5509 nfsauth_cache_get() could spend a lot of time walking exi_cache

[illumos-gate.git] / usr / src / uts / common / fs / nfs / nfs4_srv_ns.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2014 Nexenta Systems, Inc.  All rights reserved.
 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
 */

#include <sys/systm.h>

#include <nfs/nfs.h>
#include <nfs/export.h>
#include <sys/cmn_err.h>
#include <sys/avl.h>

#define PSEUDOFS_SUFFIX         " (pseudo)"

/*
 * A version of VOP_FID that deals with a remote VOP_FID for nfs.
 * If vp is an nfs node, nfs4_fid() returns EREMOTE, nfs3_fid() and nfs_fid()
 * returns the filehandle of vp as its fid. When nfs uses fid to set the
 * exportinfo filehandle template, a remote nfs filehandle would be too big for
 * the fid of the exported directory. This routine remaps the value of the
 * attribute va_nodeid of vp to be the fid of vp, so that the fid can fit.
 *
 * We need this fid mainly for setting up NFSv4 server namespace where an
 * nfs filesystem is also part of it. Thus, need to be able to setup a pseudo
 * exportinfo for an nfs node.
 *
 * e.g. mount a filesystem on top of a nfs dir, and then share the new mount
 *      (like exporting a local disk from a "diskless" client)
 */
int
vop_fid_pseudo(vnode_t *vp, fid_t *fidp)
{
        struct vattr va;
        int error;

        error = VOP_FID(vp, fidp, NULL);

        /*
         * XXX nfs4_fid() does nothing and returns EREMOTE.
         * XXX nfs3_fid()/nfs_fid() returns nfs filehandle as its fid
         * which has a bigger length than local fid.
         * NFS_FH4MAXDATA is the size of
         * fhandle4_t.fh_xdata[NFS_FH4MAXDATA].
         *
         * Note: nfs[2,3,4]_fid() only gets called for diskless clients.
         */
        if (error == EREMOTE ||
            (error == 0 && fidp->fid_len > NFS_FH4MAXDATA)) {

                va.va_mask = AT_NODEID;
                error = VOP_GETATTR(vp, &va, 0, CRED(), NULL);
                if (error)
                        return (error);

                fidp->fid_len = sizeof (va.va_nodeid);
                bcopy(&va.va_nodeid, fidp->fid_data, fidp->fid_len);
                return (0);
        }

        return (error);
}

/*
 * Get an nfsv4 vnode of the given fid from the visible list of an
 * nfs filesystem or get the exi_vp if it is the root node.
 */
int
nfs4_vget_pseudo(struct exportinfo *exi, vnode_t **vpp, fid_t *fidp)
{
        fid_t exp_fid;
        struct exp_visible *visp;
        int error;

        /* check if the given fid is in the visible list */

        for (visp = exi->exi_visible; visp; visp = visp->vis_next) {
                if (EQFID(fidp, &visp->vis_fid)) {
                        VN_HOLD(visp->vis_vp);
                        *vpp = visp->vis_vp;
                        return (0);
                }
        }

        /* check if the given fid is the same as the exported node */

        bzero(&exp_fid, sizeof (exp_fid));
        exp_fid.fid_len = MAXFIDSZ;
        error = vop_fid_pseudo(exi->exi_vp, &exp_fid);
        if (error)
                return (error);

        if (EQFID(fidp, &exp_fid)) {
                VN_HOLD(exi->exi_vp);
                *vpp = exi->exi_vp;
                return (0);
        }

        return (ENOENT);
}

/*
 * Create a pseudo export entry
 *
 * This is an export entry that's created as the
 * side-effect of a "real" export.  As a part of
 * a real export, the pathname to the export is
 * checked to see if all the directory components
 * are accessible via an NFSv4 client, i.e. are
 * exported.  If treeclimb_export() finds an unexported
 * mountpoint along the path, then it calls this
 * function to export it.
 *
 * This pseudo export differs from a real export in that
 * it only allows read-only access.  A "visible" list of
 * directories is added to filter lookup and readdir results
 * to only contain dirnames which lead to descendant shares.
 *
 * A visible list has a per-file-system scope.  Any exportinfo
 * struct (real or pseudo) can have a visible list as long as
 * a) its export root is VROOT
 * b) a descendant of the export root is shared
 */
struct exportinfo *
pseudo_exportfs(vnode_t *vp, fid_t *fid, struct exp_visible *vis_head,
            struct exportdata *exdata)
{
        struct exportinfo *exi;
        struct exportdata *kex;
        fsid_t fsid;
        int vpathlen;
        int i;

