linux-kernel - Re: [PATCH v13 3/7] pagemap,pmem: Introduce ->memory

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Date:   Thu, 21 Apr 2022 16:24:23 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>
CC:     <djwong@...nel.org>, <dan.j.williams@...el.com>,
        <david@...morbit.com>, <hch@...radead.org>, <jane.chu@...cle.com>,
        Christoph Hellwig <hch@....de>, <linux-kernel@...r.kernel.org>,
        <linux-xfs@...r.kernel.org>, <nvdimm@...ts.linux.dev>,
        <linux-mm@...ck.org>, <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH v13 3/7] pagemap,pmem: Introduce ->memory_failure()

On 2022/4/19 12:50, Shiyang Ruan wrote:
> When memory-failure occurs, we call this function which is implemented
> by each kind of devices.  For the fsdax case, pmem device driver
> implements it.  Pmem device driver will find out the filesystem in which
> the corrupted page located in.
> 
> With dax_holder notify support, we are able to notify the memory failure
> from pmem driver to upper layers.  If there is something not support in
> the notify routine, memory_failure will fall back to the generic hanlder.
> 
> Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
> Reviewed-by: Christoph Hellwig <hch@....de>
> Reviewed-by: Dan Williams <dan.j.williams@...el.com>
> ---
>  drivers/nvdimm/pmem.c    | 17 +++++++++++++++++
>  include/linux/memremap.h | 12 ++++++++++++
>  mm/memory-failure.c      | 14 ++++++++++++++
>  3 files changed, 43 insertions(+)
> 
> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
> index 58d95242a836..bd502957cfdf 100644
> --- a/drivers/nvdimm/pmem.c
> +++ b/drivers/nvdimm/pmem.c
> @@ -366,6 +366,21 @@ static void pmem_release_disk(void *__pmem)
>  	blk_cleanup_disk(pmem->disk);
>  }
>  
> +static int pmem_pagemap_memory_failure(struct dev_pagemap *pgmap,
> +		unsigned long pfn, unsigned long nr_pages, int mf_flags)
> +{
> +	struct pmem_device *pmem =
> +			container_of(pgmap, struct pmem_device, pgmap);
> +	u64 offset = PFN_PHYS(pfn) - pmem->phys_addr - pmem->data_offset;
> +	u64 len = nr_pages << PAGE_SHIFT;
> +
> +	return dax_holder_notify_failure(pmem->dax_dev, offset, len, mf_flags);
> +}
> +
> +static const struct dev_pagemap_ops fsdax_pagemap_ops = {
> +	.memory_failure		= pmem_pagemap_memory_failure,
> +};
> +
>  static int pmem_attach_disk(struct device *dev,
>  		struct nd_namespace_common *ndns)
>  {
> @@ -427,6 +442,7 @@ static int pmem_attach_disk(struct device *dev,
>  	pmem->pfn_flags = PFN_DEV;
>  	if (is_nd_pfn(dev)) {
>  		pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
> +		pmem->pgmap.ops = &fsdax_pagemap_ops;
>  		addr = devm_memremap_pages(dev, &pmem->pgmap);
>  		pfn_sb = nd_pfn->pfn_sb;
>  		pmem->data_offset = le64_to_cpu(pfn_sb->dataoff);
> @@ -440,6 +456,7 @@ static int pmem_attach_disk(struct device *dev,
>  		pmem->pgmap.range.end = res->end;
>  		pmem->pgmap.nr_range = 1;
>  		pmem->pgmap.type = MEMORY_DEVICE_FS_DAX;
> +		pmem->pgmap.ops = &fsdax_pagemap_ops;
>  		addr = devm_memremap_pages(dev, &pmem->pgmap);
>  		pmem->pfn_flags |= PFN_MAP;
>  		bb_range = pmem->pgmap.range;
> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
> index ad6062d736cd..bcfb6bf4ce5a 100644
> --- a/include/linux/memremap.h
> +++ b/include/linux/memremap.h
> @@ -79,6 +79,18 @@ struct dev_pagemap_ops {
>  	 * the page back to a CPU accessible page.
>  	 */
>  	vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
> +
> +	/*
> +	 * Handle the memory failure happens on a range of pfns.  Notify the
> +	 * processes who are using these pfns, and try to recover the data on
> +	 * them if necessary.  The mf_flags is finally passed to the recover
> +	 * function through the whole notify routine.
> +	 *
> +	 * When this is not implemented, or it returns -EOPNOTSUPP, the caller
> +	 * will fall back to a common handler called mf_generic_kill_procs().
> +	 */
> +	int (*memory_failure)(struct dev_pagemap *pgmap, unsigned long pfn,
> +			      unsigned long nr_pages, int mf_flags);
>  };
>  
>  #define PGMAP_ALTMAP_VALID	(1 << 0)
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 7c8c047bfdc8..a40e79e634a4 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1741,6 +1741,20 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
>  	if (!pgmap_pfn_valid(pgmap, pfn))
>  		goto out;
>  
> +	/*
> +	 * Call driver's implementation to handle the memory failure, otherwise
> +	 * fall back to generic handler.
> +	 */
> +	if (pgmap->ops->memory_failure) {
> +		rc = pgmap->ops->memory_failure(pgmap, pfn, 1, flags);
> +		/*
> +		 * Fall back to generic handler too if operation is not
> +		 * supported inside the driver/device/filesystem.
> +		 */
> +		if (rc != -EOPNOTSUPP)
> +			goto out;
> +	}
> +

Thanks for your patch. There are two questions:

1.Is dax_lock_page + dax_unlock_page pair needed here?
2.hwpoison_filter and SetPageHWPoison will be handled by the callback or they're just ignored deliberately?

Thanks!

>  	rc = mf_generic_kill_procs(pfn, flags, pgmap);
>  out:
>  	/* drop pgmap ref acquired in caller */
>