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

     /*
      * Copyright (c) 1982, 1986, 1989, 1993
      *      The Regents of the University of California.  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.
     * 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.
     *
     *      @(#)vm_swap.c   8.5 (Berkeley) 2/17/94
     * $FreeBSD: releng/5.1/sys/vm/vm_swap.c 111936 2003-03-05 23:50:15Z rwatson $
     */
    
    #include "opt_mac.h"
    #include "opt_swap.h"
    #include "opt_vm.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/sysproto.h>
    #include <sys/bio.h>
    #include <sys/buf.h>
    #include <sys/proc.h>
    #include <sys/namei.h>
    #include <sys/vnode.h>
    #include <sys/fcntl.h>
    #include <sys/blist.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/conf.h>
    #include <sys/disk.h>
    #include <sys/stat.h>
    #include <sys/sysctl.h>
    #include <sys/mac.h>
    #include <sys/mount.h>
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    #include <vm/vm_param.h>
    #include <vm/vm_pageout.h>
    #include <vm/swap_pager.h>
    #include <vm/uma.h>
    
    /*
     * Indirect driver for multi-controller paging.
     */
    
    typedef int32_t swblk_t;        /* swap offset */
    
    #ifndef NSWAPDEV
    #define NSWAPDEV        4
    #endif
    static struct swdevt should_be_malloced[NSWAPDEV];
    struct swdevt *swdevt = should_be_malloced;
    static int nswap;               /* first block after the interleaved devs */
    int nswdev = NSWAPDEV;
    int vm_swap_size;
    static int swdev_syscall_active = 0; /* serialize swap(on|off) */
    
    
    static int swapdev_strategy(struct vop_strategy_args *ap);
    struct vnode *swapdev_vp;
    
    /*
     *      swapdev_strategy:
     *
     *      VOP_STRATEGY() for swapdev_vp.
     *      Perform swap strategy interleave device selection.
     *
     *      The bp is expected to be locked and *not* B_DONE on call.
     */
    static int
    swapdev_strategy(ap)
            struct vop_strategy_args /* {
                    struct vnode *a_vp;
                    struct buf *a_bp;
            } */ *ap;
   {
           int s, sz, off, seg, index;
           struct swdevt *sp;
           struct vnode *vp;
           struct buf *bp;
   
           bp = ap->a_bp;
           sz = howmany(bp->b_bcount, PAGE_SIZE);
   
           /*
            * Convert interleaved swap into per-device swap.  Note that
            * the block size is left in PAGE_SIZE'd chunks (for the newswap)
            * here.
            */
           if (nswdev > 1) {
                   off = bp->b_blkno % dmmax;
                   if (off + sz > dmmax) {
                           bp->b_error = EINVAL;
                           bp->b_ioflags |= BIO_ERROR;
                           bufdone(bp);
                           return 0;
                   }
                   seg = bp->b_blkno / dmmax;
                   index = seg % nswdev;
                   seg /= nswdev;
                   bp->b_blkno = seg * dmmax + off;
           } else {
                   index = 0;
           }
           sp = &swdevt[index];
           if (bp->b_blkno + sz > sp->sw_nblks) {
                   bp->b_error = EINVAL;
                   bp->b_ioflags |= BIO_ERROR;
                   bufdone(bp);
                   return 0;
           }
           bp->b_dev = sp->sw_device;
           if (sp->sw_vp == NULL) {
                   bp->b_error = ENODEV;
                   bp->b_ioflags |= BIO_ERROR;
                   bufdone(bp);
                   return 0;
           }
   
           /*
            * Convert from PAGE_SIZE'd to DEV_BSIZE'd chunks for the actual I/O
            */
           bp->b_blkno = ctodb(bp->b_blkno);
   
           vhold(sp->sw_vp);
           s = splvm();
           if (bp->b_iocmd == BIO_WRITE) {
                   vp = bp->b_vp;
                   if (vp) {
                           VI_LOCK(vp);
                           vp->v_numoutput--;
                           if ((vp->v_iflag & VI_BWAIT) && vp->v_numoutput <= 0) {
                                   vp->v_iflag &= ~VI_BWAIT;
                                   wakeup(&vp->v_numoutput);
                           }
                           VI_UNLOCK(vp);
                   }
                   VI_LOCK(sp->sw_vp);
                   sp->sw_vp->v_numoutput++;
                   VI_UNLOCK(sp->sw_vp);
           }
           bp->b_vp = sp->sw_vp;
           splx(s);
           if (bp->b_vp->v_type == VCHR)
                   VOP_SPECSTRATEGY(bp->b_vp, bp);
           else
                   VOP_STRATEGY(bp->b_vp, bp);
           return 0;
   }
   
