[PATCH] mm: __GFP_NOFAIL fix

In __alloc_pages():

if ((p->flags & (PF_MEMALLOC | PF_MEMDIE)) && !in_interrupt()) {
         /* go through the zonelist yet again, ignoring mins */
         for (i = 0; zones[i] != NULL; i++) {
                 struct zone *z = zones[i];

                 page = buffered_rmqueue(z, order, gfp_mask);
                 if (page) {
                         zone_statistics(zonelist, z);
                         goto got_pg;
                 }
         }
         goto nopage;                <<<< HERE!!! FAIL...
}

kswapd (which has PF_MEMALLOC flag) can fail to allocate memory even when
it allocates it with __GFP_NOFAIL flag.

Signed-Off-By: Pavel Emelianov <xemul@sw.ru>
Signed-Off-By: Denis Lunev <den@sw.ru>
Signed-Off-By: Kirill Korotaev <dev@sw.ru>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 987225bdd66..b37dc0f78d0 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -895,6 +895,7 @@ zone_reclaim_retry:
         if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
                         && !in_interrupt()) {
                 if (!(gfp_mask & __GFP_NOMEMALLOC)) {
+nofail_alloc:
                         /* go through the zonelist yet again, ignoring mins */
                         for (i = 0; (z = zones[i]) != NULL; i++) {
                                 if (!cpuset_zone_allowed(z, gfp_mask))
@@ -903,6 +904,10 @@ zone_reclaim_retry:
                                 if (page)
                                         goto got_pg;
                         }
+                        if (gfp_mask & __GFP_NOFAIL) {
+                                blk_congestion_wait(WRITE, HZ/50);
+                                goto nofail_alloc;
+                        }
                 }
                 goto nopage;
         }