linux-kernel - Re: [PATCH v2 1/4] kernfs: remove page_mkwrite() from vm_operations

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Message-ID: <Zmna_AmrLgTgfdHw@slm.duckdns.org>
Date: Wed, 12 Jun 2024 07:29:32 -1000
From: Tejun Heo <tj@...nel.org>
To: Martin Oliveira <martin.oliveira@...eticom.com>
Cc: linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, Jason Gunthorpe <jgg@...pe.ca>,
	Leon Romanovsky <leon@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Logan Gunthorpe <logang@...tatee.com>,
	Mike Marciniszyn <mike.marciniszyn@...el.com>,
	Shiraz Saleem <shiraz.saleem@...el.com>,
	Michael Guralnik <michaelgur@...dia.com>,
	Artemy Kovalyov <artemyko@...dia.com>
Subject: Re: [PATCH v2 1/4] kernfs: remove page_mkwrite() from
 vm_operations_struct

On Tue, Jun 11, 2024 at 12:27:29PM -0600, Martin Oliveira wrote:
> The .page_mkwrite operator of kernfs just calls file_update_time().
> This is the same behaviour that the fault code does if .page_mkwrite is
> not set.
> 
> Furthermore, having the page_mkwrite() operator causes
> writable_file_mapping_allowed() to fail due to
> vma_needs_dirty_tracking() on the gup flow, which is a pre-requisite for
> enabling P2PDMA over RDMA.
> 
> There are no users of .page_mkwrite and no known valid use cases, so
> just remove the .page_mkwrite from kernfs_ops and return -EINVAL if an
> mmap() implementation sets .page_mkwrite.
> 
> Co-developed-by: Logan Gunthorpe <logang@...tatee.com>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Signed-off-by: Martin Oliveira <martin.oliveira@...eticom.com>

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun