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: releng/12.0/sys/vm/sg_pager.c 326272 2017-11-27 15:23:17Z pfg $");
   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/vmmeter.h>
   44 
   45 #include <vm/vm.h>
   46 #include <vm/vm_param.h>
   47 #include <vm/vm_object.h>
   48 #include <vm/vm_page.h>
   49 #include <vm/vm_pager.h>
   50 #include <vm/vm_phys.h>
   51 #include <vm/uma.h>
   52 
   53 static vm_object_t sg_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
   54     vm_ooffset_t, struct ucred *);
   55 static void sg_pager_dealloc(vm_object_t);
   56 static int sg_pager_getpages(vm_object_t, vm_page_t *, int, int *, int *);
   57 static void sg_pager_putpages(vm_object_t, vm_page_t *, int, 
   58                 boolean_t, int *);
   59 static boolean_t sg_pager_haspage(vm_object_t, vm_pindex_t, int *,
   60                 int *);
   61 
   62 struct pagerops sgpagerops = {
   63         .pgo_alloc =    sg_pager_alloc,
   64         .pgo_dealloc =  sg_pager_dealloc,
   65         .pgo_getpages = sg_pager_getpages,
   66         .pgo_putpages = sg_pager_putpages,
   67         .pgo_haspage =  sg_pager_haspage,
   68 };
   69 
   70 static vm_object_t
   71 sg_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
   72     vm_ooffset_t foff, struct ucred *cred)
   73 {
   74         struct sglist *sg;
   75         vm_object_t object;
   76         vm_pindex_t npages, pindex;
   77         int i;
   78 
   79         /*
   80          * Offset should be page aligned.
   81          */
   82         if (foff & PAGE_MASK)
   83                 return (NULL);
   84 
   85         /*
   86          * The scatter/gather list must only include page-aligned
   87          * ranges.
   88          */
   89         npages = 0;
   90         sg = handle;
   91         for (i = 0; i < sg->sg_nseg; i++) {
   92                 if ((sg->sg_segs[i].ss_paddr % PAGE_SIZE) != 0 ||
   93                     (sg->sg_segs[i].ss_len % PAGE_SIZE) != 0)
   94                         return (NULL);
   95                 npages += sg->sg_segs[i].ss_len / PAGE_SIZE;
   96         }
   97 
   98         /*
   99          * The scatter/gather list has a fixed size.  Refuse requests
  100          * to map beyond that.
  101          */
  102         size = round_page(size);
  103         pindex = UOFF_TO_IDX(foff) + UOFF_TO_IDX(size);
  104         if (pindex > npages || pindex < UOFF_TO_IDX(foff) ||
  105             pindex < UOFF_TO_IDX(size))
  106                 return (NULL);
  107 
  108         /*
  109          * Allocate a new object and associate it with the
  110          * scatter/gather list.  It is ok for our purposes to have
  111          * multiple VM objects associated with the same scatter/gather
  112          * list because scatter/gather lists are static.  This is also
  113          * simpler than ensuring a unique object per scatter/gather
  114          * list.
  115          */
  116         object = vm_object_allocate(OBJT_SG, npages);
  117         object->handle = sglist_hold(sg);
  118         TAILQ_INIT(&object->un_pager.sgp.sgp_pglist);
  119         return (object);
  120 }
  121 
  122 static void
  123 sg_pager_dealloc(vm_object_t object)
  124 {
  125         struct sglist *sg;
  126         vm_page_t m;
  127 
  128         /*
  129          * Free up our fake pages.
  130          */
  131         while ((m = TAILQ_FIRST(&object->un_pager.sgp.sgp_pglist)) != 0) {
  132                 TAILQ_REMOVE(&object->un_pager.sgp.sgp_pglist, m, plinks.q);
  133                 vm_page_putfake(m);
  134         }
  135         
  136         sg = object->handle;
  137         sglist_free(sg);
  138         object->handle = NULL;
  139         object->type = OBJT_DEAD;
  140 }
  141 
  142 static int
  143 sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int *rbehind,
  144     int *rahead)
  145 {
  146         struct sglist *sg;
  147         vm_page_t m_paddr, page;
  148         vm_pindex_t offset;
  149         vm_paddr_t paddr;
  150         vm_memattr_t memattr;
  151         size_t space;
  152         int i;
  153 
  154         /* Since our haspage reports zero after/before, the count is 1. */
  155         KASSERT(count == 1, ("%s: count %d", __func__, count));
  156         VM_OBJECT_ASSERT_WLOCKED(object);
  157         sg = object->handle;
  158         memattr = object->memattr;
  159         VM_OBJECT_WUNLOCK(object);
  160         offset = m[0]->pindex;
  161 
  162         /*
  163          * Lookup the physical address of the requested page.  An initial
  164          * value of '1' instead of '' is used so we can assert that the
  165          * page is found since '' can be a valid page-aligned physical
  166          * address.
  167          */
  168         space = 0;
  169         paddr = 1;
  170         for (i = 0; i < sg->sg_nseg; i++) {
  171                 if (space + sg->sg_segs[i].ss_len <= (offset * PAGE_SIZE)) {
  172                         space += sg->sg_segs[i].ss_len;
  173                         continue;
  174                 }
  175                 paddr = sg->sg_segs[i].ss_paddr + offset * PAGE_SIZE - space;
  176                 break;
  177         }
  178         KASSERT(paddr != 1, ("invalid SG page index"));
  179 
  180         /* If "paddr" is a real page, perform a sanity check on "memattr". */
  181         if ((m_paddr = vm_phys_paddr_to_vm_page(paddr)) != NULL &&
  182             pmap_page_get_memattr(m_paddr) != memattr) {
  183                 memattr = pmap_page_get_memattr(m_paddr);
  184                 printf(
  185             "WARNING: A device driver has set \"memattr\" inconsistently.\n");
  186         }
  187 
  188         /* Return a fake page for the requested page. */
  189         KASSERT(!(m[0]->flags & PG_FICTITIOUS),
  190             ("backing page for SG is fake"));
  191 
  192         /* Construct a new fake page. */
  193         page = vm_page_getfake(paddr, memattr);
  194         VM_OBJECT_WLOCK(object);
  195         TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, plinks.q);
  196         vm_page_replace_checked(page, object, offset, m[0]);
  197         vm_page_lock(m[0]);
  198         vm_page_free(m[0]);
  199         vm_page_unlock(m[0]);
  200         m[0] = page;
  201         page->valid = VM_PAGE_BITS_ALL;
  202 
  203         if (rbehind)
  204                 *rbehind = 0;
  205         if (rahead)
  206                 *rahead = 0;
  207 
  208         return (VM_PAGER_OK);
  209 }
  210 
  211 static void
  212 sg_pager_putpages(vm_object_t object, vm_page_t *m, int count,
  213     boolean_t sync, int *rtvals)
  214 {
  215 
  216         panic("sg_pager_putpage called");
  217 }
  218 
  219 static boolean_t
  220 sg_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
  221     int *after)
  222 {
  223 
  224         if (before != NULL)
  225                 *before = 0;
  226         if (after != NULL)
  227                 *after = 0;
  228         return (TRUE);
  229 }

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

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sys/vm/sg_pager.c