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Date: Wed, 13 Jan 2021 18:04:46 +0800
From: zhong jiang <zhongjiang-ali@...ux.alibaba.com>
To: Ruan Shiyang <ruansy.fnst@...fujitsu.com>, Jan Kara <jack@...e.cz>
Cc: linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
linux-nvdimm@...ts.01.org, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org, linux-raid@...r.kernel.org,
darrick.wong@...cle.com, dan.j.williams@...el.com,
david@...morbit.com, hch@....de, song@...nel.org, rgoldwyn@...e.de,
qi.fuli@...itsu.com, y-goto@...itsu.com
Subject: Re: [PATCH 04/10] mm, fsdax: Refactor memory-failure handler for dax
mapping
On 2021/1/12 10:55 上午, Ruan Shiyang wrote:
>
>
> 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@...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()".
>
IMO, an fsdax page can be shared by multiple files rather than
multiple pgoffs if fs query support reflink. Because an page only
located in an mapping(page->mapping is exclusive), hence it only has
an pgoff or index pointing at the node.
or I miss something for the feature ? thanks,
> 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
>>
>
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