Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge pages to any order.

From: Zi Yan <ziy@nvidia.com>
To: Mark Brown <broonie@kernel.org>
Cc: "Ryan Roberts" <ryan.roberts@arm.com>,
	"Aishwarya TCV" <aishwarya.tcv@arm.com>,
	"\"Pankaj Raghav (Samsung)\"" <kernel@pankajraghav.com>,
	linux-mm@kvack.org,
	"\"Matthew Wilcox (Oracle)\"" <willy@infradead.org>,
	"David Hildenbrand" <david@redhat.com>,
	"Yang Shi" <shy828301@gmail.com>, "Yu Zhao" <yuzhao@google.com>,
	"\"Kirill A . Shutemov\"" <kirill.shutemov@linux.intel.com>,
	"\"Michal Koutný\"" <mkoutny@suse.com>,
	"Roman Gushchin" <roman.gushchin@linux.dev>,
	"\"Zach O'Keefe\"" <zokeefe@google.com>,
	"Hugh Dickins" <hughd@google.com>,
	"Luis Chamberlain" <mcgrof@kernel.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org
Subject: Re: [PATCH v5 8/8] mm: huge_memory: enable debugfs to split huge pages to any order.
Date: Fri, 01 Mar 2024 07:56:41 -0500	[thread overview]
Message-ID: <86C93A15-30F6-405C-A877-909B3E12C52C@nvidia.com> (raw)
In-Reply-To: <2d5f9cd5-a2c2-453e-aa52-a84a86107d1f@sirena.org.uk>

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On 1 Mar 2024, at 7:11, Mark Brown wrote:

> On Fri, Mar 01, 2024 at 10:33:15AM +0000, Ryan Roberts wrote:
>
>>   - In create_pagecache_thp_and_fd() you do *fd = open(testfile, O_CREAT ...);
>>     where testfile is /mnt/thp_fs/testfile. So if /mnt/thp_fs doesn't exist,
>>     then the open will fail I think? I'm pretty sure that's what's happening on
>>     our CI. Suggest the test needs to setup this dir itself. Is thp_fs a mounted
>>     fs or just a dir? If the latter can you just mktemp()?
>
> Mounting on /mnt would also be a bit of an issue, that's something
> people are relatively likely to have used for something so could be
> disruptive.  If the test is going to do a new mount it's probably better
> to do something like make a temporary directory then mount on top of that.

To move it to a temp folder for mounting, the test needs to do the mount.
But it is impossible to know if the running environment has the required FS or not
and where the FS is. Should I add that as a parameter to the test binary?

--
Best Regards,
Yan, Zi

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