usr/src/sys/miscfs/union/union_vfsops.c

/*
 * Copyright (c) 1994, 1995 The Regents of the University of California.
 * Copyright (c) 1994, 1995 Jan-Simon Pendry.
 * All rights reserved.
 *
 * This code is derived from software donated to Berkeley by
 * Jan-Simon Pendry.
 *
 * 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.
 *
 *      @(#)union_vfsops.c      8.20 (Berkeley) 5/20/95
 */

/*
 * Union Layer
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/malloc.h>
#include <sys/filedesc.h>
#include <sys/queue.h>
#include <miscfs/union/union.h>

/*
 * Mount union filesystem
 */
int
union_mount(mp, path, data, ndp, p)
        struct mount *mp;
        char *path;
        caddr_t data;
        struct nameidata *ndp;
        struct proc *p;
{
        int error = 0;
        struct union_args args;
        struct vnode *lowerrootvp = NULLVP;
        struct vnode *upperrootvp = NULLVP;
        struct union_mount *um = 0;
        struct ucred *cred = 0;
        struct ucred *scred;
        struct vattr va;
        char *cp;
        int len;
        u_int size;

#ifdef UNION_DIAGNOSTIC
        printf("union_mount(mp = %x)\n", mp);
#endif

        /*
         * Update is a no-op
         */
        if (mp->mnt_flag & MNT_UPDATE) {
                /*
                 * Need to provide.
                 * 1. a way to convert between rdonly and rdwr mounts.
                 * 2. support for nfs exports.
                 */
                error = EOPNOTSUPP;
                goto bad;
        }

        /*
         * Get argument
         */
        if (error = copyin(data, (caddr_t)&args, sizeof(struct union_args)))
                goto bad;

        lowerrootvp = mp->mnt_vnodecovered;
        VREF(lowerrootvp);

        /*
         * Find upper node.
         */
        NDINIT(ndp, LOOKUP, FOLLOW|WANTPARENT,
               UIO_USERSPACE, args.target, p);

        if (error = namei(ndp))
                goto bad;

        upperrootvp = ndp->ni_vp;
        vrele(ndp->ni_dvp);
        ndp->ni_dvp = NULL;

        if (upperrootvp->v_type != VDIR) {
                error = EINVAL;
                goto bad;
        }

        um = (struct union_mount *) malloc(sizeof(struct union_mount),
                                M_UFSMNT, M_WAITOK);    /* XXX */

        /*
         * Keep a held reference to the target vnodes.
         * They are vrele'd in union_unmount.
         *
         * Depending on the _BELOW flag, the filesystems are
         * viewed in a different order.  In effect, this is the
         * same as providing a mount under option to the mount syscall.
         */

        um->um_op = args.mntflags & UNMNT_OPMASK;
        switch (um->um_op) {
        case UNMNT_ABOVE:
                um->um_lowervp = lowerrootvp;
                um->um_uppervp = upperrootvp;
                break;

        case UNMNT_BELOW:
                um->um_lowervp = upperrootvp;
                um->um_uppervp = lowerrootvp;
                break;

        case UNMNT_REPLACE:
                vrele(lowerrootvp);
                lowerrootvp = NULLVP;
                um->um_uppervp = upperrootvp;
                um->um_lowervp = lowerrootvp;
                break;

        default:
                error = EINVAL;
                goto bad;
        }

        /*
         * Unless the mount is readonly, ensure that the top layer
         * supports whiteout operations
         */
        if ((mp->mnt_flag & MNT_RDONLY) == 0) {
                error = VOP_WHITEOUT(um->um_uppervp, (struct componentname *) 0, LOOKUP);
                if (error)
                        goto bad;
        }

        um->um_cred = p->p_ucred;
        crhold(um->um_cred);
        um->um_cmode = UN_DIRMODE &~ p->p_fd->fd_cmask;

        /*
         * Depending on what you think the MNT_LOCAL flag might mean,
         * you may want the && to be || on the conditional below.
         * At the moment it has been defined that the filesystem is
         * only local if it is all local, ie the MNT_LOCAL flag implies
         * that the entire namespace is local.  If you think the MNT_LOCAL
         * flag implies that some of the files might be stored locally
         * then you will want to change the conditional.
         */
        if (um->um_op == UNMNT_ABOVE) {
                if (((um->um_lowervp == NULLVP) ||
                     (um->um_lowervp->v_mount->mnt_flag & MNT_LOCAL)) &&
                    (um->um_uppervp->v_mount->mnt_flag & MNT_LOCAL))
                        mp->mnt_flag |= MNT_LOCAL;
        }

