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 PwdFpiRz 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi, David, On 3/25/2026 1:49 AM, David Hildenbrand (Arm) wrote: [..] >> >> --- a/include/linux/hugetlb.h~mm-userfaultfd-fix-hugetlb-fault-mutex-hash-calculation >> +++ a/include/linux/hugetlb.h >> @@ -796,6 +796,23 @@ static inline unsigned huge_page_shift(s >> return h->order + PAGE_SHIFT; >> } >> >> +/** >> + * hugetlb_linear_page_index() - linear_page_index() but in hugetlb >> + * page size granularity. >> + * @vma: the hugetlb VMA >> + * @address: the virtual address within the VMA >> + * >> + * Return: the page offset within the mapping in huge page units. >> + */ >> +static inline pgoff_t hugetlb_linear_page_index(struct vm_area_struct *vma, >> + unsigned long address) >> +{ >> + struct hstate *h = hstate_vma(vma); >> + >> + return ((address - vma->vm_start) >> huge_page_shift(h)) + >> + (vma->vm_pgoff >> huge_page_order(h)); >> +} >> + >> static inline bool order_is_gigantic(unsigned int order) >> { >> return order > MAX_PAGE_ORDER; >> --- a/mm/userfaultfd.c~mm-userfaultfd-fix-hugetlb-fault-mutex-hash-calculation >> +++ a/mm/userfaultfd.c >> @@ -573,7 +573,7 @@ retry: >> * in the case of shared pmds. fault mutex prevents >> * races with other faulting threads. >> */ >> - idx = linear_page_index(dst_vma, dst_addr); >> + idx = hugetlb_linear_page_index(dst_vma, dst_addr); >> mapping = dst_vma->vm_file->f_mapping; >> hash = hugetlb_fault_mutex_hash(mapping, idx); >> mutex_lock(&hugetlb_fault_mutex_table[hash]); >> _ >> > > Let's take a look at other hugetlb_fault_mutex_hash() users: > > * remove_inode_hugepages: uses folio->index >> huge_page_order(h) > -> hugetlb granularity > * hugetlbfs_fallocate(): start/index is in hugetlb granularity > -> hugetlb granularity > * memfd_alloc_folio(): idx >>= huge_page_order(h); > -> hugetlb granularity > * hugetlb_wp(): uses vma_hugecache_offset() > -> hugetlb granularity > * hugetlb_handle_userfault(): uses vmf->pgoff, which hugetlb_fault() > sets to vma_hugecache_offset() > -> hugetlb granularity > * hugetlb_no_page(): similarly uses vmf->pgoff > -> hugetlb granularity > * hugetlb_fault(): similarly uses vmf->pgoff > -> hugetlb granularity > > So this change here looks good to me > > Reviewed-by: David Hildenbrand (Arm) > > > But it raises the question: > > (1) should be convert all that to just operate on the ordinary index, > such that we don't even need hugetlb_linear_page_index()? That would be > an addon patch. > Do you mean to convert all callers of hugetlb_linear_page_index() and vma_hugepcache_offset() to use index and huge_page_order(h) ? May I add, to improve readability, rename the huge-page-granularity 'idx' to huge_idx or hidx ? > (2) Alternatively, could we replace all users of vma_hugecache_offset() > by the much cleaner hugetlb_linear_page_index() ? > The difference between the two helpers is hstate_vma() in the latter that is about 5 pointer de-references, not sure of any performance implication though. At minimum, we could have hugetlb_linear_page_index(vma, addr) -> __hugetlb_linear_page_index(h, vma, addr) basically renaming vma_hugecache_offset(). > In general, I think we should look into having idx/vmf->pgoff being > consistent with the remainder of MM, converting all code in hugetlb to > do that. > > Any takers? > I'd be happy to, just to make sure I understand the proposal clearly. thanks! -jane