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Date:   Mon, 29 Apr 2019 11:37:40 -0700
From:   tip-bot for Thomas Gleixner <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     agk@...hat.com, tglx@...utronix.de, penberg@...nel.org,
        jthumshirn@...e.de, jpoimboe@...hat.com, dsterba@...e.com,
        snitzer@...hat.com, glider@...gle.com, rodrigo.vivi@...el.com,
        mbenes@...e.cz, akpm@...ux-foundation.org, robin.murphy@....com,
        rppt@...ux.vnet.ibm.com, adobriyan@...il.com, clm@...com,
        rostedt@...dmis.org, airlied@...ux.ie,
        maarten.lankhorst@...ux.intel.com, josef@...icpanda.com,
        joonas.lahtinen@...ux.intel.com, linux-kernel@...r.kernel.org,
        jani.nikula@...ux.intel.com, catalin.marinas@....com,
        m.szyprowski@...sung.com, cl@...ux.com, dvyukov@...gle.com,
        hch@....de, mingo@...nel.org, aryabinin@...tuozzo.com,
        daniel@...ll.ch, luto@...nel.org, tom.zanussi@...ux.intel.com,
        rientjes@...gle.com, hpa@...or.com, akinobu.mita@...il.com
Subject: [tip:core/stacktrace] mm/page_owner: Simplify stack trace handling

Commit-ID:  af52bf6b92f7d8783c1e712cad6ef7d37cd773b2
Gitweb:     https://git.kernel.org/tip/af52bf6b92f7d8783c1e712cad6ef7d37cd773b2
Author:     Thomas Gleixner <tglx@...utronix.de>
AuthorDate: Thu, 25 Apr 2019 11:45:03 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Mon, 29 Apr 2019 12:37:50 +0200

mm/page_owner: Simplify stack trace handling

Replace the indirection through struct stack_trace by using the storage
array based interfaces.

The original code in all printing functions is really wrong. It allocates a
storage array on stack which is unused because depot_fetch_stack() does not
store anything in it. It overwrites the entries pointer in the stack_trace
struct so it points to the depot storage.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: linux-mm@...ck.org
Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
Cc: David Rientjes <rientjes@...gle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Alexander Potapenko <glider@...gle.com>
Cc: Alexey Dobriyan <adobriyan@...il.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Pekka Enberg <penberg@...nel.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc: kasan-dev@...glegroups.com
Cc: Akinobu Mita <akinobu.mita@...il.com>
Cc: Christoph Hellwig <hch@....de>
Cc: iommu@...ts.linux-foundation.org
Cc: Robin Murphy <robin.murphy@....com>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Johannes Thumshirn <jthumshirn@...e.de>
Cc: David Sterba <dsterba@...e.com>
Cc: Chris Mason <clm@...com>
Cc: Josef Bacik <josef@...icpanda.com>
Cc: linux-btrfs@...r.kernel.org
Cc: dm-devel@...hat.com
Cc: Mike Snitzer <snitzer@...hat.com>
Cc: Alasdair Kergon <agk@...hat.com>
Cc: Daniel Vetter <daniel@...ll.ch>
Cc: intel-gfx@...ts.freedesktop.org
Cc: Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: dri-devel@...ts.freedesktop.org
Cc: David Airlie <airlied@...ux.ie>
Cc: Jani Nikula <jani.nikula@...ux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@...el.com>
Cc: Tom Zanussi <tom.zanussi@...ux.intel.com>
Cc: Miroslav Benes <mbenes@...e.cz>
Cc: linux-arch@...r.kernel.org
Link: https://lkml.kernel.org/r/20190425094802.067210525@linutronix.de

---
 mm/page_owner.c | 79 ++++++++++++++++++++-------------------------------------
 1 file changed, 28 insertions(+), 51 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index df277e6bc3c6..addcbb2ae4e4 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -58,15 +58,10 @@ static bool need_page_owner(void)
 static __always_inline depot_stack_handle_t create_dummy_stack(void)
 {
 	unsigned long entries[4];
-	struct stack_trace dummy;
+	unsigned int nr_entries;
 
-	dummy.nr_entries = 0;
-	dummy.max_entries = ARRAY_SIZE(entries);
-	dummy.entries = &entries[0];
-	dummy.skip = 0;
-
-	save_stack_trace(&dummy);
-	return depot_save_stack(&dummy, GFP_KERNEL);
+	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 0);
+	return stack_depot_save(entries, nr_entries, GFP_KERNEL);
 }
 
 static noinline void register_dummy_stack(void)
@@ -120,46 +115,39 @@ void __reset_page_owner(struct page *page, unsigned int order)
 	}
 }
 
