f2fs: clear PageError on the read path

When running fault injection test, I hit somewhat wrong behavior in f2fs_gc ->
gc_data_segment():

0. fault injection generated some PageError'ed pages

1. gc_data_segment
 -> f2fs_get_read_data_page(REQ_RAHEAD)

2. move_data_page
 -> f2fs_get_lock_data_page()
  -> f2f_get_read_data_page()
   -> f2fs_submit_page_read()
    -> submit_bio(READ)
  -> return EIO due to PageError
  -> fail to move data
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -77,7 +77,8 @@ static void __read_end_io(struct bio *bio)
 		/* PG_error was set if any post_read step failed */
 		if (bio->bi_status || PageError(page)) {
 			ClearPageUptodate(page);
-			SetPageError(page);
+			/* will re-read again later */
+			ClearPageError(page);
 		} else {
 			SetPageUptodate(page);
 		}
@@ -591,6 +592,7 @@ static int f2fs_submit_page_read(struct inode *inode, struct page *page,
 		bio_put(bio);
 		return -EFAULT;
 	}
+	ClearPageError(page);
 	__submit_bio(F2FS_I_SB(inode), bio, DATA);
 	return 0;
 }
@@ -1579,6 +1581,7 @@ static int f2fs_mpage_readpages(struct address_space *mapping,
 		if (bio_add_page(bio, page, blocksize, 0) < blocksize)
 			goto submit_and_realloc;
 
+		ClearPageError(page);
 		last_block_in_bio = block_nr;
 		goto next_page;
 set_error_page: