FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/os/freebsd/zfs/zfs_ctldir.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 https://opensource.org/licenses/CDDL-1.0.
     * 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 (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
     * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
     * Copyright 2015, OmniTI Computer Consulting, Inc. All rights reserved.
     */
    
    /*
     * ZFS control directory (a.k.a. ".zfs")
     *
     * This directory provides a common location for all ZFS meta-objects.
     * Currently, this is only the 'snapshot' directory, but this may expand in the
     * future.  The elements are built using the GFS primitives, as the hierarchy
     * does not actually exist on disk.
     *
     * For 'snapshot', we don't want to have all snapshots always mounted, because
     * this would take up a huge amount of space in /etc/mnttab.  We have three
     * types of objects:
     *
     *      ctldir ------> snapshotdir -------> snapshot
     *                                             |
     *                                             |
     *                                             V
     *                                         mounted fs
     *
     * The 'snapshot' node contains just enough information to lookup '..' and act
     * as a mountpoint for the snapshot.  Whenever we lookup a specific snapshot, we
     * perform an automount of the underlying filesystem and return the
     * corresponding vnode.
     *
     * All mounts are handled automatically by the kernel, but unmounts are
     * (currently) handled from user land.  The main reason is that there is no
     * reliable way to auto-unmount the filesystem when it's "no longer in use".
     * When the user unmounts a filesystem, we call zfsctl_unmount(), which
     * unmounts any snapshots within the snapshot directory.
     *
     * The '.zfs', '.zfs/snapshot', and all directories created under
     * '.zfs/snapshot' (ie: '.zfs/snapshot/<snapname>') are all GFS nodes and
     * share the same vfs_t as the head filesystem (what '.zfs' lives under).
     *
     * File systems mounted ontop of the GFS nodes '.zfs/snapshot/<snapname>'
     * (ie: snapshots) are ZFS nodes and have their own unique vfs_t.
     * However, vnodes within these mounted on file systems have their v_vfsp
     * fields set to the head filesystem to make NFS happy (see
     * zfsctl_snapdir_lookup()). We VFS_HOLD the head filesystem's vfs_t
     * so that it cannot be freed until all snapshots have been unmounted.
     */
    
    #include <sys/types.h>
    #include <sys/param.h>
    #include <sys/libkern.h>
    #include <sys/dirent.h>
    #include <sys/zfs_context.h>
    #include <sys/zfs_ctldir.h>
    #include <sys/zfs_ioctl.h>
    #include <sys/zfs_vfsops.h>
    #include <sys/namei.h>
    #include <sys/stat.h>
    #include <sys/dmu.h>
    #include <sys/dsl_dataset.h>
    #include <sys/dsl_destroy.h>
    #include <sys/dsl_deleg.h>
    #include <sys/mount.h>
    #include <sys/zap.h>
    #include <sys/sysproto.h>
    
    #include "zfs_namecheck.h"
    
    #include <sys/kernel.h>
    #include <sys/ccompat.h>
    
    /* Common access mode for all virtual directories under the ctldir */
    const uint16_t zfsctl_ctldir_mode = S_IRUSR | S_IXUSR | S_IRGRP | S_IXGRP |
        S_IROTH | S_IXOTH;
    
    /*
     * "Synthetic" filesystem implementation.
     */
    
    /*
    * Assert that A implies B.
    */
   #define KASSERT_IMPLY(A, B, msg)        KASSERT(!(A) || (B), (msg));
   
   static MALLOC_DEFINE(M_SFSNODES, "sfs_nodes", "synthetic-fs nodes");
   
   typedef struct sfs_node {
           char            sn_name[ZFS_MAX_DATASET_NAME_LEN];
           uint64_t        sn_parent_id;
           uint64_t        sn_id;
   } sfs_node_t;
   
   /*
    * Check the parent's ID as well as the node's to account for a chance
    * that IDs originating from different domains (snapshot IDs, artificial
    * IDs, znode IDs) may clash.
    */
   static int
   sfs_compare_ids(struct vnode *vp, void *arg)
   {
           sfs_node_t *n1 = vp->v_data;
           sfs_node_t *n2 = arg;
           bool equal;
   
           equal = n1->sn_id == n2->sn_id &&
               n1->sn_parent_id == n2->sn_parent_id;
   
           /* Zero means equality. */
           return (!equal);
   }
   
   static int
   sfs_vnode_get(const struct mount *mp, int flags, uint64_t parent_id,
       uint64_t id, struct vnode **vpp)
   {
           sfs_node_t search;
           int err;
   
           search.sn_id = id;
           search.sn_parent_id = parent_id;
           err = vfs_hash_get(mp, (uint32_t)id, flags, curthread, vpp,
               sfs_compare_ids, &search);
           return (err);
   }
   
   static int
   sfs_vnode_insert(struct vnode *vp, int flags, uint64_t parent_id,
       uint64_t id, struct vnode **vpp)
   {
           int err;
   
