Re: [PATCH v3] mm: Change return type int to vm_fault_t for fault handlers

[Souptick Joarder]

On Mon, Jun 4, 2018 at 10:47 PM, Souptick Joarder <jrdr.linux@xxxxxxxxx> wrote:
> Use new return type vm_fault_t for fault handler. For
> now, this is just documenting that the function returns
> a VM_FAULT value rather than an errno. Once all instances
> are converted, vm_fault_t will become a distinct type.
>
> Ref-> commit 1c8f422059ae ("mm: change return type to vm_fault_t")
>
> The aim is to change the return type of finish_fault()
> and handle_mm_fault() to vm_fault_t type. As part of
> that clean up return type of all other recursively called
> functions have been changed to vm_fault_t type.
>
> The places from where handle_mm_fault() is getting invoked
> will be change to vm_fault_t type but in a separate patch.
>
> vmf_error() is the newly introduce inline function
> in 4.17-rc6.
>
> Signed-off-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
> Reviewed-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
> ---
> v2: Change patch title and fixed sparse warning.
>
> v3: Reviewed by Matthew Wilcox
>
>  fs/userfaultfd.c              |  6 +--
>  include/linux/huge_mm.h       | 10 +++--
>  include/linux/hugetlb.h       |  2 +-
>  include/linux/mm.h            | 14 +++----
>  include/linux/oom.h           |  2 +-
>  include/linux/swapops.h       |  5 ++-
>  include/linux/userfaultfd_k.h |  5 ++-
>  kernel/memremap.c             |  2 +-
>  mm/gup.c                      |  4 +-
>  mm/huge_memory.c              | 25 ++++++------
>  mm/hugetlb.c                  | 29 +++++++-------
>  mm/internal.h                 |  2 +-
>  mm/khugepaged.c               |  3 +-
>  mm/memory.c                   | 90 ++++++++++++++++++++++---------------------
>  mm/shmem.c                    | 17 ++++----
>  15 files changed, 110 insertions(+), 106 deletions(-)
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index cec550c..bf60c6a 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -336,17 +336,15 @@ static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
>   * fatal_signal_pending()s, and the mmap_sem must be released before
>   * returning it.
>   */
> -int handle_userfault(struct vm_fault *vmf, unsigned long reason)
> +vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
>  {
>         struct mm_struct *mm = vmf->vma->vm_mm;
>         struct userfaultfd_ctx *ctx;
>         struct userfaultfd_wait_queue uwq;
> -       int ret;
> +       vm_fault_t ret = VM_FAULT_SIGBUS;
>         bool must_wait, return_to_userland;
>         long blocking_state;
>
> -       ret = VM_FAULT_SIGBUS;
> -
>         /*
>          * We don't do userfault handling for the final child pid update.
>          *
> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
> index a8a1262..8c4f0a6 100644
> --- a/include/linux/huge_mm.h
> +++ b/include/linux/huge_mm.h
> @@ -3,10 +3,11 @@
>  #define _LINUX_HUGE_MM_H
>
>  #include <linux/sched/coredump.h>
> +#include <linux/mm_types.h>
>
>  #include <linux/fs.h> /* only for vma_is_dax() */
>
> -extern int do_huge_pmd_anonymous_page(struct vm_fault *vmf);
> +extern vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf);
>  extern int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
>                          pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
>                          struct vm_area_struct *vma);
> @@ -23,7 +24,7 @@ static inline void huge_pud_set_accessed(struct vm_fault *vmf, pud_t orig_pud)
>  }
>  #endif
>
> -extern int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd);
> +extern vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd);
>  extern struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
>                                           unsigned long addr,
>                                           pmd_t *pmd,
> @@ -216,7 +217,7 @@ struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
>  struct page *follow_devmap_pud(struct vm_area_struct *vma, unsigned long addr,
>                 pud_t *pud, int flags);
>
> -extern int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t orig_pmd);
> +extern vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t orig_pmd);
>
>  extern struct page *huge_zero_page;
>
> @@ -321,7 +322,8 @@ static inline spinlock_t *pud_trans_huge_lock(pud_t *pud,
>         return NULL;
>  }
>
> -static inline int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t orig_pmd)
> +static inline vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf,
> +               pmd_t orig_pmd)