        ASSERT(RW_WRITE_HELD(&exported_lock));

        fsid = vp->v_vfsp->vfs_fsid;
        exi = kmem_zalloc(sizeof (*exi), KM_SLEEP);
        exi->exi_fsid = fsid;
        exi->exi_fid = *fid;
        exi->exi_vp = vp;
        VN_HOLD(exi->exi_vp);
        exi->exi_visible = vis_head;
        exi->exi_count = 1;
        exi->exi_volatile_dev = (vfssw[vp->v_vfsp->vfs_fstype].vsw_flag &
            VSW_VOLATILEDEV) ? 1 : 0;
        mutex_init(&exi->exi_lock, NULL, MUTEX_DEFAULT, NULL);

        /*
         * Build up the template fhandle
         */
        exi->exi_fh.fh_fsid = fsid;
        ASSERT(exi->exi_fid.fid_len <= sizeof (exi->exi_fh.fh_xdata));
        exi->exi_fh.fh_xlen = exi->exi_fid.fid_len;
        bcopy(exi->exi_fid.fid_data, exi->exi_fh.fh_xdata,
            exi->exi_fid.fid_len);
        exi->exi_fh.fh_len = sizeof (exi->exi_fh.fh_data);

        kex = &exi->exi_export;
        kex->ex_flags = EX_PSEUDO;

        vpathlen = vp->v_path ? strlen(vp->v_path) : 0;
        kex->ex_pathlen = vpathlen + strlen(PSEUDOFS_SUFFIX);
        kex->ex_path = kmem_alloc(kex->ex_pathlen + 1, KM_SLEEP);

        if (vpathlen)
                (void) strcpy(kex->ex_path, vp->v_path);
        (void) strcpy(kex->ex_path + vpathlen, PSEUDOFS_SUFFIX);

        /* Transfer the secinfo data from exdata to this new pseudo node */
        if (exdata)
                srv_secinfo_exp2pseu(&exi->exi_export, exdata);

        /*
         * Initialize auth cache and auth cache lock
         */
        for (i = 0; i < AUTH_TABLESIZE; i++) {
                exi->exi_cache[i] = kmem_alloc(sizeof (avl_tree_t), KM_SLEEP);
                avl_create(exi->exi_cache[i], nfsauth_cache_clnt_compar,
                    sizeof (struct auth_cache_clnt),
                    offsetof(struct auth_cache_clnt, authc_link));
        }
        rw_init(&exi->exi_cache_lock, NULL, RW_DEFAULT, NULL);

        /*
         * Insert the new entry at the front of the export list
         */
        export_link(exi);

        return (exi);
}

/*
 * Free a list of visible directories
 */
void
free_visible(struct exp_visible *head)
{
        struct exp_visible *visp, *next;

        for (visp = head; visp; visp = next) {
                if (visp->vis_vp != NULL)
                        VN_RELE(visp->vis_vp);

                next = visp->vis_next;
                srv_secinfo_list_free(visp->vis_secinfo, visp->vis_seccnt);
                kmem_free(visp, sizeof (*visp));
        }
}

/*
 * Connects newchild (or subtree with newchild in head)
 * to the parent node. We always add it to the beginning
 * of sibling list.
 */
static void
tree_add_child(treenode_t *parent, treenode_t *newchild)
{
        newchild->tree_parent = parent;
        newchild->tree_sibling = parent->tree_child_first;
        parent->tree_child_first = newchild;
}

/* Look up among direct children a node with the exact tree_vis pointer */
static treenode_t *
tree_find_child_by_vis(treenode_t *t, exp_visible_t *vis)
{
        for (t = t->tree_child_first; t; t = t->tree_sibling)
                if (t->tree_vis == vis)
                        return (t);
        return (NULL);
}

/*
 * Add new node to the head of subtree pointed by 'n'. n can be NULL.
 * Interconnects the new treenode with exp_visible and exportinfo
 * if needed.
 */
static treenode_t *
tree_prepend_node(treenode_t *n, exp_visible_t *v, exportinfo_t *e)
{
        treenode_t *tnode = kmem_zalloc(sizeof (*tnode), KM_SLEEP);

        if (n) {
                tnode->tree_child_first = n;
                n->tree_parent = tnode;
        }
        if (v) {
                tnode->tree_vis = v;
        }
        if (e) {
                tnode->tree_exi = e;
                e->exi_tree = tnode;
        }
        return (tnode);
}

