linux-kernel - Re: [PATCH v2 4/6] iomap: correct the dirty length in page mkwrite

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Zr2ZMBS_0SC7Sysn@infradead.org>
Date: Wed, 14 Aug 2024 22:59:12 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Zhang Yi <yi.zhang@...weicloud.com>
Cc: Christoph Hellwig <hch@...radead.org>, linux-xfs@...r.kernel.org,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	djwong@...nel.org, brauner@...nel.org, david@...morbit.com,
	jack@...e.cz, willy@...radead.org, yi.zhang@...wei.com,
	chengzhihao1@...wei.com, yukuai3@...wei.com
Subject: Re: [PATCH v2 4/6] iomap: correct the dirty length in page mkwrite

On Wed, Aug 14, 2024 at 03:49:41PM +0800, Zhang Yi wrote:
> Sorry, this makes me confused. How does this could prevent setting
> redundant dirty bits?
> 
> Suppose we have a 3K regular file on a filesystem with 1K block size.
> In iomap_page_mkwrite(), the iter.len is 3K, if the folio size is 4K,
> folio_mark_dirty() will also mark all 4 bits of ifs dirty. And then,
> if we expand this file size to 4K, and this will still lead to a hole
> with dirty bit set but without any block allocated/reserved. Am I
> missing something?

No, we still need the ifs manipulation in the loop indeed.  But
the filemap_dirty_folio (and the not uptodate warning) can still
move outside the iterator.