-static inline bool check_recursive_alloc(struct stack_trace *trace,
-					unsigned long ip)
+static inline bool check_recursive_alloc(unsigned long *entries,
+					 unsigned int nr_entries,
+					 unsigned long ip)
 {
-	int i;
-
-	if (!trace->nr_entries)
-		return false;
+	unsigned int i;
 
-	for (i = 0; i < trace->nr_entries; i++) {
-		if (trace->entries[i] == ip)
+	for (i = 0; i < nr_entries; i++) {
+		if (entries[i] == ip)
 			return true;
 	}
-
 	return false;
 }
 
 static noinline depot_stack_handle_t save_stack(gfp_t flags)
 {
 	unsigned long entries[PAGE_OWNER_STACK_DEPTH];
-	struct stack_trace trace = {
-		.nr_entries = 0,
-		.entries = entries,
-		.max_entries = PAGE_OWNER_STACK_DEPTH,
-		.skip = 2
-	};
 	depot_stack_handle_t handle;
+	unsigned int nr_entries;
 
-	save_stack_trace(&trace);
+	nr_entries = stack_trace_save(entries, ARRAY_SIZE(entries), 2);
 
 	/*
-	 * We need to check recursion here because our request to stackdepot
-	 * could trigger memory allocation to save new entry. New memory
-	 * allocation would reach here and call depot_save_stack() again
-	 * if we don't catch it. There is still not enough memory in stackdepot
-	 * so it would try to allocate memory again and loop forever.
+	 * We need to check recursion here because our request to
+	 * stackdepot could trigger memory allocation to save new
+	 * entry. New memory allocation would reach here and call
+	 * stack_depot_save_entries() again if we don't catch it. There is
+	 * still not enough memory in stackdepot so it would try to
+	 * allocate memory again and loop forever.
 	 */
-	if (check_recursive_alloc(&trace, _RET_IP_))
+	if (check_recursive_alloc(entries, nr_entries, _RET_IP_))
 		return dummy_handle;
 
-	handle = depot_save_stack(&trace, flags);
+	handle = stack_depot_save(entries, nr_entries, flags);
 	if (!handle)
 		handle = failure_handle;
 
@@ -337,16 +325,10 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 		struct page *page, struct page_owner *page_owner,
 		depot_stack_handle_t handle)
 {
-	int ret;
-	int pageblock_mt, page_mt;
+	int ret, pageblock_mt, page_mt;
+	unsigned long *entries;
+	unsigned int nr_entries;
 	char *kbuf;
-	unsigned long entries[PAGE_OWNER_STACK_DEPTH];
-	struct stack_trace trace = {
-		.nr_entries = 0,
-		.entries = entries,
-		.max_entries = PAGE_OWNER_STACK_DEPTH,
-		.skip = 0
-	};
 
 	count = min_t(size_t, count, PAGE_SIZE);
 	kbuf = kmalloc(count, GFP_KERNEL);
@@ -375,8 +357,8 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn,
 	if (ret >= count)
 		goto err;
 
-	depot_fetch_stack(handle, &trace);
-	ret += snprint_stack_trace(kbuf + ret, count - ret, &trace, 0);
+	nr_entries = stack_depot_fetch(handle, &entries);
+	ret += stack_trace_snprint(kbuf + ret, count - ret, entries, nr_entries, 0);
 	if (ret >= count)
 		goto err;
 
@@ -407,14 +389,9 @@ void __dump_page_owner(struct page *page)
 {
 	struct page_ext *page_ext = lookup_page_ext(page);
 	struct page_owner *page_owner;
-	unsigned long entries[PAGE_OWNER_STACK_DEPTH];
-	struct stack_trace trace = {
-		.nr_entries = 0,
-		.entries = entries,
-		.max_entries = PAGE_OWNER_STACK_DEPTH,
-		.skip = 0
-	};
 	depot_stack_handle_t handle;
+	unsigned long *entries;
+	unsigned int nr_entries;
 	gfp_t gfp_mask;
 	int mt;
 
@@ -438,10 +415,10 @@ void __dump_page_owner(struct page *page)
 		return;
 	}
 
-	depot_fetch_stack(handle, &trace);
+	nr_entries = stack_depot_fetch(handle, &entries);
 	pr_alert("page allocated via order %u, migratetype %s, gfp_mask %#x(%pGg)\n",
 		 page_owner->order, migratetype_names[mt], gfp_mask, &gfp_mask);
-	print_stack_trace(&trace, 0);
+	stack_trace_print(entries, nr_entries, 0);
 
 	if (page_owner->last_migrate_reason != -1)
 		pr_alert("page has been migrated, last migrate reason: %s\n",

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