More minor IPI work.

[dragonfly/vkernel-mp.git] / sys / vm / vnode_pager.c

/*
 * Copyright (c) 1990 University of Utah.
 * Copyright (c) 1991 The Regents of the University of California.
 * All rights reserved.
 * Copyright (c) 1993, 1994 John S. Dyson
 * Copyright (c) 1995, David Greenman
 *
 * This code is derived from software contributed to Berkeley by
 * the Systems Programming Group of the University of Utah Computer
 * Science Department.
 *
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. 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: @(#)vnode_pager.c 7.5 (Berkeley) 4/20/91
 * $FreeBSD: src/sys/vm/vnode_pager.c,v 1.116.2.7 2002/12/31 09:34:51 dillon Exp $
 * $DragonFly: src/sys/vm/vnode_pager.c,v 1.34 2007/06/08 02:00:47 dillon Exp $
 */

/*
 * Page to/from files (vnodes).
 */

/*
 * TODO:
 *      Implement VOP_GETPAGES/PUTPAGES interface for filesystems. Will
 *      greatly re-simplify the vnode_pager.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/buf.h>
#include <sys/vmmeter.h>
#include <sys/conf.h>
#include <sys/sfbuf.h>
#include <sys/thread2.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vm_map.h>
#include <vm/vnode_pager.h>
#include <vm/vm_extern.h>

static off_t vnode_pager_addr (struct vnode *vp, off_t loffset, int *run);
static void vnode_pager_iodone (struct bio *bio);
static int vnode_pager_input_smlfs (vm_object_t object, vm_page_t m);
static int vnode_pager_input_old (vm_object_t object, vm_page_t m);
static void vnode_pager_dealloc (vm_object_t);
static int vnode_pager_getpages (vm_object_t, vm_page_t *, int, int);
static void vnode_pager_putpages (vm_object_t, vm_page_t *, int, boolean_t, int *);
static boolean_t vnode_pager_haspage (vm_object_t, vm_pindex_t, int *, int *);

struct pagerops vnodepagerops = {
        NULL,
        vnode_pager_alloc,
        vnode_pager_dealloc,
        vnode_pager_getpages,
        vnode_pager_putpages,
        vnode_pager_haspage,
        NULL
};

int vnode_pbuf_freecnt = -1;    /* start out unlimited */

/*
 * Allocate (or lookup) pager for a vnode.
 * Handle is a vnode pointer.
 */
vm_object_t
vnode_pager_alloc(void *handle, off_t size, vm_prot_t prot, off_t offset)
{
        vm_object_t object;
        struct vnode *vp;

        /*
         * Pageout to vnode, no can do yet.
         */
        if (handle == NULL)
                return (NULL);

        /*
         * XXX hack - This initialization should be put somewhere else.
         */
        if (vnode_pbuf_freecnt < 0) {
            vnode_pbuf_freecnt = nswbuf / 2 + 1;
        }

        vp = (struct vnode *) handle;

        /*
         * Prevent race condition when allocating the object. This
         * can happen with NFS vnodes since the nfsnode isn't locked.
         */
        while (vp->v_flag & VOLOCK) {
                vp->v_flag |= VOWANT;
                tsleep(vp, 0, "vnpobj", 0);
        }
        vp->v_flag |= VOLOCK;

        /*
         * If the object is being terminated, wait for it to
         * go away.
         */
        while (((object = vp->v_object) != NULL) &&
                (object->flags & OBJ_DEAD)) {
                vm_object_dead_sleep(object, "vadead");
        }

        if (vp->v_sysref.refcnt <= 0)
                panic("vnode_pager_alloc: no vnode reference");

        if (object == NULL) {
                /*
                 * And an object of the appropriate size
                 */
                object = vm_object_allocate(OBJT_VNODE, OFF_TO_IDX(round_page(size)));
                object->flags = 0;
                object->handle = handle;
                vp->v_object = object;
                vp->v_filesize = size;
        } else {
                object->ref_count++;
                if (vp->v_filesize != size)
                        kprintf("vnode_pager_alloc: Warning, filesize mismatch %lld/%lld\n", vp->v_filesize, size);
        }
        vref(vp);

