[PATCH RFC 03/11] folio_wait: move folio bit-lock and wait declarations to include/linux/folio_wait.h

[Tal Zussman]

Move ~150 lines of folio bit-lock and wait queue infrastructure from
pagemap.h to folio_wait.h. pagemap.h includes the new header so existing
users don't break.

Signed-off-by: Tal Zussman <tz2294@xxxxxxxxxxxx>
---
 include/linux/folio_wait.h | 181 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pagemap.h    | 172 +-----------------------------------------
 mm/folio_wait.c            |   2 +-
 3 files changed, 183 insertions(+), 172 deletions(-)

diff --git a/include/linux/folio_wait.h b/include/linux/folio_wait.h
new file mode 100644
index 000000000000..80ddf1ffcae4
--- /dev/null
+++ b/include/linux/folio_wait.h
@@ -0,0 +1,181 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_FOLIO_WAIT_H
+#define _LINUX_FOLIO_WAIT_H
+
+#include <linux/bitops.h>
+#include <linux/page-flags.h>
+#include <linux/wait.h>
+
+struct wait_page_key {
+	struct folio *folio;
+	int bit_nr;
+	int page_match;
+};
+
+struct wait_page_queue {
+	struct folio *folio;
+	int bit_nr;
+	wait_queue_entry_t wait;
+};
+
+static inline bool wake_page_match(struct wait_page_queue *wait_page,
+				  struct wait_page_key *key)
+{
+	if (wait_page->folio != key->folio)
+	       return false;
+	key->page_match = 1;
+
+	if (wait_page->bit_nr != key->bit_nr)
+		return false;
+
+	return true;
+}
+
+void __folio_lock(struct folio *folio);
+int __folio_lock_killable(struct folio *folio);
+vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf);
+void unlock_page(struct page *page);
+void folio_unlock(struct folio *folio);
+
+/**
+ * folio_trylock() - Attempt to lock a folio.
+ * @folio: The folio to attempt to lock.
+ *
+ * Sometimes it is undesirable to wait for a folio to be unlocked (eg
+ * when the locks are being taken in the wrong order, or if making
+ * progress through a batch of folios is more important than processing
+ * them in order).  Usually folio_lock() is the correct function to call.
+ *
+ * Context: Any context.
+ * Return: Whether the lock was successfully acquired.
+ */
+static inline bool folio_trylock(struct folio *folio)
+{
+	return likely(!test_and_set_bit_lock(PG_locked, folio_flags(folio, 0)));
+}
+
+/*
+ * Return true if the page was successfully locked
+ */
+static inline bool trylock_page(struct page *page)
+{
+	return folio_trylock(page_folio(page));
+}
+
+/**
+ * folio_lock() - Lock this folio.
+ * @folio: The folio to lock.
+ *
+ * The folio lock protects against many things, probably more than it
+ * should.  It is primarily held while a folio is being brought uptodate,
+ * either from its backing file or from swap.  It is also held while a
+ * folio is being truncated from its address_space, so holding the lock
+ * is sufficient to keep folio->mapping stable.
+ *
+ * The folio lock is also held while write() is modifying the page to
+ * provide POSIX atomicity guarantees (as long as the write does not
+ * cross a page boundary).  Other modifications to the data in the folio
+ * do not hold the folio lock and can race with writes, eg DMA and stores
+ * to mapped pages.
+ *
+ * Context: May sleep.  If you need to acquire the locks of two or