/*
 * Removes node from the tree and frees the treenode struct.
 * Does not free structures pointed by tree_exi and tree_vis,
 * they should be already freed.
 */
static void
tree_remove_node(treenode_t *node)
{
        treenode_t *parent = node->tree_parent;
        treenode_t *s; /* s for sibling */

        if (parent == NULL) {
                kmem_free(node, sizeof (*node));
                ns_root = NULL;
                return;
        }
        /* This node is first child */
        if (parent->tree_child_first == node) {
                parent->tree_child_first = node->tree_sibling;
        /* This node is not first child */
        } else {
                s = parent->tree_child_first;
                while (s->tree_sibling != node)
                        s = s->tree_sibling;
                s->tree_sibling = s->tree_sibling->tree_sibling;
        }
        kmem_free(node, sizeof (*node));
}

/*
 * When we export a new directory we need to add a new
 * path segment through the pseudofs to reach the new
 * directory. This new path is reflected in a list of
 * directories added to the "visible" list.
 *
 * Here there are two lists of visible fids: one hanging off the
 * pseudo exportinfo, and the one we want to add.  It's possible
 * that the two lists share a common path segment
 * and have some common directories.  We need to combine
 * the lists so there's no duplicate entries. Where a common
 * path component is found, the vis_count field is bumped.
 *
 * This example shows that the treenode chain (tree_head) and
 * exp_visible chain (vis_head) can differ in length. The latter
 * can be shorter. The outer loop must loop over the vis_head chain.
 *
 * share /x/a
 * mount -F ufs /dev/dsk/... /x/y
 * mkdir -p /x/y/a/b
 * share  /x/y/a/b
 *
 * When more_visible() is called during the second share,
 * the existing namespace is following:
 *                                   exp_visible_t
 *   treenode_t       exportinfo_t      v0     v1
 * ns_root+---+        +------------+  +---+  +---+
 *      t0| / |........| E0 pseudo  |->| x |->| a |
 *        +---+        +------------+  +---+  +---+
 *          |                           /    /
 *        +---+                        /    /
 *      t1| x |------------------------    /
 *        +---+                           /
 *          |                            /
 *        +---+                         /
 *      t2| a |-------------------------
 *        +---+........+------------+
 *                     | E1 real    |
 *                     +------------+
 *
 * This is being added:
 *
 *    tree_head  vis_head
 *        +---+  +---+
 *      t3| x |->| x |v2
 *        +---+  +---+
 *          |      |
 *        +---+  +---+                     v4     v5
 *      t4| y |->| y |v3  +------------+  +---+  +---+
 *        +---+\ +---+    | E2 pseudo  |->| a |->| b |
 *          |   \....... >+------------+  +---+  +---+
 *        +---+                           /      /
 *      t5| a |---------------------------      /
 *        +---+                                /
 *          |                                 /
 *        +---+-------------------------------
 *      t6| b |           +------------+
 *        +---+..........>| E3 real    |
 *                        +------------+
 *
 * more_visible() will:
 * - kmem_free() t3 and v2
 * - add t4, t5, t6 as a child of t1 (t4 will become sibling of t2)
 * - add v3 to the end of E0->exi_visible
 *
 * Note that v4 and v5 were already processed in pseudo_exportfs() and
 * added to E2. The outer loop of more_visible() will loop only over v2
 * and v3. The inner loop of more_visible() always loops over v0 and v1.
 *
 * Illustration for this scenario:
 *
 * mkdir -p /v/a/b/c
 * share /v/a/b/c
 * mkdir /v/a/b/c1
 * mkdir -p /v/a1
 * mv /v/a/b /v/a1
 * share /v/a1/b/c1
 *
 *           EXISTING
 *           treenode
 *           namespace:    +-----------+   visibles
 *                         |exportinfo |-->v->a->b->c
 * connect_point->+---+--->+-----------+
 *                | / |T0
 *                +---+
 *                  |                            NEW treenode chain:
 *         child->+---+
 *                | v |T1                          +---+<-curr
 *                +---+                          N1| v |
 *                  |                              +---+
 *                +---+                              |
 *                | a |T2                          +---+<-tree_head
 *                +---+                          N2| a1|
 *                  |                              +---+
 *                +---+                              |
 *                | b |T3                          +---+
 *                +---+                          N3| b |
 *                  |                              +---+
 *                +---+                              |
 *                | c |T4                          +---+
 *                +---+                          N4| c1|
 *                                                 +---+
 *
 * The picture above illustrates the position of following pointers after line
 * 'child = tree_find_child_by_vis(connect_point, curr->tree_vis);'
 * was executed for the first time in the outer 'for' loop:
 *
 * connect_point..parent treenode in the EXISTING namespace to which the 'curr'
 *                should be connected. If 'connect_point' already has a child
 *                with the same value of tree_vis as the curr->tree_vis is,
 *                the 'curr' will not be added, but kmem_free()d.
 * child..........the result of tree_find_child_by_vis()
 * curr...........currently processed treenode from the NEW treenode chain
 * tree_head......current head of the NEW treenode chain, in this case it was
 *                already moved down to its child - preparation for another loop
 *
 * What will happen to NEW treenodes N1, N2, N3, N4 in more_visible() later:
 *
 * N1: is merged - i.e. N1 is kmem_free()d. T0 has a child T1 with the same
 *     tree_vis as N1
 * N2: is added as a new child of T1
 *     Note: not just N2, but the whole chain N2->N3->N4 is added
 * N3: not processed separately (it was added together with N2)
 *     Even that N3 and T3 have same tree_vis, they are NOT merged, but will
 *     become duplicates.
 * N4: not processed separately
 */
static void
more_visible(struct exportinfo *exi, treenode_t *tree_head)
{
        struct exp_visible *vp1, *vp2, *vis_head, *tail, *next;
        int found;
        treenode_t *child, *curr, *connect_point;

