From d0aa00e891d3bf34e5273456a080ac9c23ac7229 Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Thu, 3 Feb 2011 23:25:41 -0800
Subject: [PATCH] kernel - Add options VM_PAGE_DEBUG

* Add options VM_PAGE_DEBUG for kernel configs.  This requires a full kernel
  rebuild (if you use the option) and supplies additional information in
  the vm_page structure to help track down problems.
---
 sys/conf/options   |  1 +
 sys/vm/vm_contig.c |  8 ++++++--
 sys/vm/vm_page.c   |  4 ++--
 sys/vm/vm_page.h   | 23 +++++++++++++++++++++++
 4 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/sys/conf/options b/sys/conf/options
index ce82ae1863..dfca7dbfe5 100644
--- a/sys/conf/options
+++ b/sys/conf/options
@@ -480,6 +480,7 @@ SOCKBUF_DEBUG		opt_global.h
 PANIC_DEBUG		opt_global.h
 MBUF_DEBUG		opt_global.h
 PMAP_DEBUG		opt_global.h
+VM_PAGE_DEBUG		opt_global.h
 
 # Sample system/interrupt PC
 DEBUG_PCTRACK		opt_pctrack.h
diff --git a/sys/vm/vm_contig.c b/sys/vm/vm_contig.c
index 60c266aa9d..55e6e2e7bf 100644
--- a/sys/vm/vm_contig.c
+++ b/sys/vm/vm_contig.c
@@ -343,12 +343,16 @@ again:
 			m->valid = VM_PAGE_BITS_ALL;
 			if (m->flags & PG_ZERO)
 				vm_page_zero_count--;
-			/* Don't clear the PG_ZERO flag, we'll need it later. */
-			m->flags &= PG_ZERO;
 			KASSERT(m->dirty == 0,
 				("vm_contig_pg_alloc: page %p was dirty", m));
 			m->wire_count = 0;
 			m->busy = 0;
+
+			/*
+			 * Clear all flags except PG_ZERO and PG_WANTED.  This
+			 * also clears PG_BUSY.
+			 */
+			vm_page_flag_clear(m, ~(PG_ZERO|PG_WANTED));
 		}
 
 		/*
diff --git a/sys/vm/vm_page.c b/sys/vm/vm_page.c
index ddb6fa029c..95ceff132d 100644
--- a/sys/vm/vm_page.c
+++ b/sys/vm/vm_page.c
@@ -1130,11 +1130,11 @@ vm_page_free_toq(vm_page_t m)
 	 * Clear the UNMANAGED flag when freeing an unmanaged page.
 	 */
 	if (m->flags & PG_UNMANAGED) {
-	    m->flags &= ~PG_UNMANAGED;
+	    vm_page_flag_clear(m, PG_UNMANAGED);
 	}
 
 	if (m->hold_count != 0) {
-		m->flags &= ~PG_ZERO;
+		vm_page_flag_clear(m, PG_ZERO);
 		m->queue = PQ_HOLD;
 	} else {
 		m->queue = PQ_FREE + m->pc;
diff --git a/sys/vm/vm_page.h b/sys/vm/vm_page.h
index d73717466d..db8e48d23a 100644
--- a/sys/vm/vm_page.h
+++ b/sys/vm/vm_page.h
@@ -184,6 +184,10 @@ struct vm_page {
 	u_char	dirty;			/* map of dirty DEV_BSIZE chunks */
 
 	int	ku_pagecnt;		/* kmalloc helper */
+#ifdef VM_PAGE_DEBUG
+	const char *busy_func;
+	int	busy_line;
+#endif
 };
 
 #ifndef __VM_PAGE_T_DEFINED__
@@ -395,6 +399,23 @@ vm_page_flag_clear(vm_page_t m, unsigned int bits)
 	atomic_clear_int(&(m)->flags, bits);
 }
 
+#ifdef VM_PAGE_DEBUG
+
+static __inline void
+_vm_page_busy(vm_page_t m, const char *func, int lineno)
+{
+	ASSERT_LWKT_TOKEN_HELD(&vm_token);
+	KASSERT((m->flags & PG_BUSY) == 0,
+		("vm_page_busy: page already busy!!!"));
+	vm_page_flag_set(m, PG_BUSY);
+	m->busy_func = func;
+	m->busy_line = lineno;
+}
+
+#define vm_page_busy(m)	_vm_page_busy(m, __func__, __LINE__)
+
+#else
+
 static __inline void
 vm_page_busy(vm_page_t m)
 {
@@ -404,6 +425,8 @@ vm_page_busy(vm_page_t m)
 	vm_page_flag_set(m, PG_BUSY);
 }
 
+#endif
+
 /*
  *	vm_page_flash:
  *
-- 
2.41.0