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System maps are prohibited from mapping vnode-backed objects. Take

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advantage of this restriction to avoid acquiring and releasing Giant when
wiring pages within a system map.

In collaboration with: tegge@
This commit is contained in:
Alan Cox 2004-09-11 18:49:59 +00:00
parent cf7b3b6562
commit 5e4bdb57cb
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=135088
1 changed files with 8 additions and 8 deletions
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16
sys/vm/vm_fault.c
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@ -172,7 +172,7 @@ _unlock_things(struct faultstate *fs, int dealloc)
mtx_unlock(&Giant);
fs->vp = NULL;
}
if (dealloc)
if (dealloc && !fs->map->system_map)
VM_UNLOCK_GIANT();
}
@ -291,11 +291,14 @@ RetryFault:;
*
* XXX vnode_pager_lock() can block without releasing the map lock.
*/
mtx_lock(&Giant);
if (!fs.map->system_map)
mtx_lock(&Giant);
VM_OBJECT_LOCK(fs.first_object);
vm_object_reference_locked(fs.first_object);
fs.vp = vnode_pager_lock(fs.first_object);
if (debug_mpsafevm)
KASSERT(fs.vp == NULL || !fs.map->system_map,
("vm_fault: vnode-backed object mapped by system map"));
if (debug_mpsafevm && !fs.map->system_map)
mtx_unlock(&Giant);
vm_object_pip_add(fs.first_object, 1);
@ -369,7 +372,8 @@ RetryFault:;
if (!vm_page_sleep_if_busy(fs.m, TRUE, "vmpfw"))
vm_page_unlock_queues();
atomic_add_int(&cnt.v_intrans, 1);
VM_UNLOCK_GIANT();
if (!fs.map->system_map)
VM_UNLOCK_GIANT();
vm_object_deallocate(fs.first_object);
goto RetryFault;
}
@ -1026,13 +1030,9 @@ vm_fault_wire(vm_map_t map, vm_offset_t start, vm_offset_t end,
* read-only sections.
*/
for (va = start; va < end; va += PAGE_SIZE) {
if (map->system_map)
mtx_lock(&Giant);
rv = vm_fault(map, va,
user_wire ? VM_PROT_READ : VM_PROT_READ | VM_PROT_WRITE,
user_wire ? VM_FAULT_USER_WIRE : VM_FAULT_CHANGE_WIRING);
if (map->system_map)
mtx_unlock(&Giant);
if (rv) {
if (va != start)
vm_fault_unwire(map, start, va, fictitious);