freebsd-dev/sys/vm/vm_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

511 lines
12 KiB
C

/*-
* Copyright (c) 1991, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* The Mach Operating System project at Carnegie-Mellon University.
*
* 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.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
*
* from: @(#)vm_pager.c 8.6 (Berkeley) 1/12/94
*
*
* Copyright (c) 1987, 1990 Carnegie-Mellon University.
* All rights reserved.
*
* Authors: Avadis Tevanian, Jr., Michael Wayne Young
*
* Permission to use, copy, modify and distribute this software and
* its documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
* School of Computer Science
* Carnegie Mellon University
* Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie the
* rights to redistribute these changes.
*/
/*
* Paging space routine stubs. Emulates a matchmaker-like interface
* for builtin pagers.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/vnode.h>
#include <sys/bio.h>
#include <sys/buf.h>
#include <sys/ucred.h>
#include <sys/malloc.h>
#include <sys/rwlock.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_extern.h>
int cluster_pbuf_freecnt = -1; /* unlimited to begin with */
static int dead_pager_getpages(vm_object_t, vm_page_t *, int, int);
static vm_object_t dead_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
vm_ooffset_t, struct ucred *);
static void dead_pager_putpages(vm_object_t, vm_page_t *, int, int, int *);
static boolean_t dead_pager_haspage(vm_object_t, vm_pindex_t, int *, int *);
static void dead_pager_dealloc(vm_object_t);
static int
dead_pager_getpages(obj, ma, count, req)
vm_object_t obj;
vm_page_t *ma;
int count;
int req;
{
return VM_PAGER_FAIL;
}
static vm_object_t
dead_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
vm_ooffset_t off, struct ucred *cred)
{
return NULL;
}
static void
dead_pager_putpages(object, m, count, flags, rtvals)
vm_object_t object;
vm_page_t *m;
int count;
int flags;
int *rtvals;
{
int i;
for (i = 0; i < count; i++) {
rtvals[i] = VM_PAGER_AGAIN;
}
}
static int
dead_pager_haspage(object, pindex, prev, next)
vm_object_t object;
vm_pindex_t pindex;
int *prev;
int *next;
{
if (prev)
*prev = 0;
if (next)
*next = 0;
return FALSE;
}
static void
dead_pager_dealloc(object)
vm_object_t object;
{
return;
}
static struct pagerops deadpagerops = {
.pgo_alloc = dead_pager_alloc,
.pgo_dealloc = dead_pager_dealloc,
.pgo_getpages = dead_pager_getpages,
.pgo_putpages = dead_pager_putpages,
.pgo_haspage = dead_pager_haspage,
};
struct pagerops *pagertab[] = {
&defaultpagerops, /* OBJT_DEFAULT */
&swappagerops, /* OBJT_SWAP */
&vnodepagerops, /* OBJT_VNODE */
&devicepagerops, /* OBJT_DEVICE */
&physpagerops, /* OBJT_PHYS */
&deadpagerops, /* OBJT_DEAD */
&sgpagerops, /* OBJT_SG */
&mgtdevicepagerops, /* OBJT_MGTDEVICE */
};
static const int npagers = sizeof(pagertab) / sizeof(pagertab[0]);
/*
* Kernel address space for mapping pages.
* Used by pagers where KVAs are needed for IO.
*
* XXX needs to be large enough to support the number of pending async
* cleaning requests (NPENDINGIO == 64) * the maximum swap cluster size
* (MAXPHYS == 64k) if you want to get the most efficiency.
*/
vm_map_t pager_map;
static int bswneeded;
static vm_offset_t swapbkva; /* swap buffers kva */
struct mtx pbuf_mtx;
static TAILQ_HEAD(swqueue, buf) bswlist;
void
vm_pager_init()
{
struct pagerops **pgops;
TAILQ_INIT(&bswlist);
/*
* Initialize known pagers
*/
for (pgops = pagertab; pgops < &pagertab[npagers]; pgops++)
if ((*pgops)->pgo_init != NULL)
(*(*pgops)->pgo_init) ();
}
void
vm_pager_bufferinit()
{
struct buf *bp;
int i;
mtx_init(&pbuf_mtx, "pbuf mutex", NULL, MTX_DEF);
bp = swbuf;
/*
* Now set up swap and physical I/O buffer headers.
