Comments & style cleanup, no functional change intended.
authormpi <mpi@openbsd.org>
Tue, 16 Feb 2021 09:10:17 +0000 (09:10 +0000)
committermpi <mpi@openbsd.org>
Tue, 16 Feb 2021 09:10:17 +0000 (09:10 +0000)
- Sync comments with NetBSD including locking details.
- Remove superfluous parenthesis and spaces.
- Add brackets, even if questionable, to reduce diff with NetBSD
- Use for (;;) instead of while(1)
- Rename a variable from 'result' into 'error'.
- Move uvm_fault() and uvm_fault_upper_lookup()
- Add an locking assert in uvm_fault_upper_lookup()

ok tb@, mlarkin@

sys/uvm/uvm_fault.c

index 0203033..bd88a60 100644 (file)
@@ -1,4 +1,4 @@
-/*     $OpenBSD: uvm_fault.c,v 1.114 2021/02/15 12:12:54 mpi Exp $     */
+/*     $OpenBSD: uvm_fault.c,v 1.115 2021/02/16 09:10:17 mpi Exp $     */
 /*     $NetBSD: uvm_fault.c,v 1.51 2000/08/06 00:22:53 thorpej Exp $   */
 
 /*
  *    read/write1     write>1                  read/write   +-cow_write/zero
  *         |             |                         |        |
  *      +--|--+       +--|--+     +-----+       +  |  +     | +-----+
- * amap |  V  |       |  ----------->new|          |        | |  ^  |
+ * amap |  V  |       |  ---------> new |          |        | |  ^  |
  *      +-----+       +-----+     +-----+       +  |  +     | +--|--+
  *                                                 |        |    |
  *      +-----+       +-----+                   +--|--+     | +--|--+
- * uobj | d/c |       | d/c |                   |  V  |     +----|  |
+ * uobj | d/c |       | d/c |                   |  V  |     +----+  |
  *      +-----+       +-----+                   +-----+       +-----+
  *
  * d/c = don't care
@@ -69,7 +69,7 @@
  *
  *   case [1]: upper layer fault [anon active]
  *     1A: [read] or [write with anon->an_ref == 1]
- *             I/O takes place in top level anon and uobj is not touched.
+ *             I/O takes place in upper level anon and uobj is not touched.
  *     1B: [write with anon->an_ref > 1]
  *             new anon is alloc'd and data is copied off ["COW"]
  *
@@ -89,7 +89,7 @@
  * the code is structured as follows:
  *
  *     - init the "IN" params in the ufi structure
- *   ReFault:
+ *   ReFault: (ERESTART returned to the loop in uvm_fault)
  *     - do lookups [locks maps], check protection, handle needs_copy
  *     - check for case 0 fault (error)
  *     - establish "range" of fault
  *    by multiple map entries, and figuring out what should wait could be
  *    complex as well...).
  *
- * we use alternative 2 currently.   maybe alternative 3 would be useful
- * in the future.    XXX keep in mind for future consideration//rechecking.
+ * we use alternative 2.  given that we are multi-threaded now we may want
+ * to reconsider the choice.
  */
 
 /*
@@ -177,7 +177,7 @@ uvmfault_anonflush(struct vm_anon **anons, int n)
        int lcv;
        struct vm_page *pg;
 