        vis_head = tree_head->tree_vis;
        connect_point = exi->exi_tree;

        /*
         * If exportinfo doesn't already have a visible
         * list just assign the entire supplied list.
         */
        if (exi->exi_visible == NULL) {
                tree_add_child(exi->exi_tree, tree_head);
                exi->exi_visible = vis_head;
                return;
        }

        /* The outer loop traverses the supplied list. */
        for (vp1 = vis_head; vp1; vp1 = next) {
                found = 0;
                next = vp1->vis_next;

                /* The inner loop searches the exportinfo visible list. */
                for (vp2 = exi->exi_visible; vp2; vp2 = vp2->vis_next) {
                        tail = vp2;
                        if (EQFID(&vp1->vis_fid, &vp2->vis_fid)) {
                                found = 1;
                                vp2->vis_count++;
                                VN_RELE(vp1->vis_vp);
                                /* Transfer vis_exported from vp1 to vp2. */
                                if (vp1->vis_exported && !vp2->vis_exported)
                                        vp2->vis_exported = 1;
                                kmem_free(vp1, sizeof (*vp1));
                                tree_head->tree_vis = vp2;
                                break;
                        }
                }

                /* If not found - add to the end of the list */
                if (! found) {
                        tail->vis_next = vp1;
                        vp1->vis_next = NULL;
                }

                curr = tree_head;
                tree_head = tree_head->tree_child_first;

                if (! connect_point) /* No longer merging */
                        continue;
                /*
                 * The inner loop could set curr->tree_vis to the EXISTING
                 * exp_visible vp2, so we can search among the children of
                 * connect_point for the curr->tree_vis. No need for EQFID.
                 */
                child = tree_find_child_by_vis(connect_point, curr->tree_vis);

                /*
                 * Merging cannot be done if a valid child->tree_exi would
                 * be overwritten by a new curr->tree_exi.
                 */
                if (child &&
                    (child->tree_exi == NULL || curr->tree_exi == NULL)) {
                        if (curr->tree_exi) { /* Transfer the exportinfo */
                                child->tree_exi = curr->tree_exi;
                                child->tree_exi->exi_tree = child;
                        }
                        kmem_free(curr, sizeof (treenode_t));
                        connect_point = child;
                } else { /* Branching */
                        tree_add_child(connect_point, curr);
                        connect_point = NULL;
                }
        }
}

