f2fs: don't trigger read IO for beyond EOF page

In f2fs_mpage_readpages(), if page is beyond EOF, we should just
zero out it, but previously, before checking previous mapping
info, we missed to check filesize boundary, fix it.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1551,6 +1551,9 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 		if (last_block > last_block_in_file)
 			last_block = last_block_in_file;
 
+		/* just zeroing out page which is beyond EOF */
+		if (block_in_file >= last_block)
+			goto zero_out;
 		/*
 		 * Map blocks using the previous result first.
 		 */
@@ -1563,16 +1566,11 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 		 * Then do more f2fs_map_blocks() calls until we are
 		 * done with this page.
 		 */
-		map.m_flags = 0;
+		map.m_lblk = block_in_file;
+		map.m_len = last_block - block_in_file;
 
-		if (block_in_file < last_block) {
-			map.m_lblk = block_in_file;
-			map.m_len = last_block - block_in_file;
-
-			if (f2fs_map_blocks(inode, &map, 0,
-						F2FS_GET_BLOCK_DEFAULT))
-				goto set_error_page;
-		}
+		if (f2fs_map_blocks(inode, &map, 0, F2FS_GET_BLOCK_DEFAULT))
+			goto set_error_page;
 got_it:
 		if ((map.m_flags & F2FS_MAP_MAPPED)) {
 			block_nr = map.m_pblk + block_in_file - map.m_lblk;
@@ -1587,6 +1585,7 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 								DATA_GENERIC))
 				goto set_error_page;
 		} else {
+zero_out:
 			zero_user_segment(page, 0, PAGE_SIZE);
 			if (!PageUptodate(page))
 				SetPageUptodate(page);