Message-Id: <20251002081247.51255-26-byungchul@sk.com>
Date: Thu,  2 Oct 2025 17:12:25 +0900
From: Byungchul Park <byungchul@...com>
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Subject: [PATCH v17 25/47] dept: track PG_locked with dept

Makes dept able to track PG_locked waits and events, which will be
useful in practice.  See the following link that shows dept worked with
PG_locked and detected real issues in practice:

   https://lore.kernel.org/lkml/1674268856-31807-1-git-send-email-byungchul.park@lge.com/

Signed-off-by: Byungchul Park <byungchul@...com>
---
 include/linux/mm_types.h   |   2 +
 include/linux/page-flags.h | 125 +++++++++++++++++++++++++++++++++----
 include/linux/pagemap.h    |  37 ++++++++++-
 mm/filemap.c               |  26 ++++++++
 mm/mm_init.c               |   2 +
 5 files changed, 179 insertions(+), 13 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index a643fae8a349..5ebc565309af 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -20,6 +20,7 @@
 #include <linux/seqlock.h>
 #include <linux/percpu_counter.h>
 #include <linux/types.h>
+#include <linux/dept.h>
 
 #include <asm/mmu.h>
 
@@ -223,6 +224,7 @@ struct page {
 	struct page *kmsan_shadow;
 	struct page *kmsan_origin;
 #endif
+	struct dept_ext_wgen pg_locked_wgen;
 } _struct_page_alignment;
 
 /*
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 8d3fa3a91ce4..d3c4954c4218 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -198,6 +198,61 @@ enum pageflags {
 
 #ifndef __GENERATING_BOUNDS_H
 
+#ifdef CONFIG_DEPT
+#include <linux/kernel.h>
+#include <linux/dept.h>
+
+extern struct dept_map pg_locked_map;
+
+/*
+ * Place the following annotations in its suitable point in code:
+ *
+ *	Annotate dept_page_set_bit() around firstly set_bit*()
+ *	Annotate dept_page_clear_bit() around clear_bit*()
+ *	Annotate dept_page_wait_on_bit() around wait_on_bit*()
+ */
+
+static inline void dept_page_set_bit(struct page *p, int bit_nr)
+{
+	if (bit_nr == PG_locked)
+		dept_request_event(&pg_locked_map, &p->pg_locked_wgen);
+}
+
+static inline void dept_page_clear_bit(struct page *p, int bit_nr)
+{
+	if (bit_nr == PG_locked)
+		dept_event(&pg_locked_map, 1UL, _RET_IP_, __func__, &p->pg_locked_wgen);
+}
+
+static inline void dept_page_wait_on_bit(struct page *p, int bit_nr)
+{
+	if (bit_nr == PG_locked)
+		dept_wait(&pg_locked_map, 1UL, _RET_IP_, __func__, 0, -1L);
+}
+
+static inline void dept_folio_set_bit(struct folio *f, int bit_nr)
+{
+	dept_page_set_bit(&f->page, bit_nr);
+}
+
+static inline void dept_folio_clear_bit(struct folio *f, int bit_nr)
+{
+	dept_page_clear_bit(&f->page, bit_nr);
+}
+
+static inline void dept_folio_wait_on_bit(struct folio *f, int bit_nr)
+{
+	dept_page_wait_on_bit(&f->page, bit_nr);
+}
+#else
+#define dept_page_set_bit(p, bit_nr)		do { } while (0)
+#define dept_page_clear_bit(p, bit_nr)		do { } while (0)
+#define dept_page_wait_on_bit(p, bit_nr)	do { } while (0)
+#define dept_folio_set_bit(f, bit_nr)		do { } while (0)
+#define dept_folio_clear_bit(f, bit_nr)		do { } while (0)
+#define dept_folio_wait_on_bit(f, bit_nr)	do { } while (0)
+#endif
+
 #ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
 DECLARE_STATIC_KEY_FALSE(hugetlb_optimize_vmemmap_key);
 
@@ -419,27 +474,51 @@ static __always_inline bool folio_test_##name(const struct folio *folio) \
 
