freebsd-dev/sys/vm/default_pager.c
Attilio Rao 89f6b8632c Switch the vm_object mutex to be a rwlock. This will enable in the
future further optimizations where the vm_object lock will be held
in read mode most of the time the page cache resident pool of pages
are accessed for reading purposes.

The change is mostly mechanical but few notes are reported:
* The KPI changes as follow:
  - VM_OBJECT_LOCK() -> VM_OBJECT_WLOCK()
  - VM_OBJECT_TRYLOCK() -> VM_OBJECT_TRYWLOCK()
  - VM_OBJECT_UNLOCK() -> VM_OBJECT_WUNLOCK()
  - VM_OBJECT_LOCK_ASSERT(MA_OWNED) -> VM_OBJECT_ASSERT_WLOCKED()
    (in order to avoid visibility of implementation details)
  - The read-mode operations are added:
    VM_OBJECT_RLOCK(), VM_OBJECT_TRYRLOCK(), VM_OBJECT_RUNLOCK(),
    VM_OBJECT_ASSERT_RLOCKED(), VM_OBJECT_ASSERT_LOCKED()
* The vm/vm_pager.h namespace pollution avoidance (forcing requiring
  sys/mutex.h in consumers directly to cater its inlining functions
  using VM_OBJECT_LOCK()) imposes that all the vm/vm_pager.h
  consumers now must include also sys/rwlock.h.
* zfs requires a quite convoluted fix to include FreeBSD rwlocks into
  the compat layer because the name clash between FreeBSD and solaris
  versions must be avoided.
  At this purpose zfs redefines the vm_object locking functions
  directly, isolating the FreeBSD components in specific compat stubs.

The KPI results heavilly broken by this commit.  Thirdy part ports must
be updated accordingly (I can think off-hand of VirtualBox, for example).

Sponsored by:	EMC / Isilon storage division
Reviewed by:	jeff
Reviewed by:	pjd (ZFS specific review)
Discussed with:	alc
Tested by:	pho
2013-03-09 02:32:23 +00:00

172 lines
5.7 KiB
C

/*-
* Copyright (c) 1995, David Greenman
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by David Greenman.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The default pager is responsible for supplying backing store to unbacked
* storage. The backing store is usually swap so we just fall through to
* the swap routines. However, since swap metadata has not been assigned,
* the swap routines assign and manage the swap backing store through the
* vm_page->swapblk field. The object is only converted when the page is
* physically freed after having been cleaned and even then vm_page->swapblk
* is maintained whenever a resident page also has swap backing store.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/lock.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/rwlock.h>
#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/swap_pager.h>
static vm_object_t default_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
vm_ooffset_t, struct ucred *);
static void default_pager_dealloc(vm_object_t);
static int default_pager_getpages(vm_object_t, vm_page_t *, int, int);
static void default_pager_putpages(vm_object_t, vm_page_t *, int,
boolean_t, int *);
static boolean_t default_pager_haspage(vm_object_t, vm_pindex_t, int *,
int *);
/*
* pagerops for OBJT_DEFAULT - "default pager".
*/
struct pagerops defaultpagerops = {
.pgo_alloc = default_pager_alloc,
.pgo_dealloc = default_pager_dealloc,
.pgo_getpages = default_pager_getpages,
.pgo_putpages = default_pager_putpages,
.pgo_haspage = default_pager_haspage,
};
/*
* no_pager_alloc just returns an initialized object.
*/
static vm_object_t
default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
vm_ooffset_t offset, struct ucred *cred)
{
vm_object_t object;
if (handle != NULL)
panic("default_pager_alloc: handle specified");
if (cred != NULL) {
if (!swap_reserve_by_cred(size, cred))
return (NULL);
crhold(cred);
}
object = vm_object_allocate(OBJT_DEFAULT,
OFF_TO_IDX(round_page(offset + size)));
if (cred != NULL) {
VM_OBJECT_WLOCK(object);
object->cred = cred;
object->charge = size;
VM_OBJECT_WUNLOCK(object);
}
return (object);
}
/*
* deallocate resources associated with default objects. The default objects
* have no special resources allocated to them, but the vm_page's being used
* in this object might. Still, we do not have to do anything - we will free
* the swapblk in the underlying vm_page's when we free the vm_page or
* garbage collect the vm_page cache list.
*/
static void
default_pager_dealloc(object)
vm_object_t object;
{
/*
* OBJT_DEFAULT objects have no special resources allocated to them.
*/
}
/*
* Load pages from backing store. Since OBJT_DEFAULT is converted to
* OBJT_SWAP at the time a swap-backed vm_page_t is freed, we will never
* see a vm_page with assigned swap here.
*/
static int
default_pager_getpages(object, m, count, reqpage)
vm_object_t object;
vm_page_t *m;
int count;
int reqpage;
{
return VM_PAGER_FAIL;
}
/*
* Store pages to backing store. We should assign swap and initiate
* I/O. We do not actually convert the object to OBJT_SWAP here. The
* object will be converted when the written-out vm_page_t is moved from the
* cache to the free list.
*/
static void
default_pager_putpages(object, m, c, sync, rtvals)
vm_object_t object;
vm_page_t *m;
int c;
boolean_t sync;
int *rtvals;
{
swappagerops.pgo_putpages(object, m, c, sync, rtvals);
}
/*
* Tell us whether the backing store for the requested (object,index) is
* synchronized. i.e. tell us whether we can throw the page away and
* reload it later. So, for example, if we are in the process of writing
* the page to its backing store, or if no backing store has been assigned,
* it is not yet synchronized.
*
* It is possible to have fully-synchronized swap assigned without the
* object having been converted. We just call swap_pager_haspage() to
* deal with it since it must already deal with it plus deal with swap
* meta-data structures.
*/
static boolean_t
default_pager_haspage(object, pindex, before, after)
vm_object_t object;
vm_pindex_t pindex;
int *before;
int *after;
{
return FALSE;
}