-       for (lcv = 0 ; lcv < n ; lcv++) {
+       for (lcv = 0; lcv < n; lcv++) {
                if (anons[lcv] == NULL)
                        continue;
                KASSERT(rw_lock_held(anons[lcv]->an_lock));
@@ -222,14 +222,14 @@ uvmfault_init(void)
 /*
  * uvmfault_amapcopy: clear "needs_copy" in a map.
  *
+ * => called with VM data structures unlocked (usually, see below)
+ * => we get a write lock on the maps and clear needs_copy for a VA
  * => if we are out of RAM we sleep (waiting for more)
  */
 static void
 uvmfault_amapcopy(struct uvm_faultinfo *ufi)
 {
-
-       /* while we haven't done the job */
-       while (1) {
+       for (;;) {
                /* no mapping?  give up. */
                if (uvmfault_lookup(ufi, TRUE) == FALSE)
                        return;
@@ -258,36 +258,46 @@ uvmfault_amapcopy(struct uvm_faultinfo *ufi)
  * uvmfault_anonget: get data in an anon into a non-busy, non-released
  * page in that anon.
  *
- * => we don't move the page on the queues [gets moved later]
- * => if we allocate a new page [we_own], it gets put on the queues.
- *    either way, the result is that the page is on the queues at return time
+ * => Map, amap and thus anon should be locked by caller.
+ * => If we fail, we unlock everything and error is returned.
+ * => If we are successful, return with everything still locked.
+ * => We do not move the page on the queues [gets moved later].  If we
+ *    allocate a new page [we_own], it gets put on the queues.  Either way,
+ *    the result is that the page is on the queues at return time
  */
 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;
+       int error;
 
        KASSERT(rw_lock_held(anon->an_lock));
        KASSERT(anon->an_lock == amap->am_lock);
 
-       result = 0;             /* XXX shut up gcc */
+       /* Increment the counters.*/
        counters_inc(uvmexp_counters, flt_anget);
-        /* bump rusage counters */
-       if (anon->an_page)
+       if (anon->an_page) {
                curproc->p_ru.ru_minflt++;
-       else
+       } else {
                curproc->p_ru.ru_majflt++;
+       }
+       error = 0;
 
-       /* loop until we get it, or fail. */
-       while (1) {
-               we_own = FALSE;         /* TRUE if we set PG_BUSY on a page */
+       /*
+        * Loop until we get the anon data, or fail.
+        */
+       for (;;) {
+               boolean_t we_own, locked;
+               /*
+                * Note: 'we_own' will become true if we set PG_BUSY on a page.
+                */
+               we_own = FALSE;
                pg = anon->an_page;
 
-               /* page there?   make sure it is not busy/released. */
+               /*
+                * Is page resident?  Make sure it is not busy/released.
+                */
                if (pg) {
                        KASSERT(pg->pg_flags & PQ_ANON);
                        KASSERT(pg->uanon == anon);
@@ -302,29 +312,31 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
                        counters_inc(uvmexp_counters, flt_pgwait);
 
                        /*
-                        * the last unlock must be an atomic unlock+wait on
-                        * the owner of page
+                        * The last unlock must be an atomic unlock and wait
+                        * on the owner of page.
                         */
                        if (pg->uobject) {
+                               /* Owner of page is UVM object. */
                                uvmfault_unlockall(ufi, amap, NULL);
                                tsleep_nsec(pg, PVM, "anonget1", INFSLP);
                        } else {
+                               /* Owner of page is anon. */
                                uvmfault_unlockall(ufi, NULL, NULL);
                                rwsleep_nsec(pg, anon->an_lock, PVM | PNORELOCK,
                                    "anonget2", INFSLP);
                        }
-                       /* ready to relock and try again */
                } else {
-                       /* no page, we must try and bring it in. */
+                       /*
+                        * No page, therefore allocate one.
+                        */
                        pg = uvm_pagealloc(NULL, 0, anon, 0);
-
-                       if (pg == NULL) {               /* out of RAM.  */
+                       if (pg == NULL) {
+                               /* Out of memory.  Wait a little. */
                                uvmfault_unlockall(ufi, amap, NULL);
                                counters_inc(uvmexp_counters, flt_noram);
                                uvm_wait("flt_noram1");
-                               /* ready to relock and try again */
                        } else {
-                               /* we set the PG_BUSY bit */
+                               /* PG_BUSY bit is set. */
                                we_own = TRUE;
                                uvmfault_unlockall(ufi, amap, NULL);
 
@@ -336,32 +348,33 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
                                 * we hold PG_BUSY on the page.
                                 */
                                counters_inc(uvmexp_counters, pageins);
-                               result = uvm_swap_get(pg, anon->an_swslot,
+                               error = uvm_swap_get(pg, anon->an_swslot,
                                    PGO_SYNCIO);
 
