Messages in this thread | | | Subject | Re: [PATCH v6 12/15] ubi: fastmap: Add all fastmap pebs into 'ai->fastmap' when fm->used_blocks>=2 | From | Zhihao Cheng <> | Date | Wed, 12 Jan 2022 11:46:28 +0800 |
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>>> ubi_wl_init() is called in both cases, with and without fastmap. >> I agree. >> >>> And ai->fastmap contains all anchor PEBs that scan_fast() found. >>> This can be the most recent but also outdated anchor PEBs. >> Is it exists a case that outdated fastmap PEBs are neither counted into >> 'fmhdr->erase_peb_count' nor scanned into 'ai->fastmap' after attaching >> by fastmap. >> > > [...] > >> I think UBI attaches failed by fastmap if kernel goes here. >> 1870 err = erase_aeb(ubi, aeb, sync); > > Hmm, I think the paranoia check in fastmap.c is too strict these days. > if (WARN_ON(count_fastmap_pebs(ai) != ubi->peb_count - > ai->bad_peb_count - fm->used_blocks)) > goto fail_bad; > > It does not account ai->fastmap. So if ai->fastmap contains old anchor PEBs > this check will trigger and force falling back to scanning mode. > With this check fixed, ubi_wl_init() will erase all old PEBs from ai->fastmap. Forgive my stubbornness, I think this strict check is good, could you show me a process to trigger this WARN_ON, it would be nice to provide a reproducer. I still insist the point(after my fix patch applied): All outdated fastmap PEBs are added into 'ai->fastmap'(full scanning case) or counted into 'fmhdr->erase_peb_count'(fast attached case). > > So I agree that this code path is wonky and can be cleaned up. But please be > extremely careful and give all your changes excessive testing with real workload > and power-cuts.Let's list all power-cut cases during fastmap updateing(I tried to simulate some of them on nandsim), in theory, I think the WARN_ON check is okay and all outdated fastmap PEBs can be erased in next attaching:
ubi_update_fastmap: 1565 for (i = 1; i < new_fm->used_blocks; i++) { 1570 if (!tmp_e) { 1571 if (old_fm && old_fm->e[i]) { /* sync erase old fm data PEBs */ power-cut!!! 1585 } else { /* async erase old fm data PEBs */ power-cut!!! 1595 } 1596 } else { 1599 if (old_fm && old_fm->e[i]) { /* async erase old fm data PEBs */ power-cut!!! 1603 } 1604 } 1605 } 1621 if (old_fm) { 1623 if (!tmp_e) { /* sync erase old fm anchor PEB */ power-cut!!! 1638 } else { /* async erase old fm anchor PEB */ power-cut!!! 1644 } 1645 } else { 1658 } 1660 ret = ubi_write_fastmap(ubi, new_fm);
ubi_write_fastmap: 1324 ret = ubi_io_write_vid_hdr(ubi, new_fm->e[0]->pnum, avbuf); power-cut!!! 1345 for (i = 1; i < new_fm->used_blocks; i++) { 1350 ret = ubi_io_write_vid_hdr(...); power-cut!!! 1356 }
1358 for (i = 0; i < new_fm->used_blocks; i++) { 1359 ret = ubi_io_write_data(...), power-cut!!! 1366 }
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