From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f197.google.com (mail-io0-f197.google.com [209.85.223.197]) by kanga.kvack.org (Postfix) with ESMTP id C9E806B0295 for ; Fri, 16 Dec 2016 09:49:44 -0500 (EST) Received: by mail-io0-f197.google.com with SMTP id 71so92397385ioe.2 for ; Fri, 16 Dec 2016 06:49:44 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id o128si6173355ioe.82.2016.12.16.06.48.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 16 Dec 2016 06:48:28 -0800 (PST) From: Andrea Arcangeli Subject: [PATCH 24/42] userfaultfd: hugetlbfs: gup: support VM_FAULT_RETRY Date: Fri, 16 Dec 2016 15:48:03 +0100 Message-Id: <20161216144821.5183-25-aarcange@redhat.com> In-Reply-To: <20161216144821.5183-1-aarcange@redhat.com> References: <20161216144821.5183-1-aarcange@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: linux-mm@kvack.org, Andrew Morton Cc: Michael Rapoport , "Dr. David Alan Gilbert" , Mike Kravetz , Pavel Emelyanov , Hillf Danton 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. Reviewed-by: Mike Kravetz Signed-off-by: Andrea Arcangeli --- include/linux/hugetlb.h | 5 +++-- mm/gup.c | 2 +- mm/hugetlb.c | 48 ++++++++++++++++++++++++++++++++++++++++-------- 3 files changed, 44 insertions(+), 11 deletions(-) diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index aab2fff..503099d 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -65,7 +65,8 @@ int hugetlb_mempolicy_sysctl_handler(struct ctl_table *, int, 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_total_pages(void) 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 --git a/mm/gup.c b/mm/gup.c index 5531555..40abe4c 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -572,7 +572,7 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, 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 --git a/mm/hugetlb.c b/mm/hugetlb.c index 621ea74..e1bb7c6 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -4046,7 +4046,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, 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; @@ -4109,16 +4109,43 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, ((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; @@ -4147,6 +4174,11 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma, 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, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org