[PATCH blktests] Fix _get_page_size()

[PATCH blktests] Fix _get_page_size()

[Jeff Moyer]

There is no CONFIG_PAGE_SHIFT stored in /boot/config-`uname -r` on RHEL
systems (maybe all systems?).  As a result, tests that make use of
_get_page_size() were doing the wrong thing.  For example, throtl/002
used it to calculate I/O sizes for direct IO.  Those sizes ended up not
being a multiple of the logical block size, and hence throtl/002 was
failing.

Fixes: 8eca9fa ("common/rc, scsi/011, zbd/010: introduce _page_size_equals() helper")
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>

diff --git a/common/rc b/common/rc
index 20f7c7a..d60a125 100644
--- a/common/rc
+++ b/common/rc
@@ -562,13 +562,8 @@ _have_systemctl_unit() {
 	return 0
 }
 
-# Get system page size from kernel conguration
 _get_page_size() {
-	local page_shift
-
-	page_shift=$(_get_kernel_option PAGE_SHIFT)
-
-	echo $((1<< page_shift))
+	getconf PAGE_SIZE
 }
 
 # Check if the system page size matches the required size (in bytes).

Re: [PATCH blktests] Fix _get_page_size()

[Shin'ichiro Kawasaki]

CC+: Omar, Chaitanya,

On Jun 18, 2026 / 10:41, Jeff Moyer wrote:
> There is no CONFIG_PAGE_SHIFT stored in /boot/config-`uname -r` on RHEL
> systems (maybe all systems?).  As a result, tests that make use of
> _get_page_size() were doing the wrong thing.  For example, throtl/002
> used it to calculate I/O sizes for direct IO.  Those sizes ended up not
> being a multiple of the logical block size, and hence throtl/002 was
> failing.
> 
> Fixes: 8eca9fa ("common/rc, scsi/011, zbd/010: introduce _page_size_equals() helper")
> Signed-off-by: Jeff Moyer <jmoyer@redhat.com>

Thanks for finding this out. When I applied the commit in the Fixes tag, I had
checked my Fedora system's /boot/config-* files and had found CONFIG_PAGE_SHIFT
defined. I wanted to avoid the dependency to getconf, and chose the way to rely
on CONFIG_PAGE_SHIFT. But that is not an option for other distros. Today I
checked my Debian system, and CONFIG_PAGE_SHIFT was not defined either. Now I
see that we should not use CONFIG_PAGE_SHIFT.

> 
> diff --git a/common/rc b/common/rc
> index 20f7c7a..d60a125 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -562,13 +562,8 @@ _have_systemctl_unit() {
>  	return 0
>  }
>  
> -# Get system page size from kernel conguration
>  _get_page_size() {
> -	local page_shift
> -
> -	page_shift=$(_get_kernel_option PAGE_SHIFT)
> -
> -	echo $((1<< page_shift))
> +	getconf PAGE_SIZE
>  }
>  
>  # Check if the system page size matches the required size (in bytes).
> 

The patch above should work, but it creates a new dependeny on the tool getconf.
There are 6 test cases that require page size and getconf. Then, we need to
check that getconf command is available for the test cases.

  $ git grep _page_size
  common/rc:_get_page_size() {
  common/rc:# Example: _page_size_equals 4096
  common/rc:_page_size_equals() {
  common/rc:      current_size=$(_get_page_size)
  tests/scsi/011: _page_size_equals 4096
  tests/throtl/002:       page_size=$(_get_page_size)
  tests/throtl/003:       page_size=$(_get_page_size)
  tests/throtl/007:       page_size=$(_get_page_size)
  tests/zbd/010:  _page_size_equals 4096
  tests/zbd/014:  page_size=$(_get_page_size)

Havind said that, I think now Linux eco-system is in the phase to add variety
of page sizes, and I expect more test cases that depend on page sizes will be
added in near future. So, this could be the good timing to add getconf to the
blktests minimal requirement list described in README.md. This means that
blktests users will need to install glibc-common package for Fedora, or
libc-bin package for Debian.

