sg_pager.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2009 Hudson River Trading LLC
    5  * Written by: John H. Baldwin <jhb@FreeBSD.org>
    6  * All rights reserved.
    7  *
    8  * Redistribution and use in source and binary forms, with or without
    9  * modification, are permitted provided that the following conditions
   10  * are met:
   11  * 1. Redistributions of source code must retain the above copyright
   12  *    notice, this list of conditions and the following disclaimer.
   13  * 2. Redistributions in binary form must reproduce the above copyright
   14  *    notice, this list of conditions and the following disclaimer in the
   15  *    documentation and/or other materials provided with the distribution.
   16  *
   17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   27  * SUCH DAMAGE.
   28  */
   29 
   30 #include <sys/cdefs.h>
   31 __FBSDID("$FreeBSD$");
   32 
   33 /*
   34  * This pager manages OBJT_SG objects.  These objects are backed by
   35  * a scatter/gather list of physical address ranges.
   36  */
   37 
   38 #include <sys/param.h>
   39 #include <sys/lock.h>
   40 #include <sys/mutex.h>
   41 #include <sys/rwlock.h>
   42 #include <sys/sglist.h>
   43 #include <sys/user.h>
   44 #include <sys/vmmeter.h>
   45 
   46 #include <vm/vm.h>
   47 #include <vm/vm_param.h>
   48 #include <vm/vm_object.h>
   49 #include <vm/vm_page.h>
   50 #include <vm/vm_pager.h>
   51 #include <vm/vm_phys.h>
   52 #include <vm/uma.h>
   53 
   54 static vm_object_t sg_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
   55     vm_ooffset_t, struct ucred *);
   56 static void sg_pager_dealloc(vm_object_t);
   57 static int sg_pager_getpages(vm_object_t, vm_page_t *, int, int *, int *);
   58 static void sg_pager_putpages(vm_object_t, vm_page_t *, int, 
   59                 boolean_t, int *);
   60 static boolean_t sg_pager_haspage(vm_object_t, vm_pindex_t, int *,
   61                 int *);
   62 
   63 const struct pagerops sgpagerops = {
   64         .pgo_kvme_type = KVME_TYPE_SG,
   65         .pgo_alloc =    sg_pager_alloc,
   66         .pgo_dealloc =  sg_pager_dealloc,
   67         .pgo_getpages = sg_pager_getpages,
   68         .pgo_putpages = sg_pager_putpages,
   69         .pgo_haspage =  sg_pager_haspage,
   70 };
   71 
   72 static vm_object_t
   73 sg_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
   74     vm_ooffset_t foff, struct ucred *cred)
   75 {
   76         struct sglist *sg;
   77         vm_object_t object;
   78         vm_pindex_t npages, pindex;
   79         int i;
   80 
   81         /*
   82          * Offset should be page aligned.
   83          */
   84         if (foff & PAGE_MASK)
   85                 return (NULL);
   86 
   87         /*
   88          * The scatter/gather list must only include page-aligned
   89          * ranges.
   90          */
   91         npages = 0;
   92         sg = handle;
   93         for (i = 0; i < sg->sg_nseg; i++) {
   94                 if ((sg->sg_segs[i].ss_paddr % PAGE_SIZE) != 0 ||
   95                     (sg->sg_segs[i].ss_len % PAGE_SIZE) != 0)
   96                         return (NULL);
   97                 npages += sg->sg_segs[i].ss_len / PAGE_SIZE;
   98         }
   99 
  100         /*
  101          * The scatter/gather list has a fixed size.  Refuse requests
  102          * to map beyond that.
  103          */
  104         size = round_page(size);
  105         pindex = OFF_TO_IDX(foff) + OFF_TO_IDX(size);
  106         if (pindex > npages || pindex < OFF_TO_IDX(foff) ||
  107             pindex < OFF_TO_IDX(size))
  108                 return (NULL);
  109 
  110         /*
  111          * Allocate a new object and associate it with the
  112          * scatter/gather list.  It is ok for our purposes to have
  113          * multiple VM objects associated with the same scatter/gather
  114          * list because scatter/gather lists are static.  This is also
  115          * simpler than ensuring a unique object per scatter/gather
  116          * list.