+ * more folios, they must be in order of ascending index, if they are
+ * in the same address_space.  If they are in different address_spaces,
+ * acquire the lock of the folio which belongs to the address_space which
+ * has the lowest address in memory first.
+ */
+static inline void folio_lock(struct folio *folio)
+{
+	might_sleep();
+	if (!folio_trylock(folio))
+		__folio_lock(folio);
+}
+
+/**
+ * lock_page() - Lock the folio containing this page.
+ * @page: The page to lock.
+ *
+ * See folio_lock() for a description of what the lock protects.
+ * This is a legacy function and new code should probably use folio_lock()
+ * instead.
+ *
+ * Context: May sleep.  Pages in the same folio share a lock, so do not
+ * attempt to lock two pages which share a folio.
+ */
+static inline void lock_page(struct page *page)
+{
+	struct folio *folio;
+	might_sleep();
+
+	folio = page_folio(page);
+	if (!folio_trylock(folio))
+		__folio_lock(folio);
+}
+
+/**
+ * folio_lock_killable() - Lock this folio, interruptible by a fatal signal.
+ * @folio: The folio to lock.
+ *
+ * Attempts to lock the folio, like folio_lock(), except that the sleep
+ * to acquire the lock is interruptible by a fatal signal.
+ *
+ * Context: May sleep; see folio_lock().
+ * Return: 0 if the lock was acquired; -EINTR if a fatal signal was received.
+ */
+static inline int folio_lock_killable(struct folio *folio)
+{
+	might_sleep();
+	if (!folio_trylock(folio))
+		return __folio_lock_killable(folio);
+	return 0;
+}
+
+/*
+ * folio_lock_or_retry - Lock the folio, unless this would block and the
+ * caller indicated that it can handle a retry.
+ *
+ * Return value and mmap_lock implications depend on flags; see
+ * __folio_lock_or_retry().
+ */
+static inline vm_fault_t folio_lock_or_retry(struct folio *folio,
+					     struct vm_fault *vmf)
+{
+	might_sleep();
+	if (!folio_trylock(folio))
+		return __folio_lock_or_retry(folio, vmf);
+	return 0;
+}
+
+/*
+ * This is exported only for folio_wait_locked/folio_wait_writeback, etc.,
+ * and should not be used directly.
+ */
+void folio_wait_bit(struct folio *folio, int bit_nr);
+int folio_wait_bit_killable(struct folio *folio, int bit_nr);
+
+/*
+ * Wait for a folio to be unlocked.
+ *
+ * This must be called with the caller "holding" the folio,
+ * ie with increased folio reference count so that the folio won't
+ * go away during the wait.
+ */
+static inline void folio_wait_locked(struct folio *folio)
+{
+	if (folio_test_locked(folio))
+		folio_wait_bit(folio, PG_locked);
+}
+
+static inline int folio_wait_locked_killable(struct folio *folio)
+{
+	if (!folio_test_locked(folio))
+		return 0;
+	return folio_wait_bit_killable(folio, PG_locked);
+}
+
+void folio_end_read(struct folio *folio, bool success);
+void folio_end_private_2(struct folio *folio);
+void folio_wait_private_2(struct folio *folio);
+int folio_wait_private_2_killable(struct folio *folio);
+
+#endif /* _LINUX_FOLIO_WAIT_H */
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 627771e82eb1..7f65c2b0097b 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -15,6 +15,7 @@
 #include <linux/bitops.h>
 #include <linux/hardirq.h> /* for in_interrupt() */
 #include <linux/hugetlb_inline.h>
+#include <linux/folio_wait.h>
 
