Author: dougm
Date: Tue Dec 31 22:20:54 2019
New Revision: 356243
URL: https://svnweb.freebsd.org/changeset/base/356243
Log:
The map-entry clipping functions modify start and end entries of an
entry in the vm_map, making invariants related to the max_free entry
field invalid. Move the clipping work into vm_map_entry_link, so that
linking is okay when the new entry clips a current entry, and the
vm_map doesn't have to be briefly corrupted. Change assertions and
conditions in SPLAY_{LEFT,RIGHT}_STEP since the max_free invariants
can now be trusted in all cases.
Tested by: pho
Reviewed by: alc
Differential Revision: https://reviews.freebsd.org/D22897
Modified:
head/sys/vm/vm_map.c
Modified: head/sys/vm/vm_map.c
==============================================================================
--- head/sys/vm/vm_map.c Tue Dec 31 22:19:33 2019 (r356242)
+++ head/sys/vm/vm_map.c Tue Dec 31 22:20:54 2019 (r356243)
@@ -1028,9 +1028,11 @@ vm_size_max(vm_size_t a, vm_size_t b)
*/ \
y = root->left; \
max_free = root->max_free; \
- KASSERT(max_free >= vm_map_entry_max_free_right(root, rlist), \
+ KASSERT(max_free == vm_size_max( \
+ vm_map_entry_max_free_left(root, llist), \
+ vm_map_entry_max_free_right(root, rlist)), \
("%s: max_free invariant fails", __func__)); \
- if (y == llist ? max_free > 0 : max_free - 1 < y->max_free) \
+ if (max_free - 1 < vm_map_entry_max_free_left(root, llist)) \
max_free = vm_map_entry_max_free_right(root, rlist); \
if (y != llist && (test)) { \
/* Rotate right and make y root. */ \
@@ -1067,9 +1069,11 @@ vm_size_max(vm_size_t a, vm_size_t b)
*/ \
y = root->right; \
max_free = root->max_free; \
- KASSERT(max_free >= vm_map_entry_max_free_left(root, llist), \
+ KASSERT(max_free == vm_size_max( \
+ vm_map_entry_max_free_left(root, llist), \
+ vm_map_entry_max_free_right(root, rlist)), \
("%s: max_free invariant fails", __func__)); \
- if (y == rlist ? max_free > 0 : max_free - 1 < y->max_free) \
+ if (max_free - 1 < vm_map_entry_max_free_right(root, rlist)) \
max_free = vm_map_entry_max_free_left(root, llist); \
if (y != rlist && (test)) { \
/* Rotate left and make y root. */ \
@@ -1356,12 +1360,17 @@ vm_map_splay(vm_map_t map, vm_offset_t addr)
/*
* vm_map_entry_{un,}link:
*
- * Insert/remove entries from maps.
+ * Insert/remove entries from maps. On linking, if new entry clips
+ * existing entry, trim existing entry to avoid overlap, and manage
+ * offsets. On unlinking, merge disappearing entry with neighbor, if
+ * called for, and manage offsets. Callers should not modify fields in
+ * entries already mapped.
*/
static void
vm_map_entry_link(vm_map_t map, vm_map_entry_t entry)
{
vm_map_entry_t header, llist, rlist, root;
+ vm_size_t max_free_left, max_free_right;
CTR3(KTR_VM,
"vm_map_entry_link: map %p, nentries %d, entry %p", map,
@@ -1370,13 +1379,48 @@ vm_map_entry_link(vm_map_t map, vm_map_entry_t entry)
map->nentries++;
header = &map->header;
root = vm_map_splay_split(map, entry->start, 0, &llist, &rlist);
- KASSERT(root == NULL,
- ("vm_map_entry_link: link object already mapped"));
- root = entry;
- root->max_free = vm_size_max(
- vm_map_splay_merge_pred(header, root, llist),
- vm_map_splay_merge_succ(header, root, rlist));
- map->root = root;
+ if (root == NULL) {
+ /*
+ * The new entry does not overlap any existing entry in the
+ * map, so it becomes the new root of the map tree.
+ */
+ max_free_left = vm_map_splay_merge_pred(header, entry, llist);
+ max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
+ } else if (entry->start == root->start) {
+ /*
+ * The new entry is a clone of root, with only the end field
+ * changed. The root entry will be shrunk to abut the new
+ * entry, and will be the right child of the new root entry in
+ * the modified map.
+ */
+ KASSERT(entry->end < root->end,
+ ("%s: clip_start not within entry", __func__));
+ vm_map_splay_findprev(root, &llist);
+ root->offset += entry->end - root->start;
+ root->start = entry->end;
+ max_free_left = vm_map_splay_merge_pred(header, entry, llist);
+ max_free_right = root->max_free = vm_size_max(
+ vm_map_splay_merge_pred(entry, root, entry),
+ vm_map_splay_merge_right(header, root, rlist));
+ } else {
+ /*
+ * The new entry is a clone of root, with only the start field
+ * changed. The root entry will be shrunk to abut the new
+ * entry, and will be the left child of the new root entry in
+ * the modified map.
+ */
+ KASSERT(entry->end == root->end,
+ ("%s: clip_start not within entry", __func__));
+ vm_map_splay_findnext(root, &rlist);
+ entry->offset += entry->start - root->start;
+ root->end = entry->start;
+ max_free_left = root->max_free = vm_size_max(
+ vm_map_splay_merge_left(header, root, llist),
+ vm_map_splay_merge_succ(entry, root, entry));
+ max_free_right = vm_map_splay_merge_succ(header, entry, rlist);
+ }
+ entry->max_free = vm_size_max(max_free_left, max_free_right);
+ map->root = entry;
VM_MAP_ASSERT_CONSISTENT(map);
}
@@ -2359,8 +2403,6 @@ _vm_map_clip_start(vm_map_t map, vm_map_entry_t entry,
* so that this entry has the specified starting address.
*/
new_entry->end = start;
- entry->offset += (start - entry->start);
- entry->start = start;
vm_map_entry_link(map, new_entry);
}
@@ -2396,8 +2438,7 @@ _vm_map_clip_end(vm_map_t map, vm_map_entry_t entry, v
* Split off the back portion. Insert the new entry AFTER this one,
* so that this entry has the specified ending address.
*/
- new_entry->start = entry->end = end;
- new_entry->offset += (end - entry->start);
+ new_entry->start = end;
vm_map_entry_link(map, new_entry);
}
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