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.

3 files changed, 9 insertions, 25 deletions

diff --git a/sys/kern/kern_exec.c b/sys/kern/kern_exec.c
index d3ae4f0a06d8..375e64459c4c 100644
--- a/sys/kern/kern_exec.c
+++ b/sys/kern/kern_exec.c
@@ -966,13 +966,10 @@ exec_map_first_page(imgp)
 		}
 		initial_pagein = i;
 		rv = vm_pager_get_pages(object, ma, initial_pagein, 0);
-		ma[0] = vm_page_lookup(object, 0);
-		if ((rv != VM_PAGER_OK) || (ma[0] == NULL)) {
-			if (ma[0] != NULL) {
-				vm_page_lock(ma[0]);
-				vm_page_free(ma[0]);
-				vm_page_unlock(ma[0]);
-			}
+		if (rv != VM_PAGER_OK) {
+			vm_page_lock(ma[0]);
+			vm_page_free(ma[0]);
+			vm_page_unlock(ma[0]);
 			VM_OBJECT_WUNLOCK(object);
 			return (EIO);
 		}
diff --git a/sys/kern/uipc_shm.c b/sys/kern/uipc_shm.c
index 3419c51506c7..fb8433027b81 100644
--- a/sys/kern/uipc_shm.c
+++ b/sys/kern/uipc_shm.c
@@ -189,14 +189,6 @@ uiomove_object_page(vm_object_t obj, size_t len, struct uio *uio)
 	if (m->valid != VM_PAGE_BITS_ALL) {
 		if (vm_pager_has_page(obj, idx, NULL, NULL)) {
 			rv = vm_pager_get_pages(obj, &m, 1, 0);
-			m = vm_page_lookup(obj, idx);
-			if (m == NULL) {
-				printf(
-		    "uiomove_object: vm_obj %p idx %jd null lookup rv %d\n",
-				    obj, idx, rv);
-				VM_OBJECT_WUNLOCK(obj);
-				return (EIO);
-			}
 			if (rv != VM_PAGER_OK) {
 				printf(
 	    "uiomove_object: vm_obj %p idx %jd valid %x pager error %d\n",
@@ -423,7 +415,7 @@ static int
 shm_dotruncate(struct shmfd *shmfd, off_t length)
 {
 	vm_object_t object;
-	vm_page_t m, ma[1];
+	vm_page_t m;
 	vm_pindex_t idx, nobjsize;
 	vm_ooffset_t delta;
 	int base, rv;
@@ -465,12 +457,10 @@ retry:
 					VM_WAIT;
 					VM_OBJECT_WLOCK(object);
 					goto retry;
-				} else if (m->valid != VM_PAGE_BITS_ALL) {
-					ma[0] = m;
-					rv = vm_pager_get_pages(object, ma, 1,
+				} else if (m->valid != VM_PAGE_BITS_ALL)
+					rv = vm_pager_get_pages(object, &m, 1,
 					    0);
-					m = vm_page_lookup(object, idx);
-				} else
+				else
 					/* A cached page was reactivated. */
 					rv = VM_PAGER_OK;
 				vm_page_lock(m);
diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index 1efe3da8a8d4..e3557ba72604 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -2026,10 +2026,7 @@ sendfile_readpage(vm_object_t obj, struct vnode *vp, int nd,
 		if (vm_pager_has_page(obj, pindex, NULL, NULL)) {
 			rv = vm_pager_get_pages(obj, &m, 1, 0);
 			SFSTAT_INC(sf_iocnt);
-			m = vm_page_lookup(obj, pindex);
-			if (m == NULL)
-				error = EIO;
-			else if (rv != VM_PAGER_OK) {
+			if (rv != VM_PAGER_OK) {
 				vm_page_lock(m);
 				vm_page_free(m);
 				vm_page_unlock(m);