 struct folio_batch;
 
@@ -1072,174 +1073,6 @@ static inline pgoff_t linear_page_index(const struct vm_area_struct *vma,
 	return pgoff;
 }
 
-struct wait_page_key {
-	struct folio *folio;
-	int bit_nr;
-	int page_match;
-};
-
-struct wait_page_queue {
-	struct folio *folio;
-	int bit_nr;
-	wait_queue_entry_t wait;
-};
-
-static inline bool wake_page_match(struct wait_page_queue *wait_page,
-				  struct wait_page_key *key)
-{
-	if (wait_page->folio != key->folio)
-	       return false;
-	key->page_match = 1;
-
-	if (wait_page->bit_nr != key->bit_nr)
-		return false;
-
-	return true;
-}
-
-void __folio_lock(struct folio *folio);
-int __folio_lock_killable(struct folio *folio);
-vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf);
-void unlock_page(struct page *page);
-void folio_unlock(struct folio *folio);
-
-/**
- * folio_trylock() - Attempt to lock a folio.
- * @folio: The folio to attempt to lock.
- *
- * Sometimes it is undesirable to wait for a folio to be unlocked (eg
- * when the locks are being taken in the wrong order, or if making
- * progress through a batch of folios is more important than processing
- * them in order).  Usually folio_lock() is the correct function to call.
- *
- * Context: Any context.
- * Return: Whether the lock was successfully acquired.
- */
-static inline bool folio_trylock(struct folio *folio)
-{
-	return likely(!test_and_set_bit_lock(PG_locked, folio_flags(folio, 0)));
-}
-
-/*
- * Return true if the page was successfully locked
- */
-static inline bool trylock_page(struct page *page)
-{
-	return folio_trylock(page_folio(page));
-}
-
-/**
- * folio_lock() - Lock this folio.
- * @folio: The folio to lock.
- *
- * The folio lock protects against many things, probably more than it
- * should.  It is primarily held while a folio is being brought uptodate,
- * either from its backing file or from swap.  It is also held while a
- * folio is being truncated from its address_space, so holding the lock
- * is sufficient to keep folio->mapping stable.
- *
- * The folio lock is also held while write() is modifying the page to
- * provide POSIX atomicity guarantees (as long as the write does not
- * cross a page boundary).  Other modifications to the data in the folio
- * do not hold the folio lock and can race with writes, eg DMA and stores
- * to mapped pages.
- *
- * Context: May sleep.  If you need to acquire the locks of two or
- * more folios, they must be in order of ascending index, if they are
- * in the same address_space.  If they are in different address_spaces,
- * acquire the lock of the folio which belongs to the address_space which
- * has the lowest address in memory first.
- */
-static inline void folio_lock(struct folio *folio)
-{
-	might_sleep();
-	if (!folio_trylock(folio))
-		__folio_lock(folio);
-}
-
-/**
- * lock_page() - Lock the folio containing this page.
- * @page: The page to lock.
- *
- * See folio_lock() for a description of what the lock protects.
- * This is a legacy function and new code should probably use folio_lock()
- * instead.
- *
- * Context: May sleep.  Pages in the same folio share a lock, so do not
- * attempt to lock two pages which share a folio.
- */
-static inline void lock_page(struct page *page)
-{
-	struct folio *folio;
-	might_sleep();
-
-	folio = page_folio(page);
-	if (!folio_trylock(folio))
-		__folio_lock(folio);
-}
-
-/**
- * folio_lock_killable() - Lock this folio, interruptible by a fatal signal.
- * @folio: The folio to lock.
- *
- * Attempts to lock the folio, like folio_lock(), except that the sleep
- * to acquire the lock is interruptible by a fatal signal.
- *
- * Context: May sleep; see folio_lock().
- * Return: 0 if the lock was acquired; -EINTR if a fatal signal was received.
- */
-static inline int folio_lock_killable(struct folio *folio)
-{
-	might_sleep();
-	if (!folio_trylock(folio))
-		return __folio_lock_killable(folio);
-	return 0;
-}
-
-/*
- * folio_lock_or_retry - Lock the folio, unless this would block and the
- * caller indicated that it can handle a retry.
- *
- * Return value and mmap_lock implications depend on flags; see
- * __folio_lock_or_retry().
- */
-static inline vm_fault_t folio_lock_or_retry(struct folio *folio,
-					     struct vm_fault *vmf)
-{
-	might_sleep();
-	if (!folio_trylock(folio))
-		return __folio_lock_or_retry(folio, vmf);
-	return 0;
-}
-
-/*
- * This is exported only for folio_wait_locked/folio_wait_writeback, etc.,
- * and should not be used directly.
- */
-void folio_wait_bit(struct folio *folio, int bit_nr);
-int folio_wait_bit_killable(struct folio *folio, int bit_nr);
-
-/* 
- * Wait for a folio to be unlocked.
- *
- * This must be called with the caller "holding" the folio,
- * ie with increased folio reference count so that the folio won't
- * go away during the wait.
- */
-static inline void folio_wait_locked(struct folio *folio)
-{
-	if (folio_test_locked(folio))
-		folio_wait_bit(folio, PG_locked);
-}
-
-static inline int folio_wait_locked_killable(struct folio *folio)
-{
-	if (!folio_test_locked(folio))
-		return 0;
-	return folio_wait_bit_killable(folio, PG_locked);
-}
-
-void folio_end_read(struct folio *folio, bool success);
 void wait_on_page_writeback(struct page *page);
 void folio_wait_writeback(struct folio *folio);
 int folio_wait_writeback_killable(struct folio *folio);
@@ -1268,9 +1101,6 @@ int filemap_migrate_folio(struct address_space *mapping, struct folio *dst,
 #else
 #define filemap_migrate_folio NULL
 #endif
-void folio_end_private_2(struct folio *folio);
-void folio_wait_private_2(struct folio *folio);
-int folio_wait_private_2_killable(struct folio *folio);
 
 /*
  * Fault in userspace address range.
diff --git a/mm/folio_wait.c b/mm/folio_wait.c
index 18b42488ce37..06156e138c09 100644
--- a/mm/folio_wait.c
+++ b/mm/folio_wait.c
@@ -8,7 +8,7 @@
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/leafops.h>
-#include <linux/pagemap.h>
+#include <linux/folio_wait.h>
 #include <linux/wait.h>
 #include <linux/hash.h>
 #include <linux/sysctl.h>

-- 
2.39.5