[patch 109/181] mm: remove src/dst mm parameter in copy_page_range()

[Andrew Morton <akpm@linux-foundation.org>]

From: Peter Xu <peterx@redhat.com>
Subject: mm: remove src/dst mm parameter in copy_page_range()

Both of the mm pointers are not needed after commit 7a4830c380f3
("mm/fork: Pass new vma pointer into copy_page_range()").

Jason Gunthorpe also reported that the ordering of copy_page_range() is
odd.  Since working at it, reorder the parameters to be logical, by (1)
always put the dst_* fields to be before src_* fields, and (2) keep the
same type of parameters together.

[peterx@redhat.com: further reorder some parameters and line format, per Jason]
  Link: https://lkml.kernel.org/r/20201002192647.7161-1-peterx@redhat.com
[peterx@redhat.com: fix warnings]
  Link: https://lkml.kernel.org/r/20201006200138.GA6026@xz-x1
Link: https://lkml.kernel.org/r/20200930204950.6668-1-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reported-by: Kirill A. Shutemov <kirill@shutemov.name>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/mm.h |    4 -
 kernel/fork.c      |    2 
 mm/memory.c        |  141 ++++++++++++++++++++++---------------------
 3 files changed, 76 insertions(+), 71 deletions(-)

--- a/include/linux/mm.h~mm-remove-src-dst-mm-parameter-in-copy_page_range
+++ a/include/linux/mm.h
@@ -1653,8 +1653,8 @@ struct mmu_notifier_range;
 
 void free_pgd_range(struct mmu_gather *tlb, unsigned long addr,
 		unsigned long end, unsigned long floor, unsigned long ceiling);
-int copy_page_range(struct mm_struct *dst, struct mm_struct *src,
-		    struct vm_area_struct *vma, struct vm_area_struct *new);
+int
+copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma);
 int follow_pte_pmd(struct mm_struct *mm, unsigned long address,
 		   struct mmu_notifier_range *range,
 		   pte_t **ptepp, pmd_t **pmdpp, spinlock_t **ptlp);
--- a/kernel/fork.c~mm-remove-src-dst-mm-parameter-in-copy_page_range
+++ a/kernel/fork.c
@@ -590,7 +590,7 @@ static __latent_entropy int dup_mmap(str
 
 		mm->map_count++;
 		if (!(tmp->vm_flags & VM_WIPEONFORK))
-			retval = copy_page_range(mm, oldmm, mpnt, tmp);
+			retval = copy_page_range(tmp, mpnt);
 
 		if (tmp->vm_ops && tmp->vm_ops->open)
 			tmp->vm_ops->open(tmp);
--- a/mm/memory.c~mm-remove-src-dst-mm-parameter-in-copy_page_range
+++ a/mm/memory.c
@@ -794,15 +794,14 @@ copy_nonpresent_pte(struct mm_struct *ds
  * lock.
  */
 static inline int
-copy_present_page(struct mm_struct *dst_mm, struct mm_struct *src_mm,
-		pte_t *dst_pte, pte_t *src_pte,
-		struct vm_area_struct *vma, struct vm_area_struct *new,
-		unsigned long addr, int *rss, struct page **prealloc,
-		pte_t pte, struct page *page)
+copy_present_page(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
+		  pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss,
+		  struct page **prealloc, pte_t pte, struct page *page)
 {
+	struct mm_struct *src_mm = src_vma->vm_mm;
 	struct page *new_page;
 
-	if (!is_cow_mapping(vma->vm_flags))
+	if (!is_cow_mapping(src_vma->vm_flags))
 		return 1;
 
 	/*
@@ -832,16 +831,16 @@ copy_present_page(struct mm_struct *dst_
 	 * over and copy the page & arm it.
 	 */
 	*prealloc = NULL;
-	copy_user_highpage(new_page, page, addr, vma);
+	copy_user_highpage(new_page, page, addr, src_vma);
 	__SetPageUptodate(new_page);
-	page_add_new_anon_rmap(new_page, new, addr, false);
-	lru_cache_add_inactive_or_unevictable(new_page, new);
+	page_add_new_anon_rmap(new_page, dst_vma, addr, false);
+	lru_cache_add_inactive_or_unevictable(new_page, dst_vma);
 	rss[mm_counter(new_page)]++;
 
