vm_pager.c

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/*-
 * SPDX-License-Identifier: (BSD-3-Clause AND MIT-CMU)
 *
 * 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.
 * 3. 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 "opt_param.h"
 
#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 <sys/user.h>
 
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_extern.h>
#include <vm/uma.h>
 
uma_zone_t pbuf_zone;
static int      pbuf_init(void *, int, int);
static int      pbuf_ctor(void *, int, void *, int);
static void     pbuf_dtor(void *, int, void *);
 
static int dead_pager_getpages(vm_object_t, vm_page_t *, int, 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 void dead_pager_getvp(vm_object_t, struct vnode **, bool *);
 
static int
dead_pager_getpages(vm_object_t obj, vm_page_t *ma, int count, int *rbehind,
    int *rahead)
{
 
        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(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(vm_object_t object, vm_pindex_t pindex, int *prev, int *next)
{
 
        if (prev != NULL)
                *prev = 0;
        if (next != NULL)
                *next = 0;
        return (FALSE);
}
 
static void
dead_pager_dealloc(vm_object_t object)
{
 
}
 
static void
dead_pager_getvp(vm_object_t object, struct vnode **vpp, bool *vp_heldp)
{
        /*
         * For OBJT_DEAD objects, v_writecount was handled in
         * vnode_pager_dealloc().
         */
}
 
static const struct pagerops deadpagerops = {
        .pgo_kvme_type = KVME_TYPE_DEAD,
        .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,
        .pgo_getvp =    dead_pager_getvp,
};
 
const struct pagerops *pagertab[16] __read_mostly = {
        [OBJT_DEFAULT] =        &defaultpagerops,
        [OBJT_SWAP] =           &swappagerops,
        [OBJT_VNODE] =          &vnodepagerops,
        [OBJT_DEVICE] =         &devicepagerops,
        [OBJT_PHYS] =           &physpagerops,
        [OBJT_DEAD] =           &deadpagerops,
        [OBJT_SG] =             &sgpagerops,
        [OBJT_MGTDEVICE] =      &mgtdevicepagerops,
};
static struct mtx pagertab_lock;
 
void
vm_pager_init(void)
{
        const struct pagerops **pgops;
        int i;
 
        mtx_init(&pagertab_lock, "dynpag", NULL, MTX_DEF);
 
        /*
         * Initialize known pagers
         */
        for (i = 0; i < OBJT_FIRST_DYN; i++) {
                pgops = &pagertab[i];
                if ((*pgops)->pgo_init != NULL)
                        (*(*pgops)->pgo_init)();
        }
}
 
static int nswbuf_max;
 
void
vm_pager_bufferinit(void)
{
 
        /* Main zone for paging bufs. */
        pbuf_zone = uma_zcreate("pbuf",
            sizeof(struct buf) + PBUF_PAGES * sizeof(vm_page_t),
            pbuf_ctor, pbuf_dtor, pbuf_init, NULL, UMA_ALIGN_CACHE,
            UMA_ZONE_NOFREE);
        /* Few systems may still use this zone directly, so it needs a limit. */
        nswbuf_max += uma_zone_set_max(pbuf_zone, NSWBUF_MIN);
}
 
uma_zone_t
pbuf_zsecond_create(const char *name, int max)
{
        uma_zone_t zone;
 
        zone = uma_zsecond_create(name, pbuf_ctor, pbuf_dtor, NULL, NULL,
            pbuf_zone);
 
#ifdef KMSAN
        /*
         * Shrink the size of the pbuf pools if KMSAN is enabled, otherwise the
         * shadows of the large KVA allocations eat up too much memory.
         */
        max /= 3;
#endif
 
        /*
         * uma_prealloc() rounds up to items per slab. If we would prealloc
         * immediately on every pbuf_zsecond_create(), we may accumulate too
         * much of difference between hard limit and prealloced items, which
         * means wasted memory.
         */
        if (nswbuf_max > 0)
                nswbuf_max += uma_zone_set_max(zone, max);
        else
                uma_prealloc(pbuf_zone, uma_zone_set_max(zone, max));
 
        return (zone);
}
 
static void
pbuf_prealloc(void *arg __unused)
{
 
        uma_prealloc(pbuf_zone, nswbuf_max);
        nswbuf_max = -1;
}
 
SYSINIT(pbuf, SI_SUB_KTHREAD_BUF, SI_ORDER_ANY, pbuf_prealloc, NULL);
 
