Hello Gao Xiang,
This is a semi-automatic email about new static checker warnings.
The patch 97e86a858bc3: "staging: erofs: tidy up decompression
frontend" from Jul 31, 2019, leads to the following Smatch complaint:
fs/erofs/zdata.c:670 z_erofs_do_read_page()
error: we previously assumed 'clt->cl' could be null (see line 596)
fs/erofs/zdata.c
595 /* didn't get a valid collection previously (very rare)
*/
596 if (!clt->cl)
^^^^^^^^
New NULL check.
597 goto restart_now;
598 goto hitted;
599 }
600
601 /* go ahead the next map_blocks */
602 debugln("%s: [out-of-range] pos %llu", __func__, offset + cur);
603
604 if (z_erofs_collector_end(clt))
605 fe->backmost = false;
606
607 map->m_la = offset + cur;
608 map->m_llen = 0;
609 err = z_erofs_map_blocks_iter(inode, map, 0);
610 if (unlikely(err))
611 goto err_out;
612
613 restart_now:
614 if (unlikely(!(map->m_flags & EROFS_MAP_MAPPED)))
615 goto hitted;
616
617 err = z_erofs_collector_begin(clt, inode, map);
618 if (unlikely(err))
619 goto err_out;
620
621 /* preload all compressed pages (maybe downgrade role if
necessary) */
622 if (should_alloc_managed_pages(fe, sbi->cache_strategy,
map->m_la))
623 cache_strategy = DELAYEDALLOC;
624 else
625 cache_strategy = DONTALLOC;
626
627 preload_compressed_pages(clt, MNGD_MAPPING(sbi),
628 cache_strategy, pagepool);
629
630 tight &= (clt->mode >= COLLECT_PRIMARY_HOOKED);
631 hitted:
632 cur = end - min_t(unsigned int, offset + end - map->m_la, end);
633 if (unlikely(!(map->m_flags & EROFS_MAP_MAPPED))) {
634 zero_user_segment(page, cur, end);
635 goto next_part;
636 }
637
638 /* let's derive page type */
639 page_type = cur ? Z_EROFS_VLE_PAGE_TYPE_HEAD :
640 (!spiltted ? Z_EROFS_PAGE_TYPE_EXCLUSIVE :
641 (tight ? Z_EROFS_PAGE_TYPE_EXCLUSIVE :
642 Z_EROFS_VLE_PAGE_TYPE_TAIL_SHARED));
643
644 if (cur)
645 tight &= (clt->mode >= COLLECT_PRIMARY_FOLLOWED);
646
647 retry:
648 err = z_erofs_attach_page(clt, page, page_type);
649 /* should allocate an additional staging page for pagevec */
650 if (err == -EAGAIN) {
651 struct page *const newpage =
652 __stagingpage_alloc(pagepool, GFP_NOFS);
653
654 err = z_erofs_attach_page(clt, newpage,
655 Z_EROFS_PAGE_TYPE_EXCLUSIVE);
656 if (likely(!err))
657 goto retry;
658 }
659
660 if (unlikely(err))
661 goto err_out;
662
663 index = page->index - (map->m_la >> PAGE_SHIFT);
664
665 z_erofs_onlinepage_fixup(page, index, true);
666
667 /* bump up the number of spiltted parts of a page */
668 ++spiltted;
669 /* also update nr_pages */
670 clt->cl->nr_pages = max_t(pgoff_t, clt->cl->nr_pages, index +
1);
^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^
Unchecked dereferences.
671 next_part:
672 /* can be used for verification */
regards,
dan carpenter
