mm: fault feedback #2

This patch completes Linus's wish that the fault return codes be made into
bit flags, which I agree makes everything nicer.  This requires requires
all handle_mm_fault callers to be modified (possibly the modifications
should go further and do things like fault accounting in handle_mm_fault --
however that would be for another patch).

[akpm@linux-foundation.org: fix alpha build]
[akpm@linux-foundation.org: fix s390 build]
[akpm@linux-foundation.org: fix sparc build]
[akpm@linux-foundation.org: fix sparc64 build]
[akpm@linux-foundation.org: fix ia64 build]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ian Molton <spyro@f2s.com>
Cc: Bryan Wu <bryan.wu@analog.com>
Cc: Mikael Starvik <starvik@axis.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: "Luck, Tony" <tony.luck@intel.com>
Cc: Hirokazu Takata <takata@linux-m32r.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Greg Ungerer <gerg@uclinux.org>
Cc: Matthew Wilcox <willy@debian.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Kazumoto Kojima <kkojima@rr.iij4u.or.jp>
Cc: Richard Curnow <rc@rc0.org.uk>
Cc: William Lee Irwin III <wli@holomorphy.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Miles Bader <uclinux-v850@lsi.nec.co.jp>
Cc: Chris Zankel <chris@zankel.net>
Acked-by: Kyle McMartin <kyle@mcmartin.ca>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Acked-by: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[ Still apparently needs some ARM and PPC loving - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

5 files changed, 52 insertions, 54 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 0876cc57255f..4fd9e3f0f48a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1322,9 +1322,7 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
         struct page *page;
         unsigned long size;
         int did_readaround = 0;
-        int ret;
-
-        ret = VM_FAULT_MINOR;
+        int ret = 0;
 
         size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
         if (vmf->pgoff >= size)
@@ -1408,7 +1406,7 @@ retry_find:
          */
         mark_page_accessed(page);
         vmf->page = page;
-        return ret | FAULT_RET_LOCKED;
+        return ret | VM_FAULT_LOCKED;
 
 outside_data_content:
         /*
diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 847d5d78163e..53ee6a299635 100644
--- a/mm/filemap_xip.c
+++ b/mm/filemap_xip.c
@@ -252,7 +252,7 @@ static int xip_file_fault(struct vm_area_struct *area, struct vm_fault *vmf)
 out:
         page_cache_get(page);
         vmf->page = page;
-        return VM_FAULT_MINOR;
+        return 0;
 }
 
 static struct vm_operations_struct xip_file_vm_ops = {
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index aaa7c1a682d9..c4a573b857bd 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -469,7 +469,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
         avoidcopy = (page_count(old_page) == 1);
         if (avoidcopy) {
                 set_huge_ptep_writable(vma, address, ptep);
-                return VM_FAULT_MINOR;
+                return 0;
         }
 
         page_cache_get(old_page);
@@ -494,7 +494,7 @@ static int hugetlb_cow(struct mm_struct *mm, struct vm_area_struct *vma,
         }
         page_cache_release(new_page);
         page_cache_release(old_page);
-        return VM_FAULT_MINOR;
+        return 0;
 }
 
 static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
@@ -551,7 +551,7 @@ retry:
         if (idx >= size)
                 goto backout;
 
-        ret = VM_FAULT_MINOR;
+        ret = 0;
         if (!pte_none(*ptep))
                 goto backout;
 
@@ -602,7 +602,7 @@ int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                 return ret;
         }
 
-        ret = VM_FAULT_MINOR;
+        ret = 0;
 
         spin_lock(&mm->page_table_lock);
         /* Check for a racing update before calling hugetlb_cow */
@@ -641,7 +641,7 @@ int follow_hugetlb_page(struct mm_struct *mm, struct vm_area_struct *vma,
                         spin_unlock(&mm->page_table_lock);
                         ret = hugetlb_fault(mm, vma, vaddr, 0);
                         spin_lock(&mm->page_table_lock);
-                        if (ret == VM_FAULT_MINOR)
+                        if (!(ret & VM_FAULT_MAJOR))
                                 continue;
 
