Re: [PATCH v3 05/11] mm, fsdax: Refactor memory-failure handler for dax mapping

zhong jiang
2021-03-16T03:22:43Z

On 2021/2/8 6:55 下午, Shiyang Ruan wrote:
> The current memory_failure_dev_pagemap() can only handle single-mapped
> dax page for fsdax mode. The dax page could be mapped by multiple files
> and offsets if we let reflink feature & fsdax mode work together. So,
> we refactor current implementation to support handle memory failure on
> each file and offset.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
> ---
> fs/dax.c | 21 ++++++++++
> include/linux/dax.h | 1 +
> include/linux/mm.h | 9 +++++
> mm/memory-failure.c | 98 ++++++++++++++++++++++++++++++++++-----------
> 4 files changed, 105 insertions(+), 24 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 26d5dcd2d69e..c64c3a0e76a6 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -378,6 +378,27 @@ 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: The offset where the DAX entry located in
> + *
> + * Return: pfn 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;
> +
> + xas_lock_irq(&xas);
> + entry = xas_load(&xas);
> + pfn = dax_to_pfn(entry);
> + xas_unlock_irq(&xas);
> +
> + return pfn;
> +}
> +
> /*
> * dax_lock_mapping_entry - Lock the DAX entry corresponding to a page
> * @page: The page whose entry we want to lock
> diff --git a/include/linux/dax.h b/include/linux/dax.h
> index b52f084aa643..89e56ceeffc7 100644
> --- a/include/linux/dax.h
> +++ b/include/linux/dax.h
> @@ -150,6 +150,7 @@ 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
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ecdf8a8cd6ae..ab52bc633d84 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1157,6 +1157,14 @@ 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;
> +}
> +
> static inline bool is_pci_p2pdma_page(const struct page *page)
> {
> return IS_ENABLED(CONFIG_DEV_PAGEMAP_OPS) &&
> @@ -3045,6 +3053,7 @@ enum mf_flags {
> MF_MUST_KILL = 1 << 2,
> MF_SOFT_OFFLINE = 1 << 3,
> };
> +extern int mf_dax_mapping_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 e9481632fcd1..158fe0c8e602 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -56,6 +56,7 @@
> #include <linux/kfifo.h>
> #include <linux/ratelimit.h>
> #include <linux/page-isolation.h>
> +#include <linux/dax.h>
> #include "internal.h"
> #include "ras/ras_event.h"
>
> @@ -120,6 +121,13 @@ 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))
> + return 0;
> + else
> + return -EINVAL;
> + }
> +
> mapping = page_mapping(p);
> if (mapping == NULL || mapping->host == NULL)
> return -EINVAL;
> @@ -286,10 +294,9 @@ void shake_page(struct page *p, int access)
> }
> 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);
> pgd_t *pgd;
> p4d_t *p4d;
> pud_t *pud;
> @@ -329,9 +336,8 @@ 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,
> - struct vm_area_struct *vma,
> - struct list_head *to_kill)
> +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)
> {
> struct to_kill *tk;
>
> @@ -342,9 +348,12 @@ 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)) {
> + if (is_device_fsdax_page(p))
> + tk->addr = vma->vm_start +
> + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
> + tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
> + } else
> tk->size_shift = page_shift(compound_head(p));
>
> /*
> @@ -492,7 +501,7 @@ 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);
> @@ -502,24 +511,19 @@ 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
> @@ -528,7 +532,7 @@ 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);
> @@ -547,7 +551,8 @@ 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), page_to_pgoff(page),
> + tokill, force_early);
> }
>
> static const char *action_name[] = {
> @@ -1214,6 +1219,50 @@ static int try_to_split_thp_page(struct page *page, const char *msg)
> return 0;
> }
>
> +int mf_dax_mapping_kill_procs(struct address_space *mapping, pgoff_t index, int flags)
> +{
> + const bool unmap_success = true;
> + unsigned long pfn, size = 0;
> + struct to_kill *tk;
> + LIST_HEAD(to_kill);
> + int rc = -EBUSY;
> + loff_t start;
> +
> + /* load the pfn of the dax mapping file */
> + pfn = dax_load_pfn(mapping, index);
> + if (!pfn)
> + return rc;
> + /*
> + * 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;

MF_ACTION_REQUIRED only kill the current execution context. A page can be shared
when reflink file be mapped by different process. We can not kill all process
shared the page. Other process still can access the posioned page ?

Thanks,
zhong jiang

> + collect_procs_file(pfn_to_page(pfn), mapping, index, &to_kill,
> + flags & MF_ACTION_REQUIRED);
> +
> + 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()
> + */
> + start = (index << PAGE_SHIFT) & ~(size - 1);
> + unmap_mapping_range(mapping, start, start + size, 0);
> + }
> +
> + kill_procs(&to_kill, flags & MF_MUST_KILL, !unmap_success,
> + pfn, flags);
> + rc = 0;
> + return rc;
> +}
> +EXPORT_SYMBOL_GPL(mf_dax_mapping_kill_procs);
> +
> static int memory_failure_hugetlb(unsigned long pfn, int flags)
> {
> struct page *p = pfn_to_page(pfn);
> @@ -1297,7 +1346,7 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> const bool unmap_success = true;
> unsigned long size = 0;
> struct to_kill *tk;
> - LIST_HEAD(tokill);
> + LIST_HEAD(to_kill);
> int rc = -EBUSY;
> loff_t start;
> dax_entry_t cookie;
> @@ -1345,9 +1394,10 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> * SIGBUS (i.e. MF_MUST_KILL)
> */
> flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
> - collect_procs(page, &tokill, flags & MF_ACTION_REQUIRED);
> + collect_procs_file(page, page->mapping, page->index, &to_kill,
> + flags & MF_ACTION_REQUIRED);
>
> - list_for_each_entry(tk, &tokill, nd)
> + list_for_each_entry(tk, &to_kill, nd)
> if (tk->size_shift)
> size = max(size, 1UL << tk->size_shift);
> if (size) {
> @@ -1360,7 +1410,7 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> start = (page->index << PAGE_SHIFT) & ~(size - 1);
> unmap_mapping_range(page->mapping, start, start + size, 0);
> }
> - kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
> + kill_procs(&to_kill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
> rc = 0;
> unlock:
> dax_unlock_page(page, cookie);