                                /*
-                                * we clean up after the i/o below in the
-                                * "we_own" case
+                                * We clean up after the I/O below in the
+                                * 'we_own' case.
                                 */
-                               /* ready to relock and try again */
                        }
                }
 
-               /* now relock and try again */
+               /*
+                * Re-lock the map and anon.
+                */
                locked = uvmfault_relock(ufi);
                if (locked || we_own) {
                        rw_enter(anon->an_lock, RW_WRITE);
                }
 
                /*
-                * 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
+                * 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).
+                *
+                * 1) Page was 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) {
@@ -387,32 +400,33 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
                                return (VM_PAGER_REFAULT);      /* refault! */
                        }
 
-                       if (result != VM_PAGER_OK) {
-                               KASSERT(result != VM_PAGER_PEND);
+                       if (error != VM_PAGER_OK) {
+                               KASSERT(error != 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
+                                * Remove the swap slot from the anon and
+                                * mark the anon as having no real slot.
+                                * Do not 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
+                                * Note: page was never !PG_BUSY, so it
+                                * cannot be mapped and thus no need to
                                 * pmap_page_protect it...
                                 */
                                uvm_lock_pageq();
                                uvm_pagefree(pg);
                                uvm_unlock_pageq();
 
-                               if (locked)
+                               if (locked) {
                                        uvmfault_unlockall(ufi, NULL, NULL);
+                               }
                                rw_exit(anon->an_lock);
                                return (VM_PAGER_ERROR);
                        }
@@ -427,7 +441,9 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
                        uvm_unlock_pageq();
                }
 
-               /* we were not able to relock.   restart fault. */
+               /*
+                * We were not able to re-lock the map - restart the fault.
+                */
                if (!locked) {
                        if (we_own) {
                                rw_exit(anon->an_lock);
@@ -435,20 +451,24 @@ uvmfault_anonget(struct uvm_faultinfo *ufi, struct vm_amap *amap,
                        return (VM_PAGER_REFAULT);
                }
 
-               /* verify no one touched the amap and moved the anon on us. */
-               if (ufi != NULL &&
-                   amap_lookup(&ufi->entry->aref,
+               /*
+                * Verify that 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);
                        return (VM_PAGER_REFAULT);
                }
 
-               /* try it again! */
+               /*
+                * Retry..
+                */
                counters_inc(uvmexp_counters, flt_anretry);
                continue;
 
-       } /* while (1) */
+       }
        /*NOTREACHED*/
 }
 
@@ -489,6 +509,23 @@ uvmfault_update_stats(struct uvm_faultinfo *ufi)
        }
 }
 
+/*
+ *   F A U L T   -   m a i n   e n t r y   p o i n t
+ */
+
+/*
+ * uvm_fault: page fault handler
+ *
+ * => called from MD code to resolve a page fault
+ * => VM data structures usually should be unlocked.   however, it is
+ *     possible to call here with the main map locked if the caller
+ *     gets a write lock, sets it recursive, and then calls us (c.f.
+ *     uvm_map_pageable).   this should be avoided because it keeps
+ *     the map locked off during I/O.
+ * => MUST NEVER BE CALLED IN INTERRUPT CONTEXT
+ */
+#define MASK(entry)     (UVM_ET_ISCOPYONWRITE(entry) ? \
+                        ~PROT_WRITE : PROT_MASK)
 struct uvm_faultctx {
        /*
         * the following members are set up by uvm_fault_check() and
@@ -504,8 +541,72 @@ struct uvm_faultctx {
        paddr_t pa_flags;
 };
 
