After careful review by David Greenman and myself, David had found a
case where blocking can occur, thereby giving other process's a chance to modify the queue where a page resides. This could cause numerous process and system failures.
This commit is contained in:
dyson
parent
f5f74ba5e1
commit
1f06055059
@ -65,7 +65,7 @@
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*
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* $Id: vm_pageout.c,v 1.72 1996/05/24 05:19:15 dyson Exp $
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* $Id: vm_pageout.c,v 1.73 1996/05/26 07:52:09 dyson Exp $
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*/
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/*
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@ -321,7 +321,6 @@ vm_pageout_flush(mc, count, sync)
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((sync || (object == kernel_object)) ? TRUE : FALSE),
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pageout_status);
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for (i = 0; i < count; i++) {
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vm_page_t mt = mc[i];
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@ -517,10 +516,9 @@ vm_pageout_map_deactivate_pages(map, entry, count, freeer)
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static int
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vm_pageout_scan()
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{
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vm_page_t m;
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int page_shortage, maxscan, maxlaunder, pcount;
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vm_page_t m, next;
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int page_shortage, addl_page_shortage, maxscan, maxlaunder, pcount;
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int pages_freed;
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vm_page_t next;
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struct proc *p, *bigproc;
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vm_offset_t size, bigsize;
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vm_object_t object;
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@ -530,7 +528,6 @@ vm_pageout_scan()
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int i;
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int s;
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pages_freed = 0;
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/*
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@ -540,38 +537,40 @@ vm_pageout_scan()
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* them.
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*/
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rescan0:
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pages_freed = 0;
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maxlaunder = (cnt.v_inactive_target > MAXLAUNDER) ?
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MAXLAUNDER : cnt.v_inactive_target;
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rescan1:
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rescan0:
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addl_page_shortage = 0;
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maxscan = cnt.v_inactive_count;
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m = TAILQ_FIRST(&vm_page_queue_inactive);
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while ((m != NULL) && (maxscan-- > 0) &&
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((cnt.v_cache_count + cnt.v_free_count) <
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(cnt.v_cache_min + cnt.v_free_target))) {
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vm_page_t next;
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for( m = TAILQ_FIRST(&vm_page_queue_inactive);
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(m != NULL) && (maxscan-- > 0) &&
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((cnt.v_cache_count + cnt.v_free_count) <
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(cnt.v_cache_min + cnt.v_free_target));
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m = next) {
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cnt.v_pdpages++;
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if (m->queue != PQ_INACTIVE)
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goto rescan0;
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next = TAILQ_NEXT(m, pageq);
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if (m->queue != PQ_INACTIVE) {
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printf("vm_pageout_scan: page not inactive?\n");
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break;
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if (m->hold_count) {
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TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
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TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
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addl_page_shortage++;
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continue;
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}
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/*
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* Dont mess with busy pages, keep in the front of the
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* queue, most likely are being paged out.
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*/
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if (m->busy || (m->flags & PG_BUSY)) {
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m = next;
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continue;
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}
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if (m->hold_count) {
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TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
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TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
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m = next;
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addl_page_shortage++;
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continue;
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}
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@ -587,7 +586,6 @@ vm_pageout_scan()
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m->flags &= ~PG_REFERENCED;
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pmap_clear_reference(VM_PAGE_TO_PHYS(m));
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vm_page_activate(m);
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m = next;
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continue;
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}
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@ -612,23 +610,44 @@ vm_pageout_scan()
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if (object->flags & OBJ_DEAD) {
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TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
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TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
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m = next;
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continue;
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}
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if (object->type == OBJT_VNODE) {
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vp = object->handle;
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if (VOP_ISLOCKED(vp) || vget(vp, 1)) {
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if (m->queue == PQ_INACTIVE) {
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if ((m->queue == PQ_INACTIVE) &&
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(m->hold_count == 0) &&
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(m->busy == 0) &&
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(m->flags & PG_BUSY) == 0) {
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TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
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TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
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}
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if (object->flags & OBJ_MIGHTBEDIRTY)
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++vnodes_skipped;
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if (next->queue != PQ_INACTIVE) {
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goto rescan0;
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}
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m = next;
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continue;
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}
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if (m->queue != PQ_INACTIVE) {
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if (object->flags & OBJ_MIGHTBEDIRTY)
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++vnodes_skipped;
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vput(vp);
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continue;
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}
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if (m->busy || (m->flags & PG_BUSY)) {
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TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
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TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
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vput(vp);
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continue;
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}
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if (m->hold_count) {
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TAILQ_REMOVE(&vm_page_queue_inactive, m, pageq);
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TAILQ_INSERT_TAIL(&vm_page_queue_inactive, m, pageq);
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if (object->flags & OBJ_MIGHTBEDIRTY)
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++vnodes_skipped;
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vput(vp);
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continue;
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}
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}
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@ -644,20 +663,8 @@ vm_pageout_scan()
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if (vp)
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vput(vp);
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if (!next) {
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break;
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}
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maxlaunder -= written;
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/*
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* if the next page has been re-activated, start
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* scanning again
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*/
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if (next->queue != PQ_INACTIVE) {
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vm_pager_sync();
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goto rescan1;
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}
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}
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m = next;
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}
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/*
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@ -666,7 +673,7 @@ vm_pageout_scan()
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* inactive.