>  {
>         return 0;
>  }
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 36fa6a2..c779b2f 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -105,7 +105,7 @@ void __unmap_hugepage_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
>  int hugetlb_report_node_meminfo(int, char *);
>  void hugetlb_show_meminfo(void);
>  unsigned long hugetlb_total_pages(void);
> -int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> +vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>                         unsigned long address, unsigned int flags);
>  int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm, pte_t *dst_pte,
>                                 struct vm_area_struct *dst_vma,
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 02a616e..2971bff 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -694,10 +694,10 @@ static inline pte_t maybe_mkwrite(pte_t pte, struct vm_area_struct *vma)
>         return pte;
>  }
>
> -int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
> +vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
>                 struct page *page);
> -int finish_fault(struct vm_fault *vmf);
> -int finish_mkwrite_fault(struct vm_fault *vmf);
> +vm_fault_t finish_fault(struct vm_fault *vmf);
> +vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf);
>  #endif
>
>  /*
> @@ -1343,8 +1343,8 @@ int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
>  int invalidate_inode_page(struct page *page);
>
>  #ifdef CONFIG_MMU
> -extern int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> -               unsigned int flags);
> +extern vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
> +                       unsigned long address, unsigned int flags);
>  extern int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
>                             unsigned long address, unsigned int fault_flags,
>                             bool *unlocked);
> @@ -1353,7 +1353,7 @@ void unmap_mapping_pages(struct address_space *mapping,
>  void unmap_mapping_range(struct address_space *mapping,
>                 loff_t const holebegin, loff_t const holelen, int even_cows);
>  #else
> -static inline int handle_mm_fault(struct vm_area_struct *vma,
> +static inline vm_fault_t handle_mm_fault(struct vm_area_struct *vma,
>                 unsigned long address, unsigned int flags)
>  {
>         /* should never happen if there's no MMU */
> @@ -2501,7 +2501,7 @@ static inline struct page *follow_page(struct vm_area_struct *vma,
>  #define FOLL_COW       0x4000  /* internal GUP flag */
>  #define FOLL_ANON      0x8000  /* don't do file mappings */
>
> -static inline int vm_fault_to_errno(int vm_fault, int foll_flags)
> +static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags)
>  {
>         if (vm_fault & VM_FAULT_OOM)
>                 return -ENOMEM;
> diff --git a/include/linux/oom.h b/include/linux/oom.h
> index 6adac11..9d30c15 100644
> --- a/include/linux/oom.h
> +++ b/include/linux/oom.h
> @@ -88,7 +88,7 @@ static inline bool mm_is_oom_victim(struct mm_struct *mm)
>   *
>   * Return 0 when the PF is safe VM_FAULT_SIGBUS otherwise.
>   */
> -static inline int check_stable_address_space(struct mm_struct *mm)
> +static inline vm_fault_t check_stable_address_space(struct mm_struct *mm)
>  {
>         if (unlikely(test_bit(MMF_UNSTABLE, &mm->flags)))
>                 return VM_FAULT_SIGBUS;
> diff --git a/include/linux/swapops.h b/include/linux/swapops.h
> index 1d3877c..9bc8ddb 100644
> --- a/include/linux/swapops.h
> +++ b/include/linux/swapops.h
> @@ -4,6 +4,7 @@
>
>  #include <linux/radix-tree.h>
>  #include <linux/bug.h>
> +#include <linux/mm_types.h>
>
>  /*
>   * swapcache pages are stored in the swapper_space radix tree.  We want to
> @@ -134,7 +135,7 @@ static inline struct page *device_private_entry_to_page(swp_entry_t entry)
>         return pfn_to_page(swp_offset(entry));
>  }
>
> -int device_private_entry_fault(struct vm_area_struct *vma,
> +vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
>                        unsigned long addr,
>                        swp_entry_t entry,
>                        unsigned int flags,
> @@ -169,7 +170,7 @@ static inline struct page *device_private_entry_to_page(swp_entry_t entry)
>         return NULL;
>  }
>
> -static inline int device_private_entry_fault(struct vm_area_struct *vma,
> +static inline vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
>                                      unsigned long addr,
>                                      swp_entry_t entry,
