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Message-Id: <20211026173822.502506-8-pasha.tatashin@soleen.com>
Date: Tue, 26 Oct 2021 17:38:21 +0000
From: Pasha Tatashin <pasha.tatashin@...een.com>
To: pasha.tatashin@...een.com, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, linux-m68k@...ts.linux-m68k.org,
anshuman.khandual@....com, willy@...radead.org,
akpm@...ux-foundation.org, william.kucharski@...cle.com,
mike.kravetz@...cle.com, vbabka@...e.cz, geert@...ux-m68k.org,
schmitzmic@...il.com, rostedt@...dmis.org, mingo@...hat.com,
hannes@...xchg.org, guro@...com, songmuchun@...edance.com,
weixugc@...gle.com, gthelen@...gle.com
Subject: [RFC 7/8] mm: remove set_page_count()
set_page_count() is dangerous because it resets _refcount to an
arbitrary value. Instead we now initialize _refcount to 1 only once,
and the rest of the time we are using add/dec/cmpxchg to have a
contiguous track of the counter.
Remove set_page_count() and add new tracing hooks to page_ref_init().
Signed-off-by: Pasha Tatashin <pasha.tatashin@...een.com>
---
include/linux/page_ref.h | 19 +++++---------
include/trace/events/page_ref.h | 46 ++++++++++++++++++++++++++++-----
mm/debug_page_ref.c | 8 +++---
3 files changed, 50 insertions(+), 23 deletions(-)
diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h
index 81a628dc9b8b..06f5760fcd06 100644
--- a/include/linux/page_ref.h
+++ b/include/linux/page_ref.h
@@ -7,7 +7,7 @@
#include <linux/page-flags.h>
#include <linux/tracepoint-defs.h>
-DECLARE_TRACEPOINT(page_ref_set);
+DECLARE_TRACEPOINT(page_ref_init);
DECLARE_TRACEPOINT(page_ref_mod);
DECLARE_TRACEPOINT(page_ref_mod_and_test);
DECLARE_TRACEPOINT(page_ref_mod_and_return);
@@ -26,7 +26,7 @@ DECLARE_TRACEPOINT(page_ref_unfreeze);
*/
#define page_ref_tracepoint_active(t) tracepoint_enabled(t)
-extern void __page_ref_set(struct page *page, int v);
+extern void __page_ref_init(struct page *page);
extern void __page_ref_mod(struct page *page, int v);
extern void __page_ref_mod_and_test(struct page *page, int v, int ret);
extern void __page_ref_mod_and_return(struct page *page, int v, int ret);
@@ -38,7 +38,7 @@ extern void __page_ref_unfreeze(struct page *page, int v);
#define page_ref_tracepoint_active(t) false
-static inline void __page_ref_set(struct page *page, int v)
+static inline void __page_ref_init(struct page *page)
{
}
static inline void __page_ref_mod(struct page *page, int v)
@@ -72,15 +72,8 @@ static inline int page_count(const struct page *page)
return atomic_read(&compound_head(page)->_refcount);
}
-static inline void set_page_count(struct page *page, int v)
-{
- atomic_set(&page->_refcount, v);
- if (page_ref_tracepoint_active(page_ref_set))
- __page_ref_set(page, v);
-}
-
/*
- * Setup the page refcount to one before being freed into the page allocator.
+ * Setup the page->_refcount to 1 before being freed into the page allocator.
* The memory might not be initialized and therefore there cannot be any
* assumptions about the current value of page->_refcount. This call should be
* done during boot when memory is being initialized, during memory hotplug
@@ -89,7 +82,9 @@ static inline void set_page_count(struct page *page, int v)
*/
static inline void page_ref_init(struct page *page)
{
- set_page_count(page, 1);
+ atomic_set(&page->_refcount, 1);
+ if (page_ref_tracepoint_active(page_ref_init))
+ __page_ref_init(page);
}
static inline int page_ref_add_return(struct page *page, int nr)
diff --git a/include/trace/events/page_ref.h b/include/trace/events/page_ref.h
index 8a99c1cd417b..87551bb1df9e 100644
--- a/include/trace/events/page_ref.h
+++ b/include/trace/events/page_ref.h
@@ -10,6 +10,45 @@
#include <linux/tracepoint.h>
#include <trace/events/mmflags.h>
+DECLARE_EVENT_CLASS(page_ref_init_template,
+
+ TP_PROTO(struct page *page),
+
+ TP_ARGS(page),
+
+ TP_STRUCT__entry(
+ __field(unsigned long, pfn)
+ __field(unsigned long, flags)
+ __field(int, count)
+ __field(int, mapcount)
+ __field(void *, mapping)
+ __field(int, mt)
+ __field(int, val)
+ ),
+
+ TP_fast_assign(
+ __entry->pfn = page_to_pfn(page);
+ __entry->flags = page->flags;
+ __entry->count = page_ref_count(page);
+ __entry->mapcount = page_mapcount(page);
+ __entry->mapping = page->mapping;
+ __entry->mt = get_pageblock_migratetype(page);
+ ),
+
+ TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d",
+ __entry->pfn,
+ show_page_flags(__entry->flags & PAGEFLAGS_MASK),
+ __entry->count,
+ __entry->mapcount, __entry->mapping, __entry->mt)
+);
+
+DEFINE_EVENT(page_ref_init_template, page_ref_init,
+
+ TP_PROTO(struct page *page),
+
+ TP_ARGS(page)
+);
+
DECLARE_EVENT_CLASS(page_ref_mod_template,
TP_PROTO(struct page *page, int v),
@@ -44,13 +83,6 @@ DECLARE_EVENT_CLASS(page_ref_mod_template,
__entry->val)
);
-DEFINE_EVENT(page_ref_mod_template, page_ref_set,
-
- TP_PROTO(struct page *page, int v),
-
- TP_ARGS(page, v)
-);
-
DEFINE_EVENT(page_ref_mod_template, page_ref_mod,
TP_PROTO(struct page *page, int v),
diff --git a/mm/debug_page_ref.c b/mm/debug_page_ref.c
index f3b2c9d3ece2..e32149734122 100644
--- a/mm/debug_page_ref.c
+++ b/mm/debug_page_ref.c
@@ -5,12 +5,12 @@
#define CREATE_TRACE_POINTS
#include <trace/events/page_ref.h>
-void __page_ref_set(struct page *page, int v)
+void __page_ref_init(struct page *page)
{
- trace_page_ref_set(page, v);
+ trace_page_ref_init(page);
}
-EXPORT_SYMBOL(__page_ref_set);
-EXPORT_TRACEPOINT_SYMBOL(page_ref_set);
+EXPORT_SYMBOL(__page_ref_init);
+EXPORT_TRACEPOINT_SYMBOL(page_ref_init);
void __page_ref_mod(struct page *page, int v)
{
--
2.33.0.1079.g6e70778dc9-goog
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