 	/* All done, just insert the new page copy in the child */
-	pte = mk_pte(new_page, new->vm_page_prot);
-	pte = maybe_mkwrite(pte_mkdirty(pte), new);
-	set_pte_at(dst_mm, addr, dst_pte, pte);
+	pte = mk_pte(new_page, dst_vma->vm_page_prot);
+	pte = maybe_mkwrite(pte_mkdirty(pte), dst_vma);
+	set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte);
 	return 0;
 }
 
@@ -850,24 +849,21 @@ copy_present_page(struct mm_struct *dst_
  * is required to copy this pte.
  */
 static inline int
-copy_present_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
-		pte_t *dst_pte, pte_t *src_pte, struct vm_area_struct *vma,
-		struct vm_area_struct *new,
-		unsigned long addr, int *rss, struct page **prealloc)
+copy_present_pte(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
+		 pte_t *dst_pte, pte_t *src_pte, unsigned long addr, int *rss,
+		 struct page **prealloc)
 {
-	unsigned long vm_flags = vma->vm_flags;
+	struct mm_struct *src_mm = src_vma->vm_mm;
+	unsigned long vm_flags = src_vma->vm_flags;
 	pte_t pte = *src_pte;
 	struct page *page;
 
-	page = vm_normal_page(vma, addr, pte);
+	page = vm_normal_page(src_vma, addr, pte);
 	if (page) {
 		int retval;
 
-		retval = copy_present_page(dst_mm, src_mm,
-			dst_pte, src_pte,
-			vma, new,
-			addr, rss, prealloc,
-			pte, page);
+		retval = copy_present_page(dst_vma, src_vma, dst_pte, src_pte,
+					   addr, rss, prealloc, pte, page);
 		if (retval <= 0)
 			return retval;
 
@@ -901,7 +897,7 @@ copy_present_pte(struct mm_struct *dst_m
 	if (!(vm_flags & VM_UFFD_WP))
 		pte = pte_clear_uffd_wp(pte);
 
-	set_pte_at(dst_mm, addr, dst_pte, pte);
+	set_pte_at(dst_vma->vm_mm, addr, dst_pte, pte);
 	return 0;
 }
 
@@ -924,11 +920,13 @@ page_copy_prealloc(struct mm_struct *src
 	return new_page;
 }
 
-static int copy_pte_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
-		   pmd_t *dst_pmd, pmd_t *src_pmd, struct vm_area_struct *vma,
-		   struct vm_area_struct *new,
-		   unsigned long addr, unsigned long end)
+static int
+copy_pte_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
+	       pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
+	       unsigned long end)
 {
+	struct mm_struct *dst_mm = dst_vma->vm_mm;
+	struct mm_struct *src_mm = src_vma->vm_mm;
 	pte_t *orig_src_pte, *orig_dst_pte;
 	pte_t *src_pte, *dst_pte;
 	spinlock_t *src_ptl, *dst_ptl;
@@ -971,15 +969,15 @@ again:
 		if (unlikely(!pte_present(*src_pte))) {
 			entry.val = copy_nonpresent_pte(dst_mm, src_mm,
 							dst_pte, src_pte,
-							vma, addr, rss);
+							src_vma, addr, rss);
 			if (entry.val)
 				break;
 			progress += 8;
 			continue;
 		}
 		/* copy_present_pte() will clear `*prealloc' if consumed */
-		ret = copy_present_pte(dst_mm, src_mm, dst_pte, src_pte,
-				       vma, new, addr, rss, &prealloc);
+		ret = copy_present_pte(dst_vma, src_vma, dst_pte, src_pte,
+				       addr, rss, &prealloc);
 		/*
 		 * If we need a pre-allocated page for this pte, drop the
 		 * locks, allocate, and try again.
@@ -1014,7 +1012,7 @@ again:
 		entry.val = 0;
 	} else if (ret) {
 		WARN_ON_ONCE(ret != -EAGAIN);
-		prealloc = page_copy_prealloc(src_mm, vma, addr);
+		prealloc = page_copy_prealloc(src_mm, src_vma, addr);
 		if (!prealloc)
 			return -ENOMEM;
 		/* We've captured and resolved the error. Reset, try again. */
@@ -1028,11 +1026,13 @@ out:
 	return ret;
 }
 
