f2fs: fix missing up_read

BugLink: https://bugs.launchpad.net/bugs/1818797

commit 89d13c38 upstream.

This patch fixes missing up_read call.

Fixes: c9b60788 ("f2fs: fix to do sanity check with block address in main area")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

fs/f2fs/node.c

@@ -1342,8 +1342,10 @@ static int f2fs_write_node_page(struct page *page,
 	}
 
 	if (__is_valid_data_blkaddr(ni.blk_addr) &&
-		!f2fs_is_valid_blkaddr(sbi, ni.blk_addr, DATA_GENERIC))
+		!f2fs_is_valid_blkaddr(sbi, ni.blk_addr, DATA_GENERIC)) {
+		up_read(&sbi->node_write);
 		goto redirty_out;
+	}
 
 	set_page_writeback(page);
 	fio.blk_addr = ni.blk_addr;