git: 1424f65bbcb3 - main - vm_pager: Remove the default pager

From: Mark Johnston <markj_at_FreeBSD.org>
Date: Sun, 17 Jul 2022 11:24:20 UTC
The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=1424f65bbcb3283c899c356bf38ef0a9930add34

commit 1424f65bbcb3283c899c356bf38ef0a9930add34
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-07-16 15:30:19 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-07-17 11:09:48 +0000

    vm_pager: Remove the default pager
    
    It's unused now.  Keep the OBJ_DEFAULT identifier, but make it an alias
    of OBJT_SWAP for the benefit of out-of-tree code.
    
    Reviewed by:    alc, imp, kib
    Tested by:      pho
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D35790
---
 sys/conf/files         |   1 -
 sys/vm/default_pager.c | 158 -------------------------------------------------
 sys/vm/vm.h            |   3 +-
 sys/vm/vm_pager.c      |   5 +-
 4 files changed, 4 insertions(+), 163 deletions(-)

diff --git a/sys/conf/files b/sys/conf/files
index 11b7e0357c79..30cd9eb7e741 100644
--- a/sys/conf/files
+++ b/sys/conf/files
@@ -5181,7 +5181,6 @@ ufs/ufs/ufs_lookup.c		optional ffs
 ufs/ufs/ufs_quota.c		optional ffs
 ufs/ufs/ufs_vfsops.c		optional ffs
 ufs/ufs/ufs_vnops.c		optional ffs
-vm/default_pager.c		standard
 vm/device_pager.c		standard
 vm/phys_pager.c			standard
 vm/redzone.c			optional DEBUG_REDZONE
diff --git a/sys/vm/default_pager.c b/sys/vm/default_pager.c
deleted file mode 100644
index d07a84f8c98e..000000000000
--- a/sys/vm/default_pager.c
+++ /dev/null
@@ -1,158 +0,0 @@
-/*-
- * SPDX-License-Identifier: BSD-4-Clause
- *
- * Copyright (c) 1995, David Greenman
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *	This product includes software developed by David Greenman.
- * 4. The name of the author may not be used to endorse or promote products
- *    derived from this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- */
-
-#include <sys/cdefs.h>
-__FBSDID("$FreeBSD$");
-
-#include <sys/param.h>
-#include <sys/systm.h>
-#include <sys/lock.h>
-#include <sys/proc.h>
-#include <sys/resourcevar.h>
-#include <sys/rwlock.h>
-#include <sys/user.h>
-
-#include <vm/vm.h>
-#include <vm/vm_object.h>
-#include <vm/vm_page.h>
-#include <vm/vm_pager.h>
-#include <vm/swap_pager.h>
-
-static vm_object_t	default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
-			    vm_ooffset_t, struct ucred *);
-static void		default_pager_dealloc(vm_object_t);
-static int		default_pager_getpages(vm_object_t, vm_page_t *, int,
-			    int *, int *);
-static void		default_pager_putpages(vm_object_t, vm_page_t *, int, 
-			    boolean_t, int *);
-static boolean_t	default_pager_haspage(vm_object_t, vm_pindex_t, int *, 
-			    int *);
-
-/*
- * pagerops for OBJT_DEFAULT - "default pager".
- *
- * This pager handles anonymous (no handle) swap-backed memory, just
- * like the swap pager.  It allows several optimizations based on the
- * fact that no pages of a default object can be swapped out.  The
- * most important optimization is in vm_fault(), where the pager is
- * never asked for a non-resident page.  Instead, a freshly allocated
- * zeroed page is used.
- *
- * On the first request to page out a page from a default object, the
- * object is converted to swap pager type.
- */
-const struct pagerops defaultpagerops = {
-	.pgo_kvme_type = KVME_TYPE_DEFAULT,
-	.pgo_alloc =	default_pager_alloc,
-	.pgo_dealloc =	default_pager_dealloc,
-	.pgo_getpages =	default_pager_getpages,
-	.pgo_putpages =	default_pager_putpages,
-	.pgo_haspage =	default_pager_haspage,
-};
-
-/*
- * Return an initialized object.
- */
-static vm_object_t
-default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
-    vm_ooffset_t offset, struct ucred *cred)
-{
-	vm_object_t object;
-
-	if (handle != NULL)
-		panic("default_pager_alloc: handle specified");
-	if (cred != NULL) {
-		if (!swap_reserve_by_cred(size, cred))
-			return (NULL);
-		crhold(cred);
-	}
-	object = vm_object_allocate(OBJT_DEFAULT,
-	    OFF_TO_IDX(round_page(offset + size)));
-	if (cred != NULL) {
-		object->cred = cred;
-		object->charge = size;
-	}
-	return (object);
-}
-
-/*
- * Deallocate resources associated with the object.
- */
-static void
-default_pager_dealloc(vm_object_t object)
-{
-
-	/* Reserved swap is released by vm_object_destroy(). */
-	object->type = OBJT_DEAD;
-}
-
-/*
- * Load pages from backing store.
- */
-static int
-default_pager_getpages(vm_object_t object, vm_page_t *m, int count,
-    int *rbehind, int *rahead)
-{
-
-	/*
-	 * Since an OBJT_DEFAULT object is converted to OBJT_SWAP by the first
-	 * call to the putpages method, this function will never be called on
-	 * a vm_page with assigned swap.
-	 */
-	return (VM_PAGER_FAIL);
-}
-
-/*
- * Store pages to backing store.
- */
-static void
-default_pager_putpages(vm_object_t object, vm_page_t *m, int count,
-    int flags, int *rtvals)
-{
-
-	/* The swap pager will convert the object to OBJT_SWAP. */
-	swappagerops.pgo_putpages(object, m, count, flags, rtvals);
-}
-
-/*
- * Tell us whether the requested (object,index) is available from the object's
- * backing store.
- */
-static boolean_t
-default_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
-    int *after)
-{
-
-	/* An OBJT_DEFAULT object has no backing store. */
-	return (FALSE);
-}
diff --git a/sys/vm/vm.h b/sys/vm/vm.h
index 72b0191298d9..d0cc399dab79 100644
--- a/sys/vm/vm.h
+++ b/sys/vm/vm.h
@@ -89,8 +89,9 @@ typedef u_char vm_prot_t;	/* protection codes */
 #define	VM_PROT_DEFAULT		VM_PROT_ALL
 