        vp->v_flag &= ~VOLOCK;
        if (vp->v_flag & VOWANT) {
                vp->v_flag &= ~VOWANT;
                wakeup(vp);
        }
        return (object);
}

static void
vnode_pager_dealloc(vm_object_t object)
{
        struct vnode *vp = object->handle;

        if (vp == NULL)
                panic("vnode_pager_dealloc: pager already dealloced");

        vm_object_pip_wait(object, "vnpdea");

        object->handle = NULL;
        object->type = OBJT_DEAD;
        vp->v_object = NULL;
        vp->v_filesize = NOOFFSET;
        vp->v_flag &= ~(VTEXT | VOBJBUF);
}

/*
 * Return whether the vnode pager has the requested page.  Return the
 * number of disk-contiguous pages before and after the requested page,
 * not including the requested page.
 */
static boolean_t
vnode_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
                    int *after)
{
        struct vnode *vp = object->handle;
        off_t loffset;
        off_t doffset;
        int voff;
        int bsize;
        int error;

        /*
         * If no vp or vp is doomed or marked transparent to VM, we do not
         * have the page.
         */
        if ((vp == NULL) || (vp->v_flag & VRECLAIMED))
                return FALSE;

        /*
         * If filesystem no longer mounted or offset beyond end of file we do
         * not have the page.
         */
        loffset = IDX_TO_OFF(pindex);

        if (vp->v_mount == NULL || loffset >= vp->v_filesize)
                return FALSE;

        bsize = vp->v_mount->mnt_stat.f_iosize;
        voff = loffset % bsize;

        error = VOP_BMAP(vp, loffset - voff, NULL, &doffset, after, before);
        if (error)
                return TRUE;
        if (doffset == NOOFFSET)
                return FALSE;

        if (before) {
                *before = (*before + voff) >> PAGE_SHIFT;
        }
        if (after) {
                *after -= voff;
                if (loffset + *after > vp->v_filesize)
                        *after = vp->v_filesize - loffset;
                *after >>= PAGE_SHIFT;
                if (*after < 0)
                        *after = 0;
        }
        return TRUE;
}

/*
 * Lets the VM system know about a change in size for a file.
 * We adjust our own internal size and flush any cached pages in
 * the associated object that are affected by the size change.
 *
 * NOTE: This routine may be invoked as a result of a pager put
 * operation (possibly at object termination time), so we must be careful.
 *
 * NOTE: vp->v_filesize is initialized to NOOFFSET (-1), be sure that
 * we do not blow up on the case.  nsize will always be >= 0, however.
 */
void
vnode_pager_setsize(struct vnode *vp, vm_ooffset_t nsize)
{
        vm_pindex_t nobjsize;
        vm_pindex_t oobjsize;
        vm_object_t object = vp->v_object;

        if (object == NULL)
                return;

        /*
         * Hasn't changed size
         */
        if (nsize == vp->v_filesize)
                return;

        /*
         * Has changed size.  Adjust the VM object's size and v_filesize
         * before we start scanning pages to prevent new pages from being
         * allocated during the scan.
         */
        nobjsize = OFF_TO_IDX(nsize + PAGE_MASK);
        oobjsize = object->size;
        object->size = nobjsize;

        /*
         * File has shrunk. Toss any cached pages beyond the new EOF.
         */
        if (nsize < vp->v_filesize) {
                vp->v_filesize = nsize;
                if (nobjsize < oobjsize) {
                        vm_object_page_remove(object, nobjsize, oobjsize,
                                              FALSE);
                }
                /*
                 * This gets rid of garbage at the end of a page that is now
                 * only partially backed by the vnode.  Since we are setting
                 * the entire page valid & clean after we are done we have
                 * to be sure that the portion of the page within the file
                 * bounds is already valid.  If it isn't then making it
                 * valid would create a corrupt block.
                 */
                if (nsize & PAGE_MASK) {
                        vm_offset_t kva;
                        vm_page_t m;