>                                      unsigned int flags,
> diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
> index f2f3b68..1f36c80 100644
> --- a/include/linux/userfaultfd_k.h
> +++ b/include/linux/userfaultfd_k.h
> @@ -28,7 +28,7 @@
>  #define UFFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
>  #define UFFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS)
>
> -extern int handle_userfault(struct vm_fault *vmf, unsigned long reason);
> +extern vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason);
>
>  extern ssize_t mcopy_atomic(struct mm_struct *dst_mm, unsigned long dst_start,
>                             unsigned long src_start, unsigned long len);
> @@ -75,7 +75,8 @@ extern void userfaultfd_unmap_complete(struct mm_struct *mm,
>  #else /* CONFIG_USERFAULTFD */
>
>  /* mm helpers */
> -static inline int handle_userfault(struct vm_fault *vmf, unsigned long reason)
> +static inline vm_fault_t handle_userfault(struct vm_fault *vmf,
> +                               unsigned long reason)
>  {
>         return VM_FAULT_SIGBUS;
>  }
> diff --git a/kernel/memremap.c b/kernel/memremap.c
> index 895e6b7..d148d09 100644
> --- a/kernel/memremap.c
> +++ b/kernel/memremap.c
> @@ -214,7 +214,7 @@ static unsigned long order_at(struct resource *res, unsigned long pgoff)
>                         pgoff += 1UL << order, order = order_at((res), pgoff))
>
>  #if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
> -int device_private_entry_fault(struct vm_area_struct *vma,
> +vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
>                        unsigned long addr,
>                        swp_entry_t entry,
>                        unsigned int flags,
> diff --git a/mm/gup.c b/mm/gup.c
> index 541904a..e3a957e 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -481,7 +481,7 @@ static int faultin_page(struct task_struct *tsk, struct vm_area_struct *vma,
>                 unsigned long address, unsigned int *flags, int *nonblocking)
>  {
>         unsigned int fault_flags = 0;
> -       int ret;
> +       vm_fault_t ret;
>
>         /* mlock all present pages, but do not fault in new pages */
>         if ((*flags & (FOLL_POPULATE | FOLL_MLOCK)) == FOLL_MLOCK)
> @@ -802,7 +802,7 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
>                      bool *unlocked)
>  {
>         struct vm_area_struct *vma;
> -       int ret, major = 0;
> +       vm_fault_t ret, major = 0;
>
>         if (unlocked)
>                 fault_flags |= FAULT_FLAG_ALLOW_RETRY;
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index a3a1815..82dc477 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -544,14 +544,14 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
>  }
>  EXPORT_SYMBOL_GPL(thp_get_unmapped_area);
>
> -static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
> -               gfp_t gfp)
> +static vm_fault_t __do_huge_pmd_anonymous_page(struct vm_fault *vmf,
> +                       struct page *page, gfp_t gfp)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct mem_cgroup *memcg;
>         pgtable_t pgtable;
>         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
> -       int ret = 0;
> +       vm_fault_t ret = 0;
>
>         VM_BUG_ON_PAGE(!PageCompound(page), page);
>
> @@ -587,7 +587,7 @@ static int __do_huge_pmd_anonymous_page(struct vm_fault *vmf, struct page *page,
>
>                 /* Deliver the page fault to userland */
>                 if (userfaultfd_missing(vma)) {
> -                       int ret;
> +                       vm_fault_t ret;
>
>                         spin_unlock(vmf->ptl);
>                         mem_cgroup_cancel_charge(page, memcg, true);
> @@ -666,7 +666,7 @@ static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
>         return true;
>  }
>
> -int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
> +vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         gfp_t gfp;
> @@ -685,7 +685,7 @@ int do_huge_pmd_anonymous_page(struct vm_fault *vmf)
>                 pgtable_t pgtable;
>                 struct page *zero_page;
>                 bool set;
> -               int ret;
> +               vm_fault_t ret;
>                 pgtable = pte_alloc_one(vma->vm_mm, haddr);
>                 if (unlikely(!pgtable))
>                         return VM_FAULT_OOM;
> @@ -1121,15 +1121,16 @@ void huge_pmd_set_accessed(struct vm_fault *vmf, pmd_t orig_pmd)
>         spin_unlock(vmf->ptl);
>  }
>
> -static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