-static inline int copy_pmd_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
-		pud_t *dst_pud, pud_t *src_pud, struct vm_area_struct *vma,
-		struct vm_area_struct *new,
-		unsigned long addr, unsigned long end)
+static inline int
+copy_pmd_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
+	       pud_t *dst_pud, pud_t *src_pud, unsigned long addr,
+	       unsigned long end)
 {
+	struct mm_struct *dst_mm = dst_vma->vm_mm;
+	struct mm_struct *src_mm = src_vma->vm_mm;
 	pmd_t *src_pmd, *dst_pmd;
 	unsigned long next;
 
@@ -1045,9 +1045,9 @@ static inline int copy_pmd_range(struct
 		if (is_swap_pmd(*src_pmd) || pmd_trans_huge(*src_pmd)
 			|| pmd_devmap(*src_pmd)) {
 			int err;
-			VM_BUG_ON_VMA(next-addr != HPAGE_PMD_SIZE, vma);
+			VM_BUG_ON_VMA(next-addr != HPAGE_PMD_SIZE, src_vma);
 			err = copy_huge_pmd(dst_mm, src_mm,
-					    dst_pmd, src_pmd, addr, vma);
+					    dst_pmd, src_pmd, addr, src_vma);
 			if (err == -ENOMEM)
 				return -ENOMEM;
 			if (!err)
@@ -1056,18 +1056,20 @@ static inline int copy_pmd_range(struct
 		}
 		if (pmd_none_or_clear_bad(src_pmd))
 			continue;
-		if (copy_pte_range(dst_mm, src_mm, dst_pmd, src_pmd,
-				   vma, new, addr, next))
+		if (copy_pte_range(dst_vma, src_vma, dst_pmd, src_pmd,
+				   addr, next))
 			return -ENOMEM;
 	} while (dst_pmd++, src_pmd++, addr = next, addr != end);
 	return 0;
 }
 
-static inline int copy_pud_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
-		p4d_t *dst_p4d, p4d_t *src_p4d, struct vm_area_struct *vma,
-		struct vm_area_struct *new,
-		unsigned long addr, unsigned long end)
+static inline int
+copy_pud_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
+	       p4d_t *dst_p4d, p4d_t *src_p4d, unsigned long addr,
+	       unsigned long end)
 {
+	struct mm_struct *dst_mm = dst_vma->vm_mm;
+	struct mm_struct *src_mm = src_vma->vm_mm;
 	pud_t *src_pud, *dst_pud;
 	unsigned long next;
 
@@ -1080,9 +1082,9 @@ static inline int copy_pud_range(struct
 		if (pud_trans_huge(*src_pud) || pud_devmap(*src_pud)) {
 			int err;
 
-			VM_BUG_ON_VMA(next-addr != HPAGE_PUD_SIZE, vma);
+			VM_BUG_ON_VMA(next-addr != HPAGE_PUD_SIZE, src_vma);
 			err = copy_huge_pud(dst_mm, src_mm,
-					    dst_pud, src_pud, addr, vma);
+					    dst_pud, src_pud, addr, src_vma);
 			if (err == -ENOMEM)
 				return -ENOMEM;
 			if (!err)
@@ -1091,18 +1093,19 @@ static inline int copy_pud_range(struct
 		}
 		if (pud_none_or_clear_bad(src_pud))
 			continue;
-		if (copy_pmd_range(dst_mm, src_mm, dst_pud, src_pud,
-				   vma, new, addr, next))
+		if (copy_pmd_range(dst_vma, src_vma, dst_pud, src_pud,
+				   addr, next))
 			return -ENOMEM;
 	} while (dst_pud++, src_pud++, addr = next, addr != end);
 	return 0;
 }
 
