linux-ext4 - [Bug 50981] ext4 : DATA CORRUPTION read and write on same 4096 page range

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Message-Id: <20121126111839.1E5D011FB81@bugzilla.kernel.org>
Date:	Mon, 26 Nov 2012 11:18:39 +0000 (UTC)
From:	bugzilla-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 50981] ext4 : DATA CORRUPTION read and write on same 4096 page 
 range

https://bugzilla.kernel.org/show_bug.cgi?id=50981





--- Comment #5 from Zheng Liu <gnehzuil.liu@...il.com>  2012-11-26 11:18:38 ---
(In reply to comment #4)
> Yes, that's what I said XFS has its own read/write exclusion. However we're
> reading/writing a single page here and page read/write shoud be atomic so we
> should _not_ see page with mixed data. Basically the page should be locked when
> we copy data from/to it,

Sorry, as my understanding, a page won't be locked when it is accessed if it
has been mark uptodate.  If we write a page that has been written recently, the
uptodate flag won't be clear.  So reader won't try to lock page, and maybe that
is not atomic.  Am I missing something?

Regards,
Zheng

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