/*
 * 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)
{
        MPASS(type < nitems(pagertab));
 
        return ((*pagertab[type]->pgo_alloc)(handle, size, prot, off, cred));
}
 
/*
 *      The object must be locked.
 */
void
vm_pager_deallocate(vm_object_t object)
{
 
        VM_OBJECT_ASSERT_WLOCKED(object);
        MPASS(object->type < nitems(pagertab));
        (*pagertab[object->type]->pgo_dealloc) (object);
}
 
static void
vm_pager_assert_in(vm_object_t object, vm_page_t *m, int count)
{
#ifdef INVARIANTS
 
        /*
         * All pages must be consecutive, busied, not mapped, not fully valid,
         * not dirty and belong to the proper object.  Some pages may be the
         * bogus page, but the first and last pages must be a real ones.
         */
 
        VM_OBJECT_ASSERT_UNLOCKED(object);
        VM_OBJECT_ASSERT_PAGING(object);
        KASSERT(count > 0, ("%s: 0 count", __func__));
        for (int i = 0 ; i < count; i++) {
                if (m[i] == bogus_page) {
                        KASSERT(i != 0 && i != count - 1,
                            ("%s: page %d is the bogus page", __func__, i));
                        continue;
                }
                vm_page_assert_xbusied(m[i]);
                KASSERT(!pmap_page_is_mapped(m[i]),
                    ("%s: page %p is mapped", __func__, m[i]));
                KASSERT(m[i]->valid != VM_PAGE_BITS_ALL,
                    ("%s: request for a valid page %p", __func__, m[i]));
                KASSERT(m[i]->dirty == 0,
                    ("%s: page %p is dirty", __func__, m[i]));
                KASSERT(m[i]->object == object,
                    ("%s: wrong object %p/%p", __func__, object, m[i]->object));
                KASSERT(m[i]->pindex == m[0]->pindex + i,
                    ("%s: page %p isn't consecutive", __func__, m[i]));
        }
#endif
}
 
/*
 * Page in the pages for the object using its associated pager.
 * The requested page must be fully valid on successful return.
 */
int
vm_pager_get_pages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
    int *rahead)
{
#ifdef INVARIANTS
        vm_pindex_t pindex = m[0]->pindex;
#endif
        int r;
 
        MPASS(object->type < nitems(pagertab));
        vm_pager_assert_in(object, m, count);
 
        r = (*pagertab[object->type]->pgo_getpages)(object, m, count, rbehind,
            rahead);
        if (r != VM_PAGER_OK)
                return (r);
 
        for (int i = 0; i < count; i++) {
                /*
                 * If pager has replaced a page, assert that it had
                 * updated the array.
                 */
#ifdef INVARIANTS
                KASSERT(m[i] == vm_page_relookup(object, pindex++),
                    ("%s: mismatch page %p pindex %ju", __func__,
                    m[i], (uintmax_t )pindex - 1));
#endif
 
                /*
                 * Zero out partially filled data.
                 */
                if (m[i]->valid != VM_PAGE_BITS_ALL)
                        vm_page_zero_invalid(m[i], TRUE);
        }
        return (VM_PAGER_OK);
}
 
int
vm_pager_get_pages_async(vm_object_t object, vm_page_t *m, int count,
    int *rbehind, int *rahead, pgo_getpages_iodone_t iodone, void *arg)
{
 
        MPASS(object->type < nitems(pagertab));
        vm_pager_assert_in(object, m, count);
 
        return ((*pagertab[object->type]->pgo_getpages_async)(object, m,
            count, rbehind, rahead, iodone, arg));
}
 
