[src/trunk]: src/sys/uvm comments

[yamt <yamt%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/fa89d1e57f9d
branches:  trunk
changeset: 771683:fa89d1e57f9d
user:      yamt <yamt%NetBSD.org@localhost>
date:      Mon Nov 28 14:06:59 2011 +0000

description:
comments

diffstat:

 sys/uvm/uvm_fault.c |  45 ++++++++++++++++++++++++++++++++++++++-------
 1 files changed, 38 insertions(+), 7 deletions(-)

diffs (71 lines):

diff -r 77d8e61be0cf -r fa89d1e57f9d sys/uvm/uvm_fault.c
--- a/sys/uvm/uvm_fault.c       Mon Nov 28 12:50:07 2011 +0000
+++ b/sys/uvm/uvm_fault.c       Mon Nov 28 14:06:59 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_fault.c,v 1.190 2011/08/06 17:25:03 rmind Exp $    */
+/*     $NetBSD: uvm_fault.c,v 1.191 2011/11/28 14:06:59 yamt Exp $     */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -32,7 +32,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.190 2011/08/06 17:25:03 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_fault.c,v 1.191 2011/11/28 14:06:59 yamt Exp $");
 
 #include "opt_uvmhist.h"
 
@@ -690,16 +690,47 @@
 #define UVM_FAULT_MAXPROT      (1 << 1)
 
 struct uvm_faultctx {
+
+       /*
+        * the following members are set up by uvm_fault_check() and
+        * read-only after that.
+        *
+        * note that narrow is used by uvm_fault_check() to change
+        * the behaviour after ERESTART.
+        *
+        * most of them might change after RESTART if the underlying
+        * map entry has been changed behind us.  an exception is
+        * wire_paging, which does never change.
+        */
        vm_prot_t access_type;
-       vm_prot_t enter_prot;
        vaddr_t startva;
        int npages;
        int centeridx;
+       bool narrow;            /* work on a single requested page only */
+       bool wire_mapping;      /* request a PMAP_WIRED mapping
+                                  (UVM_FAULT_WIRE or VM_MAPENT_ISWIRED) */
+       bool wire_paging;       /* request uvm_pagewire
+                                  (true for UVM_FAULT_WIRE) */
+       bool cow_now;           /* VM_PROT_WRITE is actually requested
+                                  (ie. should break COW and page loaning) */
+
+       /*
+        * enter_prot is set up by uvm_fault_check() and clamped
+        * (ie. drop the VM_PROT_WRITE bit) in various places in case
+        * of !cow_now.
+        */
+       vm_prot_t enter_prot;   /* prot at which we want to enter pages in */
+
+       /*
+        * the following member is for uvmfault_promote() and ERESTART.
+        */
        struct vm_anon *anon_spare;
-       bool wire_mapping;
-       bool narrow;
-       bool wire_paging;
-       bool cow_now;
+
+       /*
+        * the folloing is actually a uvm_fault_lower() internal.
+        * it's here merely for debugging.
+        * (or due to the mechanical separation of the function?)
+        */
        bool promote;
 };