                        m = vm_page_lookup(object, OFF_TO_IDX(nsize));
                        if (m && m->valid) {
                                int base = (int)nsize & PAGE_MASK;
                                int size = PAGE_SIZE - base;
                                struct sf_buf *sf;

                                /*
                                 * Clear out partial-page garbage in case
                                 * the page has been mapped.
                                 */
                                sf = sf_buf_alloc(m, SFB_CPUPRIVATE);
                                kva = sf_buf_kva(sf);
                                bzero((caddr_t)kva + base, size);
                                sf_buf_free(sf);

                                /*
                                 * XXX work around SMP data integrity race
                                 * by unmapping the page from user processes.
                                 * The garbage we just cleared may be mapped
                                 * to a user process running on another cpu
                                 * and this code is not running through normal
                                 * I/O channels which handle SMP issues for
                                 * us, so unmap page to synchronize all cpus.
                                 *
                                 * XXX should vm_pager_unmap_page() have
                                 * dealt with this?
                                 */
                                vm_page_protect(m, VM_PROT_NONE);

                                /*
                                 * Clear out partial-page dirty bits.  This
                                 * has the side effect of setting the valid
                                 * bits, but that is ok.  There are a bunch
                                 * of places in the VM system where we expected
                                 * m->dirty == VM_PAGE_BITS_ALL.  The file EOF
                                 * case is one of them.  If the page is still
                                 * partially dirty, make it fully dirty.
                                 *
                                 * note that we do not clear out the valid
                                 * bits.  This would prevent bogus_page
                                 * replacement from working properly.
                                 */
                                vm_page_set_validclean(m, base, size);
                                if (m->dirty != 0)
                                        m->dirty = VM_PAGE_BITS_ALL;
                        }
                }
        } else {
                vp->v_filesize = nsize;
        }
}

void
vnode_pager_freepage(vm_page_t m)
{
        vm_page_free(m);
}

/*
 * calculate the disk byte address of specified logical byte offset.  The
 * logical offset will be block-aligned.  Return the number of contiguous
 * pages that may be read from the underlying block device in *run.  If
 * *run is non-NULL, it will be set to a value of at least 1.
 */
static off_t
vnode_pager_addr(struct vnode *vp, off_t loffset, int *run)
{
        struct vnode *rtvp;
        off_t doffset;
        int bsize;
        int error;
        int voff;

        if (loffset < 0)
                return -1;

        if (vp->v_mount == NULL)
                return -1;

        /*
         * Align loffset to a block boundary for the BMAP, then adjust the
         * returned disk address appropriately.
         */
        bsize = vp->v_mount->mnt_stat.f_iosize;
        voff = loffset % bsize;

        /*
         * Map the block, adjust the disk offset so it represents the
         * passed loffset rather then the block containing loffset.
         */
        error = VOP_BMAP(vp, loffset - voff, &rtvp, &doffset, run, NULL);
        if (error || doffset == NOOFFSET) {
                doffset = NOOFFSET;
        } else {
                doffset += voff;

                /*
                 * When calculating *run, which is the number of pages
                 * worth of data which can be read linearly from disk,
                 * the minimum return value is 1 page.
                 */
                if (run) {
                        *run = (*run - voff) >> PAGE_SHIFT;
                        if (*run < 1)
                                *run = 1;
                }

        }
        return (doffset);
}

/*
 * interrupt routine for I/O completion
 */
static void
vnode_pager_iodone(struct bio *bio)
{
        struct buf *bp = bio->bio_buf;

        bp->b_cmd = BUF_CMD_DONE;
        wakeup(bp);
}

/*
 * small block file system vnode pager input
 */
static int
vnode_pager_input_smlfs(vm_object_t object, vm_page_t m)
{
        int i;
        struct vnode *dp, *vp;
        struct buf *bp;
        vm_offset_t kva;
        struct sf_buf *sf;
        off_t doffset;
        vm_offset_t bsize;
        int error = 0;

        vp = object->handle;
        if (vp->v_mount == NULL)
                return VM_PAGER_BAD;

        bsize = vp->v_mount->mnt_stat.f_iosize;


