On Fri, Jul 30, 2021 at 3:02 AM Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx> wrote:
>
> This function is called at the end of RMAP routine, i.e. filesystem
> recovery function. The difference between mf_generic_kill_procs() is,
> mf_dax_kill_procs() accepts file mapping and offset instead of struct
> page. It is because that different file 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@xxxxxxxxxxx>
> ---
> fs/dax.c | 45 ++++++++++++++++++++++++-------
> include/linux/dax.h | 16 ++++++++++++
> include/linux/mm.h | 10 +++++++
> mm/memory-failure.c | 64 +++++++++++++++++++++++++++++++++------------
> 4 files changed, 109 insertions(+), 26 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index da41f9363568..dce6307a12eb 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -389,6 +389,41 @@ static struct page *dax_busy_page(void *entry)
> return NULL;
> }
>
> +/**
> + * dax_load_pfn - Load pfn of the DAX entry corresponding to a page
> + * @mapping: The file whose entry we want to load
> + * @index: offset where the DAX entry located in
> + *
> + * Return: pfn number of the DAX entry
> + */
> +unsigned long dax_load_pfn(struct address_space *mapping, unsigned long index)
> +{
> + XA_STATE(xas, &mapping->i_pages, index);
> + void *entry;
> + unsigned long pfn;
> +
> + rcu_read_lock();
> + for (;;) {
> + xas_lock_irq(&xas);
> + entry = xas_load(&xas);
> + if (dax_is_locked(entry)) {
> + rcu_read_unlock();
> + wait_entry_unlocked(&xas, entry);
> + rcu_read_lock();
> + continue;
> + }
> +
> + if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry))
> + pfn = 0;
> + else
> + pfn = dax_to_pfn(entry);
> + xas_unlock_irq(&xas);
> + break;
> + }
> + rcu_read_unlock();
> + return pfn;
Instead of this I think you want a version of dax_lock_page() that
takes a mapping and index. Otherwise I don't see how this function
protects against races to teardown mapping->host, or to invalidate the
association of the mapping to the pfn.
> +}
> +
> /*
> * dax_lock_mapping_entry - Lock the DAX entry corresponding to a page
> * @page: The page whose entry we want to lock
> @@ -790,16 +825,6 @@ 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 6f4b5c97ceb0..359e809516b8 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -165,6 +165,7 @@ int dax_writeback_mapping_range(struct address_space *mapping,
>
> struct page *dax_layout_busy_page(struct address_space *mapping);
> struct page *dax_layout_busy_page_range(struct address_space *mapping, loff_t start, loff_t end);
> +unsigned long dax_load_pfn(struct address_space *mapping, unsigned long index);
> dax_entry_t dax_lock_page(struct page *page);
> void dax_unlock_page(struct page *page, dax_entry_t cookie);
> #else
> @@ -206,6 +207,12 @@ static inline int dax_writeback_mapping_range(struct address_space *mapping,
> return -EOPNOTSUPP;
> }
>
> +static inline unsigned long dax_load_pfn(struct address_space *mapping,
> + unsigned long index)
> +{
> + return 0;
> +}
> +
> static inline dax_entry_t dax_lock_page(struct page *page)
> {
> if (IS_DAX(page->mapping->host))
> @@ -259,6 +266,15 @@ 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 7ca22e6e694a..530aaf7a6eb2 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1190,6 +1190,14 @@ static inline bool is_device_private_page(const struct page *page)
> page->pgmap->type == MEMORY_DEVICE_PRIVATE;
> }
>
> +static inline bool is_device_fsdax_page(const struct page *page)
> +{
> + return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
> + IS_ENABLED(CONFIG_FS_DAX) &&
> + is_zone_device_page(page) &&
> + page->pgmap->type == MEMORY_DEVICE_FS_DAX;
> +}
The value of this helper is unclear to me. The MEMORY_DEVICE_FS_DAX
indication is for communicating page-idle notifications to filesystem
code.
