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>

2 files changed, 2 insertions, 20 deletions

diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index 716568afdff8..cff63befeb9a 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -135,26 +135,8 @@ Who:	Greg Kroah-Hartman <gregkh@suse.de>
 
 ---------------------------
 
-What:   filemap_nopage, filemap_populate
-When:   April 2007
-Why:    These legacy interfaces no longer have any callers in the kernel and
-        any functionality provided can be provided with filemap_fault. The
-        removal schedule is short because they are a big maintainence burden
-        and have some bugs.
-Who:    Nick Piggin <npiggin@suse.de>
-
----------------------------
-
-What:   vm_ops.populate, install_page
-When:   April 2007
-Why:    These legacy interfaces no longer have any callers in the kernel and
-        any functionality provided can be provided with vm_ops.fault.
-Who:    Nick Piggin <npiggin@suse.de>
-
----------------------------
-
 What:   vm_ops.nopage
-When:   February 2008, provided in-kernel callers have been converted
+When:   Soon, provided in-kernel callers have been converted
 Why:    This interface is replaced by vm_ops.fault, but it has been around
         forever, is used by a lot of drivers, and doesn't cost much to
         maintain.
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 91ec4b40ebfe..f0f825808ca4 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -510,7 +510,7 @@ More details about quota locking can be found in fs/dquot.c.
 prototypes:
         void (*open)(struct vm_area_struct*);
         void (*close)(struct vm_area_struct*);
-        struct page *(*fault)(struct vm_area_struct*, struct fault_data *);
+        int (*fault)(struct vm_area_struct*, struct vm_fault *);
         struct page *(*nopage)(struct vm_area_struct*, unsigned long, int *);
         int (*page_mkwrite)(struct vm_area_struct *, struct page *);