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Eliminate some uses of the prev and next fields of vm_map_entry_t.

Browse Source 
Since the only caller to vm_map_splay is vm_map_lookup_entry, move the
implementation of vm_map_splay into vm_map_lookup_helper, called by
vm_map_lookup_entry.

vm_map_lookup_entry returns the greatest entry less than or equal to a
given address, but in many cases the caller wants the least entry
greater than or equal to the address and uses the next pointer to get
to it. Provide an alternative interface to lookup,
vm_map_lookup_entry_ge, to provide the latter behavior, and let
callers use one or the other rather than having them use the next
pointer after a lookup miss to get what they really want.

In vm_map_growstack, the caller wants an entry that includes a given
address, and either the preceding or next entry depending on the value
of eflags in the first entry. Incorporate that behavior into
vm_map_lookup_helper, the function that implements all of these
lookups.

Eliminate some temporary variables used with vm_map_lookup_entry, but
inessential.

Reviewed by: markj (earlier version)
Approved by: kib (mentor)
Differential Revision: https://reviews.freebsd.org/D20664
This commit is contained in:
Doug Moore 2019-06-25 20:25:16 +00:00
parent eb2b51ffda
commit 52499d1739
2 changed files with 153 additions and 177 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

328
sys/vm/vm_map.c
View File

@ -983,6 +983,17 @@ vm_map_entry_max_free_right(vm_map_entry_t root, vm_map_entry_t right_ancestor)
root->right->max_free : right_ancestor->start - root->end);
}
/*
* vm_map_splay_split, vm_map_splay_merge:
*
* The Sleator and Tarjan top-down splay algorithm with the following
* variation. Max_free must be computed bottom-up, so on the downward
* pass (vm_map_splay_split), maintain the left and right spines in
* reverse order, and ensure that the max_free values for those nodes
* store the values of their descendents not on the search path. Later,
* make a second pass up each side (vm_map_splay_merge) to fix the
* pointers and compute max_free. The time bound is O(log n) amortized.
*/
#define SPLAY_LEFT_STEP(root, y, rlist, test) do { \
vm_size_t max_free; \
\
@ -1165,56 +1176,6 @@ vm_map_splay_merge(vm_map_t map, vm_map_entry_t root,
map->root = root;
}
/*
* vm_map_splay:
*
* The Sleator and Tarjan top-down splay algorithm with the
* following variation. Max_free must be computed bottom-up, so
* on the downward pass, maintain the left and right spines in
* reverse order. Then, make a second pass up each side to fix
* the pointers and compute max_free. The time bound is O(log n)
* amortized.
*
* The new root is the vm_map_entry containing "addr", or else an
* adjacent entry (lower if possible) if addr is not in the tree.
*
* The map must be locked, and leaves it so.
*
* Returns: the new root.
*/
static vm_map_entry_t
vm_map_splay(vm_map_t map, vm_offset_t addr)
{
vm_map_entry_t llist, rlist, root;
root = vm_map_splay_split(map, addr, 0, &llist, &rlist);
if (root != NULL) {
/* do nothing */
} else if (llist != &map->header) {
/*
* Recover the greatest node in the left
* subtree and make it the root.
*/
root = llist;
llist = root->right;
root->right = NULL;
} else if (rlist != &map->header) {
/*
* Recover the least node in the right
* subtree and make it the root.
*/
root = rlist;
rlist = root->left;
root->left = NULL;
} else {
/* There is no root. */
return (NULL);
}
vm_map_splay_merge(map, root, llist, rlist);
VM_MAP_ASSERT_CONSISTENT(map);
return (root);
}
/*
* vm_map_entry_{un,}link:
*
@ -1331,79 +1292,131 @@ vm_map_entry_resize(vm_map_t map, vm_map_entry_t entry, vm_size_t grow_amount)
}
/*
* vm_map_lookup_entry: [ internal use only ]