        /*
         * Copy in the upper layer's RDONLY flag.  This is for the benefit
         * of lookup() which explicitly checks the flag, rather than asking
         * the filesystem for it's own opinion.  This means, that an update
         * mount of the underlying filesystem to go from rdonly to rdwr
         * will leave the unioned view as read-only.
         */
        mp->mnt_flag |= (um->um_uppervp->v_mount->mnt_flag & MNT_RDONLY);

        mp->mnt_data = (qaddr_t) um;
        vfs_getnewfsid(mp);

        (void) copyinstr(path, mp->mnt_stat.f_mntonname, MNAMELEN - 1, &size);
        bzero(mp->mnt_stat.f_mntonname + size, MNAMELEN - size);

        switch (um->um_op) {
        case UNMNT_ABOVE:
                cp = "<above>:";
                break;
        case UNMNT_BELOW:
                cp = "<below>:";
                break;
        case UNMNT_REPLACE:
                cp = "";
                break;
        }
        len = strlen(cp);
        bcopy(cp, mp->mnt_stat.f_mntfromname, len);

        cp = mp->mnt_stat.f_mntfromname + len;
        len = MNAMELEN - len;

        (void) copyinstr(args.target, cp, len - 1, &size);
        bzero(cp + size, len - size);

#ifdef UNION_DIAGNOSTIC
        printf("union_mount: from %s, on %s\n",
                mp->mnt_stat.f_mntfromname, mp->mnt_stat.f_mntonname);
#endif
        return (0);

bad:
        if (um)
                free(um, M_UFSMNT);
        if (cred)
                crfree(cred);
        if (upperrootvp)
                vrele(upperrootvp);
        if (lowerrootvp)
                vrele(lowerrootvp);
        return (error);
}

/*
 * VFS start.  Nothing needed here - the start routine
 * on the underlying filesystem(s) will have been called
 * when that filesystem was mounted.
 */
int
union_start(mp, flags, p)
        struct mount *mp;
        int flags;
        struct proc *p;
{

        return (0);
}

/*
 * Free reference to union layer
 */
int
union_unmount(mp, mntflags, p)
        struct mount *mp;
        int mntflags;
        struct proc *p;
{
        struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
        struct vnode *um_rootvp;
        int error;
        int freeing;
        int flags = 0;

#ifdef UNION_DIAGNOSTIC
        printf("union_unmount(mp = %x)\n", mp);
#endif

        if (mntflags & MNT_FORCE)
                flags |= FORCECLOSE;

        if (error = union_root(mp, &um_rootvp))
                return (error);

        /*
         * Keep flushing vnodes from the mount list.
         * This is needed because of the un_pvp held
         * reference to the parent vnode.
         * If more vnodes have been freed on a given pass,
         * the try again.  The loop will iterate at most
         * (d) times, where (d) is the maximum tree depth
         * in the filesystem.
         */
        for (freeing = 0; vflush(mp, um_rootvp, flags) != 0;) {
                struct vnode *vp;
                int n;

                /* count #vnodes held on mount list */
                for (n = 0, vp = mp->mnt_vnodelist.lh_first;
                                vp != NULLVP;
                                vp = vp->v_mntvnodes.le_next)
                        n++;

                /* if this is unchanged then stop */
                if (n == freeing)
                        break;

                /* otherwise try once more time */
                freeing = n;
        }

        /* At this point the root vnode should have a single reference */
        if (um_rootvp->v_usecount > 1) {
                vput(um_rootvp);
                return (EBUSY);
        }

#ifdef UNION_DIAGNOSTIC
        vprint("union root", um_rootvp);
#endif
        /*
         * Discard references to upper and lower target vnodes.
         */
        if (um->um_lowervp)
                vrele(um->um_lowervp);
        vrele(um->um_uppervp);
        crfree(um->um_cred);
        /*
         * Release reference on underlying root vnode
         */
        vput(um_rootvp);
        /*
         * And blow it away for future re-use
         */
        vgone(um_rootvp);
        /*
         * Finally, throw away the union_mount structure
         */
        free(mp->mnt_data, M_UFSMNT);   /* XXX */
        mp->mnt_data = 0;
        return (0);
}

int
union_root(mp, vpp)
        struct mount *mp;
        struct vnode **vpp;
{
        struct proc *p = curproc;       /* XXX */
        struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
        int error;
        int loselock;

