[PATCH RFC 04/11] folio_wait: move folio_wait_writeback() family to mm/folio_wait.c

[Tal Zussman <tz2294@columbia.edu>]

folio_wait_writeback(), folio_wait_writeback_killable() and
folio_wait_stable() are thin wrappers around folio_wait_bit() and
folio_wait_bit_killable() on PG_writeback. Move them to mm/folio_wait.c,
next to the rest of the folio bit-wait infrastructure.

The legacy wait_on_page_writeback() wrapper stays in folio-compat.c, as
its days are numbered, and it will be deleted once the remaining callers
are converted.

Signed-off-by: Tal Zussman <tz2294@columbia.edu>
---
 include/linux/folio_wait.h |  4 +++
 include/linux/pagemap.h    |  3 ---
 mm/folio_wait.c            | 67 ++++++++++++++++++++++++++++++++++++++++++++++
 mm/page-writeback.c        | 66 ---------------------------------------------
 4 files changed, 71 insertions(+), 69 deletions(-)

diff --git a/include/linux/folio_wait.h b/include/linux/folio_wait.h
index 80ddf1ffcae4..4a5cb2fcf046 100644
--- a/include/linux/folio_wait.h
+++ b/include/linux/folio_wait.h
@@ -178,4 +178,8 @@ 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);
 
+void folio_wait_writeback(struct folio *folio);
+int folio_wait_writeback_killable(struct folio *folio);
+void folio_wait_stable(struct folio *folio);
+
 #endif /* _LINUX_FOLIO_WAIT_H */
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 7f65c2b0097b..84ccb682cca8 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -1074,13 +1074,10 @@ static inline pgoff_t linear_page_index(const struct vm_area_struct *vma,
 }
 
 void wait_on_page_writeback(struct page *page);
-void folio_wait_writeback(struct folio *folio);
-int folio_wait_writeback_killable(struct folio *folio);
 void end_page_writeback(struct page *page);
 void folio_end_writeback(struct folio *folio);
 void folio_end_writeback_no_dropbehind(struct folio *folio);
 void folio_end_dropbehind(struct folio *folio);
-void folio_wait_stable(struct folio *folio);
 void __folio_mark_dirty(struct folio *folio, struct address_space *, int warn);
 void folio_account_cleaned(struct folio *folio, struct bdi_writeback *wb);
 void __folio_cancel_dirty(struct folio *folio);
diff --git a/mm/folio_wait.c b/mm/folio_wait.c
index 06156e138c09..9d3328717bb3 100644
--- a/mm/folio_wait.c
+++ b/mm/folio_wait.c
@@ -15,6 +15,7 @@
 #include <linux/delayacct.h>
 #include <linux/psi.h>
 #include <linux/migrate.h>
+#include <trace/events/writeback.h>
 
 #include "internal.h"
 
@@ -572,6 +573,72 @@ int folio_wait_private_2_killable(struct folio *folio)
 }
 EXPORT_SYMBOL(folio_wait_private_2_killable);
 
