Re: [PATCH 00/10] convert the majority of file systems to mmap_prepare

From: Jason Gunthorpe <jgg@nvidia.com>
To: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
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Subject: Re: [PATCH 00/10] convert the majority of file systems to mmap_prepare
Date: Fri, 1 Aug 2025 11:00:57 -0300	[thread overview]
Message-ID: <20250801140057.GA245321@nvidia.com> (raw)
In-Reply-To: <cover.1750099179.git.lorenzo.stoakes@oracle.com>

On Mon, Jun 16, 2025 at 08:33:19PM +0100, Lorenzo Stoakes wrote:

> The intent is to gradually deprecate f_op->mmap, and in that vein this
> series coverts the majority of file systems to using f_op->mmap_prepare.

I saw this on lwn and just wanted to give a little bit of thought on
this topic..

It looks to me like we need some more infrastructure to convert
anything that uses remap_pfn/etc in the mmap() callback

I would like to suggest we add a vma->prepopulate() callback which is
where the remap_pfn should go. Once the VMA is finalized and fully
operational the vma_ops have the opportunity to prepopulate any PTEs.

This could then actually be locked properly so it is safe with
concurrent unmap_mapping_range() (current mmap callback is not safe)

Jason