The quilt patch titled
Subject: mm: warn about illegal __GFP_NOFAIL usage in a more appropriate location and manner
has been removed from the -mm tree. Its filename was
mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: Barry Song <v-songbaohua@xxxxxxxx>
Subject: mm: warn about illegal __GFP_NOFAIL usage in a more appropriate location and manner
Date: Sat, 31 Aug 2024 08:28:23 +1200
Three points for this change:
1. We should consolidate all warnings in one place. Currently, the
order > 1 warning is in the hotpath, while others are in less
likely scenarios. Moving all warnings to the slowpath will reduce
the overhead for order > 1 and increase the visibility of other
warnings.
2. We currently have two warnings for order: one for order > 1 in
the hotpath and another for order > costly_order in the laziest
path. I suggest standardizing on order > 1 since it's been in
use for a long time.
3. We don't need to check for __GFP_NOWARN in this case. __GFP_NOWARN
is meant to suppress allocation failure reports, but here we're
dealing with bug detection, not allocation failures. So replace
WARN_ON_ONCE_GFP by WARN_ON_ONCE.
[v-songbaohua@xxxxxxxx: also update the doc for __GFP_NOFAIL with order > 1]
Link: https://lkml.kernel.org/r/20240903223935.1697-1-21cnbao@xxxxxxxxx
Link: https://lkml.kernel.org/r/20240830202823.21478-4-21cnbao@xxxxxxxxx
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Reviewed-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: "Eugenio Pérez" <eperezma@xxxxxxxxxx>
Cc: Hailong.Liu <hailong.liu@xxxxxxxx>
Cc: Hyeonggon Yoo <42.hyeyoo@xxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Kees Cook <kees@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
Cc: Maxime Coquelin <maxime.coquelin@xxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Pekka Enberg <penberg@xxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Cc: Xie Yongji <xieyongji@xxxxxxxxxxxxx>
Cc: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
Cc: Yafang Shao <laoar.shao@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/gfp_types.h | 3 +-
mm/page_alloc.c | 50 ++++++++++++++++++------------------
2 files changed, 27 insertions(+), 26 deletions(-)
--- a/include/linux/gfp_types.h~mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner
+++ a/include/linux/gfp_types.h
@@ -253,7 +253,8 @@ enum {
* used only when there is no reasonable failure policy) but it is
* definitely preferable to use the flag rather than opencode endless
* loop around allocator.
- * Using this flag for costly allocations is _highly_ discouraged.
+ * Allocating pages from the buddy with __GFP_NOFAIL and order > 1 is
+ * not supported. Please consider using kvmalloc() instead.
*/
#define __GFP_IO ((__force gfp_t)___GFP_IO)
#define __GFP_FS ((__force gfp_t)___GFP_FS)
--- a/mm/page_alloc.c~mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner
+++ a/mm/page_alloc.c
@@ -3032,12 +3032,6 @@ struct page *rmqueue(struct zone *prefer
{
struct page *page;
- /*
- * We most definitely don't want callers attempting to
- * allocate greater than order-1 page units with __GFP_NOFAIL.
- */
- WARN_ON_ONCE((gfp_flags & __GFP_NOFAIL) && (order > 1));
-
if (likely(pcp_allowed_order(order))) {
page = rmqueue_pcplist(preferred_zone, zone, order,
migratetype, alloc_flags);
@@ -4175,6 +4169,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, u
{
bool can_direct_reclaim = gfp_mask & __GFP_DIRECT_RECLAIM;
bool can_compact = gfp_compaction_allowed(gfp_mask);
+ bool nofail = gfp_mask & __GFP_NOFAIL;
const bool costly_order = order > PAGE_ALLOC_COSTLY_ORDER;
struct page *page = NULL;
unsigned int alloc_flags;
@@ -4187,6 +4182,25 @@ __alloc_pages_slowpath(gfp_t gfp_mask, u
unsigned int zonelist_iter_cookie;
int reserve_flags;
+ if (unlikely(nofail)) {
+ /*
+ * We most definitely don't want callers attempting to
+ * allocate greater than order-1 page units with __GFP_NOFAIL.
+ */
+ WARN_ON_ONCE(order > 1);
+ /*
+ * Also we don't support __GFP_NOFAIL without __GFP_DIRECT_RECLAIM,
+ * otherwise, we may result in lockup.
+ */
+ WARN_ON_ONCE(!can_direct_reclaim);
+ /*
+ * PF_MEMALLOC request from this context is rather bizarre
+ * because we cannot reclaim anything and only can loop waiting
+ * for somebody to do a work for us.
+ */
+ WARN_ON_ONCE(current->flags & PF_MEMALLOC);
+ }
+
restart:
compaction_retries = 0;
no_progress_loops = 0;
@@ -4404,30 +4418,16 @@ nopage:
* Make sure that __GFP_NOFAIL request doesn't leak out and make sure
* we always retry
*/
- if (gfp_mask & __GFP_NOFAIL) {
+ if (unlikely(nofail)) {
/*
- * All existing users of the __GFP_NOFAIL are blockable, so warn
- * of any new users that actually require GFP_NOWAIT
+ * Lacking direct_reclaim we can't do anything to reclaim memory,
+ * we disregard these unreasonable nofail requests and still
+ * return NULL
*/
- if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
+ if (!can_direct_reclaim)
goto fail;
/*
- * PF_MEMALLOC request from this context is rather bizarre
- * because we cannot reclaim anything and only can loop waiting
- * for somebody to do a work for us
- */
- WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask);
-
- /*
- * non failing costly orders are a hard requirement which we
- * are not prepared for much so let's warn about these users
- * so that we can identify them and convert them to something
- * else.
- */
- WARN_ON_ONCE_GFP(costly_order, gfp_mask);
-
- /*
* Help non-failing allocations by giving some access to memory
* reserves normally used for high priority non-blocking
* allocations but do not use ALLOC_NO_WATERMARKS because this
_
Patches currently in -mm which might be from v-songbaohua@xxxxxxxx are