/*
 * Remove one visible entry from the pseudo exportfs.
 *
 * When we unexport a directory, we have to remove path
 * components from the visible list in the pseudo exportfs
 * entry. The supplied visible contains one fid of one path
 * component. The visible list of the export
 * is checked against provided visible, matching fid has its
 * reference count decremented.  If a reference count drops to
 * zero, then it means no paths now use this directory, so its
 * fid can be removed from the visible list.
 *
 * When the last path is removed, the visible list will be null.
 */
static void
less_visible(struct exportinfo *exi, struct exp_visible *vp1)
{
        struct exp_visible *vp2;
        struct exp_visible *prev, *next;

        for (vp2 = exi->exi_visible, prev = NULL; vp2; vp2 = next) {

                next = vp2->vis_next;

                if (vp1 == vp2) {
                        /*
                         * Decrement the ref count.
                         * Remove the entry if it's zero.
                         */
                        if (--vp2->vis_count <= 0) {
                                if (prev == NULL)
                                        exi->exi_visible = next;
                                else
                                        prev->vis_next = next;
                                VN_RELE(vp2->vis_vp);
                                srv_secinfo_list_free(vp2->vis_secinfo,
                                    vp2->vis_seccnt);
                                kmem_free(vp2, sizeof (*vp1));
                        }
                        break;
                }
                prev = vp2;
        }
}

/*
 * This function checks the path to a new export to
 * check whether all the pathname components are
 * exported. It works by climbing the file tree one
 * component at a time via "..", crossing mountpoints
 * if necessary until an export entry is found, or the
 * system root is reached.
 *
 * If an unexported mountpoint is found, then
 * a new pseudo export is added and the pathname from
 * the mountpoint down to the export is added to the
 * visible list for the new pseudo export.  If an existing
 * pseudo export is found, then the pathname is added
 * to its visible list.
 *
 * Note that there's some tests for exportdir.
 * The exportinfo entry that's passed as a parameter
 * is that of the real export and exportdir is set
 * for this case.
 *
 * Here is an example of a possible setup:
 *
 * () - a new fs; fs mount point
 * EXPORT - a real exported node
 * PSEUDO - a pseudo node
 * vis - visible list
 * f# - security flavor#
 * (f#) - security flavor# propagated from its descendents
 * "" - covered vnode
 *
 *
 *                 /
 *                 |
 *                 (a) PSEUDO (f1,f2)
 *                 |   vis: b,b,"c","n"
 *                 |
 *                 b
 *        ---------|------------------
 *        |                          |
 *        (c) EXPORT,f1(f2)          (n) PSEUDO (f1,f2)
 *        |   vis: "e","d"           |   vis: m,m,,p,q,"o"
 *        |                          |
 *  ------------------          -------------------
 *  |        |        |         |                  |
 *  (d)      (e)      f         m EXPORT,f1(f2)    p
 *  EXPORT   EXPORT             |                  |
 *  f1       f2                 |                  |
 *           |                  |                  |
 *           j                 (o) EXPORT,f2       q EXPORT f2
 *
 */
int
treeclimb_export(struct exportinfo *exip)
{
        vnode_t *dvp, *vp;
        fid_t fid;
        int error;
        int exportdir;
        struct exportinfo *exi = NULL;
        struct exportinfo *new_exi = exip;
        struct exp_visible *visp;
        struct exp_visible *vis_head = NULL;
        struct vattr va;
        treenode_t *tree_head = NULL;

        ASSERT(RW_WRITE_HELD(&exported_lock));

        vp = exip->exi_vp;
        VN_HOLD(vp);
        exportdir = 1;

        for (;;) {

                bzero(&fid, sizeof (fid));
                fid.fid_len = MAXFIDSZ;
                error = vop_fid_pseudo(vp, &fid);
                if (error)
                        break;

                if (! exportdir) {
                        /*
                         * Check if this exportroot is a VROOT dir.  If so,
                         * then attach the pseudonodes.  If not, then
                         * continue .. traversal until we hit a VROOT
                         * export (pseudo or real).
                         */
                        exi = checkexport4(&vp->v_vfsp->vfs_fsid, &fid, vp);
                        if (exi != NULL && vp->v_flag & VROOT) {
                                /*
                                 * Found an export info
                                 *
                                 * Extend the list of visible
                                 * directories whether it's a pseudo
                                 * or a real export.
                                 */
                                more_visible(exi, tree_head);
                                break;  /* and climb no further */
                        }
                }

                /*
                 * If at the root of the filesystem, need
                 * to traverse across the mountpoint
                 * and continue the climb on the mounted-on
                 * filesystem.
                 */
                if (vp->v_flag & VROOT) {

                        if (! exportdir) {
                                /*
                                 * Found the root directory of a filesystem
                                 * that isn't exported.  Need to export
                                 * this as a pseudo export so that an NFS v4
                                 * client can do lookups in it.
                                 */
                                new_exi = pseudo_exportfs(vp, &fid, vis_head,
                                    NULL);
                                vis_head = NULL;
                        }

