Author: kib
Date: Wed Nov 28 18:42:42 2018
New Revision: 341161
URL: https://svnweb.freebsd.org/changeset/base/341161
Log:
MFC r339506, r339508, r340064 (by markj), r340546 (by alc):
Tidy up code to merge vm_entry neighbors and simplify related checks.
r339506:
Reduce code duplication in merging vm_entry neighbors.
r339508:
Unindent.
r340064:
Initialize the eflags field of vm_map headers.
r340546:
Tidy up vm_map_simplify_entry() and its recently introduced helper functions.
Discussed with: markj
Modified:
stable/12/sys/kern/sys_process.c
stable/12/sys/vm/vm_map.c
stable/12/sys/vm/vm_map.h
Directory Properties:
stable/12/ (props changed)
Modified: stable/12/sys/kern/sys_process.c
==============================================================================
--- stable/12/sys/kern/sys_process.c Wed Nov 28 18:09:42 2018
(r341160)
+++ stable/12/sys/kern/sys_process.c Wed Nov 28 18:42:42 2018
(r341161)
@@ -387,8 +387,9 @@ ptrace_vm_entry(struct thread *td, struct proc *p, str
error = EINVAL;
break;
}
- while (entry != &map->header &&
- (entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
+ KASSERT((map->header.eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
+ ("Submap in map header"));
+ while ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) != 0) {
entry = entry->next;
index++;
}
Modified: stable/12/sys/vm/vm_map.c
==============================================================================
--- stable/12/sys/vm/vm_map.c Wed Nov 28 18:09:42 2018 (r341160)
+++ stable/12/sys/vm/vm_map.c Wed Nov 28 18:42:42 2018 (r341161)
@@ -796,6 +796,7 @@ _vm_map_init(vm_map_t map, pmap_t pmap, vm_offset_t mi
{
map->header.next = map->header.prev = &map->header;
+ map->header.eflags = MAP_ENTRY_HEADER;
map->needs_wakeup = FALSE;
map->system_map = 0;
map->pmap = pmap;
@@ -1277,8 +1278,8 @@ charged:
if (object->ref_count > 1 || object->shadow_count != 0)
vm_object_clear_flag(object, OBJ_ONEMAPPING);
VM_OBJECT_WUNLOCK(object);
- } else if (prev_entry != &map->header &&
- (prev_entry->eflags & ~MAP_ENTRY_USER_WIRED) == protoeflags &&
+ } else if ((prev_entry->eflags & ~MAP_ENTRY_USER_WIRED) ==
+ protoeflags &&
(cow & (MAP_STACK_GROWS_DOWN | MAP_STACK_GROWS_UP)) == 0 &&
prev_entry->end == start && (prev_entry->cred == cred ||
(prev_entry->object.vm_object != NULL &&
@@ -1644,6 +1645,54 @@ vm_map_find_min(vm_map_t map, vm_object_t object, vm_o
}
/*
+ * A map entry with any of the following flags set must not be merged with
+ * another entry.
+ */
+#define MAP_ENTRY_NOMERGE_MASK (MAP_ENTRY_GROWS_DOWN |
MAP_ENTRY_GROWS_UP | \
+ MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP)
+
+static bool
+vm_map_mergeable_neighbors(vm_map_entry_t prev, vm_map_entry_t entry)
+{
+
+ KASSERT((prev->eflags & MAP_ENTRY_NOMERGE_MASK) == 0 ||
+ (entry->eflags & MAP_ENTRY_NOMERGE_MASK) == 0,
+ ("vm_map_mergeable_neighbors: neither %p nor %p are mergeable",
+ prev, entry));
+ return (prev->end == entry->start &&
+ prev->object.vm_object == entry->object.vm_object &&
+ (prev->object.vm_object == NULL ||
+ prev->offset + (prev->end - prev->start) == entry->offset) &&
+ prev->eflags == entry->eflags &&
+ prev->protection == entry->protection &&
+ prev->max_protection == entry->max_protection &&
+ prev->inheritance == entry->inheritance &&
+ prev->wired_count == entry->wired_count &&
+ prev->cred == entry->cred);
+}
+
+static void
+vm_map_merged_neighbor_dispose(vm_map_t map, vm_map_entry_t entry)
+{
+
+ /*
+ * If the backing object is a vnode object, vm_object_deallocate()
+ * calls vrele(). However, vrele() does not lock the vnode because
+ * the vnode has additional references. Thus, the map lock can be
+ * kept without causing a lock-order reversal with the vnode lock.
+ *
+ * Since we count the number of virtual page mappings in
+ * object->un_pager.vnp.writemappings, the writemappings value
+ * should not be adjusted when the entry is disposed of.