-static inline int copy_p4d_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
-		pgd_t *dst_pgd, pgd_t *src_pgd, struct vm_area_struct *vma,
-		struct vm_area_struct *new,
-		unsigned long addr, unsigned long end)
+static inline int
+copy_p4d_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma,
+	       pgd_t *dst_pgd, pgd_t *src_pgd, unsigned long addr,
+	       unsigned long end)
 {
+	struct mm_struct *dst_mm = dst_vma->vm_mm;
 	p4d_t *src_p4d, *dst_p4d;
 	unsigned long next;
 
@@ -1114,20 +1117,22 @@ static inline int copy_p4d_range(struct
 		next = p4d_addr_end(addr, end);
 		if (p4d_none_or_clear_bad(src_p4d))
 			continue;
-		if (copy_pud_range(dst_mm, src_mm, dst_p4d, src_p4d,
-				   vma, new, addr, next))
+		if (copy_pud_range(dst_vma, src_vma, dst_p4d, src_p4d,
+				   addr, next))
 			return -ENOMEM;
 	} while (dst_p4d++, src_p4d++, addr = next, addr != end);
 	return 0;
 }
 
-int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
-		    struct vm_area_struct *vma, struct vm_area_struct *new)
+int
+copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma)
 {
 	pgd_t *src_pgd, *dst_pgd;
 	unsigned long next;
-	unsigned long addr = vma->vm_start;
-	unsigned long end = vma->vm_end;
+	unsigned long addr = src_vma->vm_start;
+	unsigned long end = src_vma->vm_end;
+	struct mm_struct *dst_mm = dst_vma->vm_mm;
+	struct mm_struct *src_mm = src_vma->vm_mm;
 	struct mmu_notifier_range range;
 	bool is_cow;
 	int ret;
@@ -1138,19 +1143,19 @@ int copy_page_range(struct mm_struct *ds
 	 * readonly mappings. The tradeoff is that copy_page_range is more
 	 * efficient than faulting.
 	 */
-	if (!(vma->vm_flags & (VM_HUGETLB | VM_PFNMAP | VM_MIXEDMAP)) &&
-			!vma->anon_vma)
+	if (!(src_vma->vm_flags & (VM_HUGETLB | VM_PFNMAP | VM_MIXEDMAP)) &&
+	    !src_vma->anon_vma)
 		return 0;
 
-	if (is_vm_hugetlb_page(vma))
-		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
+	if (is_vm_hugetlb_page(src_vma))
+		return copy_hugetlb_page_range(dst_mm, src_mm, src_vma);
 
-	if (unlikely(vma->vm_flags & VM_PFNMAP)) {
+	if (unlikely(src_vma->vm_flags & VM_PFNMAP)) {
 		/*
 		 * We do not free on error cases below as remove_vma
 		 * gets called on error from higher level routine
 		 */
-		ret = track_pfn_copy(vma);
+		ret = track_pfn_copy(src_vma);
 		if (ret)
 			return ret;
 	}
@@ -1161,11 +1166,11 @@ int copy_page_range(struct mm_struct *ds
 	 * parent mm. And a permission downgrade will only happen if
 	 * is_cow_mapping() returns true.
 	 */
-	is_cow = is_cow_mapping(vma->vm_flags);
+	is_cow = is_cow_mapping(src_vma->vm_flags);
 
 	if (is_cow) {
 		mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE,
-					0, vma, src_mm, addr, end);
+					0, src_vma, src_mm, addr, end);
 		mmu_notifier_invalidate_range_start(&range);
 	}
 
@@ -1176,8 +1181,8 @@ int copy_page_range(struct mm_struct *ds
 		next = pgd_addr_end(addr, end);
 		if (pgd_none_or_clear_bad(src_pgd))
 			continue;
-		if (unlikely(copy_p4d_range(dst_mm, src_mm, dst_pgd, src_pgd,
-					    vma, new, addr, next))) {
+		if (unlikely(copy_p4d_range(dst_vma, src_vma, dst_pgd, src_pgd,
+					    addr, next))) {
 			ret = -ENOMEM;
 			break;
 		}
_