[PATCH 6/8] vrange: Add GFP_NO_VRANGE allocation flag

From: John Stultz
Date: Wed Jun 12 2013 - 00:24:37 EST

From: Minchan Kim <minchan@xxxxxxxxxx>

In cloning the vroot tree during a fork, we have to
allocate memory while hold the vroot lock. This is problematic,
as the memory allocation can trigger reclaim, which might require
grabbing a vroot lock in order to find purgable pages.

Thus this patch introduces GFP_NO_VRANGE which will allow
us to avoid having a allocation for vrange to trigger any
volatile range purging.

XXX: We're not yet using this flag in the later purge paths, so
we still get the lockdep warnings.

Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Android Kernel Team <kernel-team@xxxxxxxxxxx>
Cc: Robert Love <rlove@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Dmitry Adamushko <dmitry.adamushko@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Andrea Righi <andrea@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Mike Hommey <mh@xxxxxxxxxxxx>
Cc: Taras Glek <tglek@xxxxxxxxxxx>
Cc: Dhaval Giani <dgiani@xxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx <linux-mm@xxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
[jstultz: Split out from a different patch, created new commit message]
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
include/linux/gfp.h | 7 +++++--
mm/vrange.c | 2 +-
2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 0f615eb..fa52199 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -35,6 +35,7 @@ struct vm_area_struct;
#define ___GFP_NO_KSWAPD 0x400000u
#define ___GFP_OTHER_NODE 0x800000u
#define ___GFP_WRITE 0x1000000u
+#define ___GFP_NO_VRANGE 0x2000000u
/* If the above are modified, __GFP_BITS_SHIFT may need updating */

@@ -70,6 +71,7 @@ struct vm_area_struct;
#define __GFP_HIGH ((__force gfp_t)___GFP_HIGH) /* Should access emergency pools? */
#define __GFP_IO ((__force gfp_t)___GFP_IO) /* Can start physical IO? */
#define __GFP_FS ((__force gfp_t)___GFP_FS) /* Can call down to low-level FS? */
+#define __GFP_NO_VRANGE ((__force gfp_t)___GFP_NO_VRANGE) /* Can't reclaim volatile pages */
#define __GFP_COLD ((__force gfp_t)___GFP_COLD) /* Cache-cold page required */
#define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) /* Suppress page allocation failure warning */
#define __GFP_REPEAT ((__force gfp_t)___GFP_REPEAT) /* See above */
@@ -99,7 +101,7 @@ struct vm_area_struct;

-#define __GFP_BITS_SHIFT 25 /* Room for N __GFP_FOO bits */
+#define __GFP_BITS_SHIFT 26 /* Room for N __GFP_FOO bits */
#define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1))

/* This equals 0, but use constants in case they ever change */
@@ -134,7 +136,8 @@ struct vm_area_struct;
/* Control page allocator reclaim behavior */

/* Control slab gfp mask during early boot */
diff --git a/mm/vrange.c b/mm/vrange.c
index f3c2465..5278939 100644
--- a/mm/vrange.c
+++ b/mm/vrange.c
@@ -204,7 +204,7 @@ int vrange_fork(struct mm_struct *new_mm, struct mm_struct *old_mm)
range = vrange_entry(next);
next = rb_next(next);

- new_range = __vrange_alloc(GFP_KERNEL);
+ new_range = __vrange_alloc(GFP_KERNEL|__GFP_NO_VRANGE);
if (!new_range)
goto fail;
__vrange_set(new_range, range->node.start,

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