           KASSERT(vp->v_data != NULL, ("sfs_vnode_insert with NULL v_data"));
           err = vfs_hash_insert(vp, (uint32_t)id, flags, curthread, vpp,
               sfs_compare_ids, vp->v_data);
           return (err);
   }
   
   static void
   sfs_vnode_remove(struct vnode *vp)
   {
           vfs_hash_remove(vp);
   }
   
   typedef void sfs_vnode_setup_fn(vnode_t *vp, void *arg);
   
   static int
   sfs_vgetx(struct mount *mp, int flags, uint64_t parent_id, uint64_t id,
       const char *tag, struct vop_vector *vops,
       sfs_vnode_setup_fn setup, void *arg,
       struct vnode **vpp)
   {
           struct vnode *vp;
           int error;
   
           error = sfs_vnode_get(mp, flags, parent_id, id, vpp);
           if (error != 0 || *vpp != NULL) {
                   KASSERT_IMPLY(error == 0, (*vpp)->v_data != NULL,
                       "sfs vnode with no data");
                   return (error);
           }
   
           /* Allocate a new vnode/inode. */
           error = getnewvnode(tag, mp, vops, &vp);
           if (error != 0) {
                   *vpp = NULL;
                   return (error);
           }
   
           /*
            * Exclusively lock the vnode vnode while it's being constructed.
            */
           lockmgr(vp->v_vnlock, LK_EXCLUSIVE, NULL);
           error = insmntque(vp, mp);
           if (error != 0) {
                   *vpp = NULL;
                   return (error);
           }
   
           setup(vp, arg);
   
           error = sfs_vnode_insert(vp, flags, parent_id, id, vpp);
           if (error != 0 || *vpp != NULL) {
                   KASSERT_IMPLY(error == 0, (*vpp)->v_data != NULL,
                       "sfs vnode with no data");
                   return (error);
           }
   
           *vpp = vp;
           return (0);
   }
   
   static void
   sfs_print_node(sfs_node_t *node)
   {
           printf("\tname = %s\n", node->sn_name);
           printf("\tparent_id = %ju\n", (uintmax_t)node->sn_parent_id);
           printf("\tid = %ju\n", (uintmax_t)node->sn_id);
   }
   
   static sfs_node_t *
   sfs_alloc_node(size_t size, const char *name, uint64_t parent_id, uint64_t id)
   {
           struct sfs_node *node;
   
           KASSERT(strlen(name) < sizeof (node->sn_name),
               ("sfs node name is too long"));
           KASSERT(size >= sizeof (*node), ("sfs node size is too small"));
           node = malloc(size, M_SFSNODES, M_WAITOK | M_ZERO);
           strlcpy(node->sn_name, name, sizeof (node->sn_name));
           node->sn_parent_id = parent_id;
           node->sn_id = id;
   
           return (node);
   }
   
   static void
   sfs_destroy_node(sfs_node_t *node)
   {
           free(node, M_SFSNODES);
   }
   
   static void *
   sfs_reclaim_vnode(vnode_t *vp)
   {
           void *data;
   
           sfs_vnode_remove(vp);
           data = vp->v_data;
           vp->v_data = NULL;
           return (data);
   }
   
   static int
   sfs_readdir_common(uint64_t parent_id, uint64_t id, struct vop_readdir_args *ap,
       zfs_uio_t *uio, off_t *offp)
   {
           struct dirent entry;
           int error;
   
           /* Reset ncookies for subsequent use of vfs_read_dirent. */
           if (ap->a_ncookies != NULL)
                   *ap->a_ncookies = 0;
   
           if (zfs_uio_resid(uio) < sizeof (entry))
                   return (SET_ERROR(EINVAL));
   
           if (zfs_uio_offset(uio) < 0)
                   return (SET_ERROR(EINVAL));
           if (zfs_uio_offset(uio) == 0) {
                   entry.d_fileno = id;
                   entry.d_type = DT_DIR;
                   entry.d_name[0] = '.';
                   entry.d_name[1] = '\0';
                   entry.d_namlen = 1;
                   entry.d_reclen = sizeof (entry);
                   error = vfs_read_dirent(ap, &entry, zfs_uio_offset(uio));
                   if (error != 0)
                           return (SET_ERROR(error));
           }
   
           if (zfs_uio_offset(uio) < sizeof (entry))
                   return (SET_ERROR(EINVAL));
           if (zfs_uio_offset(uio) == sizeof (entry)) {
                   entry.d_fileno = parent_id;
                   entry.d_type = DT_DIR;
                   entry.d_name[0] = '.';
                   entry.d_name[1] = '.';
                   entry.d_name[2] = '\0';
                   entry.d_namlen = 2;
                   entry.d_reclen = sizeof (entry);
                   error = vfs_read_dirent(ap, &entry, zfs_uio_offset(uio));
                   if (error != 0)
                           return (SET_ERROR(error));
           }
   
           if (offp != NULL)
                   *offp = 2 * sizeof (entry);
           return (0);
   }
   
