[PATCH 2/3] mm/writeback: Add wait_on_page_writeback_killable

[David Howells]

From: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>

This is the killable version of wait_on_page_writeback.

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-afs@xxxxxxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
Link: https://lore.kernel.org/r/20210320054104.1300774-3-willy@xxxxxxxxxxxxx
---

 include/linux/pagemap.h |    1 +
 mm/page-writeback.c     |   16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 8f4daac6eb4b..8c9947fd62f3 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -682,6 +682,7 @@ static inline int wait_on_page_locked_killable(struct page *page)
 
 int put_and_wait_on_page_locked(struct page *page, int state);
 void wait_on_page_writeback(struct page *page);
+int wait_on_page_writeback_killable(struct page *page);
 extern void end_page_writeback(struct page *page);
 void wait_for_stable_page(struct page *page);
 
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index eb34d204d4ee..9e35b636a393 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2833,6 +2833,22 @@ void wait_on_page_writeback(struct page *page)
 }
 EXPORT_SYMBOL_GPL(wait_on_page_writeback);
 
+/*
+ * Wait for a page to complete writeback.  Returns -EINTR if we get a
+ * fatal signal while waiting.
+ */
+int wait_on_page_writeback_killable(struct page *page)
+{
+	while (PageWriteback(page)) {
+		trace_wait_on_page_writeback(page, page_mapping(page));
+		if (wait_on_page_bit_killable(page, PG_writeback))
+			return -EINTR;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(wait_on_page_writeback_killable);
+
 /**
  * wait_for_stable_page() - wait for writeback to finish, if necessary.
  * @page:	The page to wait on.