 #define FOLIO_SET_FLAG(name, page)					\
 static __always_inline void folio_set_##name(struct folio *folio)	\
-{ set_bit(PG_##name, folio_flags(folio, page)); }
+{									\
+	set_bit(PG_##name, folio_flags(folio, page));			\
+	dept_folio_set_bit(folio, PG_##name);				\
+}
 
 #define FOLIO_CLEAR_FLAG(name, page)					\
 static __always_inline void folio_clear_##name(struct folio *folio)	\
-{ clear_bit(PG_##name, folio_flags(folio, page)); }
+{									\
+	clear_bit(PG_##name, folio_flags(folio, page));			\
+	dept_folio_clear_bit(folio, PG_##name);				\
+}
 
 #define __FOLIO_SET_FLAG(name, page)					\
 static __always_inline void __folio_set_##name(struct folio *folio)	\
-{ __set_bit(PG_##name, folio_flags(folio, page)); }
+{									\
+	__set_bit(PG_##name, folio_flags(folio, page));			\
+	dept_folio_set_bit(folio, PG_##name);				\
+}
 
 #define __FOLIO_CLEAR_FLAG(name, page)					\
 static __always_inline void __folio_clear_##name(struct folio *folio)	\
-{ __clear_bit(PG_##name, folio_flags(folio, page)); }
+{									\
+	__clear_bit(PG_##name, folio_flags(folio, page));		\
+	dept_folio_clear_bit(folio, PG_##name);				\
+}
 
 #define FOLIO_TEST_SET_FLAG(name, page)					\
 static __always_inline bool folio_test_set_##name(struct folio *folio)	\
-{ return test_and_set_bit(PG_##name, folio_flags(folio, page)); }
+{									\
+	bool __ret = test_and_set_bit(PG_##name, folio_flags(folio, page)); \
+									\
+	if (!__ret)							\
+		dept_folio_set_bit(folio, PG_##name);			\
+	return __ret;							\
+}
 
 #define FOLIO_TEST_CLEAR_FLAG(name, page)				\
 static __always_inline bool folio_test_clear_##name(struct folio *folio) \
-{ return test_and_clear_bit(PG_##name, folio_flags(folio, page)); }
+{									\
+	bool __ret = test_and_clear_bit(PG_##name, folio_flags(folio, page)); \
+									\
+	if (__ret)							\
+		dept_folio_clear_bit(folio, PG_##name);			\
+	return __ret;							\
+}
 
 #define FOLIO_FLAG(name, page)						\
 FOLIO_TEST_FLAG(name, page)						\
@@ -454,32 +533,54 @@ static __always_inline int Page##uname(const struct page *page)		\
 #define SETPAGEFLAG(uname, lname, policy)				\
 FOLIO_SET_FLAG(lname, FOLIO_##policy)					\
 static __always_inline void SetPage##uname(struct page *page)		\
-{ set_bit(PG_##lname, &policy(page, 1)->flags); }
+{									\
+	set_bit(PG_##lname, &policy(page, 1)->flags);			\
+	dept_page_set_bit(page, PG_##lname);				\
+}
 
 #define CLEARPAGEFLAG(uname, lname, policy)				\
 FOLIO_CLEAR_FLAG(lname, FOLIO_##policy)					\
 static __always_inline void ClearPage##uname(struct page *page)		\
-{ clear_bit(PG_##lname, &policy(page, 1)->flags); }
+{									\
+	clear_bit(PG_##lname, &policy(page, 1)->flags);			\
+	dept_page_clear_bit(page, PG_##lname);				\
+}
 
 #define __SETPAGEFLAG(uname, lname, policy)				\
 __FOLIO_SET_FLAG(lname, FOLIO_##policy)					\
 static __always_inline void __SetPage##uname(struct page *page)		\
-{ __set_bit(PG_##lname, &policy(page, 1)->flags); }
+{									\
+	__set_bit(PG_##lname, &policy(page, 1)->flags);			\
+	dept_page_set_bit(page, PG_##lname);				\
+}
 
