Simplify locking by using an intermediate lock variable.

While here get rid of the unused returned value of uvmpd_scan_inactive().

ok jsg@, kn@

diff --git a/sys/uvm/uvm_pdaemon.c b/sys/uvm/uvm_pdaemon.c
index 52baa2e..020ee69 100644 (file)
--- a/sys/uvm/uvm_pdaemon.c
+++ b/sys/uvm/uvm_pdaemon.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: uvm_pdaemon.c,v 1.101 2022/06/28 19:31:30 mpi Exp $   */
+/*     $OpenBSD: uvm_pdaemon.c,v 1.102 2022/08/22 12:03:32 mpi Exp $   */
 /*     $NetBSD: uvm_pdaemon.c,v 1.23 2000/08/20 10:24:14 bjh21 Exp $   */
 
 /*
@@ -102,7 +102,7 @@ extern void drmbackoff(long);
  */
 
 void           uvmpd_scan(struct uvm_pmalloc *);
-boolean_t      uvmpd_scan_inactive(struct uvm_pmalloc *, struct pglist *);
+void           uvmpd_scan_inactive(struct uvm_pmalloc *, struct pglist *);
 void           uvmpd_tune(void);
 void           uvmpd_drop(struct pglist *);
 
@@ -377,17 +377,16 @@ uvm_aiodone_daemon(void *arg)
  * => we handle the building of swap-backed clusters
  * => we return TRUE if we are exiting because we met our target
  */
-
-boolean_t
+void
 uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
 {
-       boolean_t retval = FALSE;       /* assume we haven't hit target */
        int free, result;
        struct vm_page *p, *nextpg;
        struct uvm_object *uobj;
        struct vm_page *pps[SWCLUSTPAGES], **ppsp;
        int npages;
        struct vm_page *swpps[SWCLUSTPAGES];    /* XXX: see below */
+       struct rwlock *slock;
        int swnpages, swcpages;                         /* XXX: see below */
        int swslot;
        struct vm_anon *anon;
@@ -402,7 +401,6 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
         */
        swslot = 0;
        swnpages = swcpages = 0;
-       free = 0;
        dirtyreacts = 0;
        p = NULL;
 
@@ -431,18 +429,14 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                 */
                uobj = NULL;
                anon = NULL;
-
                if (p) {
                        /*
-                        * update our copy of "free" and see if we've met
-                        * our target
+                        * see if we've met our target
                         */
                        free = uvmexp.free - BUFPAGES_DEFICIT;
                        if (((pma == NULL || (pma->pm_flags & UVM_PMA_FREED)) &&
                            (free + uvmexp.paging >= uvmexp.freetarg << 2)) ||
                            dirtyreacts == UVMPD_NUMDIRTYREACTS) {
-                               retval = TRUE;
-
                                if (swslot == 0) {
                                        /* exit now if no swap-i/o pending */
                                        break;
@@ -450,9 +444,9 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
 
                                /* set p to null to signal final swap i/o */
                                p = NULL;
+                               nextpg = NULL;
                        }
                }
-
                if (p) {        /* if (we have a new page to consider) */
                        /*
                         * we are below target and have a new page to consider.
@@ -460,11 +454,12 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                        uvmexp.pdscans++;
                        nextpg = TAILQ_NEXT(p, pageq);
 
+                       anon = p->uanon;
+                       uobj = p->uobject;
                        if (p->pg_flags & PQ_ANON) {
-                               anon = p->uanon;
                                KASSERT(anon != NULL);
-                               if (rw_enter(anon->an_lock,
-                                   RW_WRITE|RW_NOSLEEP)) {
+                               slock = anon->an_lock;
+                               if (rw_enter(slock, RW_WRITE|RW_NOSLEEP)) {
                                        /* lock failed, skip this page */
                                        continue;
                                }
@@ -474,23 +469,20 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                                 */
                                if (pmap_is_referenced(p)) {
                                        uvm_pageactivate(p);
-                                       rw_exit(anon->an_lock);
+                                       rw_exit(slock);
                                        uvmexp.pdreact++;
                                        continue;
                                }
                                if (p->pg_flags & PG_BUSY) {
-                                       rw_exit(anon->an_lock);
+                                       rw_exit(slock);
                                        uvmexp.pdbusy++;
-                                       /* someone else owns page, skip it */
                                        continue;
                                }
                                uvmexp.pdanscan++;
                        } else {
-                               uobj = p->uobject;
                                KASSERT(uobj != NULL);
-                               if (rw_enter(uobj->vmobjlock,
-                                   RW_WRITE|RW_NOSLEEP)) {
-                                       /* lock failed, skip this page */
+                               slock = uobj->vmobjlock;
+                               if (rw_enter(slock, RW_WRITE|RW_NOSLEEP)) {
                                        continue;
                                }
                                /*
@@ -499,14 +491,13 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                                 */
                                if (pmap_is_referenced(p)) {
                                        uvm_pageactivate(p);
-                                       rw_exit(uobj->vmobjlock);
+                                       rw_exit(slock);
                                        uvmexp.pdreact++;
                                        continue;
                                }
                                if (p->pg_flags & PG_BUSY) {
-                                       rw_exit(uobj->vmobjlock);
+                                       rw_exit(slock);
                                        uvmexp.pdbusy++;
-                                       /* someone else owns page, skip it */
                                        continue;
                                }
                                uvmexp.pdobscan++;
@@ -539,10 +530,8 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
 
