f2fs: don't set GC_FAILURE_PIN for background GC

So that it can reduce the possibility that file be unpinned forcely by
foreground GC due to .i_gc_failures[GC_FAILURE_PIN] exceeds threshold.
Signed-off-by: Chao Yu <chao.yu@oppo.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -1202,7 +1202,8 @@ static int move_data_block(struct inode *inode, block_t bidx,
 	}
 
 	if (f2fs_is_pinned_file(inode)) {
-		f2fs_pin_file_control(inode, true);
+		if (gc_type == FG_GC)
+			f2fs_pin_file_control(inode, true);
 		err = -EAGAIN;
 		goto out;
 	}