 enum obj_type {
-	OBJT_DEFAULT,
+	OBJT_RESERVED = 0,	/* was OBJT_DEFAULT */
 	OBJT_SWAP,
+	OBJT_DEFAULT = OBJT_SWAP,
 	OBJT_VNODE,
 	OBJT_DEVICE,
 	OBJT_PHYS,
diff --git a/sys/vm/vm_pager.c b/sys/vm/vm_pager.c
index 9b66964b8d8f..2f8afd69a1b4 100644
--- a/sys/vm/vm_pager.c
+++ b/sys/vm/vm_pager.c
@@ -166,7 +166,6 @@ static const struct pagerops deadpagerops = {
 };
 
 const struct pagerops *pagertab[16] __read_mostly = {
-	[OBJT_DEFAULT] =	&defaultpagerops,
 	[OBJT_SWAP] =		&swappagerops,
 	[OBJT_VNODE] =		&vnodepagerops,
 	[OBJT_DEVICE] =		&devicepagerops,
@@ -190,7 +189,7 @@ vm_pager_init(void)
 	 */
 	for (i = 0; i < OBJT_FIRST_DYN; i++) {
 		pgops = &pagertab[i];
-		if ((*pgops)->pgo_init != NULL)
+		if (*pgops != NULL && (*pgops)->pgo_init != NULL)
 			(*(*pgops)->pgo_init)();
 	}
 }
@@ -402,7 +401,7 @@ vm_pager_alloc_dyn_type(struct pagerops *ops, int base_type)
 
 	mtx_lock(&pagertab_lock);
 	MPASS(base_type == -1 ||
-	    (base_type >= OBJT_DEFAULT && base_type < nitems(pagertab)));
+	    (base_type >= OBJT_SWAP && base_type < nitems(pagertab)));
 	for (res = OBJT_FIRST_DYN; res < nitems(pagertab); res++) {
 		if (pagertab[res] == NULL)
 			break;