On 3/12/2024 8:23 PM, Matthew Wilcox wrote:
On Tue, Mar 12, 2024 at 07:07:10PM -0700, Jane Chu wrote:
On 2/29/2024 1:20 PM, Matthew Wilcox (Oracle) wrote:
Unify the KSM and DAX codepaths by calculating the addr in
add_to_kill_fsdax() instead of telling __add_to_kill() to calculate it.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
---
mm/memory-failure.c | 27 +++++++++------------------
1 file changed, 9 insertions(+), 18 deletions(-)
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 9349948f1abf..9356227a50bb 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -416,21 +416,13 @@ static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma,
* not much we can do. We just print a message and ignore otherwise.
*/
-#define FSDAX_INVALID_PGOFF ULONG_MAX
-
/*
* Schedule a process for later kill.
* Uses GFP_ATOMIC allocations to avoid potential recursions in the VM.
- *
- * Note: @fsdax_pgoff is used only when @p is a fsdax page and a
- * filesystem with a memory failure handler has claimed the
- * memory_failure event. In all other cases, page->index and
- * page->mapping are sufficient for mapping the page back to its
- * corresponding user virtual address.
*/
static void __add_to_kill(struct task_struct *tsk, struct page *p,
struct vm_area_struct *vma, struct list_head *to_kill,
- unsigned long ksm_addr, pgoff_t fsdax_pgoff)
+ unsigned long addr)
{
struct to_kill *tk;
@@ -440,12 +432,10 @@ static void __add_to_kill(struct task_struct *tsk, struct page *p,
return;
}
- tk->addr = ksm_addr ? ksm_addr : page_address_in_vma(p, vma);
- if (is_zone_device_page(p)) {
- if (fsdax_pgoff != FSDAX_INVALID_PGOFF)
- tk->addr = vma_pgoff_address(fsdax_pgoff, 1, vma);
+ tk->addr = addr ? addr : page_address_in_vma(p, vma);
+ if (is_zone_device_page(p))
tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
Not sure about the simplification. The fsdax special calculation was added by
commit c36e2024957120566efd99395b5c8cc95b5175c1
Author: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Date: Fri Jun 3 13:37:29 2022 +0800
mm: introduce mf_dax_kill_procs() for fsdax case
This new function is a variant of mf_generic_kill_procs that accepts a
file, offset pair instead of a struct to support multiple files sharing a
DAX mapping. It is intended to be called by the file systems as part of
the memory_failure handler after the file system performed a reverse
mapping from the storage address to the file and file offset.
Link: https://lkml.kernel.org/r/20220603053738.1218681-6-ruansy.fnst@xxxxxxxxxx
m
[..]
@@ -354,9 +357,15 @@ 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)) {
+ /*
+ * Since page->mapping is not used for fsdax, we need
+ * calculate the address based on the vma.
+ */
+ if (p->pgmap->type == MEMORY_DEVICE_FS_DAX)
+ tk->addr = vma_pgoff_address(fsdax_pgoff, 1, vma);
+ tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr);
+ } else
tk->size_shift = page_shift(compound_head(p));
Looks like it was to deal away with this check
unsignedlongpage_address_in_vma <https://elixir.bootlin.com/linux/v6.8/C/ident/page_address_in_vma>(structpage
<https://elixir.bootlin.com/linux/v6.8/C/ident/page>*page
<https://elixir.bootlin.com/linux/v6.8/C/ident/page>,structvm_area_struct
<https://elixir.bootlin.com/linux/v6.8/C/ident/vm_area_struct>*vma
<https://elixir.bootlin.com/linux/v6.8/C/ident/vma>)
{ [..]
}elseif(vma <https://elixir.bootlin.com/linux/v6.8/C/ident/vma>->vm_file
<https://elixir.bootlin.com/linux/v6.8/C/ident/vm_file>->f_mapping
<https://elixir.bootlin.com/linux/v6.8/C/ident/f_mapping>!=folio
<https://elixir.bootlin.com/linux/v6.8/C/ident/folio>->mapping
<https://elixir.bootlin.com/linux/v6.8/C/ident/mapping>){
return-EFAULT <https://elixir.bootlin.com/linux/v6.8/C/ident/EFAULT>;
}
But, by providing nr=1 in vma_pgoff_address(fsdax_pgoff, 1, vma), it also avoided dealing with
wrap around, which perhaps doesn't matter? perhaps noone runs fsdax on 32-bit machine?
I don't understand what you're saying is wrong with this patch.
All I'm doing (apart from the renaming of ksm_addr to addr) is moving
the vma_pgoff_address() call from __add_to_kill() to its caller.
Is there some reason this doesn't work?
Sorry for not being clear. What I meant to say is that, before the
patch, page_address_in_vma(p, vma) is the means for determining
tk->addr, except for fsdax when filesystems made a claim of wanting to
participate in the UE handling, in that case,
vma_pgoff_address(fsdax_pgoff, 1, vma) is used instead. The difference
between the two means is that, although the former eventually calls the
latter _if_ vma->vm_file->f_mapping exists and is stable, what I am
unclear from Shiyang Ruan's earlier patch is that, he seems to be
concerning a case where f_mapping is not reliable, hence his patch went
straight to call vma_pgoff_address(fsdax_pgoff, 1, vma), and on top of
that, providing nr=1 to ignore the address wrap around case.
So I don't know whether removing the fsdax special case is okay.
thanks!
-jane