   
   /*
    * .zfs inode namespace
    *
    * We need to generate unique inode numbers for all files and directories
    * within the .zfs pseudo-filesystem.  We use the following scheme:
    *
    *      ENTRY                   ZFSCTL_INODE
    *      .zfs                    1
    *      .zfs/snapshot           2
    *      .zfs/snapshot/<snap>    objectid(snap)
    */
   #define ZFSCTL_INO_SNAP(id)     (id)
   
   static struct vop_vector zfsctl_ops_root;
   static struct vop_vector zfsctl_ops_snapdir;
   static struct vop_vector zfsctl_ops_snapshot;
   
   void
   zfsctl_init(void)
   {
   }
   
   void
   zfsctl_fini(void)
   {
   }
   
   boolean_t
   zfsctl_is_node(vnode_t *vp)
   {
           return (vn_matchops(vp, zfsctl_ops_root) ||
               vn_matchops(vp, zfsctl_ops_snapdir) ||
               vn_matchops(vp, zfsctl_ops_snapshot));
   
   }
   
   typedef struct zfsctl_root {
           sfs_node_t      node;
           sfs_node_t      *snapdir;
           timestruc_t     cmtime;
   } zfsctl_root_t;
   
   
   /*
    * Create the '.zfs' directory.
    */
   void
   zfsctl_create(zfsvfs_t *zfsvfs)
   {
           zfsctl_root_t *dot_zfs;
           sfs_node_t *snapdir;
           vnode_t *rvp;
           uint64_t crtime[2];
   
           ASSERT3P(zfsvfs->z_ctldir, ==, NULL);
   
           snapdir = sfs_alloc_node(sizeof (*snapdir), "snapshot", ZFSCTL_INO_ROOT,
               ZFSCTL_INO_SNAPDIR);
           dot_zfs = (zfsctl_root_t *)sfs_alloc_node(sizeof (*dot_zfs), ".zfs", 0,
               ZFSCTL_INO_ROOT);
           dot_zfs->snapdir = snapdir;
   
           VERIFY0(VFS_ROOT(zfsvfs->z_vfs, LK_EXCLUSIVE, &rvp));
           VERIFY0(sa_lookup(VTOZ(rvp)->z_sa_hdl, SA_ZPL_CRTIME(zfsvfs),
               &crtime, sizeof (crtime)));
           ZFS_TIME_DECODE(&dot_zfs->cmtime, crtime);
           vput(rvp);
   
           zfsvfs->z_ctldir = dot_zfs;
   }
   
   /*
    * Destroy the '.zfs' directory.  Only called when the filesystem is unmounted.
    * The nodes must not have any associated vnodes by now as they should be
    * vflush-ed.
    */
   void
   zfsctl_destroy(zfsvfs_t *zfsvfs)
   {
           sfs_destroy_node(zfsvfs->z_ctldir->snapdir);
           sfs_destroy_node((sfs_node_t *)zfsvfs->z_ctldir);
           zfsvfs->z_ctldir = NULL;
   }
   
   static int
   zfsctl_fs_root_vnode(struct mount *mp, void *arg __unused, int flags,
       struct vnode **vpp)
   {
           return (VFS_ROOT(mp, flags, vpp));
   }
   
   static void
   zfsctl_common_vnode_setup(vnode_t *vp, void *arg)
   {
           ASSERT_VOP_ELOCKED(vp, __func__);
   
