mm: merge populate and nopage into fault (fixes nonlinear)

Nonlinear mappings are (AFAIKS) simply a virtual memory concept that encodes
the virtual address -> file offset differently from linear mappings.

->populate is a layering violation because the filesystem/pagecache code
should need to know anything about the virtual memory mapping.  The hitch here
is that the ->nopage handler didn't pass down enough information (ie.  pgoff).
 But it is more logical to pass pgoff rather than have the ->nopage function
calculate it itself anyway (because that's a similar layering violation).

Having the populate handler install the pte itself is likewise a nasty thing
to be doing.

This patch introduces a new fault handler that replaces ->nopage and
->populate and (later) ->nopfn.  Most of the old mechanism is still in place
so there is a lot of duplication and nice cleanups that can be removed if
everyone switches over.

The rationale for doing this in the first place is that nonlinear mappings are
subject to the pagefault vs invalidate/truncate race too, and it seemed stupid
to duplicate the synchronisation logic rather than just consolidate the two.

After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in
pagecache.  Seems like a fringe functionality anyway.

NOPAGE_REFAULT is removed.  This should be implemented with ->fault, and no
users have hit mainline yet.

[akpm@linux-foundation.org: cleanup]
[randy.dunlap@oracle.com: doc. fixes for readahead]
[akpm@linux-foundation.org: build fix]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Mark Fasheh <mark.fasheh@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 11 insertions, 12 deletions

diff --git a/fs/xfs/linux-2.6/xfs_file.c b/fs/xfs/linux-2.6/xfs_file.c
index 92b2f225712..f12e80a69c6 100644
--- a/fs/xfs/linux-2.6/xfs_file.c
+++ b/fs/xfs/linux-2.6/xfs_file.c
@@ -213,18 +213,19 @@ xfs_file_fsync(
 
 #ifdef CONFIG_XFS_DMAPI
 STATIC struct page *
-xfs_vm_nopage(
-        struct vm_area_struct   *area,
-        unsigned long           address,
-        int                     *type)
+xfs_vm_fault(
+        struct vm_area_struct   *vma,
+        struct fault_data       *fdata)
 {
-        struct inode    *inode = area->vm_file->f_path.dentry->d_inode;
+        struct inode    *inode = vma->vm_file->f_path.dentry->d_inode;
         bhv_vnode_t     *vp = vn_from_inode(inode);
 
         ASSERT_ALWAYS(vp->v_vfsp->vfs_flag & VFS_DMI);
-        if (XFS_SEND_MMAP(XFS_VFSTOM(vp->v_vfsp), area, 0))
+        if (XFS_SEND_MMAP(XFS_VFSTOM(vp->v_vfsp), vma, 0)) {
+                fdata->type = VM_FAULT_SIGBUS;
                 return NULL;
-        return filemap_nopage(area, address, type);
+        }
+        return filemap_fault(vma, fdata);
 }
 #endif /* CONFIG_XFS_DMAPI */
 
@@ -310,7 +311,7 @@ xfs_file_mmap(
         struct vm_area_struct *vma)
 {
         vma->vm_ops = &xfs_file_vm_ops;
-        vma->vm_flags |= VM_CAN_INVALIDATE;
+        vma->vm_flags |= VM_CAN_INVALIDATE | VM_CAN_NONLINEAR;
 
 #ifdef CONFIG_XFS_DMAPI
         if (vn_from_inode(filp->f_path.dentry->d_inode)->v_vfsp->vfs_flag & VFS_DMI)
@@ -465,14 +466,12 @@ const struct file_operations xfs_dir_file_operations = {
 };
 
 static struct vm_operations_struct xfs_file_vm_ops = {
-        .nopage         = filemap_nopage,
-        .populate       = filemap_populate,
+        .fault          = filemap_fault,
 };
 
 #ifdef CONFIG_XFS_DMAPI
 static struct vm_operations_struct xfs_dmapi_file_vm_ops = {
-        .nopage         = xfs_vm_nopage,
-        .populate       = filemap_populate,
+        .fault          = xfs_vm_fault,
 #ifdef HAVE_VMOP_MPROTECT
         .mprotect       = xfs_vm_mprotect,
 #endif