* vm_map_lookup_helper: [ internal use only ]
*
* Finds the map entry containing (or
* immediately preceding) the specified address
* in the given map; the entry is returned
* in the "entry" parameter. The boolean
* result indicates whether the address is
* actually contained in the map.
* Finds the map entry containing (or adjacent to) the specified address
* in the given map; the entry is returned in the "entry" parameter. The
* boolean result indicates whether the address is actually contained in
* the map. If the address is not contained in the map, parameter lesseq
* determines whether the entry provided is before or after the address.
* If the address is contained in the map, parameter nbr, if not NULL, is
* where the next or previous entry is saved, depending on the value of
* eflags in the found entry.
*/
boolean_t
vm_map_lookup_entry(
vm_map_t map,
vm_offset_t address,
vm_map_entry_t *entry) /* OUT */
static bool
vm_map_lookup_helper(vm_map_t map, vm_offset_t addr, bool lesseq,
vm_map_entry_t *entry, vm_map_entry_t *nbr) /* OUT */
{
vm_map_entry_t cur, lbound;
boolean_t locked;
vm_map_entry_t llist, rlist, root;
bool locked, found;
/*
* If the map is empty, then the map entry immediately preceding
* "address" is the map's header.
* "addr" is the map's header.
*/
cur = map->root;
if (cur == NULL) {
root = map->root;
if (root == NULL) {
*entry = &map->header;
return (FALSE);
}
if (address >= cur->start && cur->end > address) {
*entry = cur;
return (TRUE);
return (false);
}
if ((locked = vm_map_locked(map)) ||
sx_try_upgrade(&map->lock)) {
/*
* Splay requires a write lock on the map. However, it only
* restructures the binary search tree; it does not otherwise
* change the map. Thus, the map's timestamp need not change
* on a temporary upgrade.
*/
cur = vm_map_splay(map, address);
root = vm_map_splay_split(map, addr, 0, &llist, &rlist);
found = root != NULL;
*entry = root;
if (root != NULL) {
if (nbr == NULL)
; /* Ignore. */
else if ((root->eflags & MAP_ENTRY_STACK_GAP_DN) != 0) {
vm_map_splay_findnext(root, &rlist);
*nbr = rlist;
} else {
vm_map_splay_findprev(root, &llist);
*nbr = llist;
}
} else if (llist != &map->header) {
/*
* Recover the greatest node in the left
* subtree and make it the root.
*/
*entry = lesseq ? llist : rlist;
root = llist;
llist = root->right;
root->right = NULL;
} else {
/*
* Recover the least node in the right
* subtree and make it the root.
*/
*entry = lesseq ? llist : rlist;
root = rlist;
rlist = root->left;
root->left = NULL;
}
vm_map_splay_merge(map, root, llist, rlist);
VM_MAP_ASSERT_CONSISTENT(map);
if (!locked)
sx_downgrade(&map->lock);
/*
* If "address" is contained within a map entry, the new root
* is that map entry. Otherwise, the new root is a map entry
* immediately before or after "address".
*/
if (address < cur->start) {
*entry = &map->header;
return (FALSE);
}
*entry = cur;
return (address < cur->end);
return (found);
}
/*
* Since the map is only locked for read access, perform a
* standard binary search tree lookup for "address".
* standard binary search tree lookup for "addr".
*/
lbound = &map->header;
llist = rlist = &map->header;
do {
if (address < cur->start) {
cur = cur->left;
} else if (cur->end <= address) {
lbound = cur;
cur = cur->right;
if (addr < root->start) {
rlist = root;
root = root->left;
} else if (root->end <= addr) {
llist = root;
root = root->right;
} else {
*entry = cur;
return (TRUE);
*entry = root;
if (nbr == NULL);
else if ((root->eflags & MAP_ENTRY_STACK_GAP_DN) != 0) {
/* Make nbr the successor to root. */
if (root->right != NULL) {
rlist = root->right;
while (rlist->left != NULL)
rlist = rlist->left;
}
*nbr = rlist;
} else {
/* Make nbr the predecessor to root. */
