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Message-ID: <YklYl/Nea05Mjz32@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date: Sun, 3 Apr 2022 13:49:35 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To: Ritesh Harjani <ritesh.list@...il.com>
Cc: fstests@...r.kernel.org, riteshh@...ux.ibm.com,
linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] common/rc: Modify _require_batched_discard to improve
test coverage
On Fri, Apr 01, 2022 at 03:24:36PM +0530, Ritesh Harjani wrote:
> 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@...ux.ibm.com>
Thank you for the review Ritesh.
>
>
> 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).
You are correct, as I was not able to simulate a device with disc gran
of 40MB+ I tested this by hard coding the granularity in the kernel.
That being said, I would appreciate if anyone has any insights on using
LVM/DM to get that high a granularity so I can test it more accurately.
Regards,
Ojaswin
>
> -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@...ux.ibm.com>
> > ---
> > common/rc | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
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