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Message-ID: <20211014193241.GK24307@magnolia>
Date: Thu, 14 Oct 2021 12:32:41 -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 6/8] mm: Introduce mf_dax_kill_procs() for fsdax case
On Fri, Sep 24, 2021 at 09:09:57PM +0800, Shiyang Ruan wrote:
> This function is called at the end of RMAP routine, i.e. filesystem
> recovery function, to collect and kill processes using a shared page of
> DAX file. The difference between mf_generic_kill_procs() is,
> it accepts file's mapping,offset instead of struct page. Because
> different file's mappings and offsets may share the same page in fsdax
> mode. So, it is called when filesystem RMAP results are found.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
> ---
> fs/dax.c | 10 ------
> include/linux/dax.h | 9 +++++
> include/linux/mm.h | 2 ++
> mm/memory-failure.c | 83 ++++++++++++++++++++++++++++++++++++++++-----
> 4 files changed, 86 insertions(+), 18 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 509b65e60478..2536c105ec7f 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -852,16 +852,6 @@ static void *dax_insert_entry(struct xa_state *xas,
> return entry;
> }
>
> -static inline
> -unsigned long pgoff_address(pgoff_t pgoff, struct vm_area_struct *vma)
> -{
> - unsigned long address;
> -
> - address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
> - VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
> - return address;
> -}
> -
> /* Walk all mappings of a given index of a file and writeprotect them */
> static void dax_entry_mkclean(struct address_space *mapping, pgoff_t index,
> unsigned long pfn)
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index 65411bee4312..3d90becbd160 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -258,6 +258,15 @@ static inline bool dax_mapping(struct address_space *mapping)
> {
> return mapping->host && IS_DAX(mapping->host);
> }
> +static inline unsigned long pgoff_address(pgoff_t pgoff,
> + struct vm_area_struct *vma)
> +{
> + unsigned long address;
> +
> + address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
> + VM_BUG_ON_VMA(address < vma->vm_start || address >= vma->vm_end, vma);
> + return address;
> +}
>
> #ifdef CONFIG_DEV_DAX_HMEM_DEVICES
> void hmem_register_device(int target_nid, struct resource *r);
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 73a52aba448f..d06af0051e53 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3114,6 +3114,8 @@ enum mf_flags {
> MF_MUST_KILL = 1 << 2,
> MF_SOFT_OFFLINE = 1 << 3,
> };
> +extern int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
> + size_t size, int 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 85eab206b68f..a9d0d487d205 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -302,10 +302,9 @@ void shake_page(struct page *p)
> }
> EXPORT_SYMBOL_GPL(shake_page);
>
> -static unsigned long dev_pagemap_mapping_shift(struct page *page,
> +static unsigned long dev_pagemap_mapping_shift(unsigned long address,
> struct vm_area_struct *vma)
> {
> - unsigned long address = vma_address(page, vma);
> pgd_t *pgd;
> p4d_t *p4d;
> pud_t *pud;
> @@ -345,7 +344,7 @@ 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.
> */
> -static void add_to_kill(struct task_struct *tsk, struct page *p,
> +static void add_to_kill(struct task_struct *tsk, struct page *p, pgoff_t pgoff,
Hm, so I guess you're passing the page and the pgoff now because
page->index is meaningless for shared dax pages? Ok.
> struct vm_area_struct *vma,
> struct list_head *to_kill)
> {
> @@ -358,9 +357,15 @@ 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 no more used for fsdax, we should
> + * calculate the address in a fsdax way.
> + */
> + if (p->pgmap->type == MEMORY_DEVICE_FS_DAX)
> + tk->addr = pgoff_address(pgoff, vma);
> + tk->size_shift = dev_pagemap_mapping_shift(tk->addr, vma);
> + } else
> tk->size_shift = page_shift(compound_head(p));
>
> /*
> @@ -508,7 +513,7 @@ 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);
> @@ -544,7 +549,32 @@ 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);
> +}
> +
> +/*
> + * 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);
> @@ -1503,6 +1533,43 @@ static int mf_generic_kill_procs(unsigned long long pfn, int flags,
> return 0;
> }
>
> +/**
> + * mf_dax_kill_procs - Collect and kill processes who are using this file range
> + * @mapping: the file in use
> + * @index: start offset of the range
> + * @size: length of the range
It feels odd that one argument is in units of pgoff_t but the other is
in bytes.
> + * @flags: memory failure flags
> + */
> +int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
> + size_t size, int flags)
> +{
> + LIST_HEAD(to_kill);
> + dax_entry_t cookie;
> + struct page *page;
> + size_t end = (index << PAGE_SHIFT) + size;
> +
> + flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
Hm. What flags will we be passing to the xfs_dax_notify_failure_fn?
Does XFS itself have to care about what's in the flags values, or is it
really just a magic cookie to be passed from the mm layer into the fs
and back to mf_dax_kill_procs?
--D
> +
> + for (; (index << PAGE_SHIFT) < 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, flags);
> +unlock:
> + dax_unlock_mapping_entry(mapping, index, cookie);
> + }
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(mf_dax_kill_procs);
> +
> static int memory_failure_hugetlb(unsigned long pfn, int flags)
> {
> struct page *p = pfn_to_page(pfn);
> --
> 2.33.0
>
>
>
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