Re: [PATCH] common/rc: Modify _require_batched_discard to improve test coverage

[Ritesh Harjani <ritesh.list@gmail.com>]

On 22/04/01 11:27AM, Ojaswin Mujoo wrote:
> A recent ext4 patch discussed [1] that some devices (eg LVMs) can
> have a discard granularity as big as 42MB which makes it larger
> than the group size of ext4 FS with 1k BS. This causes the FITRIM
> IOCTL to fail on filesystems like ext4.
>
> This case was not correctly handle by "_require_batched_discard" as
> it incorrectly interpreted the FITRIM failure as fs not supporting
> the IOCTL. This caused the tests like generic/260 to incorectly
> report "not run" instead of "failed" in case of large discard
> granularity.

Ok, I looked at fstrim code and it does print [1]
"the discard operation is not supported" in case of rc == 1.
And if rc != 0 it will always returns EXIT_FAILURE.

So this patch looks good to me. Feel free to add:

Reviewed-by: Ritesh Harjani <riteshh@linux.ibm.com>


Although it will be good to check if we can add a generic test case
using maybe lvm or dm device, where this device could report large
discard_granularity for actually excercising this code path
(rather then changing kernel code to test it).

-ritesh

[1]: https://github.com/util-linux/util-linux/blob/master/sys-utils/fstrim.c

>
> Fix "_require_batched_discard" to use a more accurate method
> to determine if discard is supported.
>
> [1] commit 173b6e383d2
>     ext4: avoid trim error on fs with small groups
>
> Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
> ---
>  common/rc | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
>