On 2024/2/20 16:37, Xin Li wrote:
> On 2/19/2024 7:48 PM, Wupeng Ma wrote:
>> From: Ma Wupeng <mawupeng1@xxxxxxxxxx>
>>
>
> This patch set is all about follow_phys() cleanups, so "Cleanup for PAT"
> seems too generic.
>
>> Patch #1 move follow_phys to memtype.c since only pat use this.
>> Patch #2 cleanup parameter in follow_phys.
>> Patch #3 drop the unnecessary WARN_ON_ONCE if follow_phys fails.
>
> I'm more curious why follow_phys() ended up this way?
>
> follow_phys() was introduced in commit 28b2ee20c7cba ("access_process_vm
> device memory infrastructure") in 2008 for getting a physical page address
> for a virtual address, and used in generic_access_phys(). And later it's
> used in x86 PAT code.
>
> Commit 03668a4debf4f ("mm: use generic follow_pte() in follow_phys()") made
> follow_phys() more of a wrapper of follow_pte(), and commit 96667f8a4382d
> ("mm: Close race in generic_access_phys") replaced follow_phys() with
> follow_pte() in generic_access_phys(). And the end result is that
> follow_phys() is used in x86 PAT code only.
Thanks for the explanation. I have a better understanding of the history of
this function.
>
> As follow_phys() in untrack_pfn() can be replaced with follow_pfn(), then
Yes, this can be replaced with follow_pfn().
> maybe we don't have to keep follow_phys(), and just use follow_pte() in
> track_pfn_copy()?
As follow_phys() will return unsigned long *prot which is need in track_pfn_copy(),
we need to do something with this.
Can we replace follow_pfn with follow_phys()?
Thanks!
Ma
>
> Thanks!
> Xin
>
>>
>> Changelog since v3:
>> - rebase to latest linux
>> - fix compile warnings
>>
>> Changelog since v2:
>> - rebase to latest linux
>>
>> Changelog since v1:
>> - split patch #1 into two patches based on Boris's advise
>>
>> Ma Wupeng (3):
>> x86/mm/pat: Move follow_phys to pat-related file
>> x86/mm/pat: Cleanup unused parameter in follow_phys
>> x86/mm/pat: Remove WARN_ON_ONCE if follow_phys fails
>>
>> arch/x86/mm/pat/memtype.c | 32 ++++++++++++++++++++++++++------
>> include/linux/mm.h | 2 --
>> mm/memory.c | 28 ----------------------------
>> 3 files changed, 26 insertions(+), 36 deletions(-)
>>
>
>
