restructure vm_object_overlay() to collapse objects in more cases.
change one diag panic() to a diag printf(). from mycroft.
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mrg
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8eba4aeacb
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3b9c3fff2e
@ -1,4 +1,4 @@
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/* $NetBSD: vm_object.c,v 1.42 1997/02/21 20:30:49 thorpej Exp $ */
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/* $NetBSD: vm_object.c,v 1.43 1997/02/23 09:01:37 mrg Exp $ */
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/*-
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* Copyright (c) 1997 Charles M. Hannum. All rights reserved.
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@ -321,7 +321,7 @@ vm_object_deallocate(object)
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#ifdef DIAGNOSTIC
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if (vm_object_paging(object))
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panic("vm_object_deallocate: unreferenced object still paging");
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printf("vm_object_deallocate: unreferenced object still paging\n");
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#endif
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/*
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@ -1176,10 +1176,34 @@ vm_object_overlay(object)
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backing_object->size);
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}
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/*
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* At this point, there may still be asynchronous paging in the parent
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* object. Any pages being paged in will be represented by fake pages.
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* There are three cases:
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* 1) The page is being paged in from the parent object's own pager.
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* In this case, we just delete our copy, since it's not needed.
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* 2) The page is being paged in from the backing object. We prevent
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* this case by waiting for paging to complete on the backing object
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* before continuing.
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* 3) The page is being paged in from a backing object behind the one
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* we're deleting. We'll never notice this case, because the
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* backing object we're deleting won't have the page.
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*/
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vm_object_unlock(object);
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RetryRename:
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vm_object_unlock(backing_object);
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vm_object_paging_wait(object);
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vm_object_lock(backing_object);
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vm_object_paging_wait(backing_object);
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/*
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* While we were asleep, the parent object might have been deleted. If
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* so, the backing object will now have only one reference (the one we
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* hold). If this happened, just deallocate the backing object and
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* return failure status so vm_object_collapse() will stop. This will
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* continue vm_object_deallocate() where it stopped due to our
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* reference.
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*/
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if (backing_object->ref_count == 1)
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goto fail;
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vm_object_lock(object);
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/*
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* Next, move any pages in core from the backing object to the
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@ -1191,11 +1215,10 @@ RetryRename:
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next_page = backing_page->listq.tqe_next;
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new_offset = backing_page->offset - backing_offset;
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/*
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* If this page is currently in transit, don't mess with it.
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*/
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if (backing_page->flags & PG_BUSY)
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continue;
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#ifdef DIAGNOSTIC
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if (backing_page->flags & (PG_BUSY | PG_FAKE))
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panic("vm_object_overlay: busy or fake page in backing_object");
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#endif
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/*
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* If the parent has a page here, or if this page falls
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@ -1205,22 +1228,9 @@ RetryRename:
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*/
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if (backing_page->offset >= backing_offset &&
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new_offset < object->size &&
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((page = vm_page_lookup(object, new_offset)) == NULL ||
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(page->flags & PG_FAKE)) &&
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((page = vm_page_lookup(object, new_offset)) == NULL) &&
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(object->pager == NULL ||
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!vm_pager_has_page(object->pager, new_offset))) {
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/*
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* If the parent had a fake page with no backing store,
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* delete it and wake up anyone who might have been
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* waiting for it.
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*/
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if (page) {
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#ifdef DIAGNOSTIC
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printf("vm_object_overlay: fake page with no backing store\n");
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#endif
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FREE_PAGE(page);
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}
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/*
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* If the backing page was ever paged out, it was due
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* to it being dirty at one point. Unless we have no
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@ -1265,13 +1275,6 @@ RetryRename:
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if (backing_object->pager == NULL)
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goto done;
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/*
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* If there is still asynchronous paging on the backing object, we
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* can't do any more, so punt.
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*/
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if (vm_object_paging(backing_object))
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goto fail;
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/*
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* If the parent object has no pager, then simply move the pager
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* from the backing object.
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@ -1297,22 +1300,9 @@ RetryRename:
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* If the parent object already has this page, delete it.
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* Otherwise, start a pagein.
