linux-kernel - Re: [PATCH 12/25] memremap: add a migrate_to_ram method to struct dev_pagemap

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Message-ID: <20190627162439.GD9499@mellanox.com>
Date:   Thu, 27 Jun 2019 16:29:45 +0000
From:   Jason Gunthorpe <jgg@...lanox.com>
To:     Christoph Hellwig <hch@....de>
CC:     Dan Williams <dan.j.williams@...el.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ralph Campbell <rcampbell@...dia.com>
Subject: Re: [PATCH 12/25] memremap: add a migrate_to_ram method to struct
 dev_pagemap_ops

On Wed, Jun 26, 2019 at 02:27:11PM +0200, Christoph Hellwig wrote:
> This replaces the hacky ->fault callback, which is currently directly
> called from common code through a hmm specific data structure as an
> exercise in layering violations.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Ralph Campbell <rcampbell@...dia.com>
> ---
>  include/linux/hmm.h      |  6 ------
>  include/linux/memremap.h |  6 ++++++
>  include/linux/swapops.h  | 15 ---------------
>  kernel/memremap.c        | 35 ++++-------------------------------
>  mm/hmm.c                 | 13 +++++--------
>  mm/memory.c              |  9 ++-------
>  6 files changed, 17 insertions(+), 67 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...lanox.com>
 
I'ver heard there are some other use models for fault() here beyond
migrate to ram, but we can rename it if we ever see them.

> +static vm_fault_t hmm_devmem_migrate_to_ram(struct vm_fault *vmf)
>  {
> -	struct hmm_devmem *devmem = page->pgmap->data;
> +	struct hmm_devmem *devmem = vmf->page->pgmap->data;
>  
> -	return devmem->ops->fault(devmem, vma, addr, page, flags, pmdp);
> +	return devmem->ops->fault(devmem, vmf->vma, vmf->address, vmf->page,
> +			vmf->flags, vmf->pmd);
>  }

Next cycle we should probably rename this fault to migrate_to_ram as
well and pass in the vmf..

Jason