From: Andrea Arcangeli <aarcange@xxxxxxxxxx> Subject: userfaultfd: hugetlbfs: gup: support VM_FAULT_RETRY Add support for VM_FAULT_RETRY to follow_hugetlb_page() so that get_user_pages_unlocked/locked and "nonblocking/FOLL_NOWAIT" features will work on hugetlbfs. This is required for fully functional userfaultfd non-present support on hugetlbfs. Link: http://lkml.kernel.org/r/20161216144821.5183-25-aarcange@xxxxxxxxxx Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: "Dr. David Alan Gilbert" <dgilbert@xxxxxxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Michael Rapoport <RAPOPORT@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxxx> Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/hugetlb.h | 5 ++- mm/gup.c | 2 - mm/hugetlb.c | 48 +++++++++++++++++++++++++++++++------- 3 files changed, 44 insertions(+), 11 deletions(-) diff -puN include/linux/hugetlb.h~userfaultfd-hugetlbfs-gup-support-vm_fault_retry include/linux/hugetlb.h --- a/include/linux/hugetlb.h~userfaultfd-hugetlbfs-gup-support-vm_fault_retry +++ a/include/linux/hugetlb.h @@ -65,7 +65,8 @@ int hugetlb_mempolicy_sysctl_handler(str int copy_hugetlb_page_range(struct mm_struct *, struct mm_struct *, struct vm_area_struct *); long follow_hugetlb_page(struct mm_struct *, struct vm_area_struct *, struct page **, struct vm_area_struct **, - unsigned long *, unsigned long *, long, unsigned int); + unsigned long *, unsigned long *, long, unsigned int, + int *); void unmap_hugepage_range(struct vm_area_struct *, unsigned long, unsigned long, struct page *); void __unmap_hugepage_range_final(struct mmu_gather *tlb, @@ -136,7 +137,7 @@ static inline unsigned long hugetlb_tota return 0; } -#define follow_hugetlb_page(m,v,p,vs,a,b,i,w) ({ BUG(); 0; }) +#define follow_hugetlb_page(m,v,p,vs,a,b,i,w,n) ({ BUG(); 0; }) #define follow_huge_addr(mm, addr, write) ERR_PTR(-EINVAL) #define copy_hugetlb_page_range(src, dst, vma) ({ BUG(); 0; }) static inline void hugetlb_report_meminfo(struct seq_file *m) diff -puN mm/gup.c~userfaultfd-hugetlbfs-gup-support-vm_fault_retry mm/gup.c --- a/mm/gup.c~userfaultfd-hugetlbfs-gup-support-vm_fault_retry +++ a/mm/gup.c @@ -572,7 +572,7 @@ static long __get_user_pages(struct task if (is_vm_hugetlb_page(vma)) { i = follow_hugetlb_page(mm, vma, pages, vmas, &start, &nr_pages, i, - gup_flags); + gup_flags, nonblocking); continue; } } diff -puN mm/hugetlb.c~userfaultfd-hugetlbfs-gup-support-vm_fault_retry mm/hugetlb.c --- a/mm/hugetlb.c~userfaultfd-hugetlbfs-gup-support-vm_fault_retry +++ a/mm/hugetlb.c @@ -4065,7 +4065,7 @@ out_release_unlock: long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, struct page **pages, struct vm_area_struct **vmas, unsigned long *position, unsigned long *nr_pages, - long i, unsigned int flags) + long i, unsigned int flags, int *nonblocking) { unsigned long pfn_offset; unsigned long vaddr = *position; @@ -4128,16 +4128,43 @@ long follow_hugetlb_page(struct mm_struc ((flags & FOLL_WRITE) && !huge_pte_write(huge_ptep_get(pte)))) { int ret; + unsigned int fault_flags = 0; if (pte) spin_unlock(ptl); - ret = hugetlb_fault(mm, vma, vaddr, - (flags & FOLL_WRITE) ? FAULT_FLAG_WRITE : 0); - if (!(ret & VM_FAULT_ERROR)) - continue; - - remainder = 0; - break; + if (flags & FOLL_WRITE) + fault_flags |= FAULT_FLAG_WRITE; + if (nonblocking) + fault_flags |= FAULT_FLAG_ALLOW_RETRY; + if (flags & FOLL_NOWAIT) + fault_flags |= FAULT_FLAG_ALLOW_RETRY | + FAULT_FLAG_RETRY_NOWAIT; + if (flags & FOLL_TRIED) { + VM_WARN_ON_ONCE(fault_flags & + FAULT_FLAG_ALLOW_RETRY); + fault_flags |= FAULT_FLAG_TRIED; + } + ret = hugetlb_fault(mm, vma, vaddr, fault_flags); + if (ret & VM_FAULT_ERROR) { + remainder = 0; + break; + } + if (ret & VM_FAULT_RETRY) { + if (nonblocking) + *nonblocking = 0; + *nr_pages = 0; + /* + * VM_FAULT_RETRY must not return an + * error, it will return zero + * instead. + * + * No need to update "position" as the + * caller will not check it after + * *nr_pages is set to 0. + */ + return i; + } + continue; } pfn_offset = (vaddr & ~huge_page_mask(h)) >> PAGE_SHIFT; @@ -4166,6 +4193,11 @@ same_page: spin_unlock(ptl); } *nr_pages = remainder; + /* + * setting position is actually required only if remainder is + * not zero but it's faster not to add a "if (remainder)" + * branch. + */ *position = vaddr; return i ? i : -EFAULT; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
