On 08/30/22 09:44, Mike Kravetz wrote: > On 08/30/22 09:06, Baolin Wang wrote: > > Hi Mike, > > > > On 8/30/2022 7:40 AM, Mike Kravetz wrote: > > > During discussions of this series [1], it was suggested that hugetlb > > > handling code in follow_page_mask could be simplified. At the beginning > > > of follow_page_mask, there currently is a call to follow_huge_addr which > > > 'may' handle hugetlb pages. ia64 is the only architecture which provides > > > a follow_huge_addr routine that does not return error. Instead, at each > > > level of the page table a check is made for a hugetlb entry. If a hugetlb > > > entry is found, a call to a routine associated with that entry is made. > > > > > > Currently, there are two checks for hugetlb entries at each page table > > > level. The first check is of the form: > > > if (p?d_huge()) > > > page = follow_huge_p?d(); > > > the second check is of the form: > > > if (is_hugepd()) > > > page = follow_huge_pd(). > > > > > > We can replace these checks, as well as the special handling routines > > > such as follow_huge_p?d() and follow_huge_pd() with a single routine to > > > handle hugetlb vmas. > > > > > > A new routine hugetlb_follow_page_mask is called for hugetlb vmas at the > > > beginning of follow_page_mask. hugetlb_follow_page_mask will use the > > > existing routine huge_pte_offset to walk page tables looking for hugetlb > > > entries. huge_pte_offset can be overwritten by architectures, and already > > > handles special cases such as hugepd entries. > > > > Could you also mention that this patch will fix the lock issue for > > CONT-PTE/PMD hugetlb by changing to use huge_pte_lock()? which will help > > people to understand the issue. > > Will update message in v2. Thanks for taking a look! > One additional thought, we 'may' need a separate patch to fix the locking issues that can be easily backported. Not sure this 'simplification' is a good backport candidate. -- Mike Kravetz
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