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Date: Thu, 14 Oct 2021 11:02:33 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc: linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
nvdimm@...ts.linux.dev, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org, dan.j.williams@...el.com,
david@...morbit.com, hch@...radead.org, jane.chu@...cle.com
Subject: Re: [PATCH v7 3/8] mm: factor helpers for memory_failure_dev_pagemap
On Fri, Sep 24, 2021 at 09:09:54PM +0800, Shiyang Ruan wrote:
> memory_failure_dev_pagemap code is a bit complex before introduce RMAP
> feature for fsdax. So it is needed to factor some helper functions to
> simplify these code.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
This looks like a reasonable hoist...
Reviewed-by: Darrick J. Wong <djwong@...nel.org>
--D
> ---
> mm/memory-failure.c | 140 ++++++++++++++++++++++++--------------------
> 1 file changed, 76 insertions(+), 64 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 54879c339024..8ff9b52823c0 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1430,6 +1430,79 @@ static int try_to_split_thp_page(struct page *page, const char *msg)
> return 0;
> }
>
> +static void unmap_and_kill(struct list_head *to_kill, unsigned long pfn,
> + struct address_space *mapping, pgoff_t index, int flags)
> +{
> + struct to_kill *tk;
> + unsigned long size = 0;
> +
> + list_for_each_entry(tk, to_kill, nd)
> + if (tk->size_shift)
> + size = max(size, 1UL << tk->size_shift);
> + if (size) {
> + /*
> + * Unmap the largest mapping to avoid breaking up device-dax
> + * mappings which are constant size. The actual size of the
> + * mapping being torn down is communicated in siginfo, see
> + * kill_proc()
> + */
> + loff_t start = (index << PAGE_SHIFT) & ~(size - 1);
> +
> + unmap_mapping_range(mapping, start, size, 0);
> + }
> +
> + kill_procs(to_kill, flags & MF_MUST_KILL, false, pfn, flags);
> +}
> +
> +static int mf_generic_kill_procs(unsigned long long pfn, int flags,
> + struct dev_pagemap *pgmap)
> +{
> + struct page *page = pfn_to_page(pfn);
> + LIST_HEAD(to_kill);
> + dax_entry_t cookie;
> +
> + /*
> + * Prevent the inode from being freed while we are interrogating
> + * the address_space, typically this would be handled by
> + * lock_page(), but dax pages do not use the page lock. This
> + * also prevents changes to the mapping of this pfn until
> + * poison signaling is complete.
> + */
> + cookie = dax_lock_page(page);
> + if (!cookie)
> + return -EBUSY;
> +
> + if (hwpoison_filter(page))
> + return 0;
> +
> + if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
> + /*
> + * TODO: Handle HMM pages which may need coordination
> + * with device-side memory.
> + */
> + return -EBUSY;
> + }
> +
> + /*
> + * Use this flag as an indication that the dax page has been
> + * remapped UC to prevent speculative consumption of poison.
> + */
> + SetPageHWPoison(page);
> +
> + /*
> + * Unlike System-RAM there is no possibility to swap in a
> + * different physical page at a given virtual address, so all
> + * userspace consumption of ZONE_DEVICE memory necessitates
> + * SIGBUS (i.e. MF_MUST_KILL)
> + */
> + flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
> + collect_procs(page, &to_kill, true);
> +
> + unmap_and_kill(&to_kill, pfn, page->mapping, page->index, flags);
> + dax_unlock_page(page, cookie);
> + return 0;
> +}
> +
> static int memory_failure_hugetlb(unsigned long pfn, int flags)
> {
> struct page *p = pfn_to_page(pfn);
> @@ -1519,12 +1592,8 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> struct dev_pagemap *pgmap)
> {
> struct page *page = pfn_to_page(pfn);
> - unsigned long size = 0;
> - struct to_kill *tk;
> LIST_HEAD(tokill);
> - int rc = -EBUSY;
> - loff_t start;
> - dax_entry_t cookie;
> + int rc = -ENXIO;
>
> if (flags & MF_COUNT_INCREASED)
> /*
> @@ -1533,67 +1602,10 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> put_page(page);
>
> /* device metadata space is not recoverable */
> - if (!pgmap_pfn_valid(pgmap, pfn)) {
> - rc = -ENXIO;
> - goto out;
> - }
> -
> - /*
> - * Prevent the inode from being freed while we are interrogating
> - * the address_space, typically this would be handled by
> - * lock_page(), but dax pages do not use the page lock. This
> - * also prevents changes to the mapping of this pfn until
> - * poison signaling is complete.
> - */
> - cookie = dax_lock_page(page);
> - if (!cookie)
> + if (!pgmap_pfn_valid(pgmap, pfn))
> goto out;
>
> - if (hwpoison_filter(page)) {
> - rc = 0;
> - goto unlock;
> - }
> -
> - if (pgmap->type == MEMORY_DEVICE_PRIVATE) {
> - /*
> - * TODO: Handle HMM pages which may need coordination
> - * with device-side memory.
> - */
> - goto unlock;
> - }
> -
> - /*
> - * Use this flag as an indication that the dax page has been
> - * remapped UC to prevent speculative consumption of poison.
> - */
> - SetPageHWPoison(page);
> -
> - /*
> - * Unlike System-RAM there is no possibility to swap in a
> - * different physical page at a given virtual address, so all
> - * userspace consumption of ZONE_DEVICE memory necessitates
> - * SIGBUS (i.e. MF_MUST_KILL)
> - */
> - flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
> - collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
> -
> - list_for_each_entry(tk, &tokill, nd)
> - if (tk->size_shift)
> - size = max(size, 1UL << tk->size_shift);
> - if (size) {
> - /*
> - * Unmap the largest mapping to avoid breaking up
> - * device-dax mappings which are constant size. The
> - * actual size of the mapping being torn down is
> - * communicated in siginfo, see kill_proc()
> - */
> - start = (page->index << PAGE_SHIFT) & ~(size - 1);
> - unmap_mapping_range(page->mapping, start, size, 0);
> - }
> - kill_procs(&tokill, flags & MF_MUST_KILL, false, pfn, flags);
> - rc = 0;
> -unlock:
> - dax_unlock_page(page, cookie);
> + rc = mf_generic_kill_procs(pfn, flags, pgmap);
> out:
> /* drop pgmap ref acquired in caller */
> put_dev_pagemap(pgmap);
> --
> 2.33.0
>
>
>
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