[PATCH] mm: gfp_atomic comments

Clarify in comments that GFP_ATOMIC means both "don't sleep" and "use
emergency pools", hence both ALLOC_HARDER and ALLOC_HIGH.

Signed-off-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 8b2eab9..da7ce87 100644 (file)
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -57,6 +57,7 @@ struct vm_area_struct;
                        __GFP_NOFAIL|__GFP_NORETRY|__GFP_NO_GROW|__GFP_COMP| \
                        __GFP_NOMEMALLOC|__GFP_HARDWALL)
 
+/* GFP_ATOMIC means both !wait (__GFP_WAIT not set) and use emergency pool */
 #define GFP_ATOMIC     (__GFP_HIGH)
 #define GFP_NOIO       (__GFP_WAIT)
 #define GFP_NOFS       (__GFP_WAIT | __GFP_IO)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ce991b1..d41a066 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -931,7 +931,8 @@ restart:
         *
         * The caller may dip into page reserves a bit more if the caller
         * cannot run direct reclaim, or if the caller has realtime scheduling
-        * policy.
+        * policy or is asking for __GFP_HIGH memory.  GFP_ATOMIC requests will
+        * set both ALLOC_HARDER (!wait) and ALLOC_HIGH (__GFP_HIGH).
         */
        alloc_flags = ALLOC_WMARK_MIN;
        if ((unlikely(rt_task(p)) && !in_interrupt()) || !wait)