/* * uvm_loanbreak: break loan on a uobj page * * => called with uobj locked * => the page should be busy * => return value: * newly allocated page if succeeded */ struct vm_page * uvm_loanbreak(struct vm_page *uobjpage) { struct vm_page *pg; #ifdef DIAGNOSTIC struct uvm_object *uobj = uobjpage->uobject; #endif KASSERT(uobj != NULL); KASSERT(mutex_owned(&uobj->vmobjlock)); KASSERT(uobjpage->flags & PG_BUSY); /* alloc new un-owned page */ pg = uvm_pagealloc(NULL, 0, NULL, 0); if (pg == NULL) return NULL; /* * copy the data from the old page to the new * one and clear the fake flags on the new page (keep it busy). * force a reload of the old page by clearing it from all * pmaps. * transfer dirtiness of the old page to the new page. * then lock the page queues to rename the pages. */ uvm_pagecopy(uobjpage, pg); /* old -> new */ pg->flags &= ~PG_FAKE; pmap_page_protect(uobjpage, VM_PROT_NONE); if ((uobjpage->flags & PG_CLEAN) != 0 && !pmap_clear_modify(uobjpage)) { pmap_clear_modify(pg); pg->flags |= PG_CLEAN; } else { /* uvm_pagecopy marked it dirty */ KASSERT((pg->flags & PG_CLEAN) == 0); /* a object with a dirty page should be dirty. */ KASSERT(!UVM_OBJ_IS_CLEAN(uobj)); } if (uobjpage->flags & PG_WANTED) wakeup(uobjpage); /* uobj still locked */ uobjpage->flags &= ~(PG_WANTED|PG_BUSY); UVM_PAGE_OWN(uobjpage, NULL); mutex_enter(&uvm_pageqlock); /* * replace uobjpage with new page. */ uvm_pagereplace(uobjpage, pg); /* * if the page is no longer referenced by * an anon (i.e. we are breaking an O->K * loan), then remove it from any pageq's. */ if (uobjpage->uanon == NULL) uvm_pagedequeue(uobjpage); /* * at this point we have absolutely no * control over uobjpage */ /* install new page */ uvm_pageactivate(pg); mutex_exit(&uvm_pageqlock); /* * done! loan is broken and "pg" is * PG_BUSY. it can now replace uobjpage. */ return pg; }
int uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap, struct vm_anon *anon) { boolean_t we_own; /* we own anon's page? */ boolean_t locked; /* did we relock? */ struct vm_page *pg; int result; result = 0; /* XXX shut up gcc */ uvmexp.fltanget++; /* bump rusage counters */ if (anon->an_page) curproc->p_ru.ru_minflt++; else curproc->p_ru.ru_majflt++; /* * loop until we get it, or fail. */ while (1) { we_own = FALSE; /* TRUE if we set PG_BUSY on a page */ pg = anon->an_page; /* * if there is a resident page and it is loaned, then anon * may not own it. call out to uvm_anon_lockpage() to ensure * the real owner of the page has been identified and locked. */ if (pg && pg->loan_count) pg = uvm_anon_lockloanpg(anon); /* * page there? make sure it is not busy/released. */ if (pg) { /* * at this point, if the page has a uobject [meaning * we have it on loan], then that uobject is locked * by us! if the page is busy, we drop all the * locks (including uobject) and try again. */ if ((pg->pg_flags & (PG_BUSY|PG_RELEASED)) == 0) { return (VM_PAGER_OK); } atomic_setbits_int(&pg->pg_flags, PG_WANTED); uvmexp.fltpgwait++; /* * the last unlock must be an atomic unlock+wait on * the owner of page */ if (pg->uobject) { /* owner is uobject ? */ uvmfault_unlockall(ufi, amap, NULL, anon); UVM_UNLOCK_AND_WAIT(pg, &pg->uobject->vmobjlock, FALSE, "anonget1",0); } else { /* anon owns page */ uvmfault_unlockall(ufi, amap, NULL, NULL); UVM_UNLOCK_AND_WAIT(pg,&anon->an_lock,0, "anonget2",0); } /* ready to relock and try again */ } else { /* * no page, we must try and bring it in. */ pg = uvm_pagealloc(NULL, 0, anon, 0); if (pg == NULL) { /* out of RAM. */ uvmfault_unlockall(ufi, amap, NULL, anon); uvmexp.fltnoram++; uvm_wait("flt_noram1"); /* ready to relock and try again */ } else { /* we set the PG_BUSY bit */ we_own = TRUE; uvmfault_unlockall(ufi, amap, NULL, anon); /* * we are passing a PG_BUSY+PG_FAKE+PG_CLEAN * page into the uvm_swap_get function with * all data structures unlocked. note that * it is ok to read an_swslot here because * we hold PG_BUSY on the page. */ uvmexp.pageins++; result = uvm_swap_get(pg, anon->an_swslot, PGO_SYNCIO); /* * we clean up after the i/o below in the * "we_own" case */ /* ready to relock and try again */ } } /* * now relock and try again */ locked = uvmfault_relock(ufi); if (locked || we_own) simple_lock(&anon->an_lock); /* * if we own the page (i.e. we set PG_BUSY), then we need * to clean up after the I/O. there are three cases to * consider: * [1] page released during I/O: free anon and ReFault. * [2] I/O not OK. free the page and cause the fault * to fail. * [3] I/O OK! activate the page and sync with the * non-we_own case (i.e. drop anon lock if not locked). */ if (we_own) { if (pg->pg_flags & PG_WANTED) { /* still holding object lock */ wakeup(pg); } /* un-busy! */ atomic_clearbits_int(&pg->pg_flags, PG_WANTED|PG_BUSY|PG_FAKE); UVM_PAGE_OWN(pg, NULL); /* * if we were RELEASED during I/O, then our anon is * no longer part of an amap. we need to free the * anon and try again. */ if (pg->pg_flags & PG_RELEASED) { pmap_page_protect(pg, VM_PROT_NONE); simple_unlock(&anon->an_lock); uvm_anfree(anon); /* frees page for us */ if (locked) uvmfault_unlockall(ufi, amap, NULL, NULL); uvmexp.fltpgrele++; return (VM_PAGER_REFAULT); /* refault! */ } if (result != VM_PAGER_OK) { KASSERT(result != VM_PAGER_PEND); /* remove page from anon */ anon->an_page = NULL; /* * remove the swap slot from the anon * and mark the anon as having no real slot. * don't free the swap slot, thus preventing * it from being used again. */ uvm_swap_markbad(anon->an_swslot, 1); anon->an_swslot = SWSLOT_BAD; /* * note: page was never !PG_BUSY, so it * can't be mapped and thus no need to * pmap_page_protect it... */ uvm_lock_pageq(); uvm_pagefree(pg); uvm_unlock_pageq(); if (locked) uvmfault_unlockall(ufi, amap, NULL, anon); else simple_unlock(&anon->an_lock); return (VM_PAGER_ERROR); } /* * must be OK, clear modify (already PG_CLEAN) * and activate */ pmap_clear_modify(pg); uvm_lock_pageq(); uvm_pageactivate(pg); uvm_unlock_pageq(); if (!locked) simple_unlock(&anon->an_lock); } /* * we were not able to relock. restart fault. */ if (!locked) return (VM_PAGER_REFAULT); /* * verify no one has touched the amap and moved the anon on us. */ if (ufi != NULL && amap_lookup(&ufi->entry->aref, ufi->orig_rvaddr - ufi->entry->start) != anon) { uvmfault_unlockall(ufi, amap, NULL, anon); return (VM_PAGER_REFAULT); } /* * try it again! */ uvmexp.fltanretry++; continue; } /* while (1) */ /*NOTREACHED*/ }