                                        /* remove from object */
                                        anon->an_page = NULL;
-                                       rw_exit(anon->an_lock);
-                               } else {
-                                       rw_exit(uobj->vmobjlock);
                                }
+                               rw_exit(slock);
                                continue;
                        }
 
@@ -552,11 +541,7 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                         */
                        if ((pma == NULL || (pma->pm_flags & UVM_PMA_FREED)) &&
                            (free + uvmexp.paging > uvmexp.freetarg << 2)) {
-                               if (anon) {
-                                       rw_exit(anon->an_lock);
-                               } else {
-                                       rw_exit(uobj->vmobjlock);
-                               }
+                               rw_exit(slock);
                                continue;
                        }
 
@@ -569,11 +554,7 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                        if ((p->pg_flags & PQ_SWAPBACKED) && uvm_swapisfull()) {
                                dirtyreacts++;
                                uvm_pageactivate(p);
-                               if (anon) {
-                                       rw_exit(anon->an_lock);
-                               } else {
-                                       rw_exit(uobj->vmobjlock);
-                               }
+                               rw_exit(slock);
                                continue;
                        }
 
@@ -640,11 +621,7 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                                                    &p->pg_flags,
                                                    PG_BUSY);
                                                UVM_PAGE_OWN(p, NULL);
-                                               if (anon)
-                                                       rw_exit(anon->an_lock);
-                                               else
-                                                       rw_exit(
-                                                           uobj->vmobjlock);
+                                               rw_exit(slock);
                                                continue;
                                        }
                                        swcpages = 0;   /* cluster is empty */
@@ -676,10 +653,7 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                 */
                if (swap_backed) {
                        if (p) {        /* if we just added a page to cluster */
-                               if (anon)
-                                       rw_exit(anon->an_lock);
-                               else
-                                       rw_exit(uobj->vmobjlock);
+                               rw_exit(slock);
 
                                /* cluster not full yet? */
                                if (swcpages < swnpages)
@@ -791,10 +765,7 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
 
                        /* !swap_backed case: already locked... */
                        if (swap_backed) {
-                               if (anon)
-                                       rw_enter(anon->an_lock, RW_WRITE);
-                               else
-                                       rw_enter(uobj->vmobjlock, RW_WRITE);
+                               rw_enter(slock, RW_WRITE);
                        }
 
 #ifdef DIAGNOSTIC
@@ -855,10 +826,7 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                         * the inactive queue can't be re-queued [note: not
                         * true for active queue]).
                         */
-                       if (anon)
-                               rw_exit(anon->an_lock);
-                       else if (uobj)
-                               rw_exit(uobj->vmobjlock);
+                       rw_exit(slock);
 
                        if (nextpg && (nextpg->pg_flags & PQ_INACTIVE) == 0) {
                                nextpg = TAILQ_FIRST(pglst);    /* reload! */
@@ -877,7 +845,6 @@ uvmpd_scan_inactive(struct uvm_pmalloc *pma, struct pglist *pglst)
                        uvm_lock_pageq();
                }
        }
-       return (retval);
 }
 
 /*
@@ -925,10 +892,6 @@ uvmpd_scan(struct uvm_pmalloc *pma)
         * to inactive ones.
         */
 
-       /*
-        * alternate starting queue between swap and object based on the
-        * low bit of uvmexp.pdrevs (which we bump by one each call).
-        */
        pages_freed = uvmexp.pdfreed;
        (void) uvmpd_scan_inactive(pma, &uvm.page_inactive);
        pages_freed = uvmexp.pdfreed - pages_freed;