f2fs: remove set_page_dirty for atomic f2fs_end_io_write

We should guarantee not to do *scheduling while atomic*.
I found, in atomic f2fs_end_io_write(), there is a set_page_dirty() call
to deal with IO errors.

But, set_page_dirty() calls:
 -> f2fs_set_data_page_dirty()
   -> set_dirty_dir_page()
      -> cond_resched() which results in scheduling.

In order to avoid this, I'd like to remove simply set_page_dirty(),
since the page is already marked as ERROR and f2fs will be operated
as the read-only mode as well.
So, there is no recovery issue with this.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/segment.c

@@ -631,7 +631,6 @@ static void f2fs_end_io_write(struct bio *bio, int err)
 			if (page->mapping)
 				set_bit(AS_EIO, &page->mapping->flags);
 			set_ckpt_flags(p->sbi->ckpt, CP_ERROR_FLAG);
-			set_page_dirty(page);
 		}
 		end_page_writeback(page);
 		dec_page_count(p->sbi, F2FS_WRITEBACK);