                         remainder = 0;
diff --git a/mm/memory.c b/mm/memory.c
index 23c870479b3e..61d51da7e17c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1068,31 +1068,30 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                         cond_resched();
                         while (!(page = follow_page(vma, start, foll_flags))) {
                                 int ret;
-                                ret = __handle_mm_fault(mm, vma, start,
+                                ret = handle_mm_fault(mm, vma, start,
                                                 foll_flags & FOLL_WRITE);
+                                if (ret & VM_FAULT_ERROR) {
+                                        if (ret & VM_FAULT_OOM)
+                                                return i ? i : -ENOMEM;
+                                        else if (ret & VM_FAULT_SIGBUS)
+                                                return i ? i : -EFAULT;
+                                        BUG();
+                                }
+                                if (ret & VM_FAULT_MAJOR)
+                                        tsk->maj_flt++;
+                                else
+                                        tsk->min_flt++;
+
                                 /*
-                                 * The VM_FAULT_WRITE bit tells us that do_wp_page has
-                                 * broken COW when necessary, even if maybe_mkwrite
-                                 * decided not to set pte_write. We can thus safely do
-                                 * subsequent page lookups as if they were reads.
+                                 * The VM_FAULT_WRITE bit tells us that
+                                 * do_wp_page has broken COW when necessary,
+                                 * even if maybe_mkwrite decided not to set
+                                 * pte_write. We can thus safely do subsequent
+                                 * page lookups as if they were reads.
                                  */
                                 if (ret & VM_FAULT_WRITE)
                                         foll_flags &= ~FOLL_WRITE;
-                                
-                                switch (ret & ~VM_FAULT_WRITE) {
-                                case VM_FAULT_MINOR:
-                                        tsk->min_flt++;
-                                        break;
-                                case VM_FAULT_MAJOR:
-                                        tsk->maj_flt++;
-                                        break;
-                                case VM_FAULT_SIGBUS:
-                                        return i ? i : -EFAULT;
-                                case VM_FAULT_OOM:
-                                        return i ? i : -ENOMEM;
-                                default:
-                                        BUG();
-                                }
+
                                 cond_resched();
                         }
                         if (pages) {
@@ -1639,7 +1638,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
 {
         struct page *old_page, *new_page;
         pte_t entry;
-        int reuse = 0, ret = VM_FAULT_MINOR;
+        int reuse = 0, ret = 0;
         struct page *dirty_page = NULL;
 
         old_page = vm_normal_page(vma, address, orig_pte);
@@ -1835,8 +1834,8 @@ static int unmap_mapping_range_vma(struct vm_area_struct *vma,
         /*
          * files that support invalidating or truncating portions of the
          * file from under mmaped areas must have their ->fault function
-         * return a locked page (and FAULT_RET_LOCKED code). This provides
-         * synchronisation against concurrent unmapping here.
+         * return a locked page (and set VM_FAULT_LOCKED in the return).
+         * This provides synchronisation against concurrent unmapping here.
          */
 
 again:
@@ -2140,7 +2139,7 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         struct page *page;
         swp_entry_t entry;
         pte_t pte;
-        int ret = VM_FAULT_MINOR;
+        int ret = 0;
 
         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
                 goto out;
@@ -2208,8 +2207,9 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
         unlock_page(page);
 
         if (write_access) {
+                /* XXX: We could OR the do_wp_page code with this one? */
                 if (do_wp_page(mm, vma, address,
-                                page_table, pmd, ptl, pte) == VM_FAULT_OOM)
+                                page_table, pmd, ptl, pte) & VM_FAULT_OOM)
                         ret = VM_FAULT_OOM;
                 goto out;
         }
@@ -2280,7 +2280,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
         lazy_mmu_prot_update(entry);
 unlock:
         pte_unmap_unlock(page_table, ptl);
-        return VM_FAULT_MINOR;
+        return 0;
 release:
         page_cache_release(page);
         goto unlock;
@@ -2323,11 +2323,11 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 
         if (likely(vma->vm_ops->fault)) {
                 ret = vma->vm_ops->fault(vma, &vmf);
-                if (unlikely(ret & (VM_FAULT_ERROR | FAULT_RET_NOPAGE)))
-                        return (ret & VM_FAULT_MASK);
+                if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE)))
+                        return ret;
         } else {
                 /* Legacy ->nopage path */
-                ret = VM_FAULT_MINOR;
+                ret = 0;
                 vmf.page = vma->vm_ops->nopage(vma, address & PAGE_MASK, &ret);
                 /* no page was available -- either SIGBUS or OOM */
                 if (unlikely(vmf.page == NOPAGE_SIGBUS))
@@ -2340,7 +2340,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
          * For consistency in subsequent calls, make the faulted page always
          * locked.
          */
-        if (unlikely(!(ret & FAULT_RET_LOCKED)))
+        if (unlikely(!(ret & VM_FAULT_LOCKED)))
                 lock_page(vmf.page);
         else
                 VM_BUG_ON(!PageLocked(vmf.page));
@@ -2356,7 +2356,8 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                                 ret = VM_FAULT_OOM;
                                 goto out;
                         }
-                        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address);
+                        page = alloc_page_vma(GFP_HIGHUSER_MOVABLE,
+                                                vma, address);
                         if (!page) {
                                 ret = VM_FAULT_OOM;
                                 goto out;
@@ -2384,7 +2385,7 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                                  * is better done later.
                                  */
                                 if (!page->mapping) {
-                                        ret = VM_FAULT_MINOR;
+                                        ret = 0;
                                         anon = 1; /* no anon but release vmf.page */
                                         goto out;
                                 }
@@ -2447,7 +2448,7 @@ out_unlocked:
                 put_page(dirty_page);
         }
 
