linux-kernel - Re: [PATCH] selftests: ublk: use tmpdir for scratch files and improve relative paths use

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Message-Id: <147635F1-943E-46D5-8EF1-D1C965F85EC1@zazolabs.com>
Date: Fri, 23 Jan 2026 15:59:31 +0200
From: Alexander Atanasov <alex@...olabs.com>
To: Ming Lei <ming.lei@...hat.com>
Cc: Shuah Khan <shuah@...nel.org>,
 linux-block@...r.kernel.org,
 linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests: ublk: use tmpdir for scratch files and improve
 relative paths use

On 23 Jan 2026, at 15:33, Ming Lei <ming.lei@...hat.com> wrote:
> 
> On Fri, Jan 23, 2026 at 11:20:36AM +0000, Alexander Atanasov wrote:
>> Create a temp dir for temporary files and use it instead of
>> placing them inside source tree.
> 
> Many temporary files are backing files of file storage target, so far
> the code requires O_DIRECT, or the size could be a bit big.
> 
> In case of ramfs/tmpfs of temp dir, it may cause problem for tests.
> 

I am aware of O_DIRECT problem but you can export different TMPDIR that has working O_DIRECT.

I use sshfs mount of the build to run the tests and that is a problem sshfs/fuse does not
do O_DIRECT too.

I think test_generic_06.sh is the only one that fails due to this(thou I still have to investigate).

If O_DIRECT is required by the tests it may be possible to go thru a RAM disk which does support it,
so it works eveerywhere

Other option is to preserve working in source tree as it is now, and just add a variable to specify working directory -
UBLK_TMPDIR or something.

I get a lot of out of order io - between 0 and 10 on average on my test setup:
tools/testing/selftests/ublk/test_generic_01.sh 
Attached 3 probes
io_out_of_order: exp 564688 actual 564648
io_out_of_order: exp 564648 actual 565584
io_out_of_order: exp 565584 actual 564688
io_out_of_order: exp 565592 actual 564688
io_out_of_order: exp 566328 actual 565592
io_out_of_order: exp 882256 actual 882248
io_out_of_order: exp 883032 actual 882912
io_out_of_order: exp 882912 actual 883040
io_out_of_order: exp 883040 actual 883032

generic_01 : [FAIL]

All rq-s are there just reordered , AFAIK blk-mq does not guarantee that requests will be completed in order, what’s the idea to catch this and
consider it an error? (Latest tree with batch io and batch io fixes on top of if that matters)

Regards,
Alexander Atanasov