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List:       linux-ext4
Subject:    Re: journal forget may introduce buffer aliasing problem?
From:       <dingdinghua85 () gmail ! com>
Date:       2010-01-27 5:58:54
Message-ID: 7bb361261001262158q37fe060br93c751c1152c5738 () mail ! gmail ! com
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Oops, I haven't seen unmap_underlying_metadata code in __block_prepare_write
so just forget this mail, sorry.

2010/1/27 丁定华 <dingdinghua85@gmail.com>:
> Hi all:
>       The following is my analysis(if wrong, please point it out),
> may be I can send a patch out if it's a bug.
>       If buffer_head belongs to comitting transaction,
> jbd2_journal_forget do nothing except discard it from running
> transaction. So this buffer will happily be inserted
> into committing_transaction's checkpoint list and do write-back work,
> then this buffer may be re-used as data-block, then there are two
> buffer_heads maps to the same block, buffer aliasing occurs, and we
> can't control the writeback order of the two buffer heads, fs may be
> inconsistent.
>      The same thing will happen if buffer_head doesn't belongs to
> running or committing transaction, but lays in checkpoint list.
>
> --
> 丁定华
>



-- 
丁定华
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