git: fff19e0ed2f3 - main - vm_object: Remove redundant OBJ_SWAP checks

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=fff19e0ed2f3a56ee063f0ce1486b1dd35df6d6c

commit fff19e0ed2f3a56ee063f0ce1486b1dd35df6d6c
Author:     Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2022-07-16 15:29:53 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2022-07-17 11:09:48 +0000

    vm_object: Remove redundant OBJ_SWAP checks
    
    With the removal of OBJT_DEFAULT, OBJ_ANON implies OBJ_SWAP.
    
    Note, this means that vm_object_split() is more expensive than it used
    to be, as it holds busy locks until the end of the range is reached,
    even if the object has no swap blocks allocated.
    
    Reviewed by:    alc, kib
    Tested by:      pho
    Sponsored by:   The FreeBSD Foundation
    Differential Revision:  https://reviews.freebsd.org/D35789
---
 sys/vm/vm_object.c | 52 +++++++++++++++++-----------------------------------
 1 file changed, 17 insertions(+), 35 deletions(-)

diff --git a/sys/vm/vm_object.c b/sys/vm/vm_object.c
index 7fd82239c13b..7304a42d9ae5 100644
--- a/sys/vm/vm_object.c
+++ b/sys/vm/vm_object.c
@@ -1506,7 +1506,7 @@ vm_object_shadow(vm_object_t *object, vm_ooffset_t *offset, vm_size_t length,
 void
 vm_object_split(vm_map_entry_t entry)
 {
-	vm_page_t m, m_busy, m_next;
+	vm_page_t m, m_next;
 	vm_object_t orig_object, new_object, backing_object;
 	vm_pindex_t idx, offidxstart;
 	vm_size_t size;
@@ -1559,7 +1559,6 @@ vm_object_split(vm_map_entry_t entry)
 	 * that the object is in transition.
 	 */
 	vm_object_set_flag(orig_object, OBJ_SPLIT);
-	m_busy = NULL;
 #ifdef INVARIANTS
 	idx = 0;
 #endif
@@ -1622,26 +1621,17 @@ retry:
 		 */
 		vm_reserv_rename(m, new_object, orig_object, offidxstart);
 #endif
-
-		/*
-		 * orig_object's type may change while sleeping, so keep track
-		 * of the beginning of the busied range.
-		 */
-		if (orig_object->type != OBJT_SWAP)
-			vm_page_xunbusy(m);
-		else if (m_busy == NULL)
-			m_busy = m;
-	}
-	if ((orig_object->flags & OBJ_SWAP) != 0) {
-		/*
-		 * swap_pager_copy() can sleep, in which case the orig_object's
-		 * and new_object's locks are released and reacquired. 
-		 */
-		swap_pager_copy(orig_object, new_object, offidxstart, 0);
-		if (m_busy != NULL)
-			TAILQ_FOREACH_FROM(m_busy, &new_object->memq, listq)
-				vm_page_xunbusy(m_busy);
 	}
+
+	/*
+	 * swap_pager_copy() can sleep, in which case the orig_object's
+	 * and new_object's locks are released and reacquired.
+	 */
+	swap_pager_copy(orig_object, new_object, offidxstart, 0);
+
+	TAILQ_FOREACH(m, &new_object->memq, listq)
+		vm_page_xunbusy(m);
+
 	vm_object_clear_flag(orig_object, OBJ_SPLIT);
 	VM_OBJECT_WUNLOCK(orig_object);
 	VM_OBJECT_WUNLOCK(new_object);
@@ -1963,21 +1953,13 @@ vm_object_collapse(vm_object_t object)
 
 			/*
 			 * Move the pager from backing_object to object.
+			 *
+			 * swap_pager_copy() can sleep, in which case the
+			 * backing_object's and object's locks are released and
+			 * reacquired.
 			 */
-			if ((backing_object->flags & OBJ_SWAP) != 0) {
-				/*
-				 * swap_pager_copy() can sleep, in which case
-				 * the backing_object's and object's locks are
-				 * released and reacquired.
-				 * Since swap_pager_copy() is being asked to
-				 * destroy backing_object, it will change the
-				 * type to OBJT_DEFAULT.
-				 */
-				swap_pager_copy(
-				    backing_object,
-				    object,
-				    OFF_TO_IDX(object->backing_object_offset), TRUE);
-			}
+			swap_pager_copy(backing_object, object,
+			    OFF_TO_IDX(object->backing_object_offset), TRUE);
 
 			/*
 			 * Object now shadows whatever backing_object did.