Re: [PATCH v4 2/4] mm: userfaultfd: don't pass around both mm and vma

From: Mike Rapoport
Date: Thu Mar 09 2023 - 03:44:32 EST

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In reply to: Axel Rasmussen: "[PATCH v4 2/4] mm: userfaultfd: don't pass around both mm and vma"
Next in thread: Axel Rasmussen: "[PATCH v4 3/4] mm: userfaultfd: combine 'mode' and 'wp_copy' arguments"
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On Wed, Mar 08, 2023 at 02:19:30PM -0800, Axel Rasmussen wrote:
> Quite a few userfaultfd functions took both mm and vma pointers as
> arguments. Since the mm is trivially accessible via vma->vm_mm, there's
> no reason to pass both; it just needlessly extends the already long
> argument list.
>
> Get rid of the mm pointer, where possible, to shorten the argument list.
>
> Acked-by: Peter Xu <peterx@xxxxxxxxxx>
> Signed-off-by: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>

Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>

> ---
> fs/userfaultfd.c | 2 +-
> include/linux/hugetlb.h | 5 ++-
> include/linux/shmem_fs.h | 4 +--
> include/linux/userfaultfd_k.h | 4 +--
> mm/hugetlb.c | 4 +--
> mm/shmem.c | 7 ++--
> mm/userfaultfd.c | 61 +++++++++++++++++------------------
> 7 files changed, 41 insertions(+), 46 deletions(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index 365bf00dd8dd..84d5d402214a 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -1629,7 +1629,7 @@ static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
>
> /* Reset ptes for the whole vma range if wr-protected */
> if (userfaultfd_wp(vma))
> - uffd_wp_range(mm, vma, start, vma_end - start, false);
> + uffd_wp_range(vma, start, vma_end - start, false);
>
> new_flags = vma->vm_flags & ~__VM_UFFD_FLAGS;
> prev = vma_merge(&vmi, mm, prev, start, vma_end, new_flags,
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 8f0467bf1cbd..8b9325f77ac3 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -158,7 +158,7 @@ unsigned long hugetlb_total_pages(void);
> vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> unsigned long address, unsigned int flags);
> #ifdef CONFIG_USERFAULTFD
> -int hugetlb_mfill_atomic_pte(struct mm_struct *dst_mm, pte_t *dst_pte,
> +int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> @@ -393,8 +393,7 @@ static inline void hugetlb_free_pgd_range(struct mmu_gather *tlb,
> }
>
> #ifdef CONFIG_USERFAULTFD
> -static inline int hugetlb_mfill_atomic_pte(struct mm_struct *dst_mm,
> - pte_t *dst_pte,
> +static inline int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> index 103d1000a5a2..b82916c25e61 100644
> --- a/include/linux/shmem_fs.h
> +++ b/include/linux/shmem_fs.h
> @@ -151,14 +151,14 @@ extern void shmem_uncharge(struct inode *inode, long pages);
>
> #ifdef CONFIG_USERFAULTFD
> #ifdef CONFIG_SHMEM
> -extern int shmem_mfill_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
> +extern int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> bool zeropage, bool wp_copy,
> struct page **pagep);
> #else /* !CONFIG_SHMEM */
> -#define shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr, \
> +#define shmem_mfill_atomic_pte(dst_pmd, dst_vma, dst_addr, \
> src_addr, zeropage, wp_copy, pagep) ({ BUG(); 0; })
> #endif /* CONFIG_SHMEM */
> #endif /* CONFIG_USERFAULTFD */
> diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
> index 468080125612..ba79e296fcc7 100644
> --- a/include/linux/userfaultfd_k.h
> +++ b/include/linux/userfaultfd_k.h
> @@ -56,7 +56,7 @@ enum mcopy_atomic_mode {
> MCOPY_ATOMIC_CONTINUE,
> };
>
> -extern int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
> +extern int mfill_atomic_install_pte(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr, struct page *page,
> bool newly_allocated, bool wp_copy);
> @@ -73,7 +73,7 @@ extern ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long dst
> extern int mwriteprotect_range(struct mm_struct *dst_mm,
> unsigned long start, unsigned long len,
> bool enable_wp, atomic_t *mmap_changing);
> -extern long uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *vma,
> +extern long uffd_wp_range(struct vm_area_struct *vma,
> unsigned long start, unsigned long len, bool enable_wp);
>
> /* mm helpers */
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 4c9276549394..fe043034ab46 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6157,8 +6157,7 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> * Used by userfaultfd UFFDIO_* ioctls. Based on userfaultfd's mfill_atomic_pte
> * with modifications for hugetlb pages.
