lkml.org 
[lkml]   [2023]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH 4/9] mm/rmap: change hugepage_add_new_anon_rmap to take in a folio
From
On 1/19/23 10:00 PM, Matthew Wilcox wrote:
> On Thu, Jan 19, 2023 at 01:14:41PM -0800, Sidhartha Kumar wrote:
>> @@ -5599,9 +5603,9 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma,
>> goto out_release_all;
>> }
>>
>> - copy_user_huge_page(new_page, old_page, address, vma,
>> + copy_user_huge_page(&new_folio->page, old_page, address, vma,
>> pages_per_huge_page(h));
>
> We have a folio_copy(), but it feels to me like we need a
> folio_copy_user() so that we can use copy_user_page() on machines
> with virtual caches.
>
>> @@ -6176,6 +6186,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
>> spinlock_t *ptl;
>> int ret = -ENOMEM;
>> struct page *page;
>> + struct folio *folio = NULL;
>> int writable;
>> bool page_in_pagecache = false;
>>
>> @@ -6251,12 +6262,15 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
>> *pagep = NULL;
>> }
>>
>> + if (page)
>> + folio = page_folio(page);
>> +
>> /*
>> - * The memory barrier inside __SetPageUptodate makes sure that
>> + * The memory barrier inside __folio_mark_uptodate makes sure that
>> * preceding stores to the page contents become visible before
>> * the set_pte_at() write.
>> */
>> - __SetPageUptodate(page);
>> + __folio_mark_uptodate(folio);
>

Hi Matthew,

In the snippet:

page = alloc_huge_page(dst_vma, dst_addr, 0);
if (IS_ERR(page)) {
put_page(*pagep);
ret = -ENOMEM;
*pagep = NULL;
goto out;
}
copy_user_huge_page(page, *pagep, dst_addr, dst_vma,
pages_per_huge_page(h));

I thought the IS_ERR() call does not handle the NULL case and is a check
for high memory addresses, and copy_user_huge_page() path does not seem
to handle the NULL case as well but alloc_huge_page() can possibly
return NULL so I was unsure about how to handle the folio conversion.

> I suggest that "page" can never be NULL or __SetPageUptodate() would
> have crashed.
>

\
 
 \ /
  Last update: 2023-03-26 23:50    [W:0.066 / U:0.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site