linux-kernel - Re: Partial direct-io loop regression in 5.17-rc

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Message-ID: <54f98c2a-4a40-75ed-8f66-11cc6b2fd190@gmail.com>
Date:   Fri, 4 Feb 2022 16:03:06 +0100
From:   Milan Broz <gmazyland@...il.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     linux-block <linux-block@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Ondrej Kozina <okozina@...hat.com>
Subject: Re: Partial direct-io loop regression in 5.17-rc



On 04/02/2022 14:32, Jens Axboe wrote:
> On 2/4/22 2:22 AM, Milan Broz wrote:
>> Hi Jens,
>>
>> It seems that there is a regression in direct-io over loop for partial
>> direct-io reads (or perhaps even for other situations).
>>
>> If I run this code (loop over 6M file, dd direct-io read with 4M blocks)
>>
>> IMG=tst.img
>> LOOP=/dev/loop66
>>
>> truncate -s 6M $IMG
>> losetup $LOOP $IMG
>> dd if=$LOOP of=/dev/null bs=4M iflag=direct
>> losetup -d $LOOP
>>
>>
>> on older kernel (<=5.16) it reads the whole file
>>     6291456 bytes (6.3 MB, 6.0 MiB) copied, 0.201591 s, 31.2 MB/s
>>
>>
>> while on 5.17-rc (tested on today/s Linus' git) it reads only the full blocks:
>>     4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.201904 s, 20.8 MB/s
>>
>> No error reported, exit code is 0.
> 
> Can you try:
> 
> https://git.kernel.dk/cgit/linux-block/commit/?h=block-5.17&id=3e1f941dd9f33776b3df4e30f741fe445ff773f3

Yes, it works now.
(Not sure why I did not check if this patch is mainline, as I know about it. My bad...)

So this is going to some next rc, right?

Thanks,
Milan