> */
> -int hugetlb_mfill_atomic_pte(struct mm_struct *dst_mm,
> - pte_t *dst_pte,
> +int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> @@ -6166,6 +6165,7 @@ int hugetlb_mfill_atomic_pte(struct mm_struct *dst_mm,
> struct page **pagep,
> bool wp_copy)
> {
> + struct mm_struct *dst_mm = dst_vma->vm_mm;
> bool is_continue = (mode == MCOPY_ATOMIC_CONTINUE);
> struct hstate *h = hstate_vma(dst_vma);
> struct address_space *mapping = dst_vma->vm_file->f_mapping;
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 448f393d8ab2..1d751b6cf1ac 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2415,8 +2415,7 @@ static struct inode *shmem_get_inode(struct mnt_idmap *idmap, struct super_block
> }
>
> #ifdef CONFIG_USERFAULTFD
> -int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
> - pmd_t *dst_pmd,
> +int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> @@ -2506,11 +2505,11 @@ int shmem_mfill_atomic_pte(struct mm_struct *dst_mm,
> goto out_release;
>
> ret = shmem_add_to_page_cache(folio, mapping, pgoff, NULL,
> - gfp & GFP_RECLAIM_MASK, dst_mm);
> + gfp & GFP_RECLAIM_MASK, dst_vma->vm_mm);
> if (ret)
> goto out_release;
>
> - ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
> + ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
> &folio->page, true, wp_copy);
> if (ret)
> goto out_delete_from_cache;
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index 84db5b2fad3a..4fc373476739 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -55,12 +55,13 @@ struct vm_area_struct *find_dst_vma(struct mm_struct *dst_mm,
> * This function handles both MCOPY_ATOMIC_NORMAL and _CONTINUE for both shmem
> * and anon, and for both shared and private VMAs.
> */
> -int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
> +int mfill_atomic_install_pte(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr, struct page *page,
> bool newly_allocated, bool wp_copy)
> {
> int ret;
> + struct mm_struct *dst_mm = dst_vma->vm_mm;
> pte_t _dst_pte, *dst_pte;
> bool writable = dst_vma->vm_flags & VM_WRITE;
> bool vm_shared = dst_vma->vm_flags & VM_SHARED;
> @@ -127,8 +128,7 @@ int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
> return ret;
> }
>
> -static int mfill_atomic_pte_copy(struct mm_struct *dst_mm,
> - pmd_t *dst_pmd,
> +static int mfill_atomic_pte_copy(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> @@ -190,10 +190,10 @@ static int mfill_atomic_pte_copy(struct mm_struct *dst_mm,
> __SetPageUptodate(page);
>
> ret = -ENOMEM;
> - if (mem_cgroup_charge(page_folio(page), dst_mm, GFP_KERNEL))
> + if (mem_cgroup_charge(page_folio(page), dst_vma->vm_mm, GFP_KERNEL))
> goto out_release;
>
> - ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
> + ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
> page, true, wp_copy);
> if (ret)
> goto out_release;
> @@ -204,8 +204,7 @@ static int mfill_atomic_pte_copy(struct mm_struct *dst_mm,
> goto out;
> }
>
> -static int mfill_atomic_pte_zeropage(struct mm_struct *dst_mm,
> - pmd_t *dst_pmd,
> +static int mfill_atomic_pte_zeropage(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr)
> {
> @@ -217,7 +216,7 @@ static int mfill_atomic_pte_zeropage(struct mm_struct *dst_mm,
