Diff below introduces two dummy pagers for subsystem that manipulate UVM
objects that are 'special'. Those pagers will be used to enforce checks
in functions that expect a lock to be held, like:
KASSERT(obj == NULL || UVM_OBJ_IS_PMAP(obj) ||
rw_write_held(obj->vmobjlock));
They are also used, in the diff below, to document which routines expect
such objects and a serialization offered by the KERNEL_LOCK(). More
examples can be seen in my WIP unlocking diff.
The idea is taken from NetBSD which also use such dummy pager for some
of their pmaps. I don't believe there's a need to change anything with
these usages of the uvm_obj_* API for the moment but at the same time it
helps me to have such implicit documentation.
ok?
Index: arch/amd64/amd64/pmap.c
===================================================================
RCS file: /cvs/src/sys/arch/amd64/amd64/pmap.c,v
retrieving revision 1.145
diff -u -p -r1.145 pmap.c
--- arch/amd64/amd64/pmap.c 18 Jun 2021 06:17:28 -0000 1.145
+++ arch/amd64/amd64/pmap.c 2 Sep 2021 19:55:57 -0000
@@ -671,7 +671,7 @@ pmap_bootstrap(paddr_t first_avail, padd
kpm = pmap_kernel();
for (i = 0; i < PTP_LEVELS - 1; i++) {
- uvm_obj_init(&kpm->pm_obj[i], NULL, 1);
+ uvm_obj_init(&kpm->pm_obj[i], &pmap_pager, 1);
kpm->pm_ptphint[i] = NULL;
}
memset(&kpm->pm_list, 0, sizeof(kpm->pm_list)); /* pm_list not used */
@@ -1307,7 +1307,7 @@ pmap_create(void)
/* init uvm_object */
for (i = 0; i < PTP_LEVELS - 1; i++) {
- uvm_obj_init(&pmap->pm_obj[i], NULL, 1);
+ uvm_obj_init(&pmap->pm_obj[i], &pmap_pager, 1);
pmap->pm_ptphint[i] = NULL;
}
pmap->pm_stats.wired_count = 0;
Index: arch/hppa/hppa/pmap.c
===================================================================
RCS file: /cvs/src/sys/arch/hppa/hppa/pmap.c,v
retrieving revision 1.175
diff -u -p -r1.175 pmap.c
--- arch/hppa/hppa/pmap.c 16 Jun 2021 09:02:21 -0000 1.175
+++ arch/hppa/hppa/pmap.c 2 Sep 2021 19:54:23 -0000
@@ -496,7 +496,7 @@ pmap_bootstrap(vaddr_t vstart)
*/
kpm = &kernel_pmap_store;
bzero(kpm, sizeof(*kpm));
- uvm_obj_init(&kpm->pm_obj, NULL, 1);
+ uvm_obj_init(&kpm->pm_obj, &pmap_pager, 1);
kpm->pm_space = HPPA_SID_KERNEL;
kpm->pm_pid = HPPA_PID_KERNEL;
kpm->pm_pdir_pg = NULL;
@@ -678,7 +678,7 @@ pmap_create(void)
mtx_init(&pmap->pm_mtx, IPL_VM);
- uvm_obj_init(&pmap->pm_obj, NULL, 1);
+ uvm_obj_init(&pmap->pm_obj, &pmap_pager, 1);
for (space = 1 + arc4random_uniform(hppa_sid_max);
pmap_sdir_get(space); space = (space + 1) % hppa_sid_max);
Index: arch/i386/i386/pmap.c
===================================================================
RCS file: /cvs/src/sys/arch/i386/i386/pmap.c,v
retrieving revision 1.214
diff -u -p -r1.214 pmap.c
--- arch/i386/i386/pmap.c 16 Jun 2021 09:02:21 -0000 1.214
+++ arch/i386/i386/pmap.c 2 Sep 2021 19:55:57 -0000
@@ -963,7 +963,7 @@ pmap_bootstrap(vaddr_t kva_start)
kpm = pmap_kernel();
mtx_init(&kpm->pm_mtx, -1); /* must not be used */
mtx_init(&kpm->pm_apte_mtx, IPL_VM);
- uvm_obj_init(&kpm->pm_obj, NULL, 1);
