linux-kernel - Re: [PATCH v5 10/12] ext4: test atomic write and ioend codepaths with bigalloc

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Message-ID: <7507dace-b789-43a5-9a5e-5bb79fe76120@oracle.com>
Date: Tue, 2 Sep 2025 16:52:17 +0100
From: John Garry <john.g.garry@...cle.com>
To: Ojaswin Mujoo <ojaswin@...ux.ibm.com>, Zorro Lang <zlang@...hat.com>,
        fstests@...r.kernel.org
Cc: Ritesh Harjani <ritesh.list@...il.com>, djwong@...nel.org, tytso@....edu,
        linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH v5 10/12] ext4: test atomic write and ioend codepaths with
 bigalloc

On 22/08/2025 09:02, Ojaswin Mujoo wrote:
> From: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>
> 
> This test does a lot of parallel RWF_ATOMIC IO on a preallocated file to
> stress the write and end-io unwritten conversion code paths. We brute
> force this for different blocksize and clustersizes and after each
> iteration we ensure the data was not torn or corrupted using fio crc
> verification.
> 
> Note that in this test we use overlapping atomic writes of same io size.
> Although serializing racing writes is not guaranteed for RWF_ATOMIC,
> NVMe and SCSI provide this guarantee as an inseparable feature to
> power-fail atomicity. Keeping the iosize as same also ensures that ext4
> doesn't tear the write due to racing ioend unwritten conversion.
> 
> The value of this test is that we make sure the RWF_ATOMIC is handled
> correctly by ext4 as well as test that the block layer doesn't split or
> only generate multiple bios for an atomic write.
> 
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>

Reviewed-by: John Garry <john.g.garry@...cle.com>