        VOP_BMAP(vp, (off_t)0, &dp, NULL, NULL, NULL);

        sf = sf_buf_alloc(m, 0);
        kva = sf_buf_kva(sf);

        for (i = 0; i < PAGE_SIZE / bsize; i++) {
                off_t loffset;

                if (vm_page_bits(i * bsize, bsize) & m->valid)
                        continue;

                loffset = IDX_TO_OFF(m->pindex) + i * bsize;
                if (loffset >= vp->v_filesize) {
                        doffset = NOOFFSET;
                } else {
                        doffset = vnode_pager_addr(vp, loffset, NULL);
                }
                if (doffset != NOOFFSET) {
                        bp = getpbuf(&vnode_pbuf_freecnt);

                        /* build a minimal buffer header */
                        bp->b_data = (caddr_t) kva + i * bsize;
                        bp->b_bio1.bio_done = vnode_pager_iodone;
                        bp->b_bio1.bio_offset = doffset;
                        bp->b_bcount = bsize;
                        bp->b_runningbufspace = bsize;
                        runningbufspace += bp->b_runningbufspace;
                        bp->b_cmd = BUF_CMD_READ;

                        /* do the input */
                        vn_strategy(dp, &bp->b_bio1);

                        /* we definitely need to be at splvm here */

                        crit_enter();
                        while (bp->b_cmd != BUF_CMD_DONE)
                                tsleep(bp, 0, "vnsrd", 0);
                        crit_exit();
                        if ((bp->b_flags & B_ERROR) != 0)
                                error = EIO;

                        /*
                         * free the buffer header back to the swap buffer pool
                         */
                        relpbuf(bp, &vnode_pbuf_freecnt);
                        if (error)
                                break;

                        vm_page_set_validclean(m, (i * bsize) & PAGE_MASK, bsize);
                } else {
                        vm_page_set_validclean(m, (i * bsize) & PAGE_MASK, bsize);
                        bzero((caddr_t) kva + i * bsize, bsize);
                }
        }
        sf_buf_free(sf);
        pmap_clear_modify(m);
        vm_page_flag_clear(m, PG_ZERO);
        if (error) {
                return VM_PAGER_ERROR;
        }
        return VM_PAGER_OK;

}


/*
 * old style vnode pager output routine
 */
static int
vnode_pager_input_old(vm_object_t object, vm_page_t m)
{
        struct uio auio;
        struct iovec aiov;
        int error;
        int size;
        vm_offset_t kva;
        struct sf_buf *sf;
        struct vnode *vp;

        error = 0;
        vp = object->handle;

        /*
         * Return failure if beyond current EOF
         */
        if (IDX_TO_OFF(m->pindex) >= vp->v_filesize) {
                return VM_PAGER_BAD;
        } else {
                size = PAGE_SIZE;
                if (IDX_TO_OFF(m->pindex) + size > vp->v_filesize)
                        size = vp->v_filesize - IDX_TO_OFF(m->pindex);

                /*
                 * Allocate a kernel virtual address and initialize so that
                 * we can use VOP_READ/WRITE routines.
                 */
                sf = sf_buf_alloc(m, 0);
                kva = sf_buf_kva(sf);

                aiov.iov_base = (caddr_t) kva;
                aiov.iov_len = size;
                auio.uio_iov = &aiov;
                auio.uio_iovcnt = 1;
                auio.uio_offset = IDX_TO_OFF(m->pindex);
                auio.uio_segflg = UIO_SYSSPACE;
                auio.uio_rw = UIO_READ;
                auio.uio_resid = size;
                auio.uio_td = curthread;

                error = VOP_READ(((struct vnode *)object->handle),
                                &auio, 0, proc0.p_ucred);
                if (!error) {
                        int count = size - auio.uio_resid;

                        if (count == 0)
                                error = EINVAL;
                        else if (count != PAGE_SIZE)
                                bzero((caddr_t) kva + count, PAGE_SIZE - count);
                }
                sf_buf_free(sf);
        }
        pmap_clear_modify(m);
        vm_page_undirty(m);
        vm_page_flag_clear(m, PG_ZERO);
        if (!error)
                m->valid = VM_PAGE_BITS_ALL;
        return error ? VM_PAGER_ERROR : VM_PAGER_OK;
}