-int    uvm_fault_lower(struct uvm_faultinfo *, struct uvm_faultctx *,
-           struct vm_page **, vm_fault_t);
+int            uvm_fault_check(
+                   struct uvm_faultinfo *, struct uvm_faultctx *,
+                   struct vm_anon ***);
+
+int            uvm_fault_upper(
+                   struct uvm_faultinfo *, struct uvm_faultctx *,
+                   struct vm_anon **, vm_fault_t);
+boolean_t      uvm_fault_upper_lookup(
+                   struct uvm_faultinfo *, const struct uvm_faultctx *,
+                   struct vm_anon **, struct vm_page **);
+
+int            uvm_fault_lower(
+                   struct uvm_faultinfo *, struct uvm_faultctx *,
+                   struct vm_page **, vm_fault_t);
+
+int
+uvm_fault(vm_map_t orig_map, vaddr_t vaddr, vm_fault_t fault_type,
+    vm_prot_t access_type)
+{
+       struct uvm_faultinfo ufi;
+       struct uvm_faultctx flt;
+       boolean_t shadowed;
+       struct vm_anon *anons_store[UVM_MAXRANGE], **anons;
+       struct vm_page *pages[UVM_MAXRANGE];
+       int error;
+
+       counters_inc(uvmexp_counters, faults);
+       TRACEPOINT(uvm, fault, vaddr, fault_type, access_type, NULL);
+
+       /*
+        * init the IN parameters in the ufi
+        */
+       ufi.orig_map = orig_map;
+       ufi.orig_rvaddr = trunc_page(vaddr);
+       ufi.orig_size = PAGE_SIZE;      /* can't get any smaller than this */
+       if (fault_type == VM_FAULT_WIRE)
+               flt.narrow = TRUE;      /* don't look for neighborhood
+                                        * pages on wire */
+       else
+               flt.narrow = FALSE;     /* normal fault */
+       flt.access_type = access_type;
+
+
+       error = ERESTART;
+       while (error == ERESTART) { /* ReFault: */
+               anons = anons_store;
+
+               error = uvm_fault_check(&ufi, &flt, &anons);
+               if (error != 0)
+                       continue;
+
+               /* True if there is an anon at the faulting address */
+               shadowed = uvm_fault_upper_lookup(&ufi, &flt, anons, pages);
+               if (shadowed == TRUE) {
+                       /* case 1: fault on an anon in our amap */
+                       error = uvm_fault_upper(&ufi, &flt, anons, fault_type);
+               } else {
+                       /* case 2: fault on backing object or zero fill */
+                       KERNEL_LOCK();
+                       error = uvm_fault_lower(&ufi, &flt, pages, fault_type);
+                       KERNEL_UNLOCK();
+               }
+       }
+
+       return error;
+}
 
 /*
  * uvm_fault_check: check prot, handle needs-copy, etc.
@@ -530,10 +631,13 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
        struct uvm_object *uobj;
        int nback, nforw;
 
-       /* lookup and lock the maps */
+       /*
+        * lookup and lock the maps
+        */
        if (uvmfault_lookup(ufi, FALSE) == FALSE) {
-               return (EFAULT);
+               return EFAULT;
        }
+       /* locked: maps(read) */
 
 #ifdef DIAGNOSTIC
        if ((ufi->map->flags & VM_MAP_PAGEABLE) == 0)
@@ -541,10 +645,12 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
                    ufi->map, ufi->orig_rvaddr);
 #endif
 
-       /* check protection */
+       /*
+        * check protection
+        */
        if ((ufi->entry->protection & flt->access_type) != flt->access_type) {
                uvmfault_unlockmaps(ufi, FALSE);
-               return (EACCES);
+               return EACCES;
        }
 
        /*
@@ -568,7 +674,7 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
                        uvmfault_unlockmaps(ufi, FALSE);
                        uvmfault_amapcopy(ufi);
                        counters_inc(uvmexp_counters, flt_amcopy);
-                       return (ERESTART);
+                       return ERESTART;
                } else {
                        /*
                         * ensure that we pmap_enter page R/O since
@@ -578,9 +684,11 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
                }
        }
 
-       /* identify the players */
-       amap = ufi->entry->aref.ar_amap;        /* top layer */
-       uobj = ufi->entry->object.uvm_obj;      /* bottom layer */
+       /*
+        * identify the players
+        */
+       amap = ufi->entry->aref.ar_amap;        /* upper layer */
+       uobj = ufi->entry->object.uvm_obj;      /* lower layer */
 
