Make KPI of vm_pager_get_pages() more strict: if a pager changes a page

in the requested array, then it is responsible for disposition of previous
page and is responsible for updating the entry in the requested array.
Now consumers of KPI do not need to re-lookup the pages after call to
vm_pager_get_pages().

Reviewed by:	kib
Sponsored by:	Netflix
Sponsored by:	Nginx, Inc.

1 files changed, 8 insertions, 9 deletions

diff --git a/sys/vm/vm_glue.c b/sys/vm/vm_glue.c
index c9ee890824a5..1ff17c29c3e6 100644
--- a/sys/vm/vm_glue.c
+++ b/sys/vm/vm_glue.c
@@ -230,7 +230,7 @@ vsunlock(void *addr, size_t len)
 static vm_page_t
 vm_imgact_hold_page(vm_object_t object, vm_ooffset_t offset)
 {
-	vm_page_t m, ma[1];
+	vm_page_t m;
 	vm_pindex_t pindex;
 	int rv;
 
@@ -238,11 +238,7 @@ vm_imgact_hold_page(vm_object_t object, vm_ooffset_t offset)
 	pindex = OFF_TO_IDX(offset);
 	m = vm_page_grab(object, pindex, VM_ALLOC_NORMAL);
 	if (m->valid != VM_PAGE_BITS_ALL) {
-		ma[0] = m;
-		rv = vm_pager_get_pages(object, ma, 1, 0);
-		m = vm_page_lookup(object, pindex);
-		if (m == NULL)
-			goto out;
+		rv = vm_pager_get_pages(object, &m, 1, 0);
 		if (rv != VM_PAGER_OK) {
 			vm_page_lock(m);
 			vm_page_free(m);
@@ -571,7 +567,7 @@ vm_thread_swapin(struct thread *td)
 {
 	vm_object_t ksobj;
 	vm_page_t ma[KSTACK_MAX_PAGES];
-	int i, j, k, pages, rv;
+	int i, j, pages, rv;
 
 	pages = td->td_kstack_pages;
 	ksobj = td->td_kstack_obj;
@@ -593,9 +589,12 @@ vm_thread_swapin(struct thread *td)
 			if (rv != VM_PAGER_OK)
 	panic("vm_thread_swapin: cannot get kstack for proc: %d",
 				    td->td_proc->p_pid);
+			/*
+			 * All pages in the array are in place, due to the
+			 * pager is always the swap pager, which doesn't
+			 * free or remove wired non-req pages from object.
+			 */
 			vm_object_pip_wakeup(ksobj);
-			for (k = i; k < j; k++)
-				ma[k] = vm_page_lookup(ksobj, k);
 			vm_page_xunbusy(ma[i]);
 		} else if (vm_page_xbusied(ma[i]))
 			vm_page_xunbusy(ma[i]);