+ */
+ if (entry->object.vm_object != NULL)
+ vm_object_deallocate(entry->object.vm_object);
+ if (entry->cred != NULL)
+ crfree(entry->cred);
+ vm_map_entry_dispose(map, entry);
+}
+
+/*
* vm_map_simplify_entry:
*
* Simplify the given map entry by merging with either neighbor. This
@@ -1659,81 +1708,27 @@ void
vm_map_simplify_entry(vm_map_t map, vm_map_entry_t entry)
{
vm_map_entry_t next, prev;
- vm_size_t prevsize, esize;
- if ((entry->eflags & (MAP_ENTRY_GROWS_DOWN | MAP_ENTRY_GROWS_UP |
- MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_IS_SUB_MAP)) != 0)
+ if ((entry->eflags & MAP_ENTRY_NOMERGE_MASK) != 0)
return;
-
prev = entry->prev;
- if (prev != &map->header) {
- prevsize = prev->end - prev->start;
- if ( (prev->end == entry->start) &&
- (prev->object.vm_object == entry->object.vm_object) &&
- (!prev->object.vm_object ||
- (prev->offset + prevsize == entry->offset)) &&
- (prev->eflags == entry->eflags) &&
- (prev->protection == entry->protection) &&
- (prev->max_protection == entry->max_protection) &&
- (prev->inheritance == entry->inheritance) &&
- (prev->wired_count == entry->wired_count) &&
- (prev->cred == entry->cred)) {
- vm_map_entry_unlink(map, prev);
- entry->start = prev->start;
- entry->offset = prev->offset;
- if (entry->prev != &map->header)
- vm_map_entry_resize_free(map, entry->prev);
-
- /*
- * If the backing object is a vnode object,
- * vm_object_deallocate() calls vrele().
- * However, vrele() does not lock the vnode
- * because the vnode has additional
- * references. Thus, the map lock can be kept
- * without causing a lock-order reversal with
- * the vnode lock.
- *
- * Since we count the number of virtual page
- * mappings in object->un_pager.vnp.writemappings,
- * the writemappings value should not be adjusted
- * when the entry is disposed of.
- */
- if (prev->object.vm_object)
- vm_object_deallocate(prev->object.vm_object);
- if (prev->cred != NULL)
- crfree(prev->cred);
- vm_map_entry_dispose(map, prev);
- }
+ if (vm_map_mergeable_neighbors(prev, entry)) {
+ vm_map_entry_unlink(map, prev);
+ entry->start = prev->start;
+ entry->offset = prev->offset;
+ if (entry->prev != &map->header)
+ vm_map_entry_resize_free(map, entry->prev);
+ vm_map_merged_neighbor_dispose(map, prev);
}
-
next = entry->next;
- if (next != &map->header) {
- esize = entry->end - entry->start;
- if ((entry->end == next->start) &&
- (next->object.vm_object == entry->object.vm_object) &&
- (!entry->object.vm_object ||
- (entry->offset + esize == next->offset)) &&
- (next->eflags == entry->eflags) &&
- (next->protection == entry->protection) &&
- (next->max_protection == entry->max_protection) &&
- (next->inheritance == entry->inheritance) &&
- (next->wired_count == entry->wired_count) &&
- (next->cred == entry->cred)) {
- vm_map_entry_unlink(map, next);
- entry->end = next->end;
- vm_map_entry_resize_free(map, entry);
-
- /*
- * See comment above.
- */
- if (next->object.vm_object)
- vm_object_deallocate(next->object.vm_object);
- if (next->cred != NULL)
- crfree(next->cred);
- vm_map_entry_dispose(map, next);
- }
+ if (vm_map_mergeable_neighbors(entry, next)) {
+ vm_map_entry_unlink(map, next);
+ entry->end = next->end;
+ vm_map_entry_resize_free(map, entry);
+ vm_map_merged_neighbor_dispose(map, next);
}
}
+
/*
* vm_map_clip_start: [ internal use only ]
*
Modified: stable/12/sys/vm/vm_map.h
==============================================================================
--- stable/12/sys/vm/vm_map.h Wed Nov 28 18:09:42 2018 (r341160)
+++ stable/12/sys/vm/vm_map.h Wed Nov 28 18:42:42 2018 (r341161)
@@ -146,6 +146,7 @@ struct vm_map_entry {
#define MAP_ENTRY_GUARD 0x10000
#define MAP_ENTRY_STACK_GAP_DN 0x20000
#define MAP_ENTRY_STACK_GAP_UP 0x40000
+#define MAP_ENTRY_HEADER 0x80000
#ifdef _KERNEL
static __inline u_char
@@ -175,24 +176,22 @@ vm_map_entry_system_wired_count(vm_map_entry_t entry)
* list. Both structures are ordered based upon the start and
* end addresses contained within each map entry.
*
- * Counterintuitively, the map's min offset value is stored in
- * map->header.end, and its max offset value is stored in
- * map->header.start.
- *
- * The list header has max start value and min end value to act
- * as sentinels for sequential search of the doubly-linked list.
* Sleator and Tarjan's top-down splay algorithm is employed to
* control height imbalance in the binary search tree.
*
+ * The map's min offset value is stored in map->header.end, and
+ * its max offset value is stored in map->header.start. These
+ * values act as sentinels for any forward or backward address
+ * scan of the list. The map header has a special value for the
+ * eflags field, MAP_ENTRY_HEADER, that is set initially, is
+ * never changed, and prevents an eflags match of the header
+ * with any other map entry.
+ *
* List of locks
* (c) const until freed
*/
struct vm_map {
struct vm_map_entry header; /* List of entries */
-/*
- map min_offset header.end (c)
- map max_offset header.start (c)
-*/
struct sx lock; /* Lock for map data */
struct mtx system_mtx;
int nentries; /* Number of entries */
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