        /*
         * check for a case 0 fault.  if nothing backing the entry then
@@ -588,7 +696,7 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
         */
        if (amap == NULL && uobj == NULL) {
                uvmfault_unlockmaps(ufi, FALSE);
-               return (EFAULT);
+               return EFAULT;
        }
 
        /*
@@ -621,7 +729,9 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
                flt->centeridx = 0;
        }
 
-       /* if we've got an amap, extract current anons. */
+       /*
+        * if we've got an amap then lock it and extract current anons.
+        */
        if (amap) {
                amap_lock(amap);
                amap_lookups(&ufi->entry->aref,
@@ -662,11 +772,100 @@ uvm_fault_check(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
 }
 
 /*
- * uvm_fault_upper: handle upper fault (case 1A & 1B)
+ * uvm_fault_upper_lookup: look up existing h/w mapping and amap.
+ *
+ * iterate range of interest:
+ *     1. check if h/w mapping exists.  if yes, we don't care
+ *     2. check if anon exists.  if not, page is lower.
+ *     3. if anon exists, enter h/w mapping for neighbors.
+ *
+ * => called with amap locked (if exists).
+ */
+boolean_t
+uvm_fault_upper_lookup(struct uvm_faultinfo *ufi,
+    const struct uvm_faultctx *flt, struct vm_anon **anons,
+    struct vm_page **pages)
+{
+       struct vm_amap *amap = ufi->entry->aref.ar_amap;
+       struct vm_anon *anon;
+       boolean_t shadowed;
+       vaddr_t currva;
+       paddr_t pa;
+       int lcv;
+
+       /* locked: maps(read), amap(if there) */
+       KASSERT(amap == NULL ||
+           rw_write_held(amap->am_lock));
+
+       /*
+        * map in the backpages and frontpages we found in the amap in hopes
+        * of preventing future faults.    we also init the pages[] array as
+        * we go.
+        */
+       currva = flt->startva;
+       shadowed = FALSE;
+       for (lcv = 0; lcv < flt->npages; lcv++, currva += PAGE_SIZE) {
+               /*
+                * dont play with VAs that are already mapped
+                * except for center)
+                */
+               if (lcv != flt->centeridx &&
+                   pmap_extract(ufi->orig_map->pmap, currva, &pa)) {
+                       pages[lcv] = PGO_DONTCARE;
+                       continue;
+               }
+
+               /*
+                * unmapped or center page. check if any anon at this level.
+                */
+               if (amap == NULL || anons[lcv] == NULL) {
+                       pages[lcv] = NULL;
+                       continue;
+               }
+
+               /*
+                * check for present page and map if possible.
+                */
+               pages[lcv] = PGO_DONTCARE;
+               if (lcv == flt->centeridx) {    /* save center for later! */
+                       shadowed = TRUE;
+                       continue;
+               }
+               anon = anons[lcv];
+               KASSERT(anon->an_lock == amap->am_lock);
+               if (anon->an_page &&
+                   (anon->an_page->pg_flags & (PG_RELEASED|PG_BUSY)) == 0) {
+                       uvm_lock_pageq();
+                       uvm_pageactivate(anon->an_page);        /* reactivate */
+                       uvm_unlock_pageq();
+                       counters_inc(uvmexp_counters, flt_namap);
+
+                       /*
+                        * Since this isn't the page that's actually faulting,
+                        * ignore pmap_enter() failures; it's not critical
+                        * that we enter these right now.
+                        */
+                       (void) pmap_enter(ufi->orig_map->pmap, currva,
+                           VM_PAGE_TO_PHYS(anon->an_page) | flt->pa_flags,
+                           (anon->an_ref > 1) ?
+                           (flt->enter_prot & ~PROT_WRITE) : flt->enter_prot,
+                           PMAP_CANFAIL |
+                            (VM_MAPENT_ISWIRED(ufi->entry) ? PMAP_WIRED : 0));
+               }
+       }
+       if (flt->npages > 1)
+               pmap_update(ufi->orig_map->pmap);
+
+       return shadowed;
+}
+
+/*
+ * uvm_fault_upper: handle upper fault.
  *
- *     1. get anon.  let uvmfault_anonget do the dirty work.
- *     2. if COW, promote data to new anon
- *     3. enter h/w mapping
+ *     1. acquire anon lock.
+ *     2. get anon.  let uvmfault_anonget do the dirty work.
+ *     3. if COW, promote data to new anon
+ *     4. enter h/w mapping
  */
 int
 uvm_fault_upper(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
@@ -686,7 +885,11 @@ uvm_fault_upper(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
         */
        /*
         * let uvmfault_anonget do the dirty work.
+        * if it fails (!OK) it will unlock everything for us.
+        * if it succeeds, locks are still valid and locked.
         * also, if it is OK, then the anon's page is on the queues.
+        * if the page is on loan from a uvm_object, then anonget will
+        * lock that object for us if it does not fail.
         */
        error = uvmfault_anonget(ufi, amap, anon);
        switch (error) {
@@ -722,7 +925,7 @@ uvm_fault_upper(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
         * it is > 1 and we are only dropping one ref.
         *
         * in the (hopefully very rare) case that we are out of RAM we
-        * will wait for more RAM, and refault.
+        * will unlock, wait for more RAM, and refault.
         *
         * if we are out of anon VM we wait for RAM to become available.
         */
@@ -785,10 +988,7 @@ uvm_fault_upper(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
        }
 
