mm: fault feedback #1

Change ->fault prototype.  We now return an int, which contains
VM_FAULT_xxx code in the low byte, and FAULT_RET_xxx code in the next byte.
 FAULT_RET_ code tells the VM whether a page was found, whether it has been
locked, and potentially other things.  This is not quite the way he wanted
it yet, but that's changed in the next patch (which requires changes to
arch code).

This means we no longer set VM_CAN_INVALIDATE in the vma in order to say
that a page is locked which requires filemap_nopage to go away (because we
can no longer remain backward compatible without that flag), but we were
going to do that anyway.

struct fault_data is renamed to struct vm_fault as Linus asked. address
is now a void __user * that we should firmly encourage drivers not to use
without really good reason.

The page is now returned via a page pointer in the vm_fault struct.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 16 insertions, 69 deletions

diff --git a/mm/fremap.c b/mm/fremap.c
index 01e51f01b84e..5f50d736a037 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -20,13 +20,14 @@
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
-static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
+static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
                         unsigned long addr, pte_t *ptep)
 {
         pte_t pte = *ptep;
-        struct page *page = NULL;
 
         if (pte_present(pte)) {
+                struct page *page;
+
                 flush_cache_page(vma, addr, pte_pfn(pte));
                 pte = ptep_clear_flush(vma, addr, ptep);
                 page = vm_normal_page(vma, addr, pte);
@@ -35,68 +36,21 @@ static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
                                 set_page_dirty(page);
                         page_remove_rmap(page, vma);
                         page_cache_release(page);
+                        update_hiwater_rss(mm);
+                        dec_mm_counter(mm, file_rss);
                 }
         } else {
                 if (!pte_file(pte))
                         free_swap_and_cache(pte_to_swp_entry(pte));
                 pte_clear_not_present_full(mm, addr, ptep, 0);
         }
-        return !!page;
 }
 
 /*
- * Install a file page to a given virtual memory address, release any
- * previously existing mapping.
- */
-int install_page(struct mm_struct *mm, struct vm_area_struct *vma,
-                unsigned long addr, struct page *page, pgprot_t prot)
-{
-        struct inode *inode;
-        pgoff_t size;
-        int err = -ENOMEM;
-        pte_t *pte;
-        pte_t pte_val;
-        spinlock_t *ptl;
-
-        pte = get_locked_pte(mm, addr, &ptl);
-        if (!pte)
-                goto out;
-
-        /*
-         * This page may have been truncated. Tell the
-         * caller about it.
-         */
-        err = -EINVAL;
-        inode = vma->vm_file->f_mapping->host;
-        size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-        if (!page->mapping || page->index >= size)
-                goto unlock;
-        err = -ENOMEM;
-        if (page_mapcount(page) > INT_MAX/2)
-                goto unlock;
-
-        if (pte_none(*pte) || !zap_pte(mm, vma, addr, pte))
-                inc_mm_counter(mm, file_rss);
-
-        flush_icache_page(vma, page);
-        pte_val = mk_pte(page, prot);
-        set_pte_at(mm, addr, pte, pte_val);
-        page_add_file_rmap(page);
-        update_mmu_cache(vma, addr, pte_val);
-        lazy_mmu_prot_update(pte_val);
-        err = 0;
-unlock:
-        pte_unmap_unlock(pte, ptl);
-out:
-        return err;
-}
-EXPORT_SYMBOL(install_page);
-
-/*
  * Install a file pte to a given virtual memory address, release any
  * previously existing mapping.
  */
-int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
+static int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
                 unsigned long addr, unsigned long pgoff, pgprot_t prot)
 {
         int err = -ENOMEM;
@@ -107,10 +61,8 @@ int install_file_pte(struct mm_struct *mm, struct vm_area_struct *vma,
         if (!pte)
                 goto out;
 
-        if (!pte_none(*pte) && zap_pte(mm, vma, addr, pte)) {
-                update_hiwater_rss(mm);
-                dec_mm_counter(mm, file_rss);
-        }
+        if (!pte_none(*pte))
+                zap_pte(mm, vma, addr, pte);
 
         set_pte_at(mm, addr, pte, pgoff_to_pte(pgoff));
         /*
@@ -208,8 +160,7 @@ asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
         if (vma->vm_private_data && !(vma->vm_flags & VM_NONLINEAR))
                 goto out;
 
-        if ((!vma->vm_ops || !vma->vm_ops->populate) &&
-                                        !(vma->vm_flags & VM_CAN_NONLINEAR))
+        if (!vma->vm_flags & VM_CAN_NONLINEAR)
                 goto out;
 
         if (end <= start || start < vma->vm_start || end > vma->vm_end)
@@ -239,18 +190,14 @@ asmlinkage long sys_remap_file_pages(unsigned long start, unsigned long size,
                 spin_unlock(&mapping->i_mmap_lock);
         }
 
-        if (vma->vm_flags & VM_CAN_NONLINEAR) {
-                err = populate_range(mm, vma, start, size, pgoff);
-                if (!err && !(flags & MAP_NONBLOCK)) {
-                        if (unlikely(has_write_lock)) {
-                                downgrade_write(&mm->mmap_sem);
-                                has_write_lock = 0;
-                        }
-                        make_pages_present(start, start+size);
+        err = populate_range(mm, vma, start, size, pgoff);
+        if (!err && !(flags & MAP_NONBLOCK)) {
+                if (unlikely(has_write_lock)) {
+                        downgrade_write(&mm->mmap_sem);
+                        has_write_lock = 0;
                 }
-        } else
-                err = vma->vm_ops->populate(vma, start, size, vma->vm_page_prot,
-                                                pgoff, flags & MAP_NONBLOCK);
+                make_pages_present(start, start+size);
+        }
 
         /*
          * We can't clear VM_NONLINEAR because we'd have to do