From 3180f7573a4686b4fbb9e361b72e7dea064f2d44 Mon Sep 17 00:00:00 2001
From: Alan Cox <alc@FreeBSD.org>
Date: Wed, 11 Jun 2014 16:11:12 +0000
Subject: [PATCH] Correct a bug in the management of the population map on
 big-endian machines.  Specifically, there was a mismatch between how the
 routine allocation and deallocation operations accessed the population map
 and how the aggressively optimized reservation-breaking operation accessed
 it.  So, problems only occurred when reservations were broken. This change
 makes the routine operations access the population map in the same way as the
 reservation breaking operation.

This bug was introduced in r259999.

PR:		187080
Tested by:	jmg (on an "armeb" machine)
Sponsored by:	EMC / Isilon Storage Division
---
 sys/vm/vm_reserv.c | 56 +++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 48 insertions(+), 8 deletions(-)

diff --git a/sys/vm/vm_reserv.c b/sys/vm/vm_reserv.c
index c8de47e14b8..2a38d017520 100644
--- a/sys/vm/vm_reserv.c
+++ b/sys/vm/vm_reserv.c
@@ -107,6 +107,46 @@ typedef	u_long		popmap_t;
  */
 #define	NPOPMAP		howmany(VM_LEVEL_0_NPAGES, NBPOPMAP)
 
+/*
+ * Clear a bit in the population map.
+ */
+static __inline void
+popmap_clear(popmap_t popmap[], int i)
+{
+
+	popmap[i / NBPOPMAP] &= ~(1UL << (i % NBPOPMAP));
+}
+
+/*
+ * Set a bit in the population map.
+ */
+static __inline void
+popmap_set(popmap_t popmap[], int i)
+{
+
+	popmap[i / NBPOPMAP] |= 1UL << (i % NBPOPMAP);
+}
+
+/*
+ * Is a bit in the population map clear?
+ */
+static __inline boolean_t
+popmap_is_clear(popmap_t popmap[], int i)
+{
+
+	return ((popmap[i / NBPOPMAP] & (1UL << (i % NBPOPMAP))) == 0);
+}
+
+/*
+ * Is a bit in the population map set?
+ */
+static __inline boolean_t
+popmap_is_set(popmap_t popmap[], int i)
+{
+
+	return ((popmap[i / NBPOPMAP] & (1UL << (i % NBPOPMAP))) != 0);
+}
+
 /*
  * The reservation structure
  *
@@ -241,7 +281,7 @@ vm_reserv_depopulate(vm_reserv_t rv, int index)
 	mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
 	KASSERT(rv->object != NULL,
 	    ("vm_reserv_depopulate: reserv %p is free", rv));
-	KASSERT(isset(rv->popmap, index),
+	KASSERT(popmap_is_set(rv->popmap, index),
 	    ("vm_reserv_depopulate: reserv %p's popmap[%d] is clear", rv,
 	    index));
 	KASSERT(rv->popcnt > 0,
@@ -255,7 +295,7 @@ vm_reserv_depopulate(vm_reserv_t rv, int index)
 		    rv));
 		rv->pages->psind = 0;
 	}
-	clrbit(rv->popmap, index);
+	popmap_clear(rv->popmap, index);
 	rv->popcnt--;
 	if (rv->popcnt == 0) {
 		LIST_REMOVE(rv, objq);
@@ -302,7 +342,7 @@ vm_reserv_populate(vm_reserv_t rv, int index)
 	mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
 	KASSERT(rv->object != NULL,
 	    ("vm_reserv_populate: reserv %p is free", rv));
-	KASSERT(isclr(rv->popmap, index),
+	KASSERT(popmap_is_clear(rv->popmap, index),
 	    ("vm_reserv_populate: reserv %p's popmap[%d] is set", rv,
 	    index));
 	KASSERT(rv->popcnt < VM_LEVEL_0_NPAGES,
@@ -313,7 +353,7 @@ vm_reserv_populate(vm_reserv_t rv, int index)
 		TAILQ_REMOVE(&vm_rvq_partpop, rv, partpopq);
 		rv->inpartpopq = FALSE;
 	}
-	setbit(rv->popmap, index);
+	popmap_set(rv->popmap, index);
 	rv->popcnt++;
 	if (rv->popcnt < VM_LEVEL_0_NPAGES) {
 		rv->inpartpopq = TRUE;
@@ -503,7 +543,7 @@ found:
 		return (NULL);
 	/* Handle vm_page_rename(m, new_object, ...). */
 	for (i = 0; i < npages; i++)
-		if (isset(rv->popmap, index + i))
+		if (popmap_is_set(rv->popmap, index + i))
 			return (NULL);
 	for (i = 0; i < npages; i++)
 		vm_reserv_populate(rv, index + i);
@@ -628,7 +668,7 @@ found:
 	index = VM_RESERV_INDEX(object, pindex);
 	m = &rv->pages[index];
 	/* Handle vm_page_rename(m, new_object, ...). */
-	if (isset(rv->popmap, index))
+	if (popmap_is_set(rv->popmap, index))
 		return (NULL);
 	vm_reserv_populate(rv, index);
 	return (m);
@@ -662,9 +702,9 @@ vm_reserv_break(vm_reserv_t rv, vm_page_t m)
 		 * to the physical memory allocator.
 		 */
 		i = m - rv->pages;
-		KASSERT(isclr(rv->popmap, i),
+		KASSERT(popmap_is_clear(rv->popmap, i),
 		    ("vm_reserv_break: reserv %p's popmap is corrupted", rv));
-		setbit(rv->popmap, i);
+		popmap_set(rv->popmap, i);
 		rv->popcnt++;
 	}
 	i = hi = 0;