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Date: Thu, 14 Jan 2021 09:44:14 +0800
From: Ruan Shiyang <ruansy.fnst@...fujitsu.com>
To: zhong jiang <zhongjiang-ali@...ux.alibaba.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 2021/1/13 下午6:04, zhong jiang wrote:
>
> 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,
Yes, a fsdax page is shared by multiple files because of reflink. I
think my description of 'pgoff' here is not correct. This 'pgoff' means
the offset within the a file. (We use rmap to find out all the sharing
files and their offsets.) So, I said that "can be shared by multiple
pgoffs". It's my bad.
I think I should name it another word to avoid misunderstandings.
--
Thanks,
Ruan Shiyang.
>
>> 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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