp_event = true;
+		rc = drmem_update_dt();
+		rtas_hp_event = false;
+	}
+
 	unlock_device_hotplug();
 	return rc;
 }