This is a rather fundamental change, so I would like to ask opinions from
other blktests users, especially Omar and Chaitanya. What do you think about
the idea to add getconf to the requirement list?

Re: [PATCH blktests] Fix _get_page_size()

[Bart Van Assche]

On 6/20/26 3:26 AM, Shin'ichiro Kawasaki wrote:
> This is a rather fundamental change, so I would like to ask opinions from
> other blktests users, especially Omar and Chaitanya. What do you think about
> the idea to add getconf to the requirement list?

CONFIG_PAGE_SHIFT was introduced in the Linux kernel in February 2024
(commit ba89f9c8ccba ("arch: consolidate existing CONFIG_PAGE_SIZE_*KB
definitions")). Older kernels had CONFIG_PAGE_SIZE_4KB,
CONFIG_PAGE_SIZE_16KB, etc. This means that it is possible to derive the
kernel page size from the kernel configuration file for all upstream and
distro kernels, isn't it?

Thanks,

Bart.

Re: [PATCH blktests] Fix _get_page_size()

[Shin'ichiro Kawasaki]

On Jun 20, 2026 / 05:55, Bart Van Assche wrote:
> On 6/20/26 3:26 AM, Shin'ichiro Kawasaki wrote:
> > This is a rather fundamental change, so I would like to ask opinions from
> > other blktests users, especially Omar and Chaitanya. What do you think about
> > the idea to add getconf to the requirement list?
> 
> CONFIG_PAGE_SHIFT was introduced in the Linux kernel in February 2024
> (commit ba89f9c8ccba ("arch: consolidate existing CONFIG_PAGE_SIZE_*KB
> definitions")). Older kernels had CONFIG_PAGE_SIZE_4KB,
> CONFIG_PAGE_SIZE_16KB, etc. This means that it is possible to derive the
> kernel page size from the kernel configuration file for all upstream and
> distro kernels, isn't it?

I checked the commit is in the tag v6.9. My Debian bookworm system has kernel
v6.1, then the config file at /boot does not have CONFIG_PAGE_SHIFT as expected.
But it does not have CONFIG_PAGE_SIZE_* either... I'm still afraid that kernel
config file approach is not reliable.

$ uname -a
Linux testnode3 6.1.0-49-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.174-1 (2026-05-26) x86_64 GNU/Linux
$ grep PAGE_S /boot/config-6.1.0-49-amd64
CONFIG_PAGE_SIZE_LESS_THAN_64KB=y
CONFIG_PAGE_SIZE_LESS_THAN_256KB=y

Re: [PATCH blktests] Fix _get_page_size()

[Bart Van Assche]

On 6/20/26 6:51 AM, Shin'ichiro Kawasaki wrote:
> On Jun 20, 2026 / 05:55, Bart Van Assche wrote:
>> On 6/20/26 3:26 AM, Shin'ichiro Kawasaki wrote:
>>> This is a rather fundamental change, so I would like to ask opinions from
>>> other blktests users, especially Omar and Chaitanya. What do you think about
>>> the idea to add getconf to the requirement list?
>>
>> CONFIG_PAGE_SHIFT was introduced in the Linux kernel in February 2024
>> (commit ba89f9c8ccba ("arch: consolidate existing CONFIG_PAGE_SIZE_*KB
>> definitions")). Older kernels had CONFIG_PAGE_SIZE_4KB,
>> CONFIG_PAGE_SIZE_16KB, etc. This means that it is possible to derive the
>> kernel page size from the kernel configuration file for all upstream and
>> distro kernels, isn't it?
> 
> I checked the commit is in the tag v6.9. My Debian bookworm system has kernel
> v6.1, then the config file at /boot does not have CONFIG_PAGE_SHIFT as expected.
> But it does not have CONFIG_PAGE_SIZE_* either... I'm still afraid that kernel
> config file approach is not reliable.

Right, for older kernels CONFIG_PAGE_SIZE_*KB is only available for some
but not for all supported architectures.

It is not clear to me where the desire to avoid the dependency on
getconf comes from? As far as I know it is available on all Linux
distro's. Since it is typically included in the C library package it
should not introduce a new dependency.

Thanks,

Bart.