if (root->left != NULL) {
llist = root->left;
while (llist->right != NULL)
llist = llist->right;
}
*nbr = llist;
}
return (true);
}
} while (cur != NULL);
*entry = lbound;
return (FALSE);
} while (root != NULL);
*entry = lesseq ? llist : rlist;
return (false);
}
bool
vm_map_lookup_entry(vm_map_t map, vm_offset_t addr,
vm_map_entry_t *entry) /* OUT */
{
return (vm_map_lookup_helper(map, addr, true, entry, NULL));
}
static bool
vm_map_lookup_entry_ge(vm_map_t map, vm_offset_t addr,
vm_map_entry_t *entry) /* OUT */
{
return (vm_map_lookup_helper(map, addr, false, entry, NULL));
}
/*
@ -1422,7 +1435,7 @@ int
vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
vm_offset_t start, vm_offset_t end, vm_prot_t prot, vm_prot_t max, int cow)
{
vm_map_entry_t new_entry, prev_entry, temp_entry;
vm_map_entry_t new_entry, prev_entry;
struct ucred *cred;
vm_eflags_t protoeflags;
vm_inherit_t inheritance;
@ -1447,11 +1460,9 @@ vm_map_insert(vm_map_t map, vm_object_t object, vm_ooffset_t offset,
* Find the entry prior to the proposed starting address; if it's part
* of an existing entry, this range is bogus.
*/
if (vm_map_lookup_entry(map, start, &temp_entry))
if (vm_map_lookup_entry(map, start, &prev_entry))
return (KERN_NO_SPACE);
prev_entry = temp_entry;
/*
* Assert that the next entry doesn't overlap the end point.
*/
@ -2314,10 +2325,8 @@ vm_map_submap(
VM_MAP_RANGE_CHECK(map, start, end);
if (vm_map_lookup_entry(map, start, &entry)) {
if (vm_map_lookup_entry_ge(map, start, &entry))
vm_map_clip_start(map, entry, start);
} else
entry = entry->next;
vm_map_clip_end(map, entry, end);
@ -2472,8 +2481,7 @@ vm_map_protect(vm_map_t map, vm_offset_t start, vm_offset_t end,
VM_MAP_RANGE_CHECK(map, start, end);
if (!vm_map_lookup_entry(map, start, &entry))
entry = entry->next;
vm_map_lookup_entry_ge(map, start, &entry);
/*
* Make a first pass to check for protection violations.
@ -2663,11 +2671,9 @@ vm_map_madvise(
*/
VM_MAP_RANGE_CHECK(map, start, end);
if (vm_map_lookup_entry(map, start, &entry)) {
if (vm_map_lookup_entry_ge(map, start, &entry)) {
if (modify_map)
vm_map_clip_start(map, entry, start);
} else {
entry = entry->next;
}
if (modify_map) {
@ -2799,7 +2805,6 @@ vm_map_inherit(vm_map_t map, vm_offset_t start, vm_offset_t end,
vm_inherit_t new_inheritance)
{
vm_map_entry_t entry;
vm_map_entry_t temp_entry;
switch (new_inheritance) {
case VM_INHERIT_NONE:
@ -2814,11 +2819,8 @@ vm_map_inherit(vm_map_t map, vm_offset_t start, vm_offset_t end,
return (KERN_SUCCESS);
vm_map_lock(map);
VM_MAP_RANGE_CHECK(map, start, end);
if (vm_map_lookup_entry(map, start, &temp_entry)) {
entry = temp_entry;
if (vm_map_lookup_entry_ge(map, start, &entry))
vm_map_clip_start(map, entry, start);
} else
entry = temp_entry->next;
while (entry->start < end) {
vm_map_clip_end(map, entry, end);
if ((entry->eflags & MAP_ENTRY_GUARD) == 0 ||
@ -2851,10 +2853,8 @@ vm_map_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
user_unwire = (flags & VM_MAP_WIRE_USER) ? TRUE : FALSE;
vm_map_lock(map);
VM_MAP_RANGE_CHECK(map, start, end);
if (!vm_map_lookup_entry(map, start, &first_entry)) {
if (flags & VM_MAP_WIRE_HOLESOK)
first_entry = first_entry->next;
else {
if (!vm_map_lookup_entry_ge(map, start, &first_entry)) {
if ((flags & VM_MAP_WIRE_HOLESOK) == 0) {
vm_map_unlock(map);
return (KERN_INVALID_ADDRESS);
}
@ -2882,11 +2882,9 @@ vm_map_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
* Specifically, the entry may have been
* clipped, merged, or deleted.
*/
if (!vm_map_lookup_entry(map, saved_start,
if (!vm_map_lookup_entry_ge(map, saved_start,
&tmp_entry)) {
if (flags & VM_MAP_WIRE_HOLESOK)
tmp_entry = tmp_entry->next;
else {
if ((flags & VM_MAP_WIRE_HOLESOK) == 0) {
