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From:   Qi Zheng <zhengqi.arch@bytedance.com>
To:     akinobu.mita@gmail.com, akpm@linux-foundation.org, vbabka@suse.cz,
        gregkh@linuxfoundation.org, jirislaby@kernel.org,
        rostedt@goodmis.org
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [PATCH 1/2] mm: fix missing handler for __GFP_NOWARN
Date:   Tue, 10 May 2022 19:38:08 +0800
Message-Id: <20220510113809.80626-1-zhengqi.arch@bytedance.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

We expect no warnings to be issued when we specify __GFP_NOWARN, but
currently in paths like alloc_pages() and kmalloc(), there are still
some warnings printed, fix it.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 include/linux/fault-inject.h |  2 ++
 lib/fault-inject.c           |  3 +++
 mm/failslab.c                |  3 +++
 mm/internal.h                | 11 +++++++++++
 mm/page_alloc.c              | 22 ++++++++++++----------
 5 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/include/linux/fault-inject.h b/include/linux/fault-inject.h
index 2d04f6448cde..9f6e25467844 100644
--- a/include/linux/fault-inject.h
+++ b/include/linux/fault-inject.h
@@ -20,6 +20,7 @@ struct fault_attr {
 	atomic_t space;
 	unsigned long verbose;
 	bool task_filter;
+	bool no_warn;
 	unsigned long stacktrace_depth;
 	unsigned long require_start;
 	unsigned long require_end;
@@ -39,6 +40,7 @@ struct fault_attr {
 		.ratelimit_state = RATELIMIT_STATE_INIT_DISABLED,	\
 		.verbose = 2,						\
 		.dname = NULL,						\
+		.no_warn = false,					\
 	}
 
 #define DECLARE_FAULT_ATTR(name) struct fault_attr name = FAULT_ATTR_INITIALIZER
diff --git a/lib/fault-inject.c b/lib/fault-inject.c
index ce12621b4275..423784d9c058 100644
--- a/lib/fault-inject.c
+++ b/lib/fault-inject.c
@@ -41,6 +41,9 @@ EXPORT_SYMBOL_GPL(setup_fault_attr);
 
 static void fail_dump(struct fault_attr *attr)
 {
+	if (attr->no_warn)
+		return;
+
 	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
 		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
 		       "name %pd, interval %lu, probability %lu, "
diff --git a/mm/failslab.c b/mm/failslab.c
index f92fed91ac23..58df9789f1d2 100644
--- a/mm/failslab.c
+++ b/mm/failslab.c
@@ -30,6 +30,9 @@ bool __should_failslab(struct kmem_cache *s, gfp_t gfpflags)
 	if (failslab.cache_filter && !(s->flags & SLAB_FAILSLAB))
 		return false;
 
+	if (gfpflags & __GFP_NOWARN)
+		failslab.attr.no_warn = true;
+
 	return should_fail(&failslab.attr, s->object_size);
 }
 
diff --git a/mm/internal.h b/mm/internal.h
index cf16280ce132..7a268fac6559 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -35,6 +35,17 @@ struct folio_batch;
 /* Do not use these with a slab allocator */
 #define GFP_SLAB_BUG_MASK (__GFP_DMA32|__GFP_HIGHMEM|~__GFP_BITS_MASK)
 
+#define WARN_ON_ONCE_GFP(cond, gfp)	({				\
+	static bool __section(".data.once") __warned;			\
+	int __ret_warn_once = !!(cond);					\
+									\
+	if (unlikely(!(gfp & __GFP_NOWARN) && __ret_warn_once && !__warned)) { \
+		__warned = true;					\
+		WARN_ON(1);						\
+	}								\
+	unlikely(__ret_warn_once);					\
+})
+
 void page_writeback_init(void);
 
 static inline void *folio_raw_mapping(struct folio *folio)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 0e42038382c1..2bf4ce4d0e2f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3722,7 +3722,7 @@ struct page *rmqueue(struct zone *preferred_zone,
 	 * 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));
+	WARN_ON_ONCE_GFP((gfp_flags & __GFP_NOFAIL) && (order > 1), gfp_flags);
 
 	do {
 		page = NULL;
@@ -3799,6 +3799,9 @@ static bool __should_fail_alloc_page(gfp_t gfp_mask, unsigned int order)
 			(gfp_mask & __GFP_DIRECT_RECLAIM))
 		return false;
 
+	if (gfp_mask & __GFP_NOWARN)
+		fail_page_alloc.attr.no_warn = true;
+
 	return should_fail(&fail_page_alloc.attr, 1 << order);
 }
 
@@ -4346,7 +4349,8 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
 	 */
 
 	/* Exhausted what can be done so it's blame time */
-	if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) {
+	if (out_of_memory(&oc) ||
+	    WARN_ON_ONCE_GFP(gfp_mask & __GFP_NOFAIL, gfp_mask)) {
 		*did_some_progress = 1;
 
 		/*
@@ -4902,8 +4906,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 	 * We also sanity check to catch abuse of atomic reserves being used by
 	 * callers that are not in atomic context.
 	 */
-	if (WARN_ON_ONCE((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
-				(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)))
+	if (WARN_ON_ONCE_GFP((gfp_mask & (__GFP_ATOMIC|__GFP_DIRECT_RECLAIM)) ==
+				(__GFP_ATOMIC|__GFP_DIRECT_RECLAIM), gfp_mask))
 		gfp_mask &= ~__GFP_ATOMIC;
 
 retry_cpuset:
@@ -5117,7 +5121,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 		 * All existing users of the __GFP_NOFAIL are blockable, so warn
 		 * of any new users that actually require GFP_NOWAIT
 		 */
-		if (WARN_ON_ONCE(!can_direct_reclaim))
+		if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask))
 			goto fail;
 
 		/*
@@ -5125,7 +5129,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 		 * 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);
+		WARN_ON_ONCE_GFP(current->flags & PF_MEMALLOC, gfp_mask);
 
 		/*
 		 * non failing costly orders are a hard requirement which we
@@ -5133,7 +5137,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
 		 * so that we can identify them and convert them to something
 		 * else.
 		 */
-		WARN_ON_ONCE(order > PAGE_ALLOC_COSTLY_ORDER);
+		WARN_ON_ONCE_GFP(order > PAGE_ALLOC_COSTLY_ORDER, gfp_mask);
 
 		/*
 		 * Help non-failing allocations by giving them access to memory
@@ -5379,10 +5383,8 @@ struct page *__alloc_pages(gfp_t gfp, unsigned int order, int preferred_nid,
 	 * There are several places where we assume that the order value is sane
 	 * so bail out early if the request is out of bound.
 	 */
-	if (unlikely(order >= MAX_ORDER)) {
-		WARN_ON_ONCE(!(gfp & __GFP_NOWARN));
+	if (WARN_ON_ONCE_GFP(order >= MAX_ORDER, gfp))
 		return NULL;
-	}
 
 	gfp &= gfp_allowed_mask;
 	/*
-- 
2.20.1