On Sep 17, 2024 / 14:32, Damien Le Moal wrote:
> Commit 734e1a860312 ("block: Prevent deadlocks when switching
> elevators") introduced the function elv_iosched_load_module() to allow
> loading an elevator module outside of elv_iosched_store() with the
> target device queue not frozen, to avoid deadlocks. However, the "none"
> scheduler does not have a module and as a result,
> elv_iosched_load_module() always returns an error when trying to switch
> to this valid scheduler.
This unexpected behavior (setting none scheduler has no effect) was found
by the blktests test case scsi/008 failure. This test case invokes the fio
command with the --ioscheduler=none option.
>
> Fix this by checking that the requested scheduler is "none" and doing
> nothing in that case.
I confirmed this fix patch avoids the unexpected behavior, and makes scsi/008
pass.
>
> Reported-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
> Fixes: 734e1a860312 ("block: Prevent deadlocks when switching elevators")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
I also run whole blktests applying this patch on top of the v6.11 kernel, and
observed no regression. Looks good from testing point of view.
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@xxxxxxx>