> +
> static inline bool is_pci_p2pdma_page(const struct page *page)
> {
> return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
> @@ -3113,6 +3121,8 @@ 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,
> + 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 ab3eda335acd..520664c405fc 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -134,6 +134,12 @@ static int hwpoison_filter_dev(struct page *p)
> if (PageSlab(p))
> return -EINVAL;
>
> + if (pfn_valid(page_to_pfn(p))) {
> + if (is_device_fsdax_page(p))
hwpoison_filter was built to test triggering failures in hard to reach
places of the page cache. I think you can make an argument the
hwpoison_filter does not apply to DAX since DAX by definition
eliminates page cache. So, I'd consult pgmap->memory_failure()
*instead* of the hwpoison_filter, don't teach the filter to ignore
fsdax pages. By definition if the ->memory_failure() says -EOPNOTSUPP
then hwpoison_filter can be consulted per usual.
> + return 0;
> + } else
> + return -EINVAL;
> +
> mapping = page_mapping(p);
> if (mapping == NULL || mapping->host == NULL)
> return -EINVAL;
> @@ -304,10 +310,9 @@ void shake_page(struct page *p, int access)
> }
> 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;
> @@ -347,7 +352,7 @@ 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,
> struct vm_area_struct *vma,
> struct list_head *to_kill)
> {
> @@ -360,9 +365,14 @@ 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 (is_device_fsdax_page(p))
> + 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));
>
> /*
> @@ -510,7 +520,7 @@ 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);
> @@ -520,24 +530,20 @@ static void collect_procs_anon(struct page *page, struct list_head *to_kill,
> /*
> * Collect processes when the error hit a file mapped page.
> */
> -static void collect_procs_file(struct page *page, struct list_head *to_kill,
> - int force_early)
> +static void collect_procs_file(struct page *page, struct address_space *mapping,
> + pgoff_t pgoff, struct list_head *to_kill, int force_early)
> {
> struct vm_area_struct *vma;
> struct task_struct *tsk;
> - struct address_space *mapping = page->mapping;
> - pgoff_t pgoff;
>
> i_mmap_lock_read(mapping);
> read_lock(&tasklist_lock);
> - pgoff = page_to_pgoff(page);
> for_each_process(tsk) {
> struct task_struct *t = task_early_kill(tsk, force_early);
>
> if (!t)
> continue;
> - vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff,
> - pgoff) {
> + vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
> /*
> * Send early kill signal to tasks where a vma covers
> * the page but the corrupted page is not necessarily
> @@ -546,7 +552,7 @@ 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, pgoff, vma, to_kill);
> }
> }
> read_unlock(&tasklist_lock);
> @@ -565,7 +571,8 @@ static void collect_procs(struct page *page, struct list_head *tokill,
> if (PageAnon(page))
> collect_procs_anon(page, tokill, force_early);
> else
> - collect_procs_file(page, tokill, force_early);
> + collect_procs_file(page, page->mapping, page->index, tokill,
> + force_early);
> }
>
> struct hwp_walk {
> @@ -1477,6 +1484,31 @@ static int mf_generic_kill_procs(unsigned long long pfn, int flags)
> return 0;
> }
>
> +int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, int flags)
> +{
> + LIST_HEAD(to_kill);
> + /* load the pfn of the dax mapping file */
> + unsigned long pfn = dax_load_pfn(mapping, index);
> +
> + /* the failure pfn may not actually be mmapped, so no need to
> + * unmap and kill procs */
> + if (!pfn)
pfn-0 is a valid pfn. I think you should use a cookie value like
dax_load_page() to indicate failure.
> + return 0;
> +
> + /*
> + * 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_file(pfn_to_page(pfn), mapping, index, &to_kill, true);
> +
> + unmap_and_kill(&to_kill, pfn, mapping, index, flags);
> + 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);
> --
> 2.32.0
>
>
>