> -               struct page *page)
> +static vm_fault_t do_huge_pmd_wp_page_fallback(struct vm_fault *vmf,
> +                       pmd_t orig_pmd, struct page *page)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
>         struct mem_cgroup *memcg;
>         pgtable_t pgtable;
>         pmd_t _pmd;
> -       int ret = 0, i;
> +       int i;
> +       vm_fault_t ret = 0;
>         struct page **pages;
>         unsigned long mmun_start;       /* For mmu_notifiers */
>         unsigned long mmun_end;         /* For mmu_notifiers */
> @@ -1239,7 +1240,7 @@ static int do_huge_pmd_wp_page_fallback(struct vm_fault *vmf, pmd_t orig_pmd,
>         goto out;
>  }
>
> -int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
> +vm_fault_t do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct page *page = NULL, *new_page;
> @@ -1248,7 +1249,7 @@ int do_huge_pmd_wp_page(struct vm_fault *vmf, pmd_t orig_pmd)
>         unsigned long mmun_start;       /* For mmu_notifiers */
>         unsigned long mmun_end;         /* For mmu_notifiers */
>         gfp_t huge_gfp;                 /* for allocation and charge */
> -       int ret = 0;
> +       vm_fault_t ret = 0;
>
>         vmf->ptl = pmd_lockptr(vma->vm_mm, vmf->pmd);
>         VM_BUG_ON_VMA(!vma->anon_vma, vma);
> @@ -1459,7 +1460,7 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
>  }
>
>  /* NUMA hinting page fault entry point for trans huge pmds */
> -int do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
> +vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf, pmd_t pmd)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct anon_vma *anon_vma = NULL;
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 2186791..d17b186 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -3499,14 +3499,15 @@ static void unmap_ref_private(struct mm_struct *mm, struct vm_area_struct *vma,
>   * cannot race with other handlers or page migration.
>   * Keep the pte_same checks anyway to make transition from the mutex easier.
>   */
> -static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
> +static vm_fault_t hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
>                        unsigned long address, pte_t *ptep,
>                        struct page *pagecache_page, spinlock_t *ptl)
>  {
>         pte_t pte;
>         struct hstate *h = hstate_vma(vma);
>         struct page *old_page, *new_page;
> -       int ret = 0, outside_reserve = 0;
> +       int outside_reserve = 0;
> +       vm_fault_t ret = 0;
>         unsigned long mmun_start;       /* For mmu_notifiers */
>         unsigned long mmun_end;         /* For mmu_notifiers */
>
> @@ -3570,8 +3571,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
>                         return 0;
>                 }
>
> -               ret = (PTR_ERR(new_page) == -ENOMEM) ?
> -                       VM_FAULT_OOM : VM_FAULT_SIGBUS;
> +               ret = vmf_error(PTR_ERR(new_page));
>                 goto out_release_old;
>         }
>
> @@ -3675,12 +3675,13 @@ int huge_add_to_page_cache(struct page *page, struct address_space *mapping,
>         return 0;
>  }
>
> -static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> -                          struct address_space *mapping, pgoff_t idx,
> -                          unsigned long address, pte_t *ptep, unsigned int flags)
> +static vm_fault_t hugetlb_no_page(struct mm_struct *mm,
> +                       struct vm_area_struct *vma,
> +                       struct address_space *mapping, pgoff_t idx,
> +                       unsigned long address, pte_t *ptep, unsigned int flags)
>  {
>         struct hstate *h = hstate_vma(vma);
> -       int ret = VM_FAULT_SIGBUS;
> +       vm_fault_t ret = VM_FAULT_SIGBUS;
>         int anon_rmap = 0;
>         unsigned long size;
>         struct page *page;
> @@ -3742,11 +3743,7 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
>
>                 page = alloc_huge_page(vma, address, 0);
>                 if (IS_ERR(page)) {
> -                       ret = PTR_ERR(page);
> -                       if (ret == -ENOMEM)
> -                               ret = VM_FAULT_OOM;
> -                       else
> -                               ret = VM_FAULT_SIGBUS;
> +                       ret = vmf_error(PTR_ERR(page));
>                         goto out;
>                 }
>                 clear_huge_page(page, address, pages_per_huge_page(h));
> @@ -3870,12 +3867,12 @@ u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
