[src/trunk]: src/sys/miscfs/genfs PR/14781: Matthew Fredette: Clamp the numbe...

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

details:   https://anonhg.NetBSD.org/src/rev/bbed66bf9917
branches:  trunk
changeset: 518450:bbed66bf9917
user:      christos <christos%NetBSD.org@localhost>
date:      Fri Nov 30 15:18:39 2001 +0000

description:
PR/14781: Matthew Fredette: Clamp the number of read-ahead pages to 16 because
other code has this limit. Also while I am here, convert the magic 16 into
a #define constant and use it in the appropriate places. This is a temporary
fix, since all this read-ahead business is XXXUBC anyway.

diffstat:

 sys/miscfs/genfs/genfs_vnops.c |  20 +++++++++++++-------
 1 files changed, 13 insertions(+), 7 deletions(-)

diffs (68 lines):

diff -r a5928e1a1f43 -r bbed66bf9917 sys/miscfs/genfs/genfs_vnops.c
--- a/sys/miscfs/genfs/genfs_vnops.c    Fri Nov 30 14:22:33 2001 +0000
+++ b/sys/miscfs/genfs/genfs_vnops.c    Fri Nov 30 15:18:39 2001 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: genfs_vnops.c,v 1.40 2001/11/10 13:33:41 lukem Exp $   */
+/*     $NetBSD: genfs_vnops.c,v 1.41 2001/11/30 15:18:39 christos Exp $        */
 
 /*
  * Copyright (c) 1982, 1986, 1989, 1993
@@ -35,7 +35,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: genfs_vnops.c,v 1.40 2001/11/10 13:33:41 lukem Exp $");
+__KERNEL_RCSID(0, "$NetBSD: genfs_vnops.c,v 1.41 2001/11/30 15:18:39 christos Exp $");
 
 #include "opt_nfsserver.h"
 
@@ -66,6 +66,8 @@
 #include <nfs/nfs_var.h>
 #endif
 
+#define MAX_READ_AHEAD 16      /* XXXUBC 16 */
+
 int
 genfs_poll(v)
        void *v;
@@ -464,7 +466,7 @@
        struct vnode *devvp;
        struct genfs_node *gp = VTOG(vp);
        struct uvm_object *uobj = &vp->v_uobj;
-       struct vm_page *pg, *pgs[16];                   /* XXXUBC 16 */
+       struct vm_page *pg, *pgs[MAX_READ_AHEAD];
        struct ucred *cred = curproc->p_ucred;          /* XXXUBC curproc */
        boolean_t async = (flags & PGO_SYNCIO) == 0;
        boolean_t write = (ap->a_access_type & VM_PROT_WRITE) != 0;
@@ -476,7 +478,7 @@
                    vp, ap->a_offset >> 32, ap->a_offset, *ap->a_count);
 
        /* XXXUBC temp limit */
-       if (*ap->a_count > 16) {
+       if (*ap->a_count > MAX_READ_AHEAD) {
                panic("genfs_getpages: too many pages");
        }
 
@@ -851,15 +853,19 @@
 raout:
        if (!error && !async && !write && ((int)raoffset & 0xffff) == 0 &&
            PAGE_SHIFT <= 16) {
+               off_t rasize;
                int racount;
 
-               racount = 1 << (16 - PAGE_SHIFT);
+               /* XXXUBC temp limit, from above */
+               racount = MIN(1 << (16 - PAGE_SHIFT), MAX_READ_AHEAD);
+               rasize = racount << PAGE_SHIFT;
                (void) VOP_GETPAGES(vp, raoffset, NULL, &racount, 0,
                                    VM_PROT_READ, 0, 0);
                simple_lock(&uobj->vmobjlock);
 
-               racount = 1 << (16 - PAGE_SHIFT);
-               (void) VOP_GETPAGES(vp, raoffset + 0x10000, NULL, &racount, 0,
+               /* XXXUBC temp limit, from above */
+               racount = MIN(1 << (16 - PAGE_SHIFT), MAX_READ_AHEAD);
+               (void) VOP_GETPAGES(vp, raoffset + rasize, NULL, &racount, 0,
                                    VM_PROT_READ, 0, 0);
                simple_lock(&uobj->vmobjlock);
        }