[src/yamt-pagecache]: src/sys/miscfs/genfs - g/c #if 0'ed code

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

details:   https://anonhg.NetBSD.org/src/rev/2e0fc4d8594a
branches:  yamt-pagecache
changeset: 770864:2e0fc4d8594a
user:      yamt <yamt%NetBSD.org@localhost>
date:      Tue Jan 24 02:09:34 2012 +0000

description:
- g/c #if 0'ed code
- minor optimization
- comments

diffstat:

 sys/miscfs/genfs/genfs_io.c |  43 ++++++++++++++++++++++++-------------------
 1 files changed, 24 insertions(+), 19 deletions(-)

diffs (104 lines):

diff -r c4bf48899fd2 -r 2e0fc4d8594a sys/miscfs/genfs/genfs_io.c
--- a/sys/miscfs/genfs/genfs_io.c       Mon Jan 23 03:21:18 2012 +0000
+++ b/sys/miscfs/genfs/genfs_io.c       Tue Jan 24 02:09:34 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: genfs_io.c,v 1.53.2.8 2012/01/18 02:09:05 yamt Exp $   */
+/*     $NetBSD: genfs_io.c,v 1.53.2.9 2012/01/24 02:09:34 yamt Exp $   */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.53.2.8 2012/01/18 02:09:05 yamt Exp $");
+__KERNEL_RCSID(0, "$NetBSD: genfs_io.c,v 1.53.2.9 2012/01/24 02:09:34 yamt Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -224,6 +224,10 @@
                        error = EBUSY;
                        goto out_err;
                }
+               /*
+                * lock and unlock g_glock to ensure that no one is truncating
+                * the file behind us.
+                */
                if (!genfs_node_rdtrylock(vp)) {
                        genfs_rel_pages(ap->a_m, npages);
 
@@ -590,19 +594,13 @@
                            iobytes);
                        skipbytes += iobytes;
 
-                       mutex_enter(uobj->vmobjlock);
-                       for (i = 0; i < holepages; i++) {
-#if 0
-                               if (memwrite) {
-                                       uvm_pagemarkdirty(pgs[pidx + i],
-                                           UVM_PAGE_STATUS_DIRTY);
-                               }
-#endif
-                               if (!blockalloc) {
+                       if (!blockalloc) {
+                               mutex_enter(uobj->vmobjlock);
+                               for (i = 0; i < holepages; i++) {
                                        pgs[pidx + i]->flags |= PG_HOLE;
                                }
+                               mutex_exit(uobj->vmobjlock);
                        }
-                       mutex_exit(uobj->vmobjlock);
                        continue;
                }
 
@@ -887,7 +885,6 @@
            (origflags & PGO_JOURNALLOCKED) == 0);
 
 retry:
-       written = false;
        flags = origflags;
        KASSERT((vp->v_iflag & VI_ONWORKLST) != 0 ||
            (vp->v_iflag & VI_WRMAPDIRTY) == 0);
@@ -939,10 +936,6 @@
 
        error = 0;
        wasclean = (vp->v_numoutput == 0);
-       nextoff = startoff;
-       if (endoff == 0 || flags & PGO_ALLPAGES) {
-               endoff = trunc_page(LLONG_MAX);
-       }
 
        /*
         * if this vnode is known not to have dirty pages,
@@ -959,9 +952,14 @@
        }
 
        /*
-        * start the loop.
+        * start the loop to scan pages.
         */
 
+       written = false;
+       nextoff = startoff;
+       if (endoff == 0 || flags & PGO_ALLPAGES) {
+               endoff = trunc_page(LLONG_MAX);
+       }
        freeflag = pagedaemon ? PG_PAGEOUT : PG_RELEASED;
        tryclean = true;
        uvm_page_array_init(&a);
@@ -1102,7 +1100,14 @@
 
                        /*
                         * XXX PG_PAGER1 incompatibility check.
-                        * this is a kludge for nfs.
+                        *
+                        * this is a kludge for nfs.  nfs has two kind of dirty
+                        * pages:
+                        *      - not written to the server yet
+                        *      - written to the server but not committed yet
+                        * the latter is marked as PG_NEEDCOMMIT. (== PG_PAGER1)
+                        * nfs doesn't want them being clustered together.
+                        *
                         * probably it's better to make PG_NEEDCOMMIT a first
                         * level citizen for uvm/genfs.
                         */