FreeBSD/Linux Kernel Cross Reference
sys/vm/vm_pager.c

     /*-
      * 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_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 != NULL && (*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)
   {
           vm_object_t object;
   
           MPASS(type < nitems(pagertab));
   
           object = (*pagertab[type]->pgo_alloc)(handle, size, prot, off, cred);
           if (object != NULL)
                   object->type = type;
           return (object);
   }
   
   /*
    *      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_SWAP && 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);
                   FIX(page_inserted);
                   FIX(page_removed);
                   FIX(can_alloc_page);
   #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;
   
           TSENTER();
   
           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;
   
           TSEXIT();
   
           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);
   }

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