Re: [PATCH 04/10] mm, fsdax: Refactor memory-failure handler for dax mapping

Ruan Shiyang
2021-01-12T02:56:51Z

On 2021/1/6 下午11:41, Jan Kara wrote:
> On Thu 31-12-20 00:55:55, 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>
>
> Overall this looks OK to me, a few comments below.
>
>> ---
>> fs/dax.c | 21 +++++++++++
>> include/linux/dax.h | 1 +
>> include/linux/mm.h | 9 +++++
>> mm/memory-failure.c | 91 ++++++++++++++++++++++++++++++++++-----------
>> 4 files changed, 100 insertions(+), 22 deletions(-)

...

>>
>> @@ -345,9 +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);
>
> It seems strange to use 'pgoff' for dax pages and not for any other page.
> Why? I'd rather pass correct pgoff from all callers of add_to_kill() and
> avoid this special casing...

Because one fsdax page can be shared by multiple pgoffs. I have to pass
each pgoff in each iteration to calculate the address in vma (for
tk->addr). Other kinds of pages don't need this. They can get their
unique address by calling "page_address_in_vma()".

So, I added this fsdax case here. This patchset only implemented the
fsdax case, other cases also need to be added here if to be implemented.

--
Thanks,
Ruan Shiyang.

>
>> + tk->size_shift = dev_pagemap_mapping_shift(p, vma, tk->addr);
>> + } else
>> tk->size_shift = page_shift(compound_head(p));
>>
>> /*
>> @@ -495,7 +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, NULL, 0, vma, to_kill);
>> }
>> }
>> read_unlock(&tasklist_lock);
>> @@ -505,24 +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
>> @@ -531,7 +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, mapping, pgoff, vma, to_kill);
>> }
>> }
>> read_unlock(&tasklist_lock);
>> @@ -550,7 +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_to_pgoff(page),
>
> Why not use page_mapping() helper here? It would be safer for THPs if they
> ever get here...
>
> Honza
>