>  }
>  #endif
>
> -int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> +vm_fault_t hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
>                         unsigned long address, unsigned int flags)
>  {
>         pte_t *ptep, entry;
>         spinlock_t *ptl;
> -       int ret;
> +       vm_fault_t ret;
>         u32 hash;
>         pgoff_t idx;
>         struct page *page = NULL;
> @@ -4206,7 +4203,7 @@ long follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
>                 if (absent || is_swap_pte(huge_ptep_get(pte)) ||
>                     ((flags & FOLL_WRITE) &&
>                       !huge_pte_write(huge_ptep_get(pte)))) {
> -                       int ret;
> +                       vm_fault_t ret;
>                         unsigned int fault_flags = 0;
>
>                         if (pte)
> diff --git a/mm/internal.h b/mm/internal.h
> index 502d141..4044456 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -38,7 +38,7 @@
>
>  void page_writeback_init(void);
>
> -int do_swap_page(struct vm_fault *vmf);
> +vm_fault_t do_swap_page(struct vm_fault *vmf);
>
>  void free_pgtables(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
>                 unsigned long floor, unsigned long ceiling);
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index d7b2a4b..778fd40 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -880,7 +880,8 @@ static bool __collapse_huge_page_swapin(struct mm_struct *mm,
>                                         unsigned long address, pmd_t *pmd,
>                                         int referenced)
>  {
> -       int swapped_in = 0, ret = 0;
> +       int swapped_in = 0;
> +       vm_fault_t ret = 0;
>         struct vm_fault vmf = {
>                 .vma = vma,
>                 .address = address,
> diff --git a/mm/memory.c b/mm/memory.c
> index 01f5464..cee8245 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2360,9 +2360,9 @@ static gfp_t __get_fault_gfp_mask(struct vm_area_struct *vma)
>   *
>   * We do this without the lock held, so that it can sleep if it needs to.
>   */
> -static int do_page_mkwrite(struct vm_fault *vmf)
> +static vm_fault_t do_page_mkwrite(struct vm_fault *vmf)
>  {
> -       int ret;
> +       vm_fault_t ret;
>         struct page *page = vmf->page;
>         unsigned int old_flags = vmf->flags;
>
> @@ -2466,7 +2466,7 @@ static inline void wp_page_reuse(struct vm_fault *vmf)
>   *   held to the old page, as well as updating the rmap.
>   * - In any case, unlock the PTL and drop the reference we took to the old page.
>   */
> -static int wp_page_copy(struct vm_fault *vmf)
> +static vm_fault_t wp_page_copy(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct mm_struct *mm = vma->vm_mm;
> @@ -2614,7 +2614,7 @@ static int wp_page_copy(struct vm_fault *vmf)
>   * The function expects the page to be locked or other protection against
>   * concurrent faults / writeback (such as DAX radix tree locks).
>   */
> -int finish_mkwrite_fault(struct vm_fault *vmf)
> +vm_fault_t finish_mkwrite_fault(struct vm_fault *vmf)
>  {
>         WARN_ON_ONCE(!(vmf->vma->vm_flags & VM_SHARED));
>         vmf->pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd, vmf->address,
> @@ -2635,12 +2635,12 @@ int finish_mkwrite_fault(struct vm_fault *vmf)
>   * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED
>   * mapping
>   */
> -static int wp_pfn_shared(struct vm_fault *vmf)
> +static vm_fault_t wp_pfn_shared(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>
>         if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
> -               int ret;
> +               vm_fault_t ret;
>
>                 pte_unmap_unlock(vmf->pte, vmf->ptl);
>                 vmf->flags |= FAULT_FLAG_MKWRITE;
> @@ -2653,7 +2653,7 @@ static int wp_pfn_shared(struct vm_fault *vmf)
>         return VM_FAULT_WRITE;
>  }
>
> -static int wp_page_shared(struct vm_fault *vmf)
> +static vm_fault_t wp_page_shared(struct vm_fault *vmf)
>         __releases(vmf->ptl)
>  {
>         struct vm_area_struct *vma = vmf->vma;
> @@ -2661,7 +2661,7 @@ static int wp_page_shared(struct vm_fault *vmf)
>         get_page(vmf->page);
>
>         if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
> -               int tmp;
> +               vm_fault_t tmp;
>
>                 pte_unmap_unlock(vmf->pte, vmf->ptl);
>                 tmp = do_page_mkwrite(vmf);
> @@ -2704,7 +2704,7 @@ static int wp_page_shared(struct vm_fault *vmf)
>   * but allow concurrent faults), with pte both mapped and locked.
