+ mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner.patch added to mm-unstable branch

+ mm-warn-about-illegal-__gfp_nofail-usage-in-a-more-appropriate-location-and-manner.patch added to mm-unstable branch

[Andrew Morton]

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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@oppo.com>
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@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David Rientjes <rientjes@google.com>
Cc: "Eugenio Pérez" <eperezma@redhat.com>
Cc: Hailong.Liu <hailong.liu@oppo.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Xie Yongji <xieyongji@bytedance.com>
Cc: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Cc: Yafang Shao <laoar.shao@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 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@oppo.com 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