 #define __CLEARPAGEFLAG(uname, lname, policy)				\
 __FOLIO_CLEAR_FLAG(lname, FOLIO_##policy)				\
 static __always_inline void __ClearPage##uname(struct page *page)	\
-{ __clear_bit(PG_##lname, &policy(page, 1)->flags); }
+{									\
+	__clear_bit(PG_##lname, &policy(page, 1)->flags);		\
+	dept_page_clear_bit(page, PG_##lname);				\
+}
 
 #define TESTSETFLAG(uname, lname, policy)				\
 FOLIO_TEST_SET_FLAG(lname, FOLIO_##policy)				\
 static __always_inline int TestSetPage##uname(struct page *page)	\
-{ return test_and_set_bit(PG_##lname, &policy(page, 1)->flags); }
+{									\
+	bool ret = test_and_set_bit(PG_##lname, &policy(page, 1)->flags);\
+	if (!ret)							\
+		dept_page_set_bit(page, PG_##lname);			\
+	return ret;							\
+}
 
 #define TESTCLEARFLAG(uname, lname, policy)				\
 FOLIO_TEST_CLEAR_FLAG(lname, FOLIO_##policy)				\
 static __always_inline int TestClearPage##uname(struct page *page)	\
-{ return test_and_clear_bit(PG_##lname, &policy(page, 1)->flags); }
+{									\
+	bool ret = test_and_clear_bit(PG_##lname, &policy(page, 1)->flags);\
+	if (ret)							\
+		dept_page_clear_bit(page, PG_##lname);			\
+	return ret;							\
+}
 
 #define PAGEFLAG(uname, lname, policy)					\
 	TESTPAGEFLAG(uname, lname, policy)				\
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 12a12dae727d..53b68b7a3f17 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1093,7 +1093,12 @@ void folio_unlock(struct folio *folio);
  */
 static inline bool folio_trylock(struct folio *folio)
 {
-	return likely(!test_and_set_bit_lock(PG_locked, folio_flags(folio, 0)));
+	bool ret = !test_and_set_bit_lock(PG_locked, folio_flags(folio, 0));
+
+	if (ret)
+		dept_page_set_bit(&folio->page, PG_locked);
+
+	return likely(ret);
 }
 
 /*
@@ -1129,6 +1134,16 @@ static inline bool trylock_page(struct page *page)
 static inline void folio_lock(struct folio *folio)
 {
 	might_sleep();
+
+	/*
+	 * dept_page_wait_on_bit() will be called if __folio_lock() goes
+	 * through a real wait path.  However, for better job to detect
+	 * *potential* deadlocks, let's assume that folio_lock() always
+	 * goes through wait so that dept can take into account all the
+	 * potential cases.
+	 */
+	dept_page_wait_on_bit(&folio->page, PG_locked);
+
 	if (!folio_trylock(folio))
 		__folio_lock(folio);
 }
@@ -1149,6 +1164,15 @@ static inline void lock_page(struct page *page)
 	struct folio *folio;
 	might_sleep();
 
+	/*
+	 * dept_page_wait_on_bit() will be called if __folio_lock() goes
+	 * through a real wait path.  However, for better job to detect
+	 * *potential* deadlocks, let's assume that lock_page() always
+	 * goes through wait so that dept can take into account all the
+	 * potential cases.
+	 */
+	dept_page_wait_on_bit(page, PG_locked);
+
 	folio = page_folio(page);
 	if (!folio_trylock(folio))
 		__folio_lock(folio);
@@ -1167,6 +1191,17 @@ static inline void lock_page(struct page *page)
 static inline int folio_lock_killable(struct folio *folio)
 {
 	might_sleep();
+
+	/*
+	 * dept_page_wait_on_bit() will be called if
+	 * __folio_lock_killable() goes through a real wait path.
+	 * However, for better job to detect *potential* deadlocks,
+	 * let's assume that folio_lock_killable() always goes through
+	 * wait so that dept can take into account all the potential
+	 * cases.
+	 */
+	dept_page_wait_on_bit(&folio->page, PG_locked);
+
 	if (!folio_trylock(folio))
 		return __folio_lock_killable(folio);
 	return 0;
diff --git a/mm/filemap.c b/mm/filemap.c
index 751838ef05e5..edb0710ddb3f 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -48,6 +48,7 @@
 #include <linux/rcupdate_wait.h>
 #include <linux/sched/mm.h>
 #include <linux/sysctl.h>
+#include <linux/dept.h>
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 #include "internal.h"
@@ -1145,6 +1146,7 @@ static int wake_page_function(wait_queue_entry_t *wait, unsigned mode, int sync,
 		if (flags & WQ_FLAG_CUSTOM) {
 			if (test_and_set_bit(key->bit_nr, &key->folio->flags))
 				return -1;
+			dept_page_set_bit(&key->folio->page, key->bit_nr);
 			flags |= WQ_FLAG_DONE;
 		}
 	}
@@ -1228,6 +1230,7 @@ static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
 	if (wait->flags & WQ_FLAG_EXCLUSIVE) {
 		if (test_and_set_bit(bit_nr, &folio->flags))
 			return false;
+		dept_page_set_bit(&folio->page, bit_nr);
 	} else if (test_bit(bit_nr, &folio->flags))
 		return false;
 
