mm: page_mkwrite change prototype to match fault

Change the page_mkwrite prototype to take a struct vm_fault, and return
VM_FAULT_xxx flags.  There should be no functional change.

This makes it possible to return much more detailed error information to
the VM (and also can provide more information eg.  virtual_address to the
driver, which might be important in some special cases).

This is required for a subsequent fix.  And will also make it easier to
merge page_mkwrite() with fault() in future.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <joel.becker@oracle.com>
Cc: Artem Bityutskiy <dedekind@infradead.org>
Cc: Felix Blyakher <felixb@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 22 insertions, 4 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 5b4ad5e4f98d..cf6873e91c6a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1945,6 +1945,15 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                  * get_user_pages(.write=1, .force=1).
                  */
                 if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
+                        struct vm_fault vmf;
+                        int tmp;
+
+                        vmf.virtual_address = (void __user *)(address &
+                                                                PAGE_MASK);
+                        vmf.pgoff = old_page->index;
+                        vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE;
+                        vmf.page = old_page;
+
                         /*
                          * Notify the address space that the page is about to
                          * become writable so that it can prohibit this or wait
@@ -1956,8 +1965,12 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
                         page_cache_get(old_page);
                         pte_unmap_unlock(page_table, ptl);
 
-                        if (vma->vm_ops->page_mkwrite(vma, old_page) < 0)
+                        tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
+                        if (unlikely(tmp &
+                                        (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
+                                ret = tmp;
                                 goto unwritable_page;
+                        }
 
                         /*
                          * Since we dropped the lock we need to revalidate
@@ -2106,7 +2119,7 @@ oom:
 
 unwritable_page:
         page_cache_release(old_page);
-        return VM_FAULT_SIGBUS;
+        return ret;
 }
 
 /*
@@ -2648,9 +2661,14 @@ static int __do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                          * to become writable
                          */
                         if (vma->vm_ops->page_mkwrite) {
+                                int tmp;
+
                                 unlock_page(page);
-                                if (vma->vm_ops->page_mkwrite(vma, page) < 0) {
-                                        ret = VM_FAULT_SIGBUS;
+                                vmf.flags |= FAULT_FLAG_MKWRITE;
+                                tmp = vma->vm_ops->page_mkwrite(vma, &vmf);
+                                if (unlikely(tmp &
+                                          (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) {
+                                        ret = tmp;
                                         anon = 1; /* no anon but release vmf.page */
                                         goto out_unlocked;
                                 }