[12/17] Virtual Compound page allocation from interrupt context.

[Christoph Lameter]

In an interrupt context we cannot wait for the vmlist_lock in
__get_vm_area_node(). So use a trylock instead. If the trylock fails
then the atomic allocation will fail and subsequently be retried.

This only works because the flush_cache_vunmap in use for
allocation is never performing any IPIs in contrast to flush_tlb_...
in use for freeing.  flush_cache_vunmap is only used on architectures
with a virtually mapped cache (xtensa, pa-risc).

[Note: Nick Piggin is working on a scheme to make this simpler by
no longer requiring flushes]

Signed-off-by: Christoph Lameter <clameter@xxxxxxx>

---
 mm/vmalloc.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

Index: linux-2.6/mm/vmalloc.c
===================================================================
--- linux-2.6.orig/mm/vmalloc.c	2007-09-24 16:03:49.000000000 -0700
+++ linux-2.6/mm/vmalloc.c	2007-09-24 16:04:32.000000000 -0700
@@ -289,7 +289,6 @@ static struct vm_struct *__get_vm_area_n
 	unsigned long align = 1;
 	unsigned long addr;
 
-	BUG_ON(in_interrupt());
 	if (flags & VM_IOREMAP) {
 		int bit = fls(size);
 
@@ -314,7 +313,14 @@ static struct vm_struct *__get_vm_area_n
 	 */
 	size += PAGE_SIZE;
 
-	write_lock(&vmlist_lock);
+	if (gfp_mask & __GFP_WAIT)
+		write_lock(&vmlist_lock);
+	else {
+		if (!write_trylock(&vmlist_lock)) {
+			kfree(area);
+			return NULL;
+		}
+	}
 	for (p = &vmlist; (tmp = *p) != NULL ;p = &tmp->next) {
 		if ((unsigned long)tmp->addr < addr) {
 			if((unsigned long)tmp->addr + tmp->size >= addr)

-- 
-
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