>   * We return with mmap_sem still held, but pte unmapped and unlocked.
>   */
> -static int do_wp_page(struct vm_fault *vmf)
> +static vm_fault_t do_wp_page(struct vm_fault *vmf)
>         __releases(vmf->ptl)
>  {
>         struct vm_area_struct *vma = vmf->vma;
> @@ -2880,7 +2880,7 @@ void unmap_mapping_range(struct address_space *mapping,
>   * We return with the mmap_sem locked or unlocked in the same cases
>   * as does filemap_fault().
>   */
> -int do_swap_page(struct vm_fault *vmf)
> +vm_fault_t do_swap_page(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct page *page = NULL, *swapcache;
> @@ -2889,7 +2889,7 @@ int do_swap_page(struct vm_fault *vmf)
>         pte_t pte;
>         int locked;
>         int exclusive = 0;
> -       int ret = 0;
> +       vm_fault_t ret = 0;
>
>         if (!pte_unmap_same(vma->vm_mm, vmf->pmd, vmf->pte, vmf->orig_pte))
>                 goto out;
> @@ -3100,12 +3100,12 @@ int do_swap_page(struct vm_fault *vmf)
>   * but allow concurrent faults), and pte mapped but not yet locked.
>   * We return with mmap_sem still held, but pte unmapped and unlocked.
>   */
> -static int do_anonymous_page(struct vm_fault *vmf)
> +static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct mem_cgroup *memcg;
>         struct page *page;
> -       int ret = 0;
> +       vm_fault_t ret = 0;
>         pte_t entry;
>
>         /* File mapping without ->vm_ops ? */
> @@ -3214,10 +3214,10 @@ static int do_anonymous_page(struct vm_fault *vmf)
>   * released depending on flags and vma->vm_ops->fault() return value.
>   * See filemap_fault() and __lock_page_retry().
>   */
> -static int __do_fault(struct vm_fault *vmf)
> +static vm_fault_t __do_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
> -       int ret;
> +       vm_fault_t ret;
>
>         ret = vma->vm_ops->fault(vmf);
>         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY |
> @@ -3251,7 +3251,7 @@ static int pmd_devmap_trans_unstable(pmd_t *pmd)
>         return pmd_devmap(*pmd) || pmd_trans_unstable(pmd);
>  }
>
> -static int pte_alloc_one_map(struct vm_fault *vmf)
> +static vm_fault_t pte_alloc_one_map(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>
> @@ -3327,13 +3327,14 @@ static void deposit_prealloc_pte(struct vm_fault *vmf)
>         vmf->prealloc_pte = NULL;
>  }
>
> -static int do_set_pmd(struct vm_fault *vmf, struct page *page)
> +static vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         bool write = vmf->flags & FAULT_FLAG_WRITE;
>         unsigned long haddr = vmf->address & HPAGE_PMD_MASK;
>         pmd_t entry;
> -       int i, ret;
> +       int i;
> +       vm_fault_t ret;
>
>         if (!transhuge_vma_suitable(vma, haddr))
>                 return VM_FAULT_FALLBACK;
> @@ -3383,7 +3384,7 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page)
>         return ret;
>  }
>  #else
> -static int do_set_pmd(struct vm_fault *vmf, struct page *page)
> +static vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page)
>  {
>         BUILD_BUG();
>         return 0;
> @@ -3404,13 +3405,13 @@ static int do_set_pmd(struct vm_fault *vmf, struct page *page)
>   * Target users are page handler itself and implementations of
>   * vm_ops->map_pages.
>   */
> -int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
> +vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
>                 struct page *page)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         bool write = vmf->flags & FAULT_FLAG_WRITE;
>         pte_t entry;
> -       int ret;
> +       vm_fault_t ret;
>
>         if (pmd_none(*vmf->pmd) && PageTransCompound(page) &&
>                         IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE)) {
> @@ -3469,10 +3470,10 @@ int alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg,
>   * The function expects the page to be locked and on success it consumes a
>   * reference of a page being mapped (for the PTE which maps it).