  117          */
  118         object = vm_object_allocate(OBJT_SG, npages);
  119         object->handle = sglist_hold(sg);
  120         TAILQ_INIT(&object->un_pager.sgp.sgp_pglist);
  121         return (object);
  122 }
  123 
  124 static void
  125 sg_pager_dealloc(vm_object_t object)
  126 {
  127         struct sglist *sg;
  128         vm_page_t m;
  129 
  130         /*
  131          * Free up our fake pages.
  132          */
  133         while ((m = TAILQ_FIRST(&object->un_pager.sgp.sgp_pglist)) != 0) {
  134                 if (vm_page_busy_acquire(m, VM_ALLOC_WAITFAIL) == 0)
  135                         continue;
  136                 TAILQ_REMOVE(&object->un_pager.sgp.sgp_pglist, m, plinks.q);
  137                 vm_page_putfake(m);
  138         }
  139 
  140         sg = object->handle;
  141         sglist_free(sg);
  142         object->handle = NULL;
  143         object->type = OBJT_DEAD;
  144 }
  145 
  146 static int
  147 sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
  148     int *rahead)
  149 {
  150         struct sglist *sg;
  151         vm_page_t m_paddr, page;
  152         vm_pindex_t offset;
  153         vm_paddr_t paddr;
  154         vm_memattr_t memattr;
  155         size_t space;
  156         int i;
  157 
  158         /* Since our haspage reports zero after/before, the count is 1. */
  159         KASSERT(count == 1, ("%s: count %d", __func__, count));
  160         /* Handle is stable while paging is in progress. */
  161         sg = object->handle;
  162         memattr = object->memattr;
  163         offset = m[0]->pindex;
  164 
  165         /*
  166          * Lookup the physical address of the requested page.  An initial
  167          * value of '1' instead of '' is used so we can assert that the
  168          * page is found since '' can be a valid page-aligned physical
  169          * address.
  170          */
  171         space = 0;
  172         paddr = 1;
  173         for (i = 0; i < sg->sg_nseg; i++) {
  174                 if (space + sg->sg_segs[i].ss_len <= (offset * PAGE_SIZE)) {
  175                         space += sg->sg_segs[i].ss_len;
  176                         continue;
  177                 }
  178                 paddr = sg->sg_segs[i].ss_paddr + offset * PAGE_SIZE - space;
  179                 break;
  180         }
  181         KASSERT(paddr != 1, ("invalid SG page index"));
  182 
  183         /* If "paddr" is a real page, perform a sanity check on "memattr". */
  184         if ((m_paddr = vm_phys_paddr_to_vm_page(paddr)) != NULL &&
  185             pmap_page_get_memattr(m_paddr) != memattr) {
  186                 memattr = pmap_page_get_memattr(m_paddr);
  187                 printf(
  188             "WARNING: A device driver has set \"memattr\" inconsistently.\n");
  189         }
  190 
  191         /* Return a fake page for the requested page. */
  192         KASSERT(!(m[0]->flags & PG_FICTITIOUS),
  193             ("backing page for SG is fake"));
  194 
  195         /* Construct a new fake page. */
  196         page = vm_page_getfake(paddr, memattr);
  197         VM_OBJECT_WLOCK(object);
  198         TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, plinks.q);
  199         vm_page_replace(page, object, offset, m[0]);
  200         VM_OBJECT_WUNLOCK(object);
  201         m[0] = page;
  202         vm_page_valid(page);
  203 
  204         if (rbehind)
  205                 *rbehind = 0;
  206         if (rahead)
  207                 *rahead = 0;
  208 
  209         return (VM_PAGER_OK);
  210 }
  211 
  212 static void
  213 sg_pager_putpages(vm_object_t object, vm_page_t *m, int count,
  214     boolean_t sync, int *rtvals)
  215 {
  216 
  217         panic("sg_pager_putpage called");
  218 }
  219 
  220 static boolean_t
  221 sg_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
  222     int *after)
  223 {
  224 
  225         if (before != NULL)
  226                 *before = 0;
  227         if (after != NULL)
  228                 *after = 0;
  229         return (TRUE);
  230 }

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

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