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Move anonymous object copying for fork into its own routine and so that we

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can avoid locking non-anonymous objects.

Reviewed by:	kib
Differential Revision:	https://reviews.freebsd.org/D22472
This commit is contained in:
jeff 2019-11-25 07:13:05 +00:00
parent 8a7e572e89
commit 0adc679b4c
1 changed files with 57 additions and 34 deletions
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91
sys/vm/vm_map.c
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@ -3722,6 +3722,56 @@ vm_map_check_protection(vm_map_t map, vm_offset_t start, vm_offset_t end,
return (TRUE);
}
/*
*
* vm_map_copy_anon_object:
*
* Copies an anonymous object from an existing map entry to a
* new one. Carries forward the swap charge. May change the
* src object on return.
*/
static void
vm_map_copy_anon_object(vm_map_entry_t src_entry, vm_map_entry_t dst_entry,
vm_offset_t size, vm_ooffset_t *fork_charge)
{
vm_object_t src_object;
struct ucred *cred;
int charged;
src_object = src_entry->object.vm_object;
VM_OBJECT_WLOCK(src_object);
charged = ENTRY_CHARGED(src_entry);
vm_object_collapse(src_object);
if ((src_object->flags & OBJ_ONEMAPPING) != 0) {
vm_object_split(src_entry);
src_object = src_entry->object.vm_object;
}
vm_object_reference_locked(src_object);
vm_object_clear_flag(src_object, OBJ_ONEMAPPING);
if (src_entry->cred != NULL &&
!(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
KASSERT(src_object->cred == NULL,
("OVERCOMMIT: vm_map_copy_anon_entry: cred %p",
src_object));
src_object->cred = src_entry->cred;
src_object->charge = size;
}
VM_OBJECT_WUNLOCK(src_object);
dst_entry->object.vm_object = src_object;
if (charged) {
cred = curthread->td_ucred;
crhold(cred);
dst_entry->cred = cred;
*fork_charge += size;
if (!(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
crhold(cred);
src_entry->cred = cred;
*fork_charge += size;
}
}
}
/*
* vm_map_copy_entry:
*
@ -3739,8 +3789,6 @@ vm_map_copy_entry(
vm_object_t src_object;
vm_map_entry_t fake_entry;
vm_offset_t size;
struct ucred *cred;
int charged;
VM_MAP_ASSERT_LOCKED(dst_map);
@ -3766,39 +3814,14 @@ vm_map_copy_entry(
*/
size = src_entry->end - src_entry->start;
if ((src_object = src_entry->object.vm_object) != NULL) {
VM_OBJECT_WLOCK(src_object);
charged = ENTRY_CHARGED(src_entry);
if ((src_object->flags & OBJ_ANON) != 0) {
vm_object_collapse(src_object);
if ((src_object->flags & OBJ_ONEMAPPING) != 0) {
vm_object_split(src_entry);
src_object =
src_entry->object.vm_object;
}
}
vm_object_reference_locked(src_object);
vm_object_clear_flag(src_object, OBJ_ONEMAPPING);
if (src_entry->cred != NULL &&
!(src_entry->eflags & MAP_ENTRY_NEEDS_COPY)) {
KASSERT(src_object->cred == NULL,
("OVERCOMMIT: vm_map_copy_entry: cred %p",
src_object));
src_object->cred = src_entry->cred;
src_object->charge = size;
}
VM_OBJECT_WUNLOCK(src_object);
dst_entry->object.vm_object = src_object;
if (charged) {
cred = curthread->td_ucred;
crhold(cred);
dst_entry->cred = cred;
*fork_charge += size;
if (!(src_entry->eflags &
MAP_ENTRY_NEEDS_COPY)) {
crhold(cred);
src_entry->cred = cred;
*fork_charge += size;
}
vm_map_copy_anon_object(src_entry, dst_entry,
size, fork_charge);
/* May have split/collapsed, reload obj. */
src_object = src_entry->object.vm_object;
} else {
vm_object_reference(src_object);
dst_entry->object.vm_object = src_object;
}
src_entry->eflags |= MAP_ENTRY_COW |
MAP_ENTRY_NEEDS_COPY;