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
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