>
> _dst_pte = pte_mkspecial(pfn_pte(my_zero_pfn(dst_addr),
> dst_vma->vm_page_prot));
> - dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
> + dst_pte = pte_offset_map_lock(dst_vma->vm_mm, dst_pmd, dst_addr, &ptl);
> if (dst_vma->vm_file) {
> /* the shmem MAP_PRIVATE case requires checking the i_size */
> inode = dst_vma->vm_file->f_inode;
> @@ -230,7 +229,7 @@ static int mfill_atomic_pte_zeropage(struct mm_struct *dst_mm,
> ret = -EEXIST;
> if (!pte_none(*dst_pte))
> goto out_unlock;
> - set_pte_at(dst_mm, dst_addr, dst_pte, _dst_pte);
> + set_pte_at(dst_vma->vm_mm, dst_addr, dst_pte, _dst_pte);
> /* No need to invalidate - it was non-present before */
> update_mmu_cache(dst_vma, dst_addr, dst_pte);
> ret = 0;
> @@ -240,8 +239,7 @@ static int mfill_atomic_pte_zeropage(struct mm_struct *dst_mm,
> }
>
> /* Handles UFFDIO_CONTINUE for all shmem VMAs (shared or private). */
> -static int mfill_atomic_pte_continue(struct mm_struct *dst_mm,
> - pmd_t *dst_pmd,
> +static int mfill_atomic_pte_continue(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> bool wp_copy)
> @@ -269,7 +267,7 @@ static int mfill_atomic_pte_continue(struct mm_struct *dst_mm,
> goto out_release;
> }
>
> - ret = mfill_atomic_install_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
> + ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
> page, false, wp_copy);
> if (ret)
> goto out_release;
> @@ -310,7 +308,7 @@ static pmd_t *mm_alloc_pmd(struct mm_struct *mm, unsigned long address)
> * mfill_atomic processing for HUGETLB vmas. Note that this routine is
> * called with mmap_lock held, it will release mmap_lock before returning.
> */
> -static __always_inline ssize_t mfill_atomic_hugetlb(struct mm_struct *dst_mm,
> +static __always_inline ssize_t mfill_atomic_hugetlb(
> struct vm_area_struct *dst_vma,
> unsigned long dst_start,
> unsigned long src_start,
> @@ -318,6 +316,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(struct mm_struct *dst_mm,
> enum mcopy_atomic_mode mode,
> bool wp_copy)
> {
> + struct mm_struct *dst_mm = dst_vma->vm_mm;
> int vm_shared = dst_vma->vm_flags & VM_SHARED;
> ssize_t err;
> pte_t *dst_pte;
> @@ -411,7 +410,7 @@ static __always_inline ssize_t mfill_atomic_hugetlb(struct mm_struct *dst_mm,
> goto out_unlock;
> }
>
> - err = hugetlb_mfill_atomic_pte(dst_mm, dst_pte, dst_vma,
> + err = hugetlb_mfill_atomic_pte(dst_pte, dst_vma,
> dst_addr, src_addr, mode, &page,
> wp_copy);
>
> @@ -463,17 +462,15 @@ static __always_inline ssize_t mfill_atomic_hugetlb(struct mm_struct *dst_mm,
> }
> #else /* !CONFIG_HUGETLB_PAGE */
> /* fail at build time if gcc attempts to use this */
> -extern ssize_t mfill_atomic_hugetlb(struct mm_struct *dst_mm,
> - struct vm_area_struct *dst_vma,
> - unsigned long dst_start,
> - unsigned long src_start,
> - unsigned long len,
> - enum mcopy_atomic_mode mode,
> - bool wp_copy);
> +extern ssize_t mfill_atomic_hugetlb(struct vm_area_struct *dst_vma,
> + unsigned long dst_start,
> + unsigned long src_start,
> + unsigned long len,
> + enum mcopy_atomic_mode mode,
> + bool wp_copy);
> #endif /* CONFIG_HUGETLB_PAGE */
>
> -static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
