linux-kernel - Re: [PATCH v6 12/15] ubi: fastmap: Add all fastmap pebs into 'ai->fastmap' when fm->used

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Date:   Tue, 11 Jan 2022 21:23:52 +0800
From:   Zhihao Cheng <chengzhihao1@...wei.com>
To:     Richard Weinberger <richard@....at>
CC:     Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        mcoquelin stm32 <mcoquelin.stm32@...il.com>,
        "kirill shutemov" <kirill.shutemov@...ux.intel.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        linux-mtd <linux-mtd@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 12/15] ubi: fastmap: Add all fastmap pebs into
 'ai->fastmap' when fm->used_blocks>=2

在 2022/1/11 19:57, Richard Weinberger 写道:
> 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 This can be the most recent but also outdated anchor PEBs.
Is it exists a case that outdated fastmap PEBs are neither counted into 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.

1853                         if (ubi->lookuptbl[aeb->pnum]) 

1854                                 continue; 

1855 

1856                         /* 

1857                          * The fastmap update code might not find a 
free PEB for
1858                          * writing the fastmap anchor to and then 
reuses the
1859                          * current fastmap anchor PEB. When this 
PEB gets erased
1860                          * and a power cut happens before it is 
written again we
1861                          * must make sure that the fastmap attach 
code doesn't
1862                          * find any outdated fastmap anchors, hence 
we erase the
1863                          * outdated fastmap anchor PEBs 
synchronously here.
1864                          */ 

1865                         if (aeb->vol_id == UBI_FM_SB_VOLUME_ID) 

1866                                 sync = true;

I think UBI attaches failed by fastmap if kernel goes here.
1870                         err = erase_aeb(ubi, aeb, sync);