/*
 * 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);
}
 
int
vm_pager_alloc_dyn_type(struct pagerops *ops, int base_type)
{
        int res;
 
        mtx_lock(&pagertab_lock);
        MPASS(base_type == -1 ||
            (base_type >= OBJT_DEFAULT && base_type < nitems(pagertab)));
        for (res = OBJT_FIRST_DYN; res < nitems(pagertab); res++) {
                if (pagertab[res] == NULL)
                        break;
        }
        if (res == nitems(pagertab)) {
                mtx_unlock(&pagertab_lock);
                return (-1);
        }
        if (base_type != -1) {
                MPASS(pagertab[base_type] != NULL);
#define FIX(n)                                                          \
                if (ops->pgo_##n == NULL)                               \
                        ops->pgo_##n = pagertab[base_type]->pgo_##n
                FIX(init);
                FIX(alloc);
                FIX(dealloc);
                FIX(getpages);
                FIX(getpages_async);
                FIX(putpages);
                FIX(haspage);
                FIX(populate);
                FIX(pageunswapped);
                FIX(update_writecount);
                FIX(release_writecount);
                FIX(set_writeable_dirty);
                FIX(mightbedirty);
                FIX(getvp);
                FIX(freespace);
#undef FIX
        }
        pagertab[res] = ops;    /* XXXKIB should be rel, but acq is too much */
        mtx_unlock(&pagertab_lock);
        return (res);
}
 
void
vm_pager_free_dyn_type(objtype_t type)
{
        MPASS(type >= OBJT_FIRST_DYN && type < nitems(pagertab));
 
        mtx_lock(&pagertab_lock);
        MPASS(pagertab[type] != NULL);
        pagertab[type] = NULL;
        mtx_unlock(&pagertab_lock);
}
 
static int
pbuf_ctor(void *mem, int size, void *arg, int flags)
{
        struct buf *bp = mem;
 
        bp->b_vp = NULL;
        bp->b_bufobj = NULL;
 
        /* copied from initpbuf() */
        bp->b_rcred = NOCRED;
        bp->b_wcred = NOCRED;
        bp->b_qindex = 0;       /* On no queue (QUEUE_NONE) */
        bp->b_data = bp->b_kvabase;
        bp->b_xflags = 0;
        bp->b_flags = B_MAXPHYS;
        bp->b_ioflags = 0;
        bp->b_iodone = NULL;
        bp->b_error = 0;
        BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL);
 
        return (0);
}
 
static void
pbuf_dtor(void *mem, int size, void *arg)
{
        struct buf *bp = mem;
 
        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;
        }
 
        BUF_UNLOCK(bp);
}
 
static const char pbuf_wmesg[] = "pbufwait";
 
static int
pbuf_init(void *mem, int size, int flags)
{
        struct buf *bp = mem;
 
        bp->b_kvabase = (void *)kva_alloc(ptoa(PBUF_PAGES));
        if (bp->b_kvabase == NULL)
                return (ENOMEM);
        bp->b_kvasize = ptoa(PBUF_PAGES);
        BUF_LOCKINIT(bp, pbuf_wmesg);
        LIST_INIT(&bp->b_dep);
        bp->b_rcred = bp->b_wcred = NOCRED;
        bp->b_xflags = 0;
 
        return (0);
}
 
/*
 * 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"));
        KASSERT((bp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN)) == 0,
            ("pbrelvp: pager buf on vnode list."));
 
        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"));
        KASSERT((bp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN)) == 0,
            ("pbrelbo: pager buf on vnode list."));
 
        bp->b_bufobj = NULL;
        bp->b_flags &= ~B_PAGING;
}
 
void
vm_object_set_writeable_dirty(vm_object_t object)
{
        pgo_set_writeable_dirty_t *method;
 
        MPASS(object->type < nitems(pagertab));
 
        method = pagertab[object->type]->pgo_set_writeable_dirty;
        if (method != NULL)
                method(object);
}
 
bool
vm_object_mightbedirty(vm_object_t object)
{
        pgo_mightbedirty_t *method;
 
        MPASS(object->type < nitems(pagertab));
 
        method = pagertab[object->type]->pgo_mightbedirty;
        if (method == NULL)
                return (false);
        return (method(object));
}
 
/*
 * Return the kvme type of the given object.
 * If vpp is not NULL, set it to the object's vm_object_vnode() or NULL.
 */
int
vm_object_kvme_type(vm_object_t object, struct vnode **vpp)
{
        VM_OBJECT_ASSERT_LOCKED(object);
        MPASS(object->type < nitems(pagertab));
 
        if (vpp != NULL)
                *vpp = vm_object_vnode(object);
        return (pagertab[object->type]->pgo_kvme_type);
}