/*
 * generic vnode pager input routine
 */

/*
 * EOPNOTSUPP is no longer legal.  For local media VFS's that do not
 * implement their own VOP_GETPAGES, their VOP_GETPAGES should call to
 * vnode_pager_generic_getpages() to implement the previous behaviour.
 *
 * All other FS's should use the bypass to get to the local media
 * backing vp's VOP_GETPAGES.
 */
static int
vnode_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
{
        int rtval;
        struct vnode *vp;
        int bytes = count * PAGE_SIZE;

        vp = object->handle;
        /* 
         * XXX temporary diagnostic message to help track stale FS code,
         * Returning EOPNOTSUPP from here may make things unhappy.
         */
        rtval = VOP_GETPAGES(vp, m, bytes, reqpage, 0);
        if (rtval == EOPNOTSUPP) {
            kprintf("vnode_pager: *** WARNING *** stale FS getpages\n");
            rtval = vnode_pager_generic_getpages( vp, m, bytes, reqpage);
        }
        return rtval;
}


/*
 * This is now called from local media FS's to operate against their
 * own vnodes if they fail to implement VOP_GETPAGES.
 */
int
vnode_pager_generic_getpages(struct vnode *vp, vm_page_t *m, int bytecount,
    int reqpage)
{
        vm_object_t object;
        vm_offset_t kva;
        off_t foff, tfoff, nextoff;
        int i, size, bsize, first;
        off_t firstaddr;
        struct vnode *dp;
        int runpg;
        int runend;
        struct buf *bp;
        int count;
        int error = 0;

        object = vp->v_object;
        count = bytecount / PAGE_SIZE;

        if (vp->v_mount == NULL)
                return VM_PAGER_BAD;

        bsize = vp->v_mount->mnt_stat.f_iosize;

        /* get the UNDERLYING device for the file with VOP_BMAP() */

        /*
         * originally, we did not check for an error return value -- assuming
         * an fs always has a bmap entry point -- that assumption is wrong!!!
         */
        foff = IDX_TO_OFF(m[reqpage]->pindex);

        /*
         * if we can't bmap, use old VOP code
         */
        if (VOP_BMAP(vp, (off_t)0, &dp, NULL, NULL, NULL)) {
                for (i = 0; i < count; i++) {
                        if (i != reqpage) {
                                vnode_pager_freepage(m[i]);
                        }
                }
                mycpu->gd_cnt.v_vnodein++;
                mycpu->gd_cnt.v_vnodepgsin++;
                return vnode_pager_input_old(object, m[reqpage]);

                /*
                 * if the blocksize is smaller than a page size, then use
                 * special small filesystem code.  NFS sometimes has a small
                 * blocksize, but it can handle large reads itself.
                 */
        } else if ((PAGE_SIZE / bsize) > 1 &&
            (vp->v_mount->mnt_stat.f_type != nfs_mount_type)) {
                for (i = 0; i < count; i++) {
                        if (i != reqpage) {
                                vnode_pager_freepage(m[i]);
                        }
                }
                mycpu->gd_cnt.v_vnodein++;
                mycpu->gd_cnt.v_vnodepgsin++;
                return vnode_pager_input_smlfs(object, m[reqpage]);
        }

        /*
         * If we have a completely valid page available to us, we can
         * clean up and return.  Otherwise we have to re-read the
         * media.
         *
         * Note that this does not work with NFS, so NFS has its own
         * getpages routine.  The problem is that NFS can have partially
         * valid pages associated with the buffer cache due to the piecemeal
         * write support.  If we were to fall through and re-read the media
         * as we do here, dirty data could be lost.
         */

        if (m[reqpage]->valid == VM_PAGE_BITS_ALL) {
                for (i = 0; i < count; i++) {
                        if (i != reqpage)
                                vnode_pager_freepage(m[i]);
                }
                return VM_PAGER_OK;
        }
        m[reqpage]->valid = 0;