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*/
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page_shortage = cnt.v_inactive_target -
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page_shortage = (cnt.v_inactive_target + cnt.v_cache_min) -
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(cnt.v_free_count + cnt.v_inactive_count + cnt.v_cache_count);
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if (page_shortage <= 0) {
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if (pages_freed == 0) {
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@ -675,6 +682,11 @@ vm_pageout_scan()
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page_shortage = 1;
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}
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}
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if (addl_page_shortage) {
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if (page_shortage < 0)
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page_shortage = 0;
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page_shortage += addl_page_shortage;
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}
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pcount = cnt.v_active_count;
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s = splvm();
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@ -812,6 +824,36 @@ vm_pageout_scan()
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return force_wakeup;
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}
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static int
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vm_pageout_free_page_calc(count)
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vm_size_t count;
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{
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if (count < cnt.v_page_count)
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return 0;
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/*
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* free_reserved needs to include enough for the largest swap pager
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* structures plus enough for any pv_entry structs when paging.
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*/
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if (cnt.v_page_count > 1024)
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cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
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else
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cnt.v_free_min = 4;
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cnt.v_pageout_free_min = 2 + VM_PAGEOUT_PAGE_COUNT
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+ cnt.v_interrupt_free_min;
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cnt.v_free_reserved = cnt.v_pageout_free_min + (count / 1024);
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cnt.v_free_min += cnt.v_free_reserved;
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return 1;
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}
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int
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vm_pageout_free_pages(object, add)
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vm_object_t object;
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int add;
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{
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return vm_pageout_free_page_calc(object->size);
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}
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/*
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* vm_pageout is the high level pageout daemon.
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*/
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@ -826,19 +868,12 @@ vm_pageout()
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cnt.v_interrupt_free_min = 2;
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if (cnt.v_page_count > 1024)
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cnt.v_free_min = 4 + (cnt.v_page_count - 1024) / 200;
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else
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cnt.v_free_min = 4;
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vm_pageout_free_page_calc(cnt.v_page_count);
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/*
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* free_reserved needs to include enough for the largest swap pager
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* structures plus enough for any pv_entry structs when paging.
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*/
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cnt.v_pageout_free_min = 6 + cnt.v_page_count / 1024 +
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cnt.v_interrupt_free_min;
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cnt.v_free_reserved = cnt.v_pageout_free_min + 6;
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cnt.v_free_target = 3 * cnt.v_free_min + cnt.v_free_reserved;
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cnt.v_free_min += cnt.v_free_reserved;
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if (cnt.v_free_count > 1024) {
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cnt.v_cache_max = (cnt.v_free_count - 1024) / 2;
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@ -864,23 +899,23 @@ vm_pageout()
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int s = splvm();
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if (!vm_pages_needed ||
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((cnt.v_free_count >= cnt.v_free_reserved) &&
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(cnt.v_free_count + cnt.v_cache_count >= cnt.v_free_min))) {
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((cnt.v_free_count + cnt.v_cache_count) > cnt.v_free_min))) {
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vm_pages_needed = 0;
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tsleep(&vm_pages_needed, PVM, "psleep", 0);
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} else if (!vm_pages_needed) {
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tsleep(&vm_pages_needed, PVM, "psleep", hz/3);
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}
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inactive_target =
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(cnt.v_page_count - cnt.v_wire_count) / 4;
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if (inactive_target < 2*cnt.v_free_min)
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inactive_target = 2*cnt.v_free_min;
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cnt.v_inactive_target = inactive_target;
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if (vm_pages_needed)
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cnt.v_pdwakeups++;
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vm_pages_needed = 0;
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splx(s);
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vm_pager_sync();
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vm_pageout_scan();
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inactive_target =
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(cnt.v_page_count - cnt.v_wire_count) / 4;
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if (inactive_target < 2*cnt.v_free_min)
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inactive_target = 2*cnt.v_free_min;
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cnt.v_inactive_target = inactive_target;
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vm_pager_sync();
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wakeup(&cnt.v_free_count);
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}
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