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Do not busy pages that are resident & fetched with PGO_LOCKED.

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This is safe because the rwlock of the related object is never released until
the handler is done with the pages.

ok kettenis@, tb@
This commit is contained in:
mpi 2024-12-18 16:41:27 +00:00
parent e489b84834
commit 0528dcd014
3 changed files with 26 additions and 54 deletions
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4
sys/uvm/uvm_aobj.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: uvm_aobj.c,v 1.111 2024/11/27 10:41:38 mpi Exp $ */
/* $OpenBSD: uvm_aobj.c,v 1.112 2024/12/18 16:41:27 mpi Exp $ */
/* $NetBSD: uvm_aobj.c,v 1.39 2001/02/18 21:19:08 chs Exp $ */
/*
@ -1038,8 +1038,6 @@ uao_get(struct uvm_object *uobj, voff_t offset, struct vm_page **pps,
/*
* useful page: plug it in our result array
*/
atomic_setbits_int(&ptmp->pg_flags, PG_BUSY);
UVM_PAGE_OWN(ptmp, "uao_get1");
pps[lcv] = ptmp;
gotpages++;
}

72
sys/uvm/uvm_fault.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: uvm_fault.c,v 1.153 2024/12/15 11:02:59 mpi Exp $ */
/* $OpenBSD: uvm_fault.c,v 1.154 2024/12/18 16:41:27 mpi Exp $ */
/* $NetBSD: uvm_fault.c,v 1.51 2000/08/06 00:22:53 thorpej Exp $ */
/*
@ -1140,14 +1140,13 @@ uvm_fault_lower_lookup(
pages[lcv] == PGO_DONTCARE)
continue;
KASSERT((pages[lcv]->pg_flags & PG_BUSY) == 0);
KASSERT((pages[lcv]->pg_flags & PG_RELEASED) == 0);
/*
* if center page is resident and not
* PG_BUSY, then pgo_get made it PG_BUSY
* for us and gave us a handle to it.
* remember this page as "uobjpage."
* (for later use).
* if center page is resident and not PG_BUSY, then pgo_get
* gave us a handle to it.
* remember this page as "uobjpage." (for later use).
*/
if (lcv == flt->centeridx) {
uobjpage = pages[lcv];
@ -1155,8 +1154,13 @@ uvm_fault_lower_lookup(
}
if (pmap_extract(ufi->orig_map->pmap, currva, &pa))
goto next;
continue;
/*
* calling pgo_get with PGO_LOCKED returns us pages which
* are neither busy nor released, so we don't need to check
* for this. we can just directly enter the pages.
*/
if (pages[lcv]->wire_count == 0) {
uvm_lock_pageq();
uvm_pageactivate(pages[lcv]);
@ -1168,24 +1172,17 @@ uvm_fault_lower_lookup(
KASSERT(flt->wired == FALSE);
/*
* Since this page isn't the page that's
* actually faulting, ignore pmap_enter()
* failures; it's not critical that we
* Since this page isn't the page that's actually faulting,
* ignore pmap_enter() failures; it's not critical that we
* enter these right now.
* NOTE: page can't be PG_WANTED or PG_RELEASED because we've
* held the lock the whole time we've had the handle.
*/
(void) pmap_enter(ufi->orig_map->pmap, currva,
VM_PAGE_TO_PHYS(pages[lcv]) | flt->pa_flags,
flt->enter_prot & MASK(ufi->entry), PMAP_CANFAIL);
entered++;
/*
* NOTE: page can't be PG_WANTED because
* we've held the lock the whole time
* we've had the handle.
*/
next:
atomic_clearbits_int(&pages[lcv]->pg_flags, PG_BUSY);
UVM_PAGE_OWN(pages[lcv], NULL);
}
if (entered > 0)
pmap_update(ufi->orig_map->pmap);
@ -1273,6 +1270,11 @@ uvm_fault_lower(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
if (uobjpage) {
/* update rusage counters */
curproc->p_ru.ru_minflt++;
if (uobjpage != PGO_DONTCARE) {
uvm_lock_pageq();
uvm_pageactivate(uobjpage);
uvm_unlock_pageq();
}
} else {
error = uvm_fault_lower_io(ufi, flt, &uobj, &uobjpage);
if (error != 0)
@ -1330,21 +1332,6 @@ uvm_fault_lower(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
* out of memory resources?
*/
if (anon == NULL || pg == NULL) {
/*
* arg! must unbusy our page and fail or sleep.
*/
if (uobjpage != PGO_DONTCARE) {
uvm_lock_pageq();
uvm_pageactivate(uobjpage);
uvm_unlock_pageq();
if (uobjpage->pg_flags & PG_WANTED)
wakeup(uobjpage);
atomic_clearbits_int(&uobjpage->pg_flags,
PG_BUSY|PG_WANTED);
UVM_PAGE_OWN(uobjpage, NULL);
}
/* unlock and fail ... */
uvmfault_unlockall(ufi, amap, uobj);
if (anon == NULL)
@ -1395,16 +1382,6 @@ uvm_fault_lower(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
pmap_page_protect(uobjpage, PROT_NONE);
}
#endif
/* dispose of uobjpage. drop handle to uobj as well. */
if (uobjpage->pg_flags & PG_WANTED)
wakeup(uobjpage);
atomic_clearbits_int(&uobjpage->pg_flags,
PG_BUSY|PG_WANTED);
UVM_PAGE_OWN(uobjpage, NULL);
uvm_lock_pageq();
uvm_pageactivate(uobjpage);
uvm_unlock_pageq();
/* done with copied uobjpage. */
rw_exit(uobj->vmobjlock);
uobj = NULL;
@ -1586,15 +1563,13 @@ uvm_fault_lower_io(
locked = FALSE;
}
/* didn't get the lock? release the page and retry. */
if (locked == FALSE && pg != PGO_DONTCARE) {
/* release the page now, still holding object lock */
if (pg != PGO_DONTCARE) {
uvm_lock_pageq();
/* make sure it is in queues */
uvm_pageactivate(pg);
uvm_unlock_pageq();
if (pg->pg_flags & PG_WANTED)
/* still holding object lock */
wakeup(pg);
atomic_clearbits_int(&pg->pg_flags, PG_BUSY|PG_WANTED);
UVM_PAGE_OWN(pg, NULL);
@ -1607,7 +1582,8 @@ uvm_fault_lower_io(
}
/*
* we have the data in pg which is PG_BUSY
* we have the data in pg. we are holding object lock (so the page
* can't be released on us).
*/
*ruobj = uobj;
*ruobjpage = pg;

4
sys/uvm/uvm_vnode.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: uvm_vnode.c,v 1.135 2024/11/27 10:41:38 mpi Exp $ */
/* $OpenBSD: uvm_vnode.c,v 1.136 2024/12/18 16:41:27 mpi Exp $ */
/* $NetBSD: uvm_vnode.c,v 1.36 2000/11/24 20:34:01 chs Exp $ */
/*
@ -992,8 +992,6 @@ uvn_get(struct uvm_object *uobj, voff_t offset, struct vm_page **pps,
* useful page: busy it and plug it in our
* result array
*/
atomic_setbits_int(&ptmp->pg_flags, PG_BUSY);
UVM_PAGE_OWN(ptmp, "uvn_get1");
pps[lcv] = ptmp;
gotpages++;