f2fs: use wait_for_stable_page to avoid contention

In write_begin, if storage supports stable_page, we don't need to wait for
writeback to update its contents.
This patch introduces to use wait_for_stable_page instead of
wait_on_page_writeback.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index ea272be..f9b848a 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -86,7 +86,7 @@
 	trace_f2fs_vm_page_mkwrite(page, DATA);
 mapped:
 	/* fill the page */
-	f2fs_wait_on_page_writeback(page, DATA);
+	f2fs_wait_on_page_writeback(page, DATA, false);
 
 	/* wait for GCed encrypted page writeback */
 	if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
@@ -521,7 +521,7 @@
 	if (IS_ERR(page))
 		return 0;
 truncate_out:
-	f2fs_wait_on_page_writeback(page, DATA);
+	f2fs_wait_on_page_writeback(page, DATA, true);
 	zero_user(page, offset, PAGE_CACHE_SIZE - offset);
 	if (!cache_only || !f2fs_encrypted_inode(inode) || !S_ISREG(inode->i_mode))
 		set_page_dirty(page);
@@ -743,7 +743,7 @@
 	if (IS_ERR(page))
 		return PTR_ERR(page);
 
-	f2fs_wait_on_page_writeback(page, DATA);
+	f2fs_wait_on_page_writeback(page, DATA, true);
 	zero_user(page, start, len);
 	set_page_dirty(page);
 	f2fs_put_page(page, 1);