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Subject[PATCH] Should GFP_ATOMIC fail when we're below low watermark?
Date
Hi all.

In current git (and for a while now), an attempt to allocate memory with
GFP_ATOMIC will fail if we're below the low watermark level. The only way to
access that memory that I can see (not that I've looked that hard) is to have
PF_MEMALLOC set (ie from kswapd). I'm wondering if this behaviour is correct.
Shouldn't GFP_ATOMIC allocations ignore watermarks too? How about GFP_KERNEL?

The following patch is a potential fix for GFP_ATOMIC.

Regards,

Nigel

Signed-off-by: Nigel Cunningham <nigel@nigel.suspend2.net>

page_alloc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -ruNp 995-gfp-atomic-alloc.patch-old/mm/page_alloc.c 995-gfp-atomic-alloc.patch-new/mm/page_alloc.c
--- 995-gfp-atomic-alloc.patch-old/mm/page_alloc.c 2007-08-20 11:14:34.000000000 +1000
+++ 995-gfp-atomic-alloc.patch-new/mm/page_alloc.c 2007-08-20 11:11:09.000000000 +1000
@@ -1286,8 +1286,8 @@ restart:
/* This allocation should allow future memory freeing. */

rebalance:
- if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
- && !in_interrupt()) {
+ if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)) ||
+ (gfp_mask & GFP_ATOMIC)) && !in_interrupt()) {
if (!(gfp_mask & __GFP_NOMEMALLOC)) {
nofail_alloc:
/* go through the zonelist yet again, ignoring mins */
--
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