           /* We support shared locking. */
           VN_LOCK_ASHARE(vp);
           vp->v_type = VDIR;
           vp->v_data = arg;
   }
   
   static int
   zfsctl_root_vnode(struct mount *mp, void *arg __unused, int flags,
       struct vnode **vpp)
   {
           void *node;
           int err;
   
           node = ((zfsvfs_t *)mp->mnt_data)->z_ctldir;
           err = sfs_vgetx(mp, flags, 0, ZFSCTL_INO_ROOT, "zfs", &zfsctl_ops_root,
               zfsctl_common_vnode_setup, node, vpp);
           return (err);
   }
   
   static int
   zfsctl_snapdir_vnode(struct mount *mp, void *arg __unused, int flags,
       struct vnode **vpp)
   {
           void *node;
           int err;
   
           node = ((zfsvfs_t *)mp->mnt_data)->z_ctldir->snapdir;
           err = sfs_vgetx(mp, flags, ZFSCTL_INO_ROOT, ZFSCTL_INO_SNAPDIR, "zfs",
               &zfsctl_ops_snapdir, zfsctl_common_vnode_setup, node, vpp);
           return (err);
   }
   
   /*
    * Given a root znode, retrieve the associated .zfs directory.
    * Add a hold to the vnode and return it.
    */
   int
   zfsctl_root(zfsvfs_t *zfsvfs, int flags, vnode_t **vpp)
   {
           int error;
   
           error = zfsctl_root_vnode(zfsvfs->z_vfs, NULL, flags, vpp);
           return (error);
   }
   
   /*
    * Common open routine.  Disallow any write access.
    */
   static int
   zfsctl_common_open(struct vop_open_args *ap)
   {
           int flags = ap->a_mode;
   
           if (flags & FWRITE)
                   return (SET_ERROR(EACCES));
   
           return (0);
   }
   
   /*
    * Common close routine.  Nothing to do here.
    */
   static int
   zfsctl_common_close(struct vop_close_args *ap)
   {
           (void) ap;
           return (0);
   }
   
   /*
    * Common access routine.  Disallow writes.
    */
   static int
   zfsctl_common_access(struct vop_access_args *ap)
   {
           accmode_t accmode = ap->a_accmode;
   
           if (accmode & VWRITE)
                   return (SET_ERROR(EACCES));
           return (0);
   }
   
   /*
    * Common getattr function.  Fill in basic information.
    */
   static void
   zfsctl_common_getattr(vnode_t *vp, vattr_t *vap)
   {
           timestruc_t     now;
           sfs_node_t *node;
   
           node = vp->v_data;
   
           vap->va_uid = 0;
           vap->va_gid = 0;
           vap->va_rdev = 0;
           /*
            * We are a purely virtual object, so we have no
            * blocksize or allocated blocks.
            */
           vap->va_blksize = 0;
           vap->va_nblocks = 0;
           vap->va_gen = 0;
           vn_fsid(vp, vap);
           vap->va_mode = zfsctl_ctldir_mode;
           vap->va_type = VDIR;
           /*
            * We live in the now (for atime).
            */
           gethrestime(&now);
           vap->va_atime = now;
           /* FreeBSD: Reset chflags(2) flags. */
           vap->va_flags = 0;
   
           vap->va_nodeid = node->sn_id;
   
           /* At least '.' and '..'. */
           vap->va_nlink = 2;
   }
   
   #ifndef _OPENSOLARIS_SYS_VNODE_H_
   struct vop_fid_args {
           struct vnode *a_vp;
           struct fid *a_fid;
   };
   #endif
   
   static int
   zfsctl_common_fid(struct vop_fid_args *ap)
   {
           vnode_t         *vp = ap->a_vp;
           fid_t           *fidp = (void *)ap->a_fid;
           sfs_node_t      *node = vp->v_data;
           uint64_t        object = node->sn_id;
           zfid_short_t    *zfid;
           int             i;
   
           zfid = (zfid_short_t *)fidp;
           zfid->zf_len = SHORT_FID_LEN;
   
           for (i = 0; i < sizeof (zfid->zf_object); i++)
                   zfid->zf_object[i] = (uint8_t)(object >> (8 * i));
   
           /* .zfs nodes always have a generation number of 0 */
           for (i = 0; i < sizeof (zfid->zf_gen); i++)
                   zfid->zf_gen[i] = 0;
   
           return (0);
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct vop_reclaim_args {
           struct vnode *a_vp;
           struct thread *a_td;
   };
   #endif
   
   static int
   zfsctl_common_reclaim(struct vop_reclaim_args *ap)
   {
           vnode_t *vp = ap->a_vp;
   
           (void) sfs_reclaim_vnode(vp);
           return (0);
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct vop_print_args {
           struct vnode *a_vp;
   };
   #endif
   
   static int
   zfsctl_common_print(struct vop_print_args *ap)
   {
           sfs_print_node(ap->a_vp->v_data);
           return (0);
   }
   
   #ifndef _SYS_SYSPROTO_H_
   struct vop_getattr_args {
           struct vnode *a_vp;
           struct vattr *a_vap;
           struct ucred *a_cred;
   };
   #endif
   