        /*
-        * now map the page in ...
-        * XXX: old fault unlocks object before pmap_enter.  this seems
-        * suspect since some other thread could blast the page out from
-        * under us between the unlock and the pmap_enter.
+        * now map the page in .
         */
        if (pmap_enter(ufi->orig_map->pmap, ufi->orig_rvaddr,
            VM_PAGE_TO_PHYS(pg) | flt->pa_flags, flt->enter_prot,
@@ -830,158 +1030,18 @@ uvm_fault_upper(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
 
        uvm_unlock_pageq();
 
-       /* done case 1!  finish up by unlocking everything and returning success */
+       /*
+        * done case 1!  finish up by unlocking everything and returning success
+        */
        uvmfault_unlockall(ufi, amap, NULL);
        pmap_update(ufi->orig_map->pmap);
        return 0;
 }
 
 /*
- * uvm_fault_upper_lookup: look up existing h/w mapping and amap.
- *
- * iterate range of interest:
- *      1. check if h/w mapping exists.  if yes, we don't care
- *      2. check if anon exists.  if not, page is lower.
- *      3. if anon exists, enter h/w mapping for neighbors.
- */
-boolean_t
-uvm_fault_upper_lookup(struct uvm_faultinfo *ufi,
-    const struct uvm_faultctx *flt, struct vm_anon **anons,
-    struct vm_page **pages)
-{
-       struct vm_amap *amap = ufi->entry->aref.ar_amap;
-       struct vm_anon *anon;
-       boolean_t shadowed;
-       vaddr_t currva;
-       paddr_t pa;
-       int lcv;
-
-       /*
-        * map in the backpages and frontpages we found in the amap in hopes
-        * of preventing future faults.    we also init the pages[] array as
-        * we go.
-        */
-       currva = flt->startva;
-       shadowed = FALSE;
-       for (lcv = 0 ; lcv < flt->npages ; lcv++, currva += PAGE_SIZE) {
-               /*
-                * dont play with VAs that are already mapped
-                * except for center)
-                */
-               if (lcv != flt->centeridx &&
-                   pmap_extract(ufi->orig_map->pmap, currva, &pa)) {
-                       pages[lcv] = PGO_DONTCARE;
-                       continue;
-               }
-
-               /* unmapped or center page. check if any anon at this level. */
-               if (amap == NULL || anons[lcv] == NULL) {
-                       pages[lcv] = NULL;
-                       continue;
-               }
-
-               /* check for present page and map if possible. re-activate it */
-               pages[lcv] = PGO_DONTCARE;
-               if (lcv == flt->centeridx) {    /* save center for later! */
-                       shadowed = TRUE;
-                       continue;
-               }
-               anon = anons[lcv];
-               KASSERT(anon->an_lock == amap->am_lock);
-               if (anon->an_page &&
-                   (anon->an_page->pg_flags & (PG_RELEASED|PG_BUSY)) == 0) {
-                       uvm_lock_pageq();
-                       uvm_pageactivate(anon->an_page);        /* reactivate */
-                       uvm_unlock_pageq();
-                       counters_inc(uvmexp_counters, flt_namap);
-
-                       /*
-                        * Since this isn't the page that's actually faulting,