>   */
> -int finish_fault(struct vm_fault *vmf)
> +vm_fault_t finish_fault(struct vm_fault *vmf)
>  {
>         struct page *page;
> -       int ret = 0;
> +       vm_fault_t ret = 0;
>
>         /* Did we COW the page? */
>         if ((vmf->flags & FAULT_FLAG_WRITE) &&
> @@ -3558,12 +3559,13 @@ static int __init fault_around_debugfs(void)
>   * (and therefore to page order).  This way it's easier to guarantee
>   * that we don't cross page table boundaries.
>   */
> -static int do_fault_around(struct vm_fault *vmf)
> +static vm_fault_t do_fault_around(struct vm_fault *vmf)
>  {
>         unsigned long address = vmf->address, nr_pages, mask;
>         pgoff_t start_pgoff = vmf->pgoff;
>         pgoff_t end_pgoff;
> -       int off, ret = 0;
> +       int off;
> +       vm_fault_t ret = 0;
>
>         nr_pages = READ_ONCE(fault_around_bytes) >> PAGE_SHIFT;
>         mask = ~(nr_pages * PAGE_SIZE - 1) & PAGE_MASK;
> @@ -3613,10 +3615,10 @@ static int do_fault_around(struct vm_fault *vmf)
>         return ret;
>  }
>
> -static int do_read_fault(struct vm_fault *vmf)
> +static vm_fault_t do_read_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
> -       int ret = 0;
> +       vm_fault_t ret = 0;
>
>         /*
>          * Let's call ->map_pages() first and use ->fault() as fallback
> @@ -3640,10 +3642,10 @@ static int do_read_fault(struct vm_fault *vmf)
>         return ret;
>  }
>
> -static int do_cow_fault(struct vm_fault *vmf)
> +static vm_fault_t do_cow_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
> -       int ret;
> +       vm_fault_t ret;
>
>         if (unlikely(anon_vma_prepare(vma)))
>                 return VM_FAULT_OOM;
> @@ -3679,10 +3681,10 @@ static int do_cow_fault(struct vm_fault *vmf)
>         return ret;
>  }
>
> -static int do_shared_fault(struct vm_fault *vmf)
> +static vm_fault_t do_shared_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
> -       int ret, tmp;
> +       vm_fault_t ret, tmp;
>
>         ret = __do_fault(vmf);
>         if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY)))
> @@ -3720,10 +3722,10 @@ static int do_shared_fault(struct vm_fault *vmf)
>   * The mmap_sem may have been released depending on flags and our
>   * return value.  See filemap_fault() and __lock_page_or_retry().
>   */
> -static int do_fault(struct vm_fault *vmf)
> +static vm_fault_t do_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
> -       int ret;
> +       vm_fault_t ret;
>
>         /* The VMA was not fully populated on mmap() or missing VM_DONTEXPAND */
>         if (!vma->vm_ops->fault)
> @@ -3758,7 +3760,7 @@ static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
>         return mpol_misplaced(page, vma, addr);
>  }
>
> -static int do_numa_page(struct vm_fault *vmf)
> +static vm_fault_t do_numa_page(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct page *page = NULL;
> @@ -3848,7 +3850,7 @@ static int do_numa_page(struct vm_fault *vmf)
>         return 0;
>  }
>
> -static inline int create_huge_pmd(struct vm_fault *vmf)
> +static inline vm_fault_t create_huge_pmd(struct vm_fault *vmf)
>  {
>         if (vma_is_anonymous(vmf->vma))
>                 return do_huge_pmd_anonymous_page(vmf);
> @@ -3858,7 +3860,7 @@ static inline int create_huge_pmd(struct vm_fault *vmf)
>  }
>
>  /* `inline' is required to avoid gcc 4.1.2 build error */
> -static inline int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
> +static inline vm_fault_t wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
>  {
>         if (vma_is_anonymous(vmf->vma))
>                 return do_huge_pmd_wp_page(vmf, orig_pmd);
> @@ -3877,7 +3879,7 @@ static inline bool vma_is_accessible(struct vm_area_struct *vma)
>         return vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE);
>  }
>
> -static int create_huge_pud(struct vm_fault *vmf)
> +static vm_fault_t create_huge_pud(struct vm_fault *vmf)
>  {
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>         /* No support for anonymous transparent PUD pages yet */
> @@ -3889,7 +3891,7 @@ static int create_huge_pud(struct vm_fault *vmf)
>         return VM_FAULT_FALLBACK;
>  }
>
> -static int wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
> +static vm_fault_t wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
>  {
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>         /* No support for anonymous transparent PUD pages yet */
> @@ -3916,7 +3918,7 @@ static int wp_huge_pud(struct vm_fault *vmf, pud_t orig_pud)
>   * The mmap_sem may have been released depending on flags and our return value.
