Re: [PATCH 2/2] xfs: disable large folio support in xfile_create

From: "Darrick J. Wong" <djwong@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Christoph Hellwig <hch@lst.de>, Hugh Dickins <hughd@google.com>,
	Chandan Babu R <chandan.babu@oracle.com>,
	David Howells <dhowells@redhat.com>,
	Jarkko Sakkinen <jarkko@kernel.org>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
	Christian Koenig <christian.koenig@amd.com>,
	Huang Rui <ray.huang@amd.com>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
	Rodrigo Vivi <rodrigo.vivi@intel.com>,
	Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
	intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	x86@kernel.org, linux-sgx@vger.kernel.org, linux-mm@kvack.org,
	linux-fsdevel@vger.kernel.org, keyrings@vger.kernel.org
Subject: Re: [PATCH 2/2] xfs: disable large folio support in xfile_create
Date: Thu, 11 Jan 2024 18:22:50 -0800	[thread overview]
Message-ID: <20240112022250.GU723010@frogsfrogsfrogs> (raw)
In-Reply-To: <ZaBvoWCCChU5wHDp@casper.infradead.org>

On Thu, Jan 11, 2024 at 10:45:53PM +0000, Matthew Wilcox wrote:
> On Thu, Jan 11, 2024 at 02:00:53PM -0800, Andrew Morton wrote:
> > On Wed, 10 Jan 2024 12:04:51 -0800 "Darrick J. Wong" <djwong@kernel.org> wrote:
> > 
> > > > > Fixing this will require a bit of an API change, and prefeably sorting out
> > > > > the hwpoison story for pages vs folio and where it is placed in the shmem
> > > > > API.  For now use this one liner to disable large folios.
> > > > > 
> > > > > Reported-by: Darrick J. Wong <djwong@kernel.org>
> > > > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > > > 
> > > > Can someone who knows more about shmem.c than I do please review
> > > > https://lore.kernel.org/linux-xfs/20240103084126.513354-4-hch@lst.de/
> > > > so that I can feel slightly more confident as hch and I sort through the
> > > > xfile.c issues?
> > > > 
> > > > For this patch,
> > > > Reviewed-by: Darrick J. Wong <djwong@kernel.org>
> > > 
> > > ...except that I'm still getting 2M THPs even with this enabled, so I
> > > guess either we get to fix it now, or create our own private tmpfs mount
> > > so that we can pass in huge=never, similar to what i915 does. :(
> > 
> > What is "this"?  Are you saying that $Subject doesn't work, or that the
> > above-linked please-review patch doesn't work?
> 
> shmem pays no attention to the mapping_large_folio_support() flag,
> so the proposed fix doesn't work.  It ought to, but it has its own way
> of doing it that predates mapping_large_folio_support existing.

Yep.  It turned out to be easier to fix xfile.c to deal with large
folios than I thought it would be.  Or so I think.  We'll see what
happens on fstestscloud overnight.

--D