*/
for (i = 0; i < nswbuf; i++, bp++) {
TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
BUF_LOCKINIT(bp);
LIST_INIT(&bp->b_dep);
bp->b_rcred = bp->b_wcred = NOCRED;
bp->b_xflags = 0;
}
cluster_pbuf_freecnt = nswbuf / 2;
vnode_pbuf_freecnt = nswbuf / 2 + 1;
swapbkva = kmem_alloc_nofault(pager_map, nswbuf * MAXPHYS);
if (!swapbkva)
panic("Not enough pager_map VM space for physical buffers");
}
/*
* Allocate an instance of a pager of the given type.
* Size, protection and offset parameters are passed in for pagers that
* need to perform page-level validation (e.g. the device pager).
*/
vm_object_t
vm_pager_allocate(objtype_t type, void *handle, vm_ooffset_t size,
vm_prot_t prot, vm_ooffset_t off, struct ucred *cred)
{
vm_object_t ret;
struct pagerops *ops;
ops = pagertab[type];
if (ops)
ret = (*ops->pgo_alloc) (handle, size, prot, off, cred);
else
ret = NULL;
return (ret);
}
/*
* The object must be locked.
*/
void
vm_pager_deallocate(object)
vm_object_t object;
{
VM_OBJECT_ASSERT_WLOCKED(object);
(*pagertab[object->type]->pgo_dealloc) (object);
}
/*
* vm_pager_get_pages() - inline, see vm/vm_pager.h
* vm_pager_put_pages() - inline, see vm/vm_pager.h
* vm_pager_has_page() - inline, see vm/vm_pager.h
*/
/*
* Search the specified pager object list for an object with the
* specified handle. If an object with the specified handle is found,
* increase its reference count and return it. Otherwise, return NULL.
*
* The pager object list must be locked.
*/
vm_object_t
vm_pager_object_lookup(struct pagerlst *pg_list, void *handle)
{
vm_object_t object;
TAILQ_FOREACH(object, pg_list, pager_object_list) {
if (object->handle == handle) {
VM_OBJECT_WLOCK(object);
if ((object->flags & OBJ_DEAD) == 0) {
vm_object_reference_locked(object);
VM_OBJECT_WUNLOCK(object);
break;
}
VM_OBJECT_WUNLOCK(object);
}
}
return (object);
}
/*
* initialize a physical buffer
*/
/*
* XXX This probably belongs in vfs_bio.c
*/
static void
initpbuf(struct buf *bp)
{
KASSERT(bp->b_bufobj == NULL, ("initpbuf with bufobj"));
KASSERT(bp->b_vp == NULL, ("initpbuf with vp"));
bp->b_rcred = NOCRED;
bp->b_wcred = NOCRED;
bp->b_qindex = 0; /* On no queue (QUEUE_NONE) */
bp->b_saveaddr = (caddr_t) (MAXPHYS * (bp - swbuf)) + swapbkva;
bp->b_data = bp->b_saveaddr;
bp->b_kvabase = bp->b_saveaddr;
bp->b_kvasize = MAXPHYS;
bp->b_xflags = 0;
bp->b_flags = 0;
bp->b_ioflags = 0;
bp->b_iodone = NULL;
bp->b_error = 0;
BUF_LOCK(bp, LK_EXCLUSIVE, NULL);
}
/*
* allocate a physical buffer
*
* There are a limited number (nswbuf) of physical buffers. We need
* to make sure that no single subsystem is able to hog all of them,
* so each subsystem implements a counter which is typically initialized
* to 1/2 nswbuf. getpbuf() decrements this counter in allocation and
* increments it on release, and blocks if the counter hits zero. A
* subsystem may initialize the counter to -1 to disable the feature,
* but it must still be sure to match up all uses of getpbuf() with
* relpbuf() using the same variable.
*
* NOTE: pfreecnt can be NULL, but this 'feature' will be removed
* relatively soon when the rest of the subsystems get smart about it. XXX
*/
struct buf *
getpbuf(int *pfreecnt)
{
struct buf *bp;
mtx_lock(&pbuf_mtx);
for (;;) {
if (pfreecnt) {
while (*pfreecnt == 0) {
msleep(pfreecnt, &pbuf_mtx, PVM, "wswbuf0", 0);
}
}
/* get a bp from the swap buffer header pool */
if ((bp = TAILQ_FIRST(&bswlist)) != NULL)
break;
bswneeded = 1;
msleep(&bswneeded, &pbuf_mtx, PVM, "wswbuf1", 0);
/* loop in case someone else grabbed one */
}
TAILQ_REMOVE(&bswlist, bp, b_freelist);
if (pfreecnt)
--*pfreecnt;
mtx_unlock(&pbuf_mtx);
initpbuf(bp);
return bp;
}
/*
* allocate a physical buffer, if one is available.
