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Simplify kmem_alloc() by eliminating code that existed on account of

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external pagers in Mach.  FreeBSD doesn't implement external pagers.
Moreover, it don't pageout the kernel object.  So, the reasons for
having code don't hold.

Reviewed by:	kib
MFC after:	6 weeks
This commit is contained in:
Alan Cox 2012-02-29 05:41:29 +00:00
parent c9b01ed581
commit 9ed54e79b5
1 changed files with 0 additions and 30 deletions
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30
sys/vm/vm_kern.c
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@ -161,7 +161,6 @@ kmem_alloc(map, size)
{
vm_offset_t addr;
vm_offset_t offset;
vm_offset_t i;
size = round_page(size);
@ -186,35 +185,6 @@ kmem_alloc(map, size)
VM_PROT_ALL, VM_PROT_ALL, 0);
vm_map_unlock(map);
/*
* Guarantee that there are pages already in this object before
* calling vm_map_wire. This is to prevent the following
* scenario:
*
* 1) Threads have swapped out, so that there is a pager for the
* kernel_object. 2) The kmsg zone is empty, and so we are
* kmem_allocing a new page for it. 3) vm_map_wire calls vm_fault;
* there is no page, but there is a pager, so we call
* pager_data_request. But the kmsg zone is empty, so we must
* kmem_alloc. 4) goto 1 5) Even if the kmsg zone is not empty: when
* we get the data back from the pager, it will be (very stale)
* non-zero data. kmem_alloc is defined to return zero-filled memory.
*
* We're intentionally not activating the pages we allocate to prevent a
* race with page-out. vm_map_wire will wire the pages.
*/
VM_OBJECT_LOCK(kernel_object);
for (i = 0; i < size; i += PAGE_SIZE) {
vm_page_t mem;
mem = vm_page_grab(kernel_object, OFF_TO_IDX(offset + i),
VM_ALLOC_NOBUSY | VM_ALLOC_ZERO | VM_ALLOC_RETRY);
mem->valid = VM_PAGE_BITS_ALL;
KASSERT((mem->oflags & VPO_UNMANAGED) != 0,
("kmem_alloc: page %p is managed", mem));
}
VM_OBJECT_UNLOCK(kernel_object);
/*
* And finally, mark the data as non-pageable.
*/