> - pmd_t *dst_pmd,
> +static __always_inline ssize_t mfill_atomic_pte(pmd_t *dst_pmd,
> struct vm_area_struct *dst_vma,
> unsigned long dst_addr,
> unsigned long src_addr,
> @@ -484,7 +481,7 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
> ssize_t err;
>
> if (mode == MCOPY_ATOMIC_CONTINUE) {
> - return mfill_atomic_pte_continue(dst_mm, dst_pmd, dst_vma,
> + return mfill_atomic_pte_continue(dst_pmd, dst_vma,
> dst_addr, wp_copy);
> }
>
> @@ -500,14 +497,14 @@ static __always_inline ssize_t mfill_atomic_pte(struct mm_struct *dst_mm,
> */
> if (!(dst_vma->vm_flags & VM_SHARED)) {
> if (mode == MCOPY_ATOMIC_NORMAL)
> - err = mfill_atomic_pte_copy(dst_mm, dst_pmd, dst_vma,
> + err = mfill_atomic_pte_copy(dst_pmd, dst_vma,
> dst_addr, src_addr, page,
> wp_copy);
> else
> - err = mfill_atomic_pte_zeropage(dst_mm, dst_pmd,
> + err = mfill_atomic_pte_zeropage(dst_pmd,
> dst_vma, dst_addr);
> } else {
> - err = shmem_mfill_atomic_pte(dst_mm, dst_pmd, dst_vma,
> + err = shmem_mfill_atomic_pte(dst_pmd, dst_vma,
> dst_addr, src_addr,
> mode != MCOPY_ATOMIC_NORMAL,
> wp_copy, page);
> @@ -588,7 +585,7 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm,
> * If this is a HUGETLB vma, pass off to appropriate routine
> */
> if (is_vm_hugetlb_page(dst_vma))
> - return mfill_atomic_hugetlb(dst_mm, dst_vma, dst_start,
> + return mfill_atomic_hugetlb(dst_vma, dst_start,
> src_start, len, mcopy_mode,
> wp_copy);
>
> @@ -641,7 +638,7 @@ static __always_inline ssize_t mfill_atomic(struct mm_struct *dst_mm,
> BUG_ON(pmd_none(*dst_pmd));
> BUG_ON(pmd_trans_huge(*dst_pmd));
>
> - err = mfill_atomic_pte(dst_mm, dst_pmd, dst_vma, dst_addr,
> + err = mfill_atomic_pte(dst_pmd, dst_vma, dst_addr,
> src_addr, &page, mcopy_mode, wp_copy);
> cond_resched();
>
> @@ -710,7 +707,7 @@ ssize_t mfill_atomic_continue(struct mm_struct *dst_mm, unsigned long start,
> mmap_changing, 0);
> }
>
> -long uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma,
> +long uffd_wp_range(struct vm_area_struct *dst_vma,
> unsigned long start, unsigned long len, bool enable_wp)
> {
> unsigned int mm_cp_flags;
> @@ -730,7 +727,7 @@ long uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma,
> */
> if (!enable_wp && vma_wants_manual_pte_write_upgrade(dst_vma))
> mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
> - tlb_gather_mmu(&tlb, dst_mm);
> + tlb_gather_mmu(&tlb, dst_vma->vm_mm);
> ret = change_protection(&tlb, dst_vma, start, start + len, mm_cp_flags);
> tlb_finish_mmu(&tlb);
>
> @@ -782,7 +779,7 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
> goto out_unlock;
> }
>
> - err = uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp);
> + err = uffd_wp_range(dst_vma, start, len, enable_wp);
>
> /* Return 0 on success, <0 on failures */
> if (err > 0)
> --
> 2.40.0.rc1.284.g88254d51c5-goog
>

--
Sincerely yours,
Mike.

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In reply to: Axel Rasmussen: "[PATCH v4 2/4] mm: userfaultfd: don't pass around both mm and vma"
Next in thread: Axel Rasmussen: "[PATCH v4 3/4] mm: userfaultfd: combine 'mode' and 'wp_copy' arguments"
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