+ uvm_obj_init(&kpm->pm_obj, &pmap_pager, 1);
bzero(&kpm->pm_list, sizeof(kpm->pm_list)); /* pm_list not used */
kpm->pm_pdir = (vaddr_t)(proc0.p_addr->u_pcb.pcb_cr3 + KERNBASE);
kpm->pm_pdirpa = proc0.p_addr->u_pcb.pcb_cr3;
@@ -1348,7 +1348,7 @@ pmap_create(void)
mtx_init(&pmap->pm_apte_mtx, IPL_VM);
/* init uvm_object */
- uvm_obj_init(&pmap->pm_obj, NULL, 1);
+ uvm_obj_init(&pmap->pm_obj, &pmap_pager, 1);
pmap->pm_stats.wired_count = 0;
pmap->pm_stats.resident_count = 1; /* count the PDP allocd below */
pmap->pm_ptphint = NULL;
Index: uvm/uvm_object.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_object.c,v
retrieving revision 1.19
diff -u -p -r1.19 uvm_object.c
--- uvm/uvm_object.c 16 Jun 2021 09:02:21 -0000 1.19
+++ uvm/uvm_object.c 2 Sep 2021 20:00:03 -0000
@@ -41,6 +41,16 @@
#include <uvm/uvm.h>
+/* Dummy object used by some pmaps for sanity checks. */
+const struct uvm_pagerops pmap_pager = {
+ /* nothing */
+};
+
+/* Dummy object used by the buffer cache for sanity checks. */
+const struct uvm_pagerops bufcache_pager = {
+ /* nothing */
+};
+
/* We will fetch this page count per step */
#define FETCH_PAGECOUNT 16
@@ -159,6 +169,9 @@ uvm_obj_free(struct uvm_object *uobj)
{
struct vm_page *pg;
struct pglist pgl;
+
+ KASSERT(UVM_OBJ_IS_BUFCACHE(uobj));
+ KERNEL_ASSERT_LOCKED();
TAILQ_INIT(&pgl);
/*
Index: uvm/uvm_object.h
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_object.h,v
retrieving revision 1.26
diff -u -p -r1.26 uvm_object.h
--- uvm/uvm_object.h 16 Jun 2021 09:02:21 -0000 1.26
+++ uvm/uvm_object.h 2 Sep 2021 20:02:13 -0000
@@ -74,6 +74,8 @@ struct uvm_object {
extern const struct uvm_pagerops uvm_vnodeops;
extern const struct uvm_pagerops uvm_deviceops;
+extern const struct uvm_pagerops pmap_pager;
+extern const struct uvm_pagerops bufcache_pager;
/* For object trees */
int uvm_pagecmp(const struct vm_page *, const struct vm_page *);
@@ -91,6 +93,12 @@ RBT_PROTOTYPE(uvm_objtree, vm_page, objt
#define UVM_OBJ_IS_AOBJ(uobj)
\
((uobj)->pgops == &aobj_pager)
+
+#define UVM_OBJ_IS_PMAP(uobj) \
+ ((uobj)->pgops == &pmap_pager)
+
+#define UVM_OBJ_IS_BUFCACHE(uobj) \
+ ((uobj)->pgops == &bufcache_pager)
void uvm_obj_init(struct uvm_object *, const struct uvm_pagerops *, int);
int uvm_obj_wire(struct uvm_object *, voff_t, voff_t, struct pglist *);
Index: uvm/uvm_page.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_page.c,v
retrieving revision 1.157
diff -u -p -r1.157 uvm_page.c
--- uvm/uvm_page.c 21 Apr 2021 10:02:05 -0000 1.157
+++ uvm/uvm_page.c 2 Sep 2021 19:59:22 -0000
@@ -791,6 +791,8 @@ uvm_pagealloc_multi(struct uvm_object *o
struct vm_page *pg;
int i, r;
+ KASSERT(UVM_OBJ_IS_BUFCACHE(obj));
+ KERNEL_ASSERT_LOCKED();
TAILQ_INIT(&plist);
r = uvm_pglistalloc(size, dma_constraint.ucr_low,
@@ -823,6 +825,8 @@ uvm_pagerealloc_multi(struct uvm_object
int i, r;
voff_t offset;
+ KASSERT(UVM_OBJ_IS_BUFCACHE(obj));
+ KERNEL_ASSERT_LOCKED();
TAILQ_INIT(&plist);
if (size == 0)
