[src/trunk]: src/sys/uvm Comments explaining UBC_* flags.

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

details:   https://anonhg.NetBSD.org/src/rev/84d10ef0c5cc
branches:  trunk
changeset: 336801:84d10ef0c5cc
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Fri Mar 20 15:41:43 2015 +0000

description:
Comments explaining UBC_* flags.

diffstat:

 sys/uvm/uvm_extern.h |  18 +++++++++++-------
 1 files changed, 11 insertions(+), 7 deletions(-)

diffs (39 lines):

diff -r 57075f060754 -r 84d10ef0c5cc sys/uvm/uvm_extern.h
--- a/sys/uvm/uvm_extern.h      Fri Mar 20 14:27:06 2015 +0000
+++ b/sys/uvm/uvm_extern.h      Fri Mar 20 15:41:43 2015 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_extern.h,v 1.193 2015/02/06 18:19:22 maxv Exp $    */
+/*     $NetBSD: uvm_extern.h,v 1.194 2015/03/20 15:41:43 riastradh Exp $       */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -175,19 +175,23 @@
 /*
  * flags for ubc_alloc()
  */
-#define UBC_READ       0x001
-#define UBC_WRITE      0x002
-#define UBC_FAULTBUSY  0x004
+#define UBC_READ       0x001   /* reading from object */
+#define UBC_WRITE      0x002   /* writing to object */
+#define UBC_FAULTBUSY  0x004   /* nobody else is using these pages, so busy
+                                * them at alloc and unbusy at release (e.g.,
+                                * for writes extending a file) */
 
 /*
  * flags for ubc_release()
  */
-#define UBC_UNMAP      0x010
+#define UBC_UNMAP      0x010   /* unmap pages now -- don't leave the
+                                * mappings cached indefinitely */
 
 /*
- * flags for ubc_uiomve()
+ * flags for ubc_uiomove()
  */
-#define        UBC_PARTIALOK   0x100
+#define        UBC_PARTIALOK   0x100   /* return early on error; otherwise, zero all
+                                * remaining bytes after error */
 
 /*
  * flags for uvn_findpages().