@@ -1235,6 +1238,9 @@ static inline bool folio_trylock_flag(struct folio *folio, int bit_nr,
 	return true;
 }
 
+struct dept_map __maybe_unused pg_locked_map = DEPT_MAP_INITIALIZER(pg_locked_map, NULL);
+EXPORT_SYMBOL(pg_locked_map);
+
 static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 		int state, enum behavior behavior)
 {
@@ -1246,6 +1252,8 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 	unsigned long pflags;
 	bool in_thrashing;
 
+	dept_page_wait_on_bit(&folio->page, bit_nr);
+
 	if (bit_nr == PG_locked &&
 	    !folio_test_uptodate(folio) && folio_test_workingset(folio)) {
 		delayacct_thrashing_start(&in_thrashing);
@@ -1339,6 +1347,23 @@ static inline int folio_wait_bit_common(struct folio *folio, int bit_nr,
 		break;
 	}
 
+	/*
+	 * dept_page_set_bit() might have been called already in
+	 * folio_trylock_flag(), wake_page_function() or somewhere.
+	 * However, call it again to reset the wgen of dept to ensure
+	 * dept_page_wait_on_bit() is called prior to
+	 * dept_page_set_bit().
+	 *
+	 * Remind dept considers all the waits between
+	 * dept_page_set_bit() and dept_page_clear_bit() as potential
+	 * event disturbers. Ensure the correct sequence so that dept
+	 * can make correct decisions:
+	 *
+	 *	wait -> acquire(set bit) -> release(clear bit)
+	 */
+	if (wait->flags & WQ_FLAG_DONE)
+		dept_page_set_bit(&folio->page, bit_nr);
+
 	/*
 	 * If a signal happened, this 'finish_wait()' may remove the last
 	 * waiter from the wait-queues, but the folio waiters bit will remain
@@ -1496,6 +1521,7 @@ void folio_unlock(struct folio *folio)
 	BUILD_BUG_ON(PG_waiters != 7);
 	BUILD_BUG_ON(PG_locked > 7);
 	VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio);
+	dept_page_clear_bit(&folio->page, PG_locked);
 	if (folio_xor_flags_has_waiters(folio, 1 << PG_locked))
 		folio_wake_bit(folio, PG_locked);
 }
diff --git a/mm/mm_init.c b/mm/mm_init.c
index 5c21b3af216b..09e4ac6a73c7 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -32,6 +32,7 @@
 #include <linux/vmstat.h>
 #include <linux/kexec_handover.h>
 #include <linux/hugetlb.h>
+#include <linux/dept.h>
 #include "internal.h"
 #include "slab.h"
 #include "shuffle.h"
@@ -587,6 +588,7 @@ void __meminit __init_single_page(struct page *page, unsigned long pfn,
 	atomic_set(&page->_mapcount, -1);
 	page_cpupid_reset_last(page);
 	page_kasan_tag_reset(page);
+	dept_ext_wgen_init(&page->pg_locked_wgen);
 
 	INIT_LIST_HEAD(&page->lru);
 #ifdef WANT_PAGE_VIRTUAL
-- 
2.17.1

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