linux-kernel - [PATCH] vmap: add flag to allow lazy unmap to be disabled at runtime

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Date:	Mon, 26 Jul 2010 13:24:51 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Nick Piggin <npiggin@...e.de>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH] vmap: add flag to allow lazy unmap to be disabled at runtime



[ Nick, I forget if I sent this to you before.  Could you Ack it if it looks OK? Thanks, J ]

Add a flag to force lazy_max_pages() to zero to prevent any outstanding
mapped pages.  We'll need this for Xen.

Signed-off-by: Jeremy Fitzhardinge<jeremy.fitzhardinge@...rix.com>

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 227c2a5..b840fda 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -7,6 +7,8 @@

  struct vm_area_struct;		/* vma defining user mapping in mm_types.h */

+extern bool vmap_lazy_unmap;
+
  /* bits in flags of vmalloc's vm_struct below */
  #define VM_IOREMAP	0x00000001	/* ioremap() and friends */
  #define VM_ALLOC	0x00000002	/* vmalloc() */
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ae00746..7f35fe2 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -31,6 +31,7 @@
  #include<asm/tlbflush.h>
  #include<asm/shmparam.h>

+bool vmap_lazy_unmap __read_mostly = true;

  /*** Page table manipulation functions ***/

@@ -502,6 +503,9 @@ static unsigned long lazy_max_pages(void)
  {
  	unsigned int log;

+	if (!vmap_lazy_unmap)
+		return 0;
+
  	log = fls(num_online_cpus());

  	return log * (32UL * 1024 * 1024 / PAGE_SIZE);


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