>   * See filemap_fault() and __lock_page_or_retry().
>   */
> -static int handle_pte_fault(struct vm_fault *vmf)
> +static vm_fault_t handle_pte_fault(struct vm_fault *vmf)
>  {
>         pte_t entry;
>
> @@ -4004,8 +4006,8 @@ static int handle_pte_fault(struct vm_fault *vmf)
>   * The mmap_sem may have been released depending on flags and our
>   * return value.  See filemap_fault() and __lock_page_or_retry().
>   */
> -static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> -               unsigned int flags)
> +static vm_fault_t __handle_mm_fault(struct vm_area_struct *vma,
> +               unsigned long address, unsigned int flags)
>  {
>         struct vm_fault vmf = {
>                 .vma = vma,
> @@ -4018,7 +4020,7 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
>         struct mm_struct *mm = vma->vm_mm;
>         pgd_t *pgd;
>         p4d_t *p4d;
> -       int ret;
> +       vm_fault_t ret;
>
>         pgd = pgd_offset(mm, address);
>         p4d = p4d_alloc(mm, pgd, address);
> @@ -4093,10 +4095,10 @@ static int __handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
>   * The mmap_sem may have been released depending on flags and our
>   * return value.  See filemap_fault() and __lock_page_or_retry().
>   */
> -int handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> +vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
>                 unsigned int flags)
>  {
> -       int ret;
> +       vm_fault_t ret;
>
>         __set_current_state(TASK_RUNNING);
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 9d6c7e5..af05c35 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -123,7 +123,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
>  static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
>                 struct page **pagep, enum sgp_type sgp,
>                 gfp_t gfp, struct vm_area_struct *vma,
> -               struct vm_fault *vmf, int *fault_type);
> +               struct vm_fault *vmf, vm_fault_t *fault_type);
>
>  int shmem_getpage(struct inode *inode, pgoff_t index,
>                 struct page **pagep, enum sgp_type sgp)
> @@ -1604,7 +1604,8 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp,
>   */
>  static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
>         struct page **pagep, enum sgp_type sgp, gfp_t gfp,
> -       struct vm_area_struct *vma, struct vm_fault *vmf, int *fault_type)
> +       struct vm_area_struct *vma, struct vm_fault *vmf,
> +                       vm_fault_t *fault_type)
>  {
>         struct address_space *mapping = inode->i_mapping;
>         struct shmem_inode_info *info = SHMEM_I(inode);
> @@ -1931,14 +1932,14 @@ static int synchronous_wake_function(wait_queue_entry_t *wait, unsigned mode, in
>         return ret;
>  }
>
> -static int shmem_fault(struct vm_fault *vmf)
> +static vm_fault_t shmem_fault(struct vm_fault *vmf)
>  {
>         struct vm_area_struct *vma = vmf->vma;
>         struct inode *inode = file_inode(vma->vm_file);
>         gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
>         enum sgp_type sgp;
> -       int error;
> -       int ret = VM_FAULT_LOCKED;
> +       int err;
> +       vm_fault_t ret = VM_FAULT_LOCKED;
>
>         /*
>          * Trinity finds that probing a hole which tmpfs is punching can
> @@ -2006,10 +2007,10 @@ static int shmem_fault(struct vm_fault *vmf)
>         else if (vma->vm_flags & VM_HUGEPAGE)
>                 sgp = SGP_HUGE;
>
> -       error = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
> +       err = shmem_getpage_gfp(inode, vmf->pgoff, &vmf->page, sgp,
>                                   gfp, vma, vmf, &ret);
> -       if (error)
> -               return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
> +       if (err)
> +               ret = vmf_error(err);
>         return ret;
>  }
>
> --
> 1.9.1
>

Any further comment on this patch ?