From c652be54ae5f31f13eb03acfa533b9228843a7c0 Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Thu, 4 Mar 2010 16:06:53 -0800
Subject: [PATCH] HAMMER VFS - Ensure sufficient free memory is available
 before large allocation

* The HAMMER rebalancing code can be a heavy user of kernel memory when
  collecting B-Tree nodes to rebalance.

  Call the new vm_wait_nominal() function before allocating said memory
  in an attempt to avoid VM/VFS deadlocks when memory is low.

Reported-by: Francois Tigeot <ftigeot@wolfpond.org>
---
 sys/vfs/hammer/hammer.h           | 1 +
 sys/vfs/hammer/hammer_rebalance.c | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/sys/vfs/hammer/hammer.h b/sys/vfs/hammer/hammer.h
index cc30895523..1662b81d6d 100644
--- a/sys/vfs/hammer/hammer.h
+++ b/sys/vfs/hammer/hammer.h
@@ -58,6 +58,7 @@
 #include <sys/ktr.h>
 #include <sys/globaldata.h>
 #include <sys/limits.h>
+#include <vm/vm_extern.h>
 
 #include <sys/buf2.h>
 #include <sys/signal2.h>
diff --git a/sys/vfs/hammer/hammer_rebalance.c b/sys/vfs/hammer/hammer_rebalance.c
index 6250eb5f6a..1b8de5c37e 100644
--- a/sys/vfs/hammer/hammer_rebalance.c
+++ b/sys/vfs/hammer/hammer_rebalance.c
@@ -113,6 +113,12 @@ retry:
 
 	while (error == 0) {
 		/*
+		 * Rebalancing can be hard on the memory allocator, make
+		 * sure there is enough free memory before doing it.
+		 */
+		vm_wait_nominal();
+
+		/*
 		 * We only care about internal nodes visited for the last
 		 * time on the way up... that is, a trailing scan of the
 		 * internal node after all of its children have been recursed
-- 
2.11.4.GIT