   /*
    * Create a special vnode op vector for swapdev_vp - we only use
    * VOP_STRATEGY() and reclaim; everything else returns an error.
    */
   vop_t **swapdev_vnodeop_p;
   static struct vnodeopv_entry_desc swapdev_vnodeop_entries[] = {  
           { &vop_default_desc,            (vop_t *) vop_defaultop },
           { &vop_reclaim_desc,            (vop_t *) vop_null },
           { &vop_strategy_desc,           (vop_t *) swapdev_strategy },
           { NULL, NULL }
   };
   static struct vnodeopv_desc swapdev_vnodeop_opv_desc =
           { &swapdev_vnodeop_p, swapdev_vnodeop_entries };
   
   VNODEOP_SET(swapdev_vnodeop_opv_desc);
   
   /*
    * System call swapon(name) enables swapping on device name,
    * which must be in the swdevsw.  Return EBUSY
    * if already swapping on this device.
    */
   #ifndef _SYS_SYSPROTO_H_
   struct swapon_args {
           char *name;
   };
   #endif
   
   /* 
    * MPSAFE
    */
   /* ARGSUSED */
   int
   swapon(td, uap)
           struct thread *td;
           struct swapon_args *uap;
   {
           struct vattr attr;
           struct vnode *vp;
           struct nameidata nd;
           int error;
   
           mtx_lock(&Giant);
           error = suser(td);
           if (error)
                   goto done2;
   
           while (swdev_syscall_active)
               tsleep(&swdev_syscall_active, PUSER - 1, "swpon", 0);
           swdev_syscall_active = 1;
   
           /*
            * Swap metadata may not fit in the KVM if we have physical
            * memory of >1GB.
            */
           if (swap_zone == NULL) {
                   error = ENOMEM;
                   goto done;
           }
   
           NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->name, td);
           error = namei(&nd);
           if (error)
                   goto done;
   
           NDFREE(&nd, NDF_ONLY_PNBUF);
           vp = nd.ni_vp;
   
           if (vn_isdisk(vp, &error))
                   error = swaponvp(td, vp, vp->v_rdev, 0);
           else if (vp->v_type == VREG &&
               (vp->v_mount->mnt_vfc->vfc_flags & VFCF_NETWORK) != 0 &&
               (error = VOP_GETATTR(vp, &attr, td->td_ucred, td)) == 0) {
                   /*
                    * Allow direct swapping to NFS regular files in the same
                    * way that nfs_mountroot() sets up diskless swapping.
                    */
                   error = swaponvp(td, vp, NODEV, attr.va_size / DEV_BSIZE);
           }
   
           if (error)
                   vrele(vp);
   done:
           swdev_syscall_active = 0;
           wakeup_one(&swdev_syscall_active);
   done2:
           mtx_unlock(&Giant);
           return (error);
   }
   
   /*
    * Swfree(index) frees the index'th portion of the swap map.
    * Each of the nswdev devices provides 1/nswdev'th of the swap
    * space, which is laid out with blocks of dmmax pages circularly
    * among the devices.
    *
    * The new swap code uses page-sized blocks.  The old swap code used
    * DEV_BSIZE'd chunks.
    */
   int
   swaponvp(td, vp, dev, nblks)
           struct thread *td;
           struct vnode *vp;
           dev_t dev;
           u_long nblks;
   {
           int index;
           struct swdevt *sp;
           swblk_t vsbase;
           long blk;
           swblk_t dvbase;
           int error;
           u_long aligned_nblks;
           off_t mediasize;
   
           if (!swapdev_vp) {
                   error = getnewvnode("none", NULL, swapdev_vnodeop_p,
                       &swapdev_vp);
                   if (error)
                           panic("Cannot get vnode for swapdev");
                   swapdev_vp->v_type = VNON;      /* Untyped */
           }
   
