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Message-ID: <08e1dbde-b27c-fd99-294c-8e4715b92576@kernel.dk>
Date: Fri, 4 Feb 2022 06:32:27 -0700
From: Jens Axboe <axboe@...nel.dk>
To: Milan Broz <gmazyland@...il.com>
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 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
--
Jens Axboe
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