if (saved_start == start) {
/*
* First_entry has been deleted.
@ -2944,11 +2942,9 @@ vm_map_unwire(vm_map_t map, vm_offset_t start, vm_offset_t end,
done:
need_wakeup = FALSE;
if (first_entry == NULL) {
result = vm_map_lookup_entry(map, start, &first_entry);
if (!result && (flags & VM_MAP_WIRE_HOLESOK))
first_entry = first_entry->next;
else
KASSERT(result, ("vm_map_unwire: lookup failed"));
result = vm_map_lookup_entry_ge(map, start, &first_entry);
KASSERT(result || (flags & VM_MAP_WIRE_HOLESOK) != 0,
("vm_map_unwire: lookup failed"));
}
for (entry = first_entry; entry->start < end; entry = entry->next) {
/*
@ -3090,10 +3086,8 @@ vm_map_wire_locked(vm_map_t map, vm_offset_t start, vm_offset_t end, int flags)
prot |= VM_PROT_WRITE;
user_wire = (flags & VM_MAP_WIRE_USER) ? TRUE : FALSE;
VM_MAP_RANGE_CHECK(map, start, end);
if (!vm_map_lookup_entry(map, start, &first_entry)) {
if (flags & VM_MAP_WIRE_HOLESOK)
first_entry = first_entry->next;
else
if (!vm_map_lookup_entry_ge(map, start, &first_entry)) {
if ((flags & VM_MAP_WIRE_HOLESOK) == 0)
return (KERN_INVALID_ADDRESS);
}
last_timestamp = map->timestamp;
@ -3119,11 +3113,9 @@ vm_map_wire_locked(vm_map_t map, vm_offset_t start, vm_offset_t end, int flags)
* Specifically, the entry may have been
* clipped, merged, or deleted.
*/
if (!vm_map_lookup_entry(map, saved_start,
if (!vm_map_lookup_entry_ge(map, saved_start,
&tmp_entry)) {
if (flags & VM_MAP_WIRE_HOLESOK)
tmp_entry = tmp_entry->next;
else {
if ((flags & VM_MAP_WIRE_HOLESOK) == 0) {
if (saved_start == start) {
/*
* first_entry has been deleted.
@ -3256,11 +3248,9 @@ vm_map_wire_locked(vm_map_t map, vm_offset_t start, vm_offset_t end, int flags)
done:
need_wakeup = FALSE;
if (first_entry == NULL) {
result = vm_map_lookup_entry(map, start, &first_entry);
if (!result && (flags & VM_MAP_WIRE_HOLESOK))
first_entry = first_entry->next;
else
KASSERT(result, ("vm_map_wire: lookup failed"));
result = vm_map_lookup_entry_ge(map, start, &first_entry);
KASSERT(result || (flags & VM_MAP_WIRE_HOLESOK) != 0,
("vm_map_wire: lookup failed"));
}
for (entry = first_entry; entry->start < end; entry = entry->next) {
/*
@ -3361,7 +3351,8 @@ vm_map_sync(
if (!vm_map_lookup_entry(map, start, &entry)) {
vm_map_unlock_read(map);
return (KERN_INVALID_ADDRESS);
} else if (start == end) {
}
if (start == end) {
start = entry->start;
end = entry->end;
}
@ -3416,9 +3407,10 @@ vm_map_sync(
start += size;
vm_object_deallocate(object);
vm_map_lock_read(map);
if (last_timestamp == map->timestamp ||
!vm_map_lookup_entry(map, start, &current))
if (last_timestamp == map->timestamp)
current = current->next;
else
vm_map_lookup_entry_ge(map, start, &current);
}
vm_map_unlock_read(map);
@ -3551,7 +3543,6 @@ int
vm_map_delete(vm_map_t map, vm_offset_t start, vm_offset_t end)
{
vm_map_entry_t entry;
vm_map_entry_t first_entry;
VM_MAP_ASSERT_LOCKED(map);
if (start == end)
@ -3560,12 +3551,8 @@ vm_map_delete(vm_map_t map, vm_offset_t start, vm_offset_t end)
/*
* Find the start of the region, and clip it
*/
if (!vm_map_lookup_entry(map, start, &first_entry))
entry = first_entry->next;
else {
entry = first_entry;
if (vm_map_lookup_entry_ge(map, start, &entry))
vm_map_clip_start(map, entry, start);
}
/*
* Step through all entries in this region
@ -3583,29 +3570,22 @@ vm_map_delete(vm_map_t map, vm_offset_t start, vm_offset_t end)
vm_map_entry_system_wired_count(entry) != 0)) {
unsigned int last_timestamp;
vm_offset_t saved_start;
vm_map_entry_t tmp_entry;
saved_start = entry->start;
entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
last_timestamp = map->timestamp;
(void) vm_map_unlock_and_wait(map, 0);
vm_map_lock(map);
if (last_timestamp + 1 != map->timestamp) {
/*
* Look again for the entry because the map was