           ASSERT_VOP_UNLOCKED(vp, "swaponvp");
           for (sp = swdevt, index = 0 ; index < nswdev; index++, sp++) {
                   if (sp->sw_vp == vp)
                           return EBUSY;
                   if (!sp->sw_vp)
                           goto found;
   
           }
           return EINVAL;
       found:
           (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
   #ifdef MAC
           error = mac_check_system_swapon(td->td_ucred, vp);
           if (error == 0)
   #endif
                   error = VOP_OPEN(vp, FREAD | FWRITE, td->td_ucred, td);
           (void) VOP_UNLOCK(vp, 0, td);
           if (error)
                   return (error);
   
           error = VOP_IOCTL(vp, DIOCGMEDIASIZE, (caddr_t)&mediasize,
               FREAD, td->td_ucred, td);
           if (error == 0)
               nblks = mediasize / DEV_BSIZE;
           else
               nblks = 0;
           /*
            * XXX: We should also check that the sectorsize makes sense
            * XXX: it should be a power of two, no larger than the page size.
            */
           if (nblks == 0) {
                   (void) VOP_CLOSE(vp, FREAD | FWRITE, td->td_ucred, td);
                   return (ENXIO);
           }
   
           /*
            * If we go beyond this, we get overflows in the radix
            * tree bitmap code.
            */
           if (nblks > 0x40000000 / BLIST_META_RADIX / nswdev) {
                   printf("exceeded maximum of %d blocks per swap unit\n",
                           0x40000000 / BLIST_META_RADIX / nswdev);
                   (void) VOP_CLOSE(vp, FREAD | FWRITE, td->td_ucred, td);
                   return (ENXIO);
           }
           /*
            * nblks is in DEV_BSIZE'd chunks, convert to PAGE_SIZE'd chunks.
            * First chop nblks off to page-align it, then convert.
            * 
            * sw->sw_nblks is in page-sized chunks now too.
            */
           nblks &= ~(ctodb(1) - 1);
           nblks = dbtoc(nblks);
   
           sp->sw_vp = vp;
           sp->sw_dev = dev2udev(dev);
           sp->sw_device = dev;
           sp->sw_flags = SW_FREED;
           sp->sw_nblks = nblks;
           sp->sw_used = 0;
   
           /*
            * nblks, nswap, and dmmax are PAGE_SIZE'd parameters now, not
            * DEV_BSIZE'd.   aligned_nblks is used to calculate the
            * size of the swap bitmap, taking into account the stripe size.
            */
           aligned_nblks = (nblks + (dmmax -1)) & ~(u_long)(dmmax -1);
   
           if (aligned_nblks * nswdev > nswap)
                   nswap = aligned_nblks * nswdev;
   
           if (swapblist == NULL)
                   swapblist = blist_create(nswap);
           else
                   blist_resize(&swapblist, nswap, 0);
   
           for (dvbase = dmmax; dvbase < nblks; dvbase += dmmax) {
                   blk = min(nblks - dvbase, dmmax);
                   vsbase = index * dmmax + dvbase * nswdev;
                   blist_free(swapblist, vsbase, blk);
                   vm_swap_size += blk;
           }
   
           swap_pager_full = 0;
   
           return (0);
   }
   
   /*
    * SYSCALL: swapoff(devname)
    *
    * Disable swapping on the given device.
    */
   #ifndef _SYS_SYSPROTO_H_
   struct swapoff_args {
           char *name;
   };
   #endif
   
   /*
    * MPSAFE
    */
   /* ARGSUSED */
   int
   swapoff(td, uap)
           struct thread *td;
           struct swapoff_args *uap;
   {
           struct vnode *vp;
           struct nameidata nd;
           struct swdevt *sp;
           swblk_t dvbase, vsbase;
           u_long nblks, aligned_nblks, blk;
           int error, index;
   
           mtx_lock(&Giant);
   
           error = suser(td);
           if (error)
                   goto done2;
   
           while (swdev_syscall_active)
               tsleep(&swdev_syscall_active, PUSER - 1, "swpoff", 0);
           swdev_syscall_active = 1;
   