        /*
         * here on direct device I/O
         */

        firstaddr = -1;
        /*
         * calculate the run that includes the required page
         */
        for(first = 0, i = 0; i < count; i = runend) {
                firstaddr = vnode_pager_addr(vp, IDX_TO_OFF(m[i]->pindex),
                                             &runpg);
                if (firstaddr == -1) {
                        if (i == reqpage && foff < vp->v_filesize) {
                                /* XXX no %qd in kernel. */
                                panic("vnode_pager_getpages: unexpected missing page: firstaddr: %012llx, foff: 0x%012llx, v_filesize: 0x%012llx",
                                 firstaddr, foff, vp->v_filesize);
                        }
                        vnode_pager_freepage(m[i]);
                        runend = i + 1;
                        first = runend;
                        continue;
                }
                runend = i + runpg;
                if (runend <= reqpage) {
                        int j;
                        for (j = i; j < runend; j++) {
                                vnode_pager_freepage(m[j]);
                        }
                } else {
                        if (runpg < (count - first)) {
                                for (i = first + runpg; i < count; i++)
                                        vnode_pager_freepage(m[i]);
                                count = first + runpg;
                        }
                        break;
                }
                first = runend;
        }

        /*
         * the first and last page have been calculated now, move input pages
         * to be zero based...
         */
        if (first != 0) {
                for (i = first; i < count; i++) {
                        m[i - first] = m[i];
                }
                count -= first;
                reqpage -= first;
        }

        /*
         * calculate the file virtual address for the transfer
         */
        foff = IDX_TO_OFF(m[0]->pindex);

        /*
         * calculate the size of the transfer
         */
        size = count * PAGE_SIZE;
        if ((foff + size) > vp->v_filesize)
                size = vp->v_filesize - foff;

        /*
         * round up physical size for real devices.
         */
        if (dp->v_type == VBLK || dp->v_type == VCHR) {
                int secmask = dp->v_rdev->si_bsize_phys - 1;
                KASSERT(secmask < PAGE_SIZE, ("vnode_pager_generic_getpages: sector size %d too large\n", secmask + 1));
                size = (size + secmask) & ~secmask;
        }

        bp = getpbuf(&vnode_pbuf_freecnt);
        kva = (vm_offset_t) bp->b_data;

        /*
         * and map the pages to be read into the kva
         */
        pmap_qenter(kva, m, count);

        /* build a minimal buffer header */
        bp->b_bio1.bio_done = vnode_pager_iodone;
        bp->b_bio1.bio_offset = firstaddr;
        bp->b_bcount = size;
        bp->b_runningbufspace = size;
        runningbufspace += bp->b_runningbufspace;
        bp->b_cmd = BUF_CMD_READ;

        mycpu->gd_cnt.v_vnodein++;
        mycpu->gd_cnt.v_vnodepgsin += count;

        /* do the input */
        vn_strategy(dp, &bp->b_bio1);

        crit_enter();
        /* we definitely need to be at splvm here */

        while (bp->b_cmd != BUF_CMD_DONE)
                tsleep(bp, 0, "vnread", 0);
        crit_exit();
        if ((bp->b_flags & B_ERROR) != 0)
                error = EIO;

        if (!error) {
                if (size != count * PAGE_SIZE)
                        bzero((caddr_t) kva + size, PAGE_SIZE * count - size);
        }
        pmap_qremove(kva, count);

        /*
         * free the buffer header back to the swap buffer pool
         */
        relpbuf(bp, &vnode_pbuf_freecnt);

        for (i = 0, tfoff = foff; i < count; i++, tfoff = nextoff) {
                vm_page_t mt;

                nextoff = tfoff + PAGE_SIZE;
                mt = m[i];

                if (nextoff <= vp->v_filesize) {
                        /*
                         * Read filled up entire page.
                         */
                        mt->valid = VM_PAGE_BITS_ALL;
                        vm_page_undirty(mt);    /* should be an assert? XXX */
                        pmap_clear_modify(mt);
                } else {
                        /*
                         * Read did not fill up entire page.  Since this
                         * is getpages, the page may be mapped, so we have
                         * to zero the invalid portions of the page even
                         * though we aren't setting them valid.
                         *
                         * Currently we do not set the entire page valid,
                         * we just try to clear the piece that we couldn't
                         * read.
                         */
                        vm_page_set_validclean(mt, 0, vp->v_filesize - tfoff);
                        /* handled by vm_fault now */
                        /* vm_page_zero_invalid(mt, FALSE); */
                }
                