                        if (VN_CMP(vp, rootdir)) {
                                /* at system root */
                                /*
                                 * If sharing "/", new_exi is shared exportinfo
                                 * (exip). Otherwise, new_exi is exportinfo
                                 * created in pseudo_exportfs() above.
                                 */
                                ns_root = tree_prepend_node(tree_head, 0,
                                    new_exi);
                                break;
                        }

                        vp = untraverse(vp);
                        exportdir = 0;
                        continue;
                }

                /*
                 * Do a getattr to obtain the nodeid (inode num)
                 * for this vnode.
                 */
                va.va_mask = AT_NODEID;
                error = VOP_GETATTR(vp, &va, 0, CRED(), NULL);
                if (error)
                        break;

                /*
                 *  Add this directory fid to visible list
                 */
                visp = kmem_alloc(sizeof (*visp), KM_SLEEP);
                VN_HOLD(vp);
                visp->vis_vp = vp;
                visp->vis_fid = fid;            /* structure copy */
                visp->vis_ino = va.va_nodeid;
                visp->vis_count = 1;
                visp->vis_exported = exportdir;
                visp->vis_secinfo = NULL;
                visp->vis_seccnt = 0;
                visp->vis_next = vis_head;
                vis_head = visp;


                /*
                 * Will set treenode's pointer to exportinfo to
                 * 1. shared exportinfo (exip) - if first visit here
                 * 2. freshly allocated pseudo export (if any)
                 * 3. null otherwise
                 */
                tree_head = tree_prepend_node(tree_head, visp, new_exi);
                new_exi = NULL;

                /*
                 * Now, do a ".." to find parent dir of vp.
                 */
                error = VOP_LOOKUP(vp, "..", &dvp, NULL, 0, NULL, CRED(),
                    NULL, NULL, NULL);

                if (error == ENOTDIR && exportdir) {
                        dvp = exip->exi_dvp;
                        ASSERT(dvp != NULL);
                        VN_HOLD(dvp);
                        error = 0;
                }

                if (error)
                        break;

                exportdir = 0;
                VN_RELE(vp);
                vp = dvp;
        }

        VN_RELE(vp);

        /*
         * We can have set error due to error in:
         * 1. vop_fid_pseudo()
         * 2. VOP_GETATTR()
         * 3. VOP_LOOKUP()
         * We must free pseudo exportinfos, visibles and treenodes.
         * Visibles are referenced from treenode_t::tree_vis and
         * exportinfo_t::exi_visible. To avoid double freeing, only
         * exi_visible pointer is used, via exi_rele(), for the clean-up.
         */
        if (error) {
                /* Free unconnected visibles, if there are any. */
                if (vis_head)
                        free_visible(vis_head);

                /* Connect unconnected exportinfo, if there is any. */
                if (new_exi && new_exi != exip)
                        tree_head = tree_prepend_node(tree_head, 0, new_exi);

                while (tree_head) {
                        treenode_t *t2 = tree_head;
                        exportinfo_t *e  = tree_head->tree_exi;
                        /* exip will be freed in exportfs() */
                        if (e && e != exip) {
                                export_unlink(e);
                                exi_rele(e);
                        }
                        tree_head = tree_head->tree_child_first;
                        kmem_free(t2, sizeof (*t2));
                }
        }

        return (error);
}

/*
 * Walk up the tree and:
 * 1. release pseudo exportinfo if it has no child
 * 2. release visible in parent's exportinfo
 * 3. delete non-exported leaf nodes from tree
 *
 * Deleting of nodes will start only if the unshared
 * node was a leaf node.
 * Deleting of nodes will finish when we reach a node which
 * has children or is a real export, then we might still need
 * to continue releasing visibles, until we reach VROOT node.
 */
void
treeclimb_unexport(struct exportinfo *exip)
{
        treenode_t *tnode, *old_nd;

        ASSERT(RW_WRITE_HELD(&exported_lock));

        tnode = exip->exi_tree;
        /*
         * The unshared exportinfo was unlinked in unexport().
         * Zeroing tree_exi ensures that we will skip it.
         */
        tnode->tree_exi = NULL;

        if (tnode->tree_vis) /* system root has tree_vis == NULL */
                tnode->tree_vis->vis_exported = 0;

        while (tnode) {

                /* Stop at VROOT node which is exported or has child */
                if (TREE_ROOT(tnode) &&
                    (TREE_EXPORTED(tnode) || tnode->tree_child_first))
                        break;

