CIFS: Add launder_page operation (try #3)

Add this let us drop filemap_write_and_wait from cifs_invalidate_mapping
and simplify the code to properly process invalidate logic.
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

fs/cifs/file.c

@@ -1420,9 +1420,10 @@ static int cifs_writepages(struct address_space *mapping,
 	return rc;
 }
 
-static int cifs_writepage(struct page *page, struct writeback_control *wbc)
+static int
+cifs_writepage_locked(struct page *page, struct writeback_control *wbc)
 {
-	int rc = -EFAULT;
+	int rc;
 	int xid;
 
 	xid = GetXid();
@@ -1442,15 +1443,29 @@ static int cifs_writepage(struct page *page, struct writeback_control *wbc)
 	 * to fail to update with the state of the page correctly.
 	 */
 	set_page_writeback(page);
+retry_write:
 	rc = cifs_partialpagewrite(page, 0, PAGE_CACHE_SIZE);
-	SetPageUptodate(page); /* BB add check for error and Clearuptodate? */
-	unlock_page(page);
+	if (rc == -EAGAIN && wbc->sync_mode == WB_SYNC_ALL)
+		goto retry_write;
+	else if (rc == -EAGAIN)
+		redirty_page_for_writepage(wbc, page);
+	else if (rc != 0)
+		SetPageError(page);
+	else
+		SetPageUptodate(page);
 	end_page_writeback(page);
 	page_cache_release(page);
 	FreeXid(xid);
 	return rc;
 }
 
+static int cifs_writepage(struct page *page, struct writeback_control *wbc)
+{
+	int rc = cifs_writepage_locked(page, wbc);
+	unlock_page(page);
+	return rc;
+}
+
 static int cifs_write_end(struct file *file, struct address_space *mapping,
 			loff_t pos, unsigned len, unsigned copied,
 			struct page *page, void *fsdata)
@@ -2415,6 +2430,27 @@ static void cifs_invalidate_page(struct page *page, unsigned long offset)
 		cifs_fscache_invalidate_page(page, &cifsi->vfs_inode);
 }
 
+static int cifs_launder_page(struct page *page)
+{
+	int rc = 0;
+	loff_t range_start = page_offset(page);
+	loff_t range_end = range_start + (loff_t)(PAGE_CACHE_SIZE - 1);
+	struct writeback_control wbc = {
+		.sync_mode = WB_SYNC_ALL,
+		.nr_to_write = 0,
+		.range_start = range_start,
+		.range_end = range_end,
+	};
+
+	cFYI(1, "Launder page: %p", page);
+
+	if (clear_page_dirty_for_io(page))
+		rc = cifs_writepage_locked(page, &wbc);
+
+	cifs_fscache_invalidate_page(page, page->mapping->host);
+	return rc;
+}
+
 void cifs_oplock_break(struct work_struct *work)
 {
 	struct cifsFileInfo *cfile = container_of(work, struct cifsFileInfo,
@@ -2486,7 +2522,7 @@ const struct address_space_operations cifs_addr_ops = {
 	.set_page_dirty = __set_page_dirty_nobuffers,
 	.releasepage = cifs_release_page,
 	.invalidatepage = cifs_invalidate_page,
-	/* .direct_IO = */
+	.launder_page = cifs_launder_page,
 };
 
 /*
@@ -2503,5 +2539,5 @@ const struct address_space_operations cifs_addr_ops_smallbuf = {
 	.set_page_dirty = __set_page_dirty_nobuffers,
 	.releasepage = cifs_release_page,
 	.invalidatepage = cifs_invalidate_page,
-	/* .direct_IO = */
+	.launder_page = cifs_launder_page,
 };