*
* Note that there is no NULL hack here - all subsystems using this
* call understand how to use pfreecnt.
*/
struct buf *
trypbuf(int *pfreecnt)
{
struct buf *bp;
mtx_lock(&pbuf_mtx);
if (*pfreecnt == 0 || (bp = TAILQ_FIRST(&bswlist)) == NULL) {
mtx_unlock(&pbuf_mtx);
return NULL;
}
TAILQ_REMOVE(&bswlist, bp, b_freelist);
--*pfreecnt;
mtx_unlock(&pbuf_mtx);
initpbuf(bp);
return bp;
}
/*
* release a physical buffer
*
* NOTE: pfreecnt can be NULL, but this 'feature' will be removed
* relatively soon when the rest of the subsystems get smart about it. XXX
*/
void
relpbuf(struct buf *bp, int *pfreecnt)
{
if (bp->b_rcred != NOCRED) {
crfree(bp->b_rcred);
bp->b_rcred = NOCRED;
}
if (bp->b_wcred != NOCRED) {
crfree(bp->b_wcred);
bp->b_wcred = NOCRED;
}
KASSERT(bp->b_vp == NULL, ("relpbuf with vp"));
KASSERT(bp->b_bufobj == NULL, ("relpbuf with bufobj"));
BUF_UNLOCK(bp);
mtx_lock(&pbuf_mtx);
TAILQ_INSERT_HEAD(&bswlist, bp, b_freelist);
if (bswneeded) {
bswneeded = 0;
wakeup(&bswneeded);
}
if (pfreecnt) {
if (++*pfreecnt == 1)
wakeup(pfreecnt);
}
mtx_unlock(&pbuf_mtx);
}
/*
* Associate a p-buffer with a vnode.
*
* Also sets B_PAGING flag to indicate that vnode is not fully associated
* with the buffer. i.e. the bp has not been linked into the vnode or
* ref-counted.
*/
void
pbgetvp(struct vnode *vp, struct buf *bp)
{
KASSERT(bp->b_vp == NULL, ("pbgetvp: not free"));
KASSERT(bp->b_bufobj == NULL, ("pbgetvp: not free (bufobj)"));
bp->b_vp = vp;
bp->b_flags |= B_PAGING;
bp->b_bufobj = &vp->v_bufobj;
}
/*
* Associate a p-buffer with a vnode.
*
* Also sets B_PAGING flag to indicate that vnode is not fully associated
* with the buffer. i.e. the bp has not been linked into the vnode or
* ref-counted.
*/
void
pbgetbo(struct bufobj *bo, struct buf *bp)
{
KASSERT(bp->b_vp == NULL, ("pbgetbo: not free (vnode)"));
KASSERT(bp->b_bufobj == NULL, ("pbgetbo: not free (bufobj)"));
bp->b_flags |= B_PAGING;
bp->b_bufobj = bo;
}
/*
* Disassociate a p-buffer from a vnode.
*/
void
pbrelvp(struct buf *bp)
{
KASSERT(bp->b_vp != NULL, ("pbrelvp: NULL"));
KASSERT(bp->b_bufobj != NULL, ("pbrelvp: NULL bufobj"));
/* XXX REMOVE ME */
BO_LOCK(bp->b_bufobj);
if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
panic(
"relpbuf(): b_vp was probably reassignbuf()d %p %x",
bp,
(int)bp->b_flags
);
}
BO_UNLOCK(bp->b_bufobj);
bp->b_vp = NULL;
bp->b_bufobj = NULL;
bp->b_flags &= ~B_PAGING;
}
/*
* Disassociate a p-buffer from a bufobj.
*/
void
pbrelbo(struct buf *bp)
{
KASSERT(bp->b_vp == NULL, ("pbrelbo: vnode"));
KASSERT(bp->b_bufobj != NULL, ("pbrelbo: NULL bufobj"));
/* XXX REMOVE ME */
BO_LOCK(bp->b_bufobj);
if (TAILQ_NEXT(bp, b_bobufs) != NULL) {
panic(
"relpbuf(): b_vp was probably reassignbuf()d %p %x",
bp,
(int)bp->b_flags
);
}
BO_UNLOCK(bp->b_bufobj);
bp->b_bufobj = NULL;
bp->b_flags &= ~B_PAGING;
}