           NDINIT(&nd, LOOKUP, FOLLOW, UIO_USERSPACE, uap->name, td);
           error = namei(&nd);
           if (error)
                   goto done;
           NDFREE(&nd, NDF_ONLY_PNBUF);
           vp = nd.ni_vp;
   
           for (sp = swdevt, index = 0 ; index < nswdev; index++, sp++) {
                   if (sp->sw_vp == vp)
                           goto found;
           }
           error = EINVAL;
           goto done;
   found:
   #ifdef MAC
           (void) vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
           error = mac_check_system_swapoff(td->td_ucred, vp);
           (void) VOP_UNLOCK(vp, 0, td);
           if (error != 0)
                   goto done;
   #endif
           
           nblks = sp->sw_nblks;
   
           /*
            * We can turn off this swap device safely only if the
            * available virtual memory in the system will fit the amount
            * of data we will have to page back in, plus an epsilon so
            * the system doesn't become critically low on swap space.
            */
           if (cnt.v_free_count + cnt.v_cache_count + vm_swap_size <
               nblks + nswap_lowat) {
                   error = ENOMEM;
                   goto done;
           }
   
           /*
            * Prevent further allocations on this device.
            */
           sp->sw_flags |= SW_CLOSING;
           for (dvbase = dmmax; dvbase < nblks; dvbase += dmmax) {
                   blk = min(nblks - dvbase, dmmax);
                   vsbase = index * dmmax + dvbase * nswdev;
                   vm_swap_size -= blist_fill(swapblist, vsbase, blk);
           }
   
           /*
            * Page in the contents of the device and close it.
            */
   #ifndef NO_SWAPPING
           vm_proc_swapin_all(index);
   #endif /* !NO_SWAPPING */
           swap_pager_swapoff(index, &sp->sw_used);
   
           VOP_CLOSE(vp, FREAD | FWRITE, td->td_ucred, td);
           vrele(vp);
           sp->sw_vp = NULL;
   
           /*
            * Resize the bitmap based on the new largest swap device,
            * or free the bitmap if there are no more devices.
            */
           for (sp = swdevt, nblks = 0; sp < swdevt + nswdev; sp++) {
                   if (sp->sw_vp == NULL)
                           continue;
                   nblks = max(nblks, sp->sw_nblks);
           }
   
           aligned_nblks = (nblks + (dmmax -1)) & ~(u_long)(dmmax -1);
           nswap = aligned_nblks * nswdev;
   
           if (nswap == 0) {
                   blist_destroy(swapblist);
                   swapblist = NULL;
                   vrele(swapdev_vp);
                   swapdev_vp = NULL;
           } else
                   blist_resize(&swapblist, nswap, 0);
   
   done:
           swdev_syscall_active = 0;
           wakeup_one(&swdev_syscall_active);
   done2:
           mtx_unlock(&Giant);
           return (error);
   }
   
   static int
   sysctl_vm_swap_info(SYSCTL_HANDLER_ARGS)
   {
           int     *name = (int *)arg1;
           int     error, i, n;
           struct xswdev xs;
           struct swdevt *sp;
   
           if (arg2 != 1) /* name length */
                   return (EINVAL);
   
           for (sp = swdevt, i = 0, n = 0 ; i < nswdev; i++, sp++) {
                   if (sp->sw_vp) {
                           if (n == *name) {
                                   xs.xsw_version = XSWDEV_VERSION;
                                   xs.xsw_dev = sp->sw_dev;
                                   xs.xsw_flags = sp->sw_flags;
                                   xs.xsw_nblks = sp->sw_nblks;
                                   xs.xsw_used = sp->sw_used;
   
                                   error = SYSCTL_OUT(req, &xs, sizeof(xs));
                                   return (error);
                           }
                           n++;
                   }
   
           }
           return (ENOENT);
   }
   
   SYSCTL_INT(_vm, OID_AUTO, nswapdev, CTLFLAG_RD, &nswdev, 0,
       "Number of swap devices");
   SYSCTL_NODE(_vm, OID_AUTO, swap_info, CTLFLAG_RD, sysctl_vm_swap_info,
       "Swap statistics by device");

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