linux-ext4 - Re: [RFC 0/2] ext4: Fix stale data read exposure problem with DIO read/page

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Message-Id: <20200114223350.25E7DA4094@d06av23.portsmouth.uk.ibm.com>
Date:   Wed, 15 Jan 2020 04:03:49 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-ext4@...r.kernel.org, tytso@....edu, jack@...e.cz,
        darrick.wong@...cle.com
Subject: Re: [RFC 0/2] ext4: Fix stale data read exposure problem with DIO
 read/page_mkwrite

On 1/14/20 10:09 PM, Christoph Hellwig wrote:
>> Currently there is a small race window as pointed out by Jan [2] where, when
>> ext4 tries to allocate a written block for mapped files and if DIO read is in
>> progress, then this may result into stale data read exposure problem.
> 
> Do we have a test case for the problem?

I am not very sure if we have it in xfstests, (since I guess, DIO read 
during mmap writes is not well supported anyways).
But sure I was anyway thinking of writing one for my unit testing. Till
now I was mainly following that theoretically it is possible, although
it may be hard to catch it practically.

> Please add at very least the fsdevel and xfs lists to iomap patches.

Yes, sorry about that. Will cc' in next time.

-ritesh