Re: [PATCH 04/10] mm, fsdax: Refactor memory-failure handler for dax mapping
From: zhong jiang
Date: Thu Jan 14 2021 - 04:40:42 EST
On 2021/1/14 11:52 上午, Ruan Shiyang wrote:
On 2021/1/14 上午11:26, zhong jiang wrote:
On 2021/1/14 9:44 上午, Ruan Shiyang wrote:
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@xxxxxxxxxxxxxx>
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.
IMO, All the sharing files should be the same offset to share the
fsdax page. why not that ?
The dedupe operation can let different files share their same data
extent, though offsets are not same. So, files can share one fsdax
page at different offset.
Ok, Get it.
As you has said, a shared fadax page should be inserted to different
mapping files. but page->index and page->mapping is exclusive.
hence an page only should be placed in an mapping tree.
We can't use page->mapping and page->index here for reflink & fsdax.
And that's this patchset aims to solve. I introduced a series of
->corrupted_range(), from mm to pmem driver to block device and
finally to filesystem, to use rmap feature of filesystem to find out
all files sharing same data extent (fsdax page).
From this patch, each file has mapping tree, the shared page will be
inserted into multiple file mapping tree. then filesystem use file and
offset to get the killed process. Is it correct?
Thanks,
--
Thanks,
Ruan Shiyang.
And In the current patch, we failed to found out that all process
use the fsdax page shared by multiple files and kill them.
Thanks,
--
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