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*/
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if (((page = vm_page_lookup(object, new_offset)) == NULL ||
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(page->flags & PG_FAKE)) &&
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if (((page = vm_page_lookup(object, new_offset)) == NULL) &&
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(object->pager == NULL ||
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!vm_pager_has_page(object->pager, new_offset))) {
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/*
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* If the parent had a fake page with no backing store,
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* delete it and wake up anyone who might have been
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* waiting for it.
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*/
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if (page) {
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#ifdef DIAGNOSTIC
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printf("vm_object_overlay: fake page with no backing store\n");
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#endif
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FREE_PAGE(page);
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}
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vm_object_unlock(object);
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/*
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@ -1325,7 +1315,7 @@ RetryRename:
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vm_object_unlock(backing_object);
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VM_WAIT;
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vm_object_lock(backing_object);
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goto Retry2;
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goto RetryRename;
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}
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vm_object_paging_begin(backing_object);
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@ -1365,19 +1355,6 @@ RetryRename:
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backing_page->flags &= ~(PG_FAKE | PG_CLEAN);
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PAGE_WAKEUP(backing_page);
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Retry2:
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/*
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* While we were asleep, the parent object might have
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* been deleted. If so, the backing object will now
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* have only one reference (the one we hold). If this
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* happened, just deallocate the backing object and
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* return failure status so vm_object_collapse() will
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* stop.
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*/
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if (backing_object->ref_count == 1)
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goto fail;
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vm_object_lock(object);
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goto RetryRename;
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} else {
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/*
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@ -1444,31 +1421,20 @@ vm_object_bypass(object)
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vm_page_t backing_page, page;
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/*
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* If all of the pages in the backing object are
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* shadowed by the parent object, the parent
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* object no longer has to shadow the backing
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* object; it can shadow the next one in the
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* chain.
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* If all of the pages in the backing object are shadowed by the parent
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* object, the parent object no longer has to shadow the backing
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* object; it can shadow the next one in the chain.
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*
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* The backing object must not be paged out - we'd
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* have to check all of the paged-out pages, as
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* well.
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*/
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if (backing_object->pager != NULL)
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goto fail;
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#if 0
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/*
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* If the parent object is currently paging, punt.
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* Since we're not actually saving any space here, it's not worth
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* bothering to slog through the backing object's pager looking for
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* pages, or waiting for paging to complete.
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*
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* XXXXX FIXME
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* Why do we do this? If it's a pagein, there should be a page
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* allocated already. If it's a pageout, then there always is.
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* We should still be able to do the scan.
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* See comments in vm_object_overlay() regarding simultaneous paging in
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* the parent object.
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*/
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if (vm_object_paging(object))
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if (vm_object_paging(backing_object) ||
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backing_object->pager != NULL)
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goto fail;
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#endif
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/*
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* Should have a check for a 'small' number
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@ -1479,6 +1445,11 @@ vm_object_bypass(object)
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backing_page = backing_page->listq.tqe_next) {
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new_offset = backing_page->offset - backing_offset;
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#ifdef DIAGNOSTIC
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if (backing_page->flags & (PG_BUSY | PG_FAKE))
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panic("vm_object_bypass: busy or fake page in backing_object");
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#endif
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/*
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* If the parent has a page here, or if this page falls
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* outside the parent, keep going.
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@ -1487,8 +1458,7 @@ vm_object_bypass(object)
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*/
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if (backing_page->offset >= backing_offset &&
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new_offset < object->size &&
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((page = vm_page_lookup(object, new_offset)) == NULL ||
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(page->flags & PG_FAKE)) &&
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((page = vm_page_lookup(object, new_offset)) == NULL) &&
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(object->pager == NULL ||
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!vm_pager_has_page(object->pager, new_offset))) {
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/*
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@ -1517,8 +1487,7 @@ vm_object_bypass(object)
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/*
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* Since backing_object's ref_count was at least 2, it will not
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* vanish, but we need to decrease the reference count on the
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* backing object anyway.
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* vanish, but we need to decrease its reference count anyway.
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*/
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object_bypasses++;
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vm_object_unlock(backing_object);
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