                vm_page_flag_clear(mt, PG_ZERO);
                if (i != reqpage) {

                        /*
                         * whether or not to leave the page activated is up in
                         * the air, but we should put the page on a page queue
                         * somewhere. (it already is in the object). Result:
                         * It appears that empirical results show that
                         * deactivating pages is best.
                         */

                        /*
                         * just in case someone was asking for this page we
                         * now tell them that it is ok to use
                         */
                        if (!error) {
                                if (mt->flags & PG_WANTED)
                                        vm_page_activate(mt);
                                else
                                        vm_page_deactivate(mt);
                                vm_page_wakeup(mt);
                        } else {
                                vnode_pager_freepage(mt);
                        }
                }
        }
        if (error) {
                kprintf("vnode_pager_getpages: I/O read error\n");
        }
        return (error ? VM_PAGER_ERROR : VM_PAGER_OK);
}

/*
 * EOPNOTSUPP is no longer legal.  For local media VFS's that do not
 * implement their own VOP_PUTPAGES, their VOP_PUTPAGES should call to
 * vnode_pager_generic_putpages() to implement the previous behaviour.
 *
 * All other FS's should use the bypass to get to the local media
 * backing vp's VOP_PUTPAGES.
 */
static void
vnode_pager_putpages(vm_object_t object, vm_page_t *m, int count,
    boolean_t sync, int *rtvals)
{
        int rtval;
        struct vnode *vp;
        int bytes = count * PAGE_SIZE;

        /*
         * Force synchronous operation if we are extremely low on memory
         * to prevent a low-memory deadlock.  VOP operations often need to
         * allocate more memory to initiate the I/O ( i.e. do a BMAP 
         * operation ).  The swapper handles the case by limiting the amount
         * of asynchronous I/O, but that sort of solution doesn't scale well
         * for the vnode pager without a lot of work.
         *
         * Also, the backing vnode's iodone routine may not wake the pageout
         * daemon up.  This should be probably be addressed XXX.
         */

        if ((vmstats.v_free_count + vmstats.v_cache_count) < vmstats.v_pageout_free_min)
                sync |= OBJPC_SYNC;

        /*
         * Call device-specific putpages function
         */

        vp = object->handle;
        rtval = VOP_PUTPAGES(vp, m, bytes, sync, rtvals, 0);
        if (rtval == EOPNOTSUPP) {
            kprintf("vnode_pager: *** WARNING *** stale FS putpages\n");
            rtval = vnode_pager_generic_putpages( vp, m, bytes, sync, rtvals);
        }
}


/*
 * This is now called from local media FS's to operate against their
 * own vnodes if they fail to implement VOP_PUTPAGES.
 *
 * This is typically called indirectly via the pageout daemon and
 * clustering has already typically occured, so in general we ask the
 * underlying filesystem to write the data out asynchronously rather
 * then delayed.
 */
int
vnode_pager_generic_putpages(struct vnode *vp, vm_page_t *m, int bytecount,
    int flags, int *rtvals)
{
        int i;
        vm_object_t object;
        int count;

        int maxsize, ncount;
        vm_ooffset_t poffset;
        struct uio auio;
        struct iovec aiov;
        int error;
        int ioflags;

        object = vp->v_object;
        count = bytecount / PAGE_SIZE;

        for (i = 0; i < count; i++)
                rtvals[i] = VM_PAGER_AGAIN;

        if ((int) m[0]->pindex < 0) {
                kprintf("vnode_pager_putpages: attempt to write meta-data!!! -- 0x%lx(%x)\n",
                        (long)m[0]->pindex, m[0]->dirty);
                rtvals[0] = VM_PAGER_BAD;
                return VM_PAGER_BAD;
        }

        maxsize = count * PAGE_SIZE;
        ncount = count;

        poffset = IDX_TO_OFF(m[0]->pindex);