-                        * ignore pmap_enter() failures; it's not critical
-                        * that we enter these right now.
-                        */
-                       (void) pmap_enter(ufi->orig_map->pmap, currva,
-                           VM_PAGE_TO_PHYS(anon->an_page) | flt->pa_flags,
-                           (anon->an_ref > 1) ?
-                           (flt->enter_prot & ~PROT_WRITE) : flt->enter_prot,
-                           PMAP_CANFAIL |
-                            (VM_MAPENT_ISWIRED(ufi->entry) ? PMAP_WIRED : 0));
-               }
-       }
-       if (flt->npages > 1)
-               pmap_update(ufi->orig_map->pmap);
-
-       return shadowed;
-}
-
-/*
- *   F A U L T   -   m a i n   e n t r y   p o i n t
- */
-
-/*
- * uvm_fault: page fault handler
+ * uvm_fault_lower: handle lower fault.
  *
- * => called from MD code to resolve a page fault
- * => VM data structures usually should be unlocked.   however, it is
- *     possible to call here with the main map locked if the caller
- *     gets a write lock, sets it recursive, and then calls us (c.f.
- *     uvm_map_pageable).   this should be avoided because it keeps
- *     the map locked off during I/O.
  */
-#define MASK(entry)     (UVM_ET_ISCOPYONWRITE(entry) ? \
-                        ~PROT_WRITE : PROT_MASK)
-int
-uvm_fault(vm_map_t orig_map, vaddr_t vaddr, vm_fault_t fault_type,
-    vm_prot_t access_type)
-{
-       struct uvm_faultinfo ufi;
-       struct uvm_faultctx flt;
-       boolean_t shadowed;
-       struct vm_anon *anons_store[UVM_MAXRANGE], **anons;
-       struct vm_page *pages[UVM_MAXRANGE];
-       int error = ERESTART;
-
-       counters_inc(uvmexp_counters, faults);
-       TRACEPOINT(uvm, fault, vaddr, fault_type, access_type, NULL);
-
-       /* init the IN parameters in the ufi */
-       ufi.orig_map = orig_map;
-       ufi.orig_rvaddr = trunc_page(vaddr);
-       ufi.orig_size = PAGE_SIZE;      /* can't get any smaller than this */
-       if (fault_type == VM_FAULT_WIRE)
-               flt.narrow = TRUE;      /* don't look for neighborhood
-                                        * pages on wire */
-       else
-               flt.narrow = FALSE;     /* normal fault */
-       flt.access_type = access_type;
-
-
-       /*
-        * ReFault
-        */
-       while (error == ERESTART) {
-               anons = anons_store;
-
-               error = uvm_fault_check(&ufi, &flt, &anons);
-               if (error != 0)
-                       continue;
-
-               /* True if there is an anon at the faulting address */
-               shadowed = uvm_fault_upper_lookup(&ufi, &flt, anons, pages);
-               if (shadowed == TRUE) {
-                       /* case 1: fault on an anon in our amap */
-                       error = uvm_fault_upper(&ufi, &flt, anons, fault_type);
-               } else {
-                       /* case 2: fault on backing object or zero fill */
-                       KERNEL_LOCK();
-                       error = uvm_fault_lower(&ufi, &flt, pages, fault_type);
-                       KERNEL_UNLOCK();
-               }
-       }
-
-       return error;
-}
-
 int
 uvm_fault_lower(struct uvm_faultinfo *ufi, struct uvm_faultctx *flt,
    struct vm_page **pages, vm_fault_t fault_type)