[16/18] Virtual Compound page allocation from interrupt context.

Christoph Lameter
2007-10-04T04:04:40Z

[-- Attachment #1: vcompound_interrupt_alloc --]
[-- Type: text/plain, Size: 1527 bytes --]

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@sgi.com>

---
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 2007-10-03 16:21:10.000000000 -0700
+++ linux-2.6/mm/vmalloc.c 2007-10-03 16:25:17.000000000 -0700
@@ -177,7 +177,6 @@ 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);

@@ -202,7 +201,14 @@ 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)

--