The patch titled
Subject: mm: warn about illegal __GFP_NOFAIL usage in a more appropriate location and manner
has been added to the -mm mm-unstable branch. Its filename is
mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
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.
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>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
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: Michal Hocko <mhocko@xxxxxxxx>
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>
---
mm/page_alloc.c | 50 +++++++++++++++++++++++-----------------------
1 file changed, 25 insertions(+), 25 deletions(-)
--- a/mm/page_alloc.c~mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner
+++ a/mm/page_alloc.c
@@ -3039,12 +3039,6 @@ 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);
@@ -4182,6 +4176,7 @@ __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;
@@ -4194,6 +4189,25 @@ __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;
@@ -4411,30 +4425,16 @@ 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
mm-extend-usage-parameter-so-that-cluster_swap_free_nr-can-be-reused.patch
mm-swap-add-nr-argument-in-swapcache_prepare-and-swapcache_clear-to-support-large-folios.patch
mm-swap-add-nr-argument-in-swapcache_prepare-and-swapcache_clear-to-support-large-folios-fix.patch
mm-rename-instances-of-swap_info_struct-to-meaningful-si.patch
mm-attempt-to-batch-free-swap-entries-for-zap_pte_range.patch
mm-attempt-to-batch-free-swap-entries-for-zap_pte_range-fix.patch
mm-override-mthp-enabled-defaults-at-kernel-cmdline-fix.patch
mm-count-the-number-of-anonymous-thps-per-size.patch
mm-count-the-number-of-partially-mapped-anonymous-thps-per-size.patch
mm-add-nr-argument-in-mem_cgroup_swapin_uncharge_swap-helper-to-support-large-folios.patch
mm-document-__gfp_nofail-must-be-blockable.patch
mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner.patch
