in amap_cow_now(), handle the case where we have to sleep and some of the
already-copied pages are paged out. anons that have already been copied will have refcount == 1, whereas anons that still need to be copied will have refcount > 1. fixes PR 25392, PR 30257, PR 31924.
This commit is contained in:
chs
parent
0c24d80f02
commit
5332333501
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@ -1,4 +1,4 @@
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/* $NetBSD: uvm_amap.c,v 1.65 2005/09/13 22:00:05 yamt Exp $ */
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/* $NetBSD: uvm_amap.c,v 1.66 2005/11/06 15:57:32 chs Exp $ */
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/*
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*
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@ -42,7 +42,7 @@
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*/
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#include <sys/cdefs.h>
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__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.65 2005/09/13 22:00:05 yamt Exp $");
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__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.66 2005/11/06 15:57:32 chs Exp $");
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#undef UVM_AMAP_INLINE /* enable/disable amap inlines */
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@ -916,7 +916,6 @@ amap_cow_now(struct vm_map *map, struct vm_map_entry *entry)
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ReStart:
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amap_lock(amap);
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for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
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/*
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@ -926,89 +925,98 @@ ReStart:
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slot = amap->am_slots[lcv];
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anon = amap->am_anon[slot];
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simple_lock(&anon->an_lock);
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pg = anon->an_page;
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/*
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* page must be resident since parent is wired
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* If the anon has only one ref, we must have already copied it.
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* This can happen if we needed to sleep waiting for memory
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* in a previous run through this loop. The new page might
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* even have been paged out, since the new page is not wired.
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*/
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if (pg == NULL)
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panic("amap_cow_now: non-resident wired page in anon %p",
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anon);
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/*
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* if the anon ref count is one and the page is not loaned,
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* then we are safe (the child has exclusive access to the
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* page). if the page is loaned, then it must already be
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* mapped read-only.
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*
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* we only need to get involved when these are not true.
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* [note: if loan_count == 0, then the anon must own the page]
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*/
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if (anon->an_ref > 1 && pg->loan_count == 0) {
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/*
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* if the page is busy then we have to unlock, wait for
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* it and then restart.
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*/
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if (pg->flags & PG_BUSY) {
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pg->flags |= PG_WANTED;
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amap_unlock(amap);
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UVM_UNLOCK_AND_WAIT(pg, &anon->an_lock, FALSE,
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"cownow", 0);
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goto ReStart;
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}
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/*
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* ok, time to do a copy-on-write to a new anon
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*/
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nanon = uvm_analloc();
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if (nanon) {
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/* nanon is locked! */
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npg = uvm_pagealloc(NULL, 0, nanon, 0);
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} else
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npg = NULL; /* XXX: quiet gcc warning */
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if (nanon == NULL || npg == NULL) {
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/* out of memory */
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/*
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* XXXCDC: we should cause fork to fail, but
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* we can't ...
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*/
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if (nanon) {
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nanon->an_ref--;
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simple_unlock(&nanon->an_lock);
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uvm_anfree(nanon);
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}
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simple_unlock(&anon->an_lock);
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amap_unlock(amap);
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uvm_wait("cownowpage");
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goto ReStart;
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}
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/*
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* got it... now we can copy the data and replace anon
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* with our new one...
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*/
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uvm_pagecopy(pg, npg); /* old -> new */
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anon->an_ref--; /* can't drop to zero */
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amap->am_anon[slot] = nanon; /* replace */
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/*
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* drop PG_BUSY on new page ... since we have had it's
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* owner locked the whole time it can't be
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* PG_RELEASED | PG_WANTED.
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*/
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uvm_lock_pageq();
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uvm_pageactivate(npg);
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uvm_unlock_pageq();
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npg->flags &= ~(PG_BUSY|PG_FAKE);
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UVM_PAGE_OWN(npg, NULL);
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simple_unlock(&nanon->an_lock);
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if (anon->an_ref == 1) {
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KASSERT(anon->an_page != NULL || anon->an_swslot != 0);
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simple_unlock(&anon->an_lock);
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continue;
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}
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/*
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* The old page must be resident since the parent is wired.
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*/
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pg = anon->an_page;
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KASSERT(pg != NULL);
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KASSERT(pg->wire_count > 0);
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/*
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* If the page is loaned then it must already be mapped
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* read-only and we don't need to copy it.
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*/
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if (pg->loan_count != 0) {
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simple_unlock(&anon->an_lock);
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continue;
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}
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KASSERT(pg->uanon == anon && pg->uobject == NULL);
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/*
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* if the page is busy then we have to unlock, wait for
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* it and then restart.
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*/
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if (pg->flags & PG_BUSY) {
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pg->flags |= PG_WANTED;
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amap_unlock(amap);
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UVM_UNLOCK_AND_WAIT(pg, &anon->an_lock, FALSE,
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"cownow", 0);
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goto ReStart;
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}
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/*
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* ok, time to do a copy-on-write to a new anon
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*/
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nanon = uvm_analloc();
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if (nanon) {
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npg = uvm_pagealloc(NULL, 0, nanon, 0);
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} else
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npg = NULL; /* XXX: quiet gcc warning */
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if (nanon == NULL || npg == NULL) {
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/*
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* XXXCDC: we should cause fork to fail, but we can't.
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*/
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if (nanon) {
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nanon->an_ref--;
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simple_unlock(&nanon->an_lock);
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uvm_anfree(nanon);
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}
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simple_unlock(&anon->an_lock);
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amap_unlock(amap);
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uvm_wait("cownowpage");
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goto ReStart;
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}
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/*
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* got it... now we can copy the data and replace anon
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* with our new one...
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*/
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uvm_pagecopy(pg, npg); /* old -> new */
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anon->an_ref--; /* can't drop to zero */
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amap->am_anon[slot] = nanon; /* replace */
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/*
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* drop PG_BUSY on new page ... since we have had its owner
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* locked the whole time it can't be PG_RELEASED or PG_WANTED.
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*/
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uvm_lock_pageq();
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uvm_pageactivate(npg);
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uvm_unlock_pageq();
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npg->flags &= ~(PG_BUSY|PG_FAKE);
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UVM_PAGE_OWN(npg, NULL);
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simple_unlock(&nanon->an_lock);
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simple_unlock(&anon->an_lock);
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}
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amap_unlock(amap);
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