                /* Release pseudo export if it has no child */
                if (TREE_ROOT(tnode) && !TREE_EXPORTED(tnode) &&
                    tnode->tree_child_first == 0) {
                        export_unlink(tnode->tree_exi);
                        exi_rele(tnode->tree_exi);
                }

                /* Release visible in parent's exportinfo */
                if (tnode->tree_vis)
                        less_visible(vis2exi(tnode), tnode->tree_vis);

                /* Continue with parent */
                old_nd = tnode;
                tnode = tnode->tree_parent;

                /* Remove itself, if this is a leaf and non-exported node */
                if (old_nd->tree_child_first == NULL && !TREE_EXPORTED(old_nd))
                        tree_remove_node(old_nd);
        }
}

/*
 * Traverse backward across mountpoint from the
 * root vnode of a filesystem to its mounted-on
 * vnode.
 */
vnode_t *
untraverse(vnode_t *vp)
{
        vnode_t *tvp, *nextvp;

        tvp = vp;
        for (;;) {
                if (! (tvp->v_flag & VROOT))
                        break;

                /* lock vfs to prevent unmount of this vfs */
                vfs_lock_wait(tvp->v_vfsp);

                if ((nextvp = tvp->v_vfsp->vfs_vnodecovered) == NULL) {
                        vfs_unlock(tvp->v_vfsp);
                        break;
                }

                /*
                 * Hold nextvp to prevent unmount.  After unlock vfs and
                 * rele tvp, any number of overlays could be unmounted.
                 * Putting a hold on vfs_vnodecovered will only allow
                 * tvp's vfs to be unmounted. Of course if caller placed
                 * extra hold on vp before calling untraverse, the following
                 * hold would not be needed.  Since prev actions of caller
                 * are unknown, we need to hold here just to be safe.
                 */
                VN_HOLD(nextvp);
                vfs_unlock(tvp->v_vfsp);
                VN_RELE(tvp);
                tvp = nextvp;
        }

        return (tvp);
}

/*
 * Given an exportinfo, climb up to find the exportinfo for the VROOT
 * of the filesystem.
 *
 * e.g.         /
 *              |
 *              a (VROOT) pseudo-exportinfo
 *              |
 *              b
 *              |
 *              c  #share /a/b/c
 *              |
 *              d
 *
 * where c is in the same filesystem as a.
 * So, get_root_export(*exportinfo_for_c) returns exportinfo_for_a
 *
 * If d is shared, then c will be put into a's visible list.
 * Note: visible list is per filesystem and is attached to the
 * VROOT exportinfo.
 */
struct exportinfo *
get_root_export(struct exportinfo *exip)
{
        treenode_t *tnode = exip->exi_tree;
        exportinfo_t *exi = NULL;

        while (tnode) {
                if (TREE_ROOT(tnode)) {
                        exi = tnode->tree_exi;
                        break;
                }
                tnode = tnode->tree_parent;
        }
        ASSERT(exi);
        return (exi);
}

/*
 * Return true if the supplied vnode has a sub-directory exported.
 */
int
has_visible(struct exportinfo *exi, vnode_t *vp)
{
        struct exp_visible *visp;
        fid_t fid;
        bool_t vp_is_exported;

        vp_is_exported = VN_CMP(vp,  exi->exi_vp);

        /*
         * An exported root vnode has a sub-dir shared if it has a visible list.
         * i.e. if it does not have a visible list, then there is no node in
         * this filesystem leads to any other shared node.
         */
        if (vp_is_exported && (vp->v_flag & VROOT))
                return (exi->exi_visible ? 1 : 0);

        /*
         * Only the exportinfo of a fs root node may have a visible list.
         * Either it is a pseudo root node, or a real exported root node.
         */
        exi = get_root_export(exi);

        if (!exi->exi_visible)
                return (0);

        /* Get the fid of the vnode */
        bzero(&fid, sizeof (fid));
        fid.fid_len = MAXFIDSZ;
        if (vop_fid_pseudo(vp, &fid) != 0) {
                return (0);
        }

        /*
         * See if vp is in the visible list of the root node exportinfo.
         */
        for (visp = exi->exi_visible; visp; visp = visp->vis_next) {
                if (EQFID(&fid, &visp->vis_fid)) {
                        /*
                         * If vp is an exported non-root node with only 1 path
                         * count (for itself), it indicates no sub-dir shared
                         * using this vp as a path.
                         */
                        if (vp_is_exported && visp->vis_count < 2)
                                break;