        /*
         * Return locked reference to root.
         */
        VREF(um->um_uppervp);
        if ((um->um_op == UNMNT_BELOW) &&
             VOP_ISLOCKED(um->um_uppervp)) {
                loselock = 1;
        } else {
                vn_lock(um->um_uppervp, LK_EXCLUSIVE | LK_RETRY, p);
                loselock = 0;
        }
        if (um->um_lowervp)
                VREF(um->um_lowervp);
        error = union_allocvp(vpp, mp,
                              (struct vnode *) 0,
                              (struct vnode *) 0,
                              (struct componentname *) 0,
                              um->um_uppervp,
                              um->um_lowervp,
                              1);

        if (error) {
                if (loselock)
                        vrele(um->um_uppervp);
                else
                        vput(um->um_uppervp);
                if (um->um_lowervp)
                        vrele(um->um_lowervp);
        } else {
                if (loselock)
                        VTOUNION(*vpp)->un_flags &= ~UN_ULOCK;
        }

        return (error);
}

int
union_statfs(mp, sbp, p)
        struct mount *mp;
        struct statfs *sbp;
        struct proc *p;
{
        int error;
        struct union_mount *um = MOUNTTOUNIONMOUNT(mp);
        struct statfs mstat;
        int lbsize;

#ifdef UNION_DIAGNOSTIC
        printf("union_statfs(mp = %x, lvp = %x, uvp = %x)\n", mp,
                        um->um_lowervp,
                        um->um_uppervp);
#endif

        bzero(&mstat, sizeof(mstat));

        if (um->um_lowervp) {
                error = VFS_STATFS(um->um_lowervp->v_mount, &mstat, p);
                if (error)
                        return (error);
        }

        /* now copy across the "interesting" information and fake the rest */
#if 0
        sbp->f_type = mstat.f_type;
        sbp->f_flags = mstat.f_flags;
        sbp->f_bsize = mstat.f_bsize;
        sbp->f_iosize = mstat.f_iosize;
#endif
        lbsize = mstat.f_bsize;
        sbp->f_blocks = mstat.f_blocks;
        sbp->f_bfree = mstat.f_bfree;
        sbp->f_bavail = mstat.f_bavail;
        sbp->f_files = mstat.f_files;
        sbp->f_ffree = mstat.f_ffree;

        error = VFS_STATFS(um->um_uppervp->v_mount, &mstat, p);
        if (error)
                return (error);

        sbp->f_flags = mstat.f_flags;
        sbp->f_bsize = mstat.f_bsize;
        sbp->f_iosize = mstat.f_iosize;

        /*
         * if the lower and upper blocksizes differ, then frig the
         * block counts so that the sizes reported by df make some
         * kind of sense.  none of this makes sense though.
         */

        if (mstat.f_bsize != lbsize)
                sbp->f_blocks = sbp->f_blocks * lbsize / mstat.f_bsize;

        /*
         * The "total" fields count total resources in all layers,
         * the "free" fields count only those resources which are
         * free in the upper layer (since only the upper layer
         * is writeable).
         */
        sbp->f_blocks += mstat.f_blocks;
        sbp->f_bfree = mstat.f_bfree;
        sbp->f_bavail = mstat.f_bavail;
        sbp->f_files += mstat.f_files;
        sbp->f_ffree = mstat.f_ffree;

        if (sbp != &mp->mnt_stat) {
                sbp->f_type = mp->mnt_vfc->vfc_typenum;
                bcopy(&mp->mnt_stat.f_fsid, &sbp->f_fsid, sizeof(sbp->f_fsid));
                bcopy(mp->mnt_stat.f_mntonname, sbp->f_mntonname, MNAMELEN);
                bcopy(mp->mnt_stat.f_mntfromname, sbp->f_mntfromname, MNAMELEN);
        }
        return (0);
}

/*
 * XXX - Assumes no data cached at union layer.
 */
#define union_sync ((int (*) __P((struct mount *, int, struct ucred *, \
            struct proc *)))nullop)

#define union_fhtovp ((int (*) __P((struct mount *, struct fid *, \
            struct mbuf *, struct vnode **, int *, struct ucred **)))eopnotsupp)
int union_init __P((struct vfsconf *));
#define union_quotactl ((int (*) __P((struct mount *, int, uid_t, caddr_t, \
            struct proc *)))eopnotsupp)
#define union_sysctl ((int (*) __P((int *, u_int, void *, size_t *, void *, \
            size_t, struct proc *)))eopnotsupp)
#define union_vget ((int (*) __P((struct mount *, ino_t, struct vnode **))) \
            eopnotsupp)
#define union_vptofh ((int (*) __P((struct vnode *, struct fid *)))eopnotsupp)

struct vfsops union_vfsops = {
        union_mount,
        union_start,
        union_unmount,
        union_root,
        union_quotactl,
        union_statfs,
        union_sync,
        union_vget,
        union_fhtovp,
        union_vptofh,
        union_init,
        union_sysctl,
};