        /*
         * If the page-aligned write is larger then the actual file we
         * have to invalidate pages occuring beyond the file EOF.  However,
         * there is an edge case where a file may not be page-aligned where
         * the last page is partially invalid.  In this case the filesystem
         * may not properly clear the dirty bits for the entire page (which
         * could be VM_PAGE_BITS_ALL due to the page having been mmap()d).
         * With the page locked we are free to fix-up the dirty bits here.
         *
         * We do not under any circumstances truncate the valid bits, as
         * this will screw up bogus page replacement.
         */
        if (maxsize + poffset > vp->v_filesize) {
                if (vp->v_filesize > poffset) {
                        int pgoff;

                        maxsize = vp->v_filesize - poffset;
                        ncount = btoc(maxsize);
                        if ((pgoff = (int)maxsize & PAGE_MASK) != 0) {
                                vm_page_clear_dirty(m[ncount - 1], pgoff,
                                        PAGE_SIZE - pgoff);
                        }
                } else {
                        maxsize = 0;
                        ncount = 0;
                }
                if (ncount < count) {
                        for (i = ncount; i < count; i++) {
                                rtvals[i] = VM_PAGER_BAD;
                        }
                }
        }

        /*
         * pageouts are already clustered, use IO_ASYNC to force a bawrite()
         * rather then a bdwrite() to prevent paging I/O from saturating
         * the buffer cache.  Dummy-up the sequential heuristic to cause
         * large ranges to cluster.  If neither IO_SYNC or IO_ASYNC is set,
         * the system decides how to cluster.
         */
        ioflags = IO_VMIO;
        if (flags & (VM_PAGER_PUT_SYNC | VM_PAGER_PUT_INVAL))
                ioflags |= IO_SYNC;
        else if ((flags & VM_PAGER_CLUSTER_OK) == 0)
                ioflags |= IO_ASYNC;
        ioflags |= (flags & VM_PAGER_PUT_INVAL) ? IO_INVAL: 0;
        ioflags |= IO_SEQMAX << IO_SEQSHIFT;

        aiov.iov_base = (caddr_t) 0;
        aiov.iov_len = maxsize;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_offset = poffset;
        auio.uio_segflg = UIO_NOCOPY;
        auio.uio_rw = UIO_WRITE;
        auio.uio_resid = maxsize;
        auio.uio_td = NULL;
        error = VOP_WRITE(vp, &auio, ioflags, proc0.p_ucred);
        mycpu->gd_cnt.v_vnodeout++;
        mycpu->gd_cnt.v_vnodepgsout += ncount;

        if (error) {
                kprintf("vnode_pager_putpages: I/O error %d\n", error);
        }
        if (auio.uio_resid) {
                kprintf("vnode_pager_putpages: residual I/O %d at %lu\n",
                    auio.uio_resid, (u_long)m[0]->pindex);
        }
        for (i = 0; i < ncount; i++) {
                rtvals[i] = VM_PAGER_OK;
        }
        return rtvals[0];
}

struct vnode *
vnode_pager_lock(vm_object_t object)
{
        struct thread *td = curthread;  /* XXX */
        int error;

        for (; object != NULL; object = object->backing_object) {
                if (object->type != OBJT_VNODE)
                        continue;
                if (object->flags & OBJ_DEAD)
                        return NULL;

                for (;;) {
                        struct vnode *vp = object->handle;
                        error = vget(vp, LK_SHARED | LK_RETRY | LK_CANRECURSE);
                        if (error == 0) {
                                if (object->handle != vp) {
                                        vput(vp);
                                        continue;
                                }
                                return (vp);
                        }
                        if ((object->flags & OBJ_DEAD) ||
                            (object->type != OBJT_VNODE)) {
                                return NULL;
                        }
                        kprintf("vnode_pager_lock: vp %p error %d lockstatus %d, retrying\n", vp, error, lockstatus(&vp->v_lock, td));
                        tsleep(object->handle, 0, "vnpgrl", hz);
                }
        }
        return NULL;
}