                        return (1);
                }
        }

        return (0);
}

/*
 * Returns true if the supplied vnode is visible
 * in this export.  If vnode is visible, return
 * vis_exported in expseudo.
 */
int
nfs_visible(struct exportinfo *exi, vnode_t *vp, int *expseudo)
{
        struct exp_visible *visp;
        fid_t fid;

        /*
         * First check to see if vp is export root.
         *
         * A pseudo export root can never be exported
         * (it would be a real export then); however,
         * it is always visible.  If a pseudo root object
         * was exported by server admin, then the entire
         * pseudo exportinfo (and all visible entries) would
         * be destroyed.  A pseudo exportinfo only exists
         * to provide access to real (descendant) export(s).
         *
         * Previously, rootdir was special cased here; however,
         * the export root special case handles the rootdir
         * case also.
         */
        if (VN_CMP(vp, exi->exi_vp)) {
                *expseudo = 0;
                return (1);
        }

        /*
         * Only a PSEUDO node has a visible list or an exported VROOT
         * node may have a visible list.
         */
        if (! PSEUDO(exi))
                exi = get_root_export(exi);

        /* Get the fid of the vnode */

        bzero(&fid, sizeof (fid));
        fid.fid_len = MAXFIDSZ;
        if (vop_fid_pseudo(vp, &fid) != 0) {
                *expseudo = 0;
                return (0);
        }

        /*
         * We can't trust VN_CMP() above because of LOFS.
         * Even though VOP_CMP will do the right thing for LOFS
         * objects, VN_CMP will short circuit out early when the
         * vnode ops ptrs are different.  Just in case we're dealing
         * with LOFS, compare exi_fid/fsid here.
         *
         * expseudo is not set because this is not an export
         */
        if (EQFID(&exi->exi_fid, &fid) &&
            EQFSID(&exi->exi_fsid, &vp->v_vfsp->vfs_fsid)) {
                *expseudo = 0;
                return (1);
        }


        /* See if it matches any fid in the visible list */

        for (visp = exi->exi_visible; visp; visp = visp->vis_next) {
                if (EQFID(&fid, &visp->vis_fid)) {
                        *expseudo = visp->vis_exported;
                        return (1);
                }
        }

        *expseudo = 0;

        return (0);
}

/*
 * Returns true if the supplied vnode is the
 * directory of an export point.
 */
int
nfs_exported(struct exportinfo *exi, vnode_t *vp)
{
        struct exp_visible *visp;
        fid_t fid;

        /*
         * First check to see if vp is the export root
         * This check required for the case of lookup ..
         * where .. is a V_ROOT vnode and a pseudo exportroot.
         * Pseudo export root objects do not have an entry
         * in the visible list even though every V_ROOT
         * pseudonode is visible.  It is safe to compare
         * vp here because pseudo_exportfs put a hold on
         * it when exi_vp was initialized.
         *
         * Note: VN_CMP() won't match for LOFS shares, but they're
         * handled below w/EQFID/EQFSID.
         */
        if (VN_CMP(vp, exi->exi_vp))
                return (1);

        /* Get the fid of the vnode */

        bzero(&fid, sizeof (fid));
        fid.fid_len = MAXFIDSZ;
        if (vop_fid_pseudo(vp, &fid) != 0)
                return (0);

        if (EQFID(&fid, &exi->exi_fid) &&
            EQFSID(&vp->v_vfsp->vfs_fsid, &exi->exi_fsid)) {
                return (1);
        }

        /* See if it matches any fid in the visible list */

        for (visp = exi->exi_visible; visp; visp = visp->vis_next) {
                if (EQFID(&fid, &visp->vis_fid))
                        return (visp->vis_exported);
        }

        return (0);
}

/*
 * Returns true if the supplied inode is visible
 * in this export.  This function is used by
 * readdir which uses inode numbers from the
 * directory.
 *
 * NOTE: this code does not match inode number for ".",
 * but it isn't required because NFS4 server rddir
 * skips . and .. entries.
 */
int
nfs_visible_inode(struct exportinfo *exi, ino64_t ino, int *expseudo)
{
        struct exp_visible *visp;

        /*
         * Only a PSEUDO node has a visible list or an exported VROOT
         * node may have a visible list.
         */
        if (! PSEUDO(exi))
                exi = get_root_export(exi);

        for (visp = exi->exi_visible; visp; visp = visp->vis_next)
                if ((u_longlong_t)ino == visp->vis_ino) {
                        *expseudo = visp->vis_exported;
                        return (1);
                }

        *expseudo = 0;
        return (0);
}