* modified while it was unlocked.
* Specifically, the entry may have been
* clipped, merged, or deleted.
*/
if (!vm_map_lookup_entry(map, saved_start,
&tmp_entry))
entry = tmp_entry->next;
else {
entry = tmp_entry;
vm_map_clip_start(map, entry,
saved_start);
}
}
if (last_timestamp + 1 == map->timestamp)
continue;
/*
* Look again for the entry because the map was
* modified while it was unlocked. Specifically, the
* entry may have been clipped, merged, or deleted.
*/
if (vm_map_lookup_entry_ge(map, saved_start, &entry))
vm_map_clip_start(map, entry, saved_start);
continue;
}
vm_map_clip_end(map, entry, end);
@ -3680,11 +3660,9 @@ vm_map_check_protection(vm_map_t map, vm_offset_t start, vm_offset_t end,
vm_prot_t protection)
{
vm_map_entry_t entry;
vm_map_entry_t tmp_entry;
if (!vm_map_lookup_entry(map, start, &tmp_entry))
if (!vm_map_lookup_entry(map, start, &entry))
return (FALSE);
entry = tmp_entry;
while (start < end) {
/*
@ -4120,7 +4098,7 @@ static int
vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
vm_size_t growsize, vm_prot_t prot, vm_prot_t max, int cow)
{
vm_map_entry_t new_entry, prev_entry;
vm_map_entry_t new_entry;
vm_offset_t bot, gap_bot, gap_top, top;
vm_size_t init_ssize, sgp;
int orient, rv;
@ -4148,13 +4126,13 @@ vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
init_ssize = max_ssize - sgp;
/* If addr is already mapped, no go */
if (vm_map_lookup_entry(map, addrbos, &prev_entry))
if (vm_map_lookup_entry_ge(map, addrbos, &new_entry))
return (KERN_NO_SPACE);
/*
* If we can't accommodate max_ssize in the current mapping, no go.
*/
if (prev_entry->next->start < addrbos + max_ssize)
if (new_entry->start < addrbos + max_ssize)
return (KERN_NO_SPACE);
/*
@ -4181,7 +4159,6 @@ vm_map_stack_locked(vm_map_t map, vm_offset_t addrbos, vm_size_t max_ssize,
rv = vm_map_insert(map, NULL, 0, bot, top, prot, max, cow);
if (rv != KERN_SUCCESS)
return (rv);
new_entry = prev_entry->next;
KASSERT(new_entry->end == top || new_entry->start == bot,
("Bad entry start/end for new stack entry"));
KASSERT((orient & MAP_STACK_GROWS_DOWN) == 0 ||
@ -4240,19 +4217,18 @@ vm_map_growstack(vm_map_t map, vm_offset_t addr, vm_map_entry_t gap_entry)
vmemlim = lim_cur(curthread, RLIMIT_VMEM);
retry:
/* If addr is not in a hole for a stack grow area, no need to grow. */
if (gap_entry == NULL && !vm_map_lookup_entry(map, addr, &gap_entry))
if (gap_entry == NULL &&
!vm_map_lookup_helper(map, addr, true, &gap_entry, &stack_entry))
return (KERN_FAILURE);
if ((gap_entry->eflags & MAP_ENTRY_GUARD) == 0)
return (KERN_SUCCESS);
if ((gap_entry->eflags & MAP_ENTRY_STACK_GAP_DN) != 0) {
stack_entry = gap_entry->next;
if ((stack_entry->eflags & MAP_ENTRY_GROWS_DOWN) == 0 ||
stack_entry->start != gap_entry->end)
return (KERN_FAILURE);
grow_amount = round_page(stack_entry->start - addr);
grow_down = true;
} else if ((gap_entry->eflags & MAP_ENTRY_STACK_GAP_UP) != 0) {
stack_entry = gap_entry->prev;
if ((stack_entry->eflags & MAP_ENTRY_GROWS_UP) == 0 ||
stack_entry->end != gap_entry->start)
return (KERN_FAILURE);

2
sys/vm/vm_map.h
View File

@ -415,7 +415,7 @@ int vm_map_lookup (vm_map_t *, vm_offset_t, vm_prot_t, vm_map_entry_t *, vm_obje
int vm_map_lookup_locked(vm_map_t *, vm_offset_t, vm_prot_t, vm_map_entry_t *, vm_object_t *,
vm_pindex_t *, vm_prot_t *, boolean_t *);
void vm_map_lookup_done (vm_map_t, vm_map_entry_t);
boolean_t vm_map_lookup_entry (vm_map_t, vm_offset_t, vm_map_entry_t *);
bool vm_map_lookup_entry(vm_map_t, vm_offset_t, vm_map_entry_t *);
int vm_map_protect (vm_map_t, vm_offset_t, vm_offset_t, vm_prot_t, boolean_t);
int vm_map_remove (vm_map_t, vm_offset_t, vm_offset_t);
void vm_map_simplify_entry(vm_map_t map, vm_map_entry_t entry);