-        return (ret & VM_FAULT_MASK);
+        return ret;
 }
 
 static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
@@ -2486,7 +2487,6 @@ static noinline int do_no_pfn(struct mm_struct *mm, struct vm_area_struct *vma,
         spinlock_t *ptl;
         pte_t entry;
         unsigned long pfn;
-        int ret = VM_FAULT_MINOR;
 
         pte_unmap(page_table);
         BUG_ON(!(vma->vm_flags & VM_PFNMAP));
@@ -2498,7 +2498,7 @@ static noinline int do_no_pfn(struct mm_struct *mm, struct vm_area_struct *vma,
         else if (unlikely(pfn == NOPFN_SIGBUS))
                 return VM_FAULT_SIGBUS;
         else if (unlikely(pfn == NOPFN_REFAULT))
-                return VM_FAULT_MINOR;
+                return 0;
 
         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
 
@@ -2510,7 +2510,7 @@ static noinline int do_no_pfn(struct mm_struct *mm, struct vm_area_struct *vma,
                 set_pte_at(mm, address, page_table, entry);
         }
         pte_unmap_unlock(page_table, ptl);
-        return ret;
+        return 0;
 }
 
 /*
@@ -2531,7 +2531,7 @@ static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
         pgoff_t pgoff;
 
         if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
-                return VM_FAULT_MINOR;
+                return 0;
 
         if (unlikely(!(vma->vm_flags & VM_NONLINEAR) ||
                         !(vma->vm_flags & VM_CAN_NONLINEAR))) {
@@ -2615,13 +2615,13 @@ static inline int handle_pte_fault(struct mm_struct *mm,
         }
 unlock:
         pte_unmap_unlock(pte, ptl);
-        return VM_FAULT_MINOR;
+        return 0;
 }
 
 /*
  * By the time we get here, we already hold the mm semaphore
  */
-int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+int handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                 unsigned long address, int write_access)
 {
         pgd_t *pgd;
@@ -2650,7 +2650,7 @@ int __handle_mm_fault(struct mm_struct *mm, struct vm_area_struct *vma,
         return handle_pte_fault(mm, vma, address, pte, pmd, write_access);
 }
 
-EXPORT_SYMBOL_GPL(__handle_mm_fault);
+EXPORT_SYMBOL_GPL(handle_mm_fault);
 
 #ifndef __PAGETABLE_PUD_FOLDED
 /*
diff --git a/mm/shmem.c b/mm/shmem.c
index 0a555af8733d..ad155c7745dc 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1103,7 +1103,7 @@ static int shmem_getpage(struct inode *inode, unsigned long idx,
                 return -EFBIG;
 
         if (type)
-                *type = VM_FAULT_MINOR;
+                *type = 0;
 
         /*
          * Normally, filepage is NULL on entry, and either found
@@ -1138,9 +1138,9 @@ repeat:
                 if (!swappage) {
                         shmem_swp_unmap(entry);
                         /* here we actually do the io */
-                        if (type && *type == VM_FAULT_MINOR) {
+                        if (type && !(*type & VM_FAULT_MAJOR)) {
                                 __count_vm_event(PGMAJFAULT);
-                                *type = VM_FAULT_MAJOR;
+                                *type |= VM_FAULT_MAJOR;
                         }
                         spin_unlock(&info->lock);
                         swappage = shmem_swapin(info, swap, idx);
@@ -1323,7 +1323,7 @@ static int shmem_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
                 return ((error == -ENOMEM) ? VM_FAULT_OOM : VM_FAULT_SIGBUS);
 
         mark_page_accessed(vmf->page);
-        return ret | FAULT_RET_LOCKED;
+        return ret | VM_FAULT_LOCKED;
 }
 
 #ifdef CONFIG_NUMA