+/**
+ * folio_wait_writeback - Wait for a folio to finish writeback.
+ * @folio: The folio to wait for.
+ *
+ * If the folio is currently being written back to storage, wait for the
+ * I/O to complete.
+ *
+ * Context: Sleeps.  Must be called in process context and with
+ * no spinlocks held.  Caller should hold a reference on the folio.
+ * If the folio is not locked, writeback may start again after writeback
+ * has finished.
+ */
+void folio_wait_writeback(struct folio *folio)
+{
+	while (folio_test_writeback(folio)) {
+		trace_folio_wait_writeback(folio, folio_mapping(folio));
+		folio_wait_bit(folio, PG_writeback);
+	}
+}
+EXPORT_SYMBOL_GPL(folio_wait_writeback);
+
+/**
+ * folio_wait_writeback_killable - Wait for a folio to finish writeback.
+ * @folio: The folio to wait for.
+ *
+ * If the folio is currently being written back to storage, wait for the
+ * I/O to complete or a fatal signal to arrive.
+ *
+ * Context: Sleeps.  Must be called in process context and with
+ * no spinlocks held.  Caller should hold a reference on the folio.
+ * If the folio is not locked, writeback may start again after writeback
+ * has finished.
+ * Return: 0 on success, -EINTR if we get a fatal signal while waiting.
+ */
+int folio_wait_writeback_killable(struct folio *folio)
+{
+	while (folio_test_writeback(folio)) {
+		trace_folio_wait_writeback(folio, folio_mapping(folio));
+		if (folio_wait_bit_killable(folio, PG_writeback))
+			return -EINTR;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(folio_wait_writeback_killable);
+
+/**
+ * folio_wait_stable() - wait for writeback to finish, if necessary.
+ * @folio: The folio to wait on.
+ *
+ * This function determines if the given folio is related to a backing
+ * device that requires folio contents to be held stable during writeback.
+ * If so, then it will wait for any pending writeback to complete.
+ *
+ * Context: Sleeps.  Must be called in process context and with
+ * no spinlocks held.  Caller should hold a reference on the folio.
+ * If the folio is not locked, writeback may start again after writeback
+ * has finished.
+ */
+void folio_wait_stable(struct folio *folio)
+{
+	if (mapping_stable_writes(folio_mapping(folio)))
+		folio_wait_writeback(folio);
+}
+EXPORT_SYMBOL_GPL(folio_wait_stable);
+
 /**
  * __folio_lock - Get a lock on the folio, assuming we need to sleep to get it.
  * @folio: The folio to lock
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 833f743f309f..50f548bbb375 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -3042,69 +3042,3 @@ void __folio_start_writeback(struct folio *folio, bool keep_write)
 	VM_BUG_ON_FOLIO(access_ret != 0, folio);
 }
 EXPORT_SYMBOL(__folio_start_writeback);
-
-/**
- * folio_wait_writeback - Wait for a folio to finish writeback.
- * @folio: The folio to wait for.
- *
- * If the folio is currently being written back to storage, wait for the
- * I/O to complete.
- *
- * Context: Sleeps.  Must be called in process context and with
- * no spinlocks held.  Caller should hold a reference on the folio.
- * If the folio is not locked, writeback may start again after writeback
- * has finished.
- */
-void folio_wait_writeback(struct folio *folio)
-{
-	while (folio_test_writeback(folio)) {
-		trace_folio_wait_writeback(folio, folio_mapping(folio));
-		folio_wait_bit(folio, PG_writeback);
-	}
-}
-EXPORT_SYMBOL_GPL(folio_wait_writeback);
-
-/**
- * folio_wait_writeback_killable - Wait for a folio to finish writeback.
- * @folio: The folio to wait for.
- *
- * If the folio is currently being written back to storage, wait for the
- * I/O to complete or a fatal signal to arrive.
- *
- * Context: Sleeps.  Must be called in process context and with
- * no spinlocks held.  Caller should hold a reference on the folio.
- * If the folio is not locked, writeback may start again after writeback
- * has finished.
- * Return: 0 on success, -EINTR if we get a fatal signal while waiting.
- */
-int folio_wait_writeback_killable(struct folio *folio)
-{
-	while (folio_test_writeback(folio)) {
-		trace_folio_wait_writeback(folio, folio_mapping(folio));
-		if (folio_wait_bit_killable(folio, PG_writeback))
-			return -EINTR;
-	}
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(folio_wait_writeback_killable);
-
-/**
- * folio_wait_stable() - wait for writeback to finish, if necessary.
- * @folio: The folio to wait on.
- *
- * This function determines if the given folio is related to a backing
- * device that requires folio contents to be held stable during writeback.
- * If so, then it will wait for any pending writeback to complete.
- *
- * Context: Sleeps.  Must be called in process context and with
- * no spinlocks held.  Caller should hold a reference on the folio.
- * If the folio is not locked, writeback may start again after writeback
- * has finished.
- */
-void folio_wait_stable(struct folio *folio)
-{
-	if (mapping_stable_writes(folio_mapping(folio)))
-		folio_wait_writeback(folio);
-}
-EXPORT_SYMBOL_GPL(folio_wait_stable);

-- 
2.39.5