sys/uvm/uvm_fault.c

70  *   case [1]: upper layer fault [anon active]
71  *     1A: [read] or [write with anon->an_ref == 1]
72  *		I/O takes place in upper level anon and uobj is not touched.
73  *     1B: [write with anon->an_ref > 1]
74  *		new anon is alloc'd and data is copied off ["COW"]
80  *		data is "promoted" from uobj to a new anon.
98  *     - at the same time check pmap for unmapped areas and anon for pages
103  *           - ensure source anon is resident in RAM
104  *           - if case 1B alloc new anon and copy from source
109  *           - if case 2B alloc new anon and copy from source (could be zero
266  * uvmfault_anonget: get data in an anon into a non-busy, non-released
267  * page in that anon.
269  * => Map, amap and thus anon should be locked by caller.
278     struct vm_anon *anon)
283 	KASSERT(rw_lock_held(anon->an_lock));
284 	KASSERT(anon->an_lock == amap->am_lock);
288 	if (anon->an_page) {
296 	 * Loop until we get the anon data, or fail.
304 		pg = anon->an_page;
311 			KASSERT(pg->uanon == anon);
332 				/* Owner of page is anon. */
334 				rwsleep_nsec(pg, anon->an_lock, PVM | PNORELOCK,
341 			pg = uvm_pagealloc(NULL, 0, anon, 0);
360 				error = uvm_swap_get(pg, anon->an_swslot,
371 		 * Re-lock the map and anon.
375 			rw_enter(anon->an_lock, RW_WRITE);
383 		 * 1) Page was released during I/O: free anon and ReFault.
386 		 *    case (i.e. drop anon lock if not locked).
394 			 * if we were RELEASED during I/O, then our anon is
396 			 * anon and try again.
399 				KASSERT(anon->an_ref == 0);
405 				uvm_anon_release(anon);	/* frees page for us */
413 				/* remove page from anon */
414 				anon->an_page = NULL;
417 				 * Remove the swap slot from the anon and
418 				 * mark the anon as having no real slot.
422 				uvm_swap_markbad(anon->an_swslot, 1);
423 				anon->an_swslot = SWSLOT_BAD;
437 				rw_exit(anon->an_lock);
458 				rw_exit(anon->an_lock);
465 		 * the anon on us.
468 				ufi->orig_rvaddr - ufi->entry->start) != anon) {
604 		/* True if there is an anon at the faulting address */
607 			/* case 1: fault on an anon in our amap */
826  *	2. check if anon exists.  if not, page is lower.
827  *	3. if anon exists, enter h/w mapping for neighbors.
837 	struct vm_anon *anon;
866 		 * unmapped or center page.   check if any anon at this level.
881 		anon = anons[lcv];
882 		KASSERT(anon->an_lock == amap->am_lock);
883 		if (anon->an_page &&
884 		    (anon->an_page->pg_flags & (PG_RELEASED|PG_BUSY)) == 0) {
886 			uvm_pageactivate(anon->an_page);	/* reactivate */
896 			    VM_PAGE_TO_PHYS(anon->an_page) | flt->pa_flags,
897 			    (anon->an_ref > 1) ?
912  *	1. acquire anon lock.
913  *	2. get anon.  let uvmfault_anonget do the dirty work.
914  *	3. if COW, promote data to new anon
922 	struct vm_anon *oanon, *anon = anons[flt->centeridx];
926 	/* locked: maps(read), amap, anon */
928 	KASSERT(anon->an_lock == amap->am_lock);
932 	 * have the anon's memory resident.   ensure that now.
938 	 * also, if it is OK, then the anon's page is on the queues.
942 	error = uvmfault_anonget(ufi, amap, anon);
966 	KASSERT(anon->an_lock == amap->am_lock);
970 	 * anon to transfer the data into.   note that we have a lock
971 	 * on anon, so no one can busy or release the page until we are done.
978 	 * if we are out of anon VM we wait for RAM to become available.
981 	if ((flt->access_type & PROT_WRITE) != 0 && anon->an_ref > 1) {
983 		oanon = anon;		/* oanon = old */
984 		anon = uvm_analloc();
985 		if (anon) {
986 			anon->an_lock = amap->am_lock;
987 			pg = uvm_pagealloc(NULL, 0, anon, 0);
991 		if (anon == NULL || pg == NULL) {
993 			if (anon == NULL)
996 				anon->an_lock = NULL;
997 				anon->an_ref--;
998 				uvm_anfree(anon);
1006 			if (anon == NULL)
1013 		/* got all resources, replace anon with nanon */
1019 		    ufi->orig_rvaddr - ufi->entry->start, anon, 1);
1041 		 * note: anon is _not_ locked, but we have the sole references
1047 		oanon = anon;
1048 		pg = anon->an_page;
1049 		if (anon->an_ref > 1)     /* disallow writes to ref > 1 anons */
1086 		 * since an anon with no swap cannot be PG_CLEAN,
1090 		uvm_anon_dropswap(anon);
1213 	struct vm_anon *anon = NULL;
1251 	 * the data up to an anon during the fault.
1255 		promote = TRUE;		/* always need anon here */
1382 		 * if we are going to promote the data to an anon we
1383 		 * allocate a blank anon here and plug it into our amap.
1387 			panic("uvm_fault: want to promote data, but no anon");
1390 		anon = uvm_analloc();
1391 		if (anon) {
1398 			anon->an_lock = amap->am_lock;
1399 			pg = uvm_pagealloc(NULL, 0, anon,
1406 		if (anon == NULL || pg == NULL) {
1424 			if (anon == NULL)
1427 				anon->an_lock = NULL;
1428 				anon->an_ref--;
1429 				uvm_anfree(anon);
1437 			if (anon == NULL)
1493 		    ufi->orig_rvaddr - ufi->entry->start, anon, 0)) {
1495 			uvm_anfree(anon);
1507 	/* note: pg is either the uobjpage or the new page in the new anon */
1513 		KASSERT(anon == NULL);
1516 		KASSERT(anon == NULL || anon->an_lock == amap->am_lock);
1712 	 * but merely paging in anon data.
1828 	 * but merely paging in anon data.