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

     /*-
      * Copyright (c) 2009 Hudson River Trading LLC
      * Written by: John H. Baldwin <jhb@FreeBSD.org>
      * All rights reserved.
      *
      * 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    /*
     * This pager manages OBJT_SG objects.  These objects are backed by
     * a scatter/gather list of physical address ranges.
     */
    
    #include <sys/param.h>
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/rwlock.h>
    #include <sys/sglist.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_phys.h>
    #include <vm/uma.h>
    
    static vm_object_t sg_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
        vm_ooffset_t, struct ucred *);
    static void sg_pager_dealloc(vm_object_t);
    static int sg_pager_getpages(vm_object_t, vm_page_t *, int, int);
    static void sg_pager_putpages(vm_object_t, vm_page_t *, int, 
                    boolean_t, int *);
    static boolean_t sg_pager_haspage(vm_object_t, vm_pindex_t, int *,
                    int *);
    
    struct pagerops sgpagerops = {
            .pgo_alloc =    sg_pager_alloc,
            .pgo_dealloc =  sg_pager_dealloc,
            .pgo_getpages = sg_pager_getpages,
            .pgo_putpages = sg_pager_putpages,
            .pgo_haspage =  sg_pager_haspage,
    };
    
    static vm_object_t
    sg_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
        vm_ooffset_t foff, struct ucred *cred)
    {
            struct sglist *sg;
            vm_object_t object;
            vm_pindex_t npages, pindex;
            int i;
    
            /*
             * Offset should be page aligned.
             */
            if (foff & PAGE_MASK)
                    return (NULL);
    
            /*
             * The scatter/gather list must only include page-aligned
             * ranges.
             */
            npages = 0;
            sg = handle;
            for (i = 0; i < sg->sg_nseg; i++) {
                    if ((sg->sg_segs[i].ss_paddr % PAGE_SIZE) != 0 ||
                        (sg->sg_segs[i].ss_len % PAGE_SIZE) != 0)
                            return (NULL);
                    npages += sg->sg_segs[i].ss_len / PAGE_SIZE;
            }
    
            /*
             * The scatter/gather list has a fixed size.  Refuse requests
             * to map beyond that.
             */
            size = round_page(size);
            pindex = OFF_TO_IDX(foff + size);
           if (pindex > npages)
                   return (NULL);
   
           /*
            * Allocate a new object and associate it with the
            * scatter/gather list.  It is ok for our purposes to have
            * multiple VM objects associated with the same scatter/gather
            * list because scatter/gather lists are static.  This is also
            * simpler than ensuring a unique object per scatter/gather
            * list.
            */
           object = vm_object_allocate(OBJT_SG, npages);
           object->handle = sglist_hold(sg);
           TAILQ_INIT(&object->un_pager.sgp.sgp_pglist);
           return (object);
   }
   
   static void
   sg_pager_dealloc(vm_object_t object)
   {
           struct sglist *sg;
           vm_page_t m;
   
           /*
            * Free up our fake pages.
            */
           while ((m = TAILQ_FIRST(&object->un_pager.sgp.sgp_pglist)) != 0) {
                   TAILQ_REMOVE(&object->un_pager.sgp.sgp_pglist, m, plinks.q);
                   vm_page_putfake(m);
           }
           
           sg = object->handle;
           sglist_free(sg);
           object->handle = NULL;
           object->type = OBJT_DEAD;
   }
   
   static int
   sg_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
   {
           struct sglist *sg;
           vm_page_t m_paddr, page;
           vm_pindex_t offset;
           vm_paddr_t paddr;
           vm_memattr_t memattr;
           size_t space;
           int i;
   
           VM_OBJECT_ASSERT_WLOCKED(object);
           sg = object->handle;
           memattr = object->memattr;
           VM_OBJECT_WUNLOCK(object);
           offset = m[reqpage]->pindex;
   
           /*
            * Lookup the physical address of the requested page.  An initial
            * value of '1' instead of '' is used so we can assert that the
            * page is found since '' can be a valid page-aligned physical
            * address.
            */
           space = 0;
           paddr = 1;
           for (i = 0; i < sg->sg_nseg; i++) {
                   if (space + sg->sg_segs[i].ss_len <= (offset * PAGE_SIZE)) {
                           space += sg->sg_segs[i].ss_len;
                           continue;
                   }
                   paddr = sg->sg_segs[i].ss_paddr + offset * PAGE_SIZE - space;
                   break;
           }
           KASSERT(paddr != 1, ("invalid SG page index"));
   
           /* If "paddr" is a real page, perform a sanity check on "memattr". */
           if ((m_paddr = vm_phys_paddr_to_vm_page(paddr)) != NULL &&
               pmap_page_get_memattr(m_paddr) != memattr) {
                   memattr = pmap_page_get_memattr(m_paddr);
                   printf(
               "WARNING: A device driver has set \"memattr\" inconsistently.\n");
           }
   
           /* Return a fake page for the requested page. */
           KASSERT(!(m[reqpage]->flags & PG_FICTITIOUS),
               ("backing page for SG is fake"));
   
           /* Construct a new fake page. */
           page = vm_page_getfake(paddr, memattr);
           VM_OBJECT_WLOCK(object);
           TAILQ_INSERT_TAIL(&object->un_pager.sgp.sgp_pglist, page, plinks.q);
   
           /* Free the original pages and insert this fake page into the object. */
           for (i = 0; i < count; i++) {
                   if (i == reqpage &&
                       vm_page_replace(page, object, offset) != m[i])
                           panic("sg_pager_getpages: invalid place replacement");
                   vm_page_lock(m[i]);
                   vm_page_free(m[i]);
                   vm_page_unlock(m[i]);
           }
           m[reqpage] = page;
           page->valid = VM_PAGE_BITS_ALL;
   
           return (VM_PAGER_OK);
   }
   
   static void
   sg_pager_putpages(vm_object_t object, vm_page_t *m, int count,
       boolean_t sync, int *rtvals)
   {
   
           panic("sg_pager_putpage called");
   }
   
   static boolean_t
   sg_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
       int *after)
   {
   
           if (before != NULL)
                   *before = 0;
           if (after != NULL)
                   *after = 0;
           return (TRUE);
   }

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