Re: [PATCH v13 5/7] mm: Introduce mf_dax_kill_procs() for fsdax case

Darrick J. Wong
2022-04-20T17:58:12Z

On Tue, Apr 19, 2022 at 12:50:43PM +0800, Shiyang Ruan wrote:
> This new function is a variant of mf_generic_kill_procs that accepts a
> file, offset pair instead of a struct to support multiple files sharing
> a DAX mapping. It is intended to be called by the file systems as part
> of the memory_failure handler after the file system performed a reverse
> mapping from the storage address to the file and file offset.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Looks ok,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
> include/linux/mm.h | 2 +
> mm/memory-failure.c | 96 ++++++++++++++++++++++++++++++++++++++++-----
> 2 files changed, 88 insertions(+), 10 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ad4b6c15c814..52208d743546 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3233,6 +3233,8 @@ enum mf_flags {
> MF_SOFT_OFFLINE = 1 << 3,
> MF_UNPOISON = 1 << 4,
> };
> +int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
> + unsigned long count, int mf_flags);
> extern int memory_failure(unsigned long pfn, int flags);
> extern void memory_failure_queue(unsigned long pfn, int flags);
> extern void memory_failure_queue_kick(int cpu);
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index a40e79e634a4..dc47c5f83d85 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -295,10 +295,9 @@ void shake_page(struct page *p)
> }
> EXPORT_SYMBOL_GPL(shake_page);
>
> -static unsigned long dev_pagemap_mapping_shift(struct page *page,
> - struct vm_area_struct *vma)
> +static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
> + unsigned long address)
> {
> - unsigned long address = vma_address(page, vma);
> unsigned long ret = 0;
> pgd_t *pgd;
> p4d_t *p4d;
> @@ -338,10 +337,14 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
> /*
> * Schedule a process for later kill.
> * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
> + *
> + * Notice: @fsdax_pgoff is used only when @p is a fsdax page.
> + * In other cases, such as anonymous and file-backend page, the address to be
> + * killed can be caculated by @p itself.
> */
> static void add_to_kill(struct task_struct *tsk, struct page *p,
> - struct vm_area_struct *vma,
> - struct list_head *to_kill)
> + pgoff_t fsdax_pgoff, struct vm_area_struct *vma,
> + struct list_head *to_kill)
> {
> struct to_kill *tk;
>
> @@ -352,9 +355,15 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
> }
>
> tk->addr = page_address_in_vma(p, vma);
> - if (is_zone_device_page(p))
> - tk->size_shift = dev_pagemap_mapping_shift(p, vma);
> - else
> + if (is_zone_device_page(p)) {
> + /*
> + * Since page->mapping is not used for fsdax, we need
> + * calculate the address based on the vma.
> + */
> + if (p->pgmap->type == MEMORY_DEVICE_FS_DAX)
> + tk->addr = vma_pgoff_address(fsdax_pgoff, 1, vma);
> + tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
> + } else
> tk->size_shift = page_shift(compound_head(p));
>
> /*
> @@ -503,7 +512,7 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
> if (!page_mapped_in_vma(page, vma))
> continue;
> if (vma->vm_mm == t->mm)
> - add_to_kill(t, page, vma, to_kill);
> + add_to_kill(t, page, 0, vma, to_kill);
> }
> }
> read_unlock(&tasklist_lock);
> @@ -539,13 +548,41 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
> * to be informed of all such data corruptions.
> */
> if (vma->vm_mm == t->mm)
> - add_to_kill(t, page, vma, to_kill);
> + add_to_kill(t, page, 0, vma, to_kill);
> }
> }
> read_unlock(&tasklist_lock);
> i_mmap_unlock_read(mapping);
> }
>
> +#if IS_ENABLED(CONFIG_FS_DAX)
> +/*
> + * Collect processes when the error hit a fsdax page.
> + */
> +static void collect_procs_fsdax(struct page *page,
> + struct address_space *mapping, pgoff_t pgoff,
> + struct list_head *to_kill)
> +{
> + struct vm_area_struct *vma;
> + struct task_struct *tsk;
> +
> + i_mmap_lock_read(mapping);
> + read_lock(&tasklist_lock);
> + for_each_process(tsk) {
> + struct task_struct *t = task_early_kill(tsk, true);
> +
> + if (!t)
> + continue;
> + vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> + if (vma->vm_mm == t->mm)
> + add_to_kill(t, page, pgoff, vma, to_kill);
> + }
> + }
> + read_unlock(&tasklist_lock);
> + i_mmap_unlock_read(mapping);
> +}
> +#endif /* CONFIG_FS_DAX */
> +
> /*
> * Collect the processes who have the corrupted page mapped to kill.
> */
> @@ -1582,6 +1619,45 @@ static int mf_generic_kill_procs(unsigned long long pfn, int flags,
> return rc;
> }
>
> +#ifdef CONFIG_FS_DAX
> +/**
> + * mf_dax_kill_procs - Collect and kill processes who are using this file range
> + * @mapping: the file in use
> + * @index: start pgoff of the range within the file
> + * @count: length of the range, in unit of PAGE_SIZE
> + * @mf_flags: memory failure flags
> + */
> +int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
> + unsigned long count, int mf_flags)
> +{
> + LIST_HEAD(to_kill);
> + dax_entry_t cookie;
> + struct page *page;
> + size_t end = index + count;
> +
> + mf_flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
> +
> + for (; index < end; index++) {
> + page = NULL;
> + cookie = dax_lock_mapping_entry(mapping, index, &page);
> + if (!cookie)
> + return -EBUSY;
> + if (!page)
> + goto unlock;
> +
> + SetPageHWPoison(page);
> +
> + collect_procs_fsdax(page, mapping, index, &to_kill);
> + unmap_and_kill(&to_kill, page_to_pfn(page), mapping,
> + index, mf_flags);
> +unlock:
> + dax_unlock_mapping_entry(mapping, index, cookie);
> + }
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
> +#endif /* CONFIG_FS_DAX */
> +
> /*
> * Called from hugetlb code with hugetlb_lock held.
> *
> --
> 2.35.1
>
>
>