   /*
    * Get root directory attributes.
    */
   static int
   zfsctl_root_getattr(struct vop_getattr_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           struct vattr *vap = ap->a_vap;
           zfsctl_root_t *node = vp->v_data;
   
           zfsctl_common_getattr(vp, vap);
           vap->va_ctime = node->cmtime;
           vap->va_mtime = vap->va_ctime;
           vap->va_birthtime = vap->va_ctime;
           vap->va_nlink += 1; /* snapdir */
           vap->va_size = vap->va_nlink;
           return (0);
   }
   
   /*
    * When we lookup "." we still can be asked to lock it
    * differently, can't we?
    */
   static int
   zfsctl_relock_dot(vnode_t *dvp, int ltype)
   {
           vref(dvp);
           if (ltype != VOP_ISLOCKED(dvp)) {
                   if (ltype == LK_EXCLUSIVE)
                           vn_lock(dvp, LK_UPGRADE | LK_RETRY);
                   else /* if (ltype == LK_SHARED) */
                           vn_lock(dvp, LK_DOWNGRADE | LK_RETRY);
   
                   /* Relock for the "." case may left us with reclaimed vnode. */
                   if (VN_IS_DOOMED(dvp)) {
                           vrele(dvp);
                           return (SET_ERROR(ENOENT));
                   }
           }
           return (0);
   }
   
   /*
    * Special case the handling of "..".
    */
   static int
   zfsctl_root_lookup(struct vop_lookup_args *ap)
   {
           struct componentname *cnp = ap->a_cnp;
           vnode_t *dvp = ap->a_dvp;
           vnode_t **vpp = ap->a_vpp;
           int flags = ap->a_cnp->cn_flags;
           int lkflags = ap->a_cnp->cn_lkflags;
           int nameiop = ap->a_cnp->cn_nameiop;
           int err;
   
           ASSERT3S(dvp->v_type, ==, VDIR);
   
           if ((flags & ISLASTCN) != 0 && nameiop != LOOKUP)
                   return (SET_ERROR(ENOTSUP));
   
           if (cnp->cn_namelen == 1 && *cnp->cn_nameptr == '.') {
                   err = zfsctl_relock_dot(dvp, lkflags & LK_TYPE_MASK);
                   if (err == 0)
                           *vpp = dvp;
           } else if ((flags & ISDOTDOT) != 0) {
                   err = vn_vget_ino_gen(dvp, zfsctl_fs_root_vnode, NULL,
                       lkflags, vpp);
           } else if (strncmp(cnp->cn_nameptr, "snapshot", cnp->cn_namelen) == 0) {
                   err = zfsctl_snapdir_vnode(dvp->v_mount, NULL, lkflags, vpp);
           } else {
                   err = SET_ERROR(ENOENT);
           }
           if (err != 0)
                   *vpp = NULL;
           return (err);
   }
   
   static int
   zfsctl_root_readdir(struct vop_readdir_args *ap)
   {
           struct dirent entry;
           vnode_t *vp = ap->a_vp;
           zfsvfs_t *zfsvfs = vp->v_vfsp->vfs_data;
           zfsctl_root_t *node = vp->v_data;
           zfs_uio_t uio;
           int *eofp = ap->a_eofflag;
           off_t dots_offset;
           int error;
   
           zfs_uio_init(&uio, ap->a_uio);
   
           ASSERT3S(vp->v_type, ==, VDIR);
   
           error = sfs_readdir_common(zfsvfs->z_root, ZFSCTL_INO_ROOT, ap, &uio,
               &dots_offset);
           if (error != 0) {
                   if (error == ENAMETOOLONG) /* ran out of destination space */
                           error = 0;
                   return (error);
           }
           if (zfs_uio_offset(&uio) != dots_offset)
                   return (SET_ERROR(EINVAL));
   
           _Static_assert(sizeof (node->snapdir->sn_name) <= sizeof (entry.d_name),
               "node->snapdir->sn_name too big for entry.d_name");
           entry.d_fileno = node->snapdir->sn_id;
           entry.d_type = DT_DIR;
           strcpy(entry.d_name, node->snapdir->sn_name);
           entry.d_namlen = strlen(entry.d_name);
           entry.d_reclen = sizeof (entry);
           error = vfs_read_dirent(ap, &entry, zfs_uio_offset(&uio));
           if (error != 0) {
                   if (error == ENAMETOOLONG)
                           error = 0;
                   return (SET_ERROR(error));
           }
           if (eofp != NULL)
                   *eofp = 1;
           return (0);
   }
   
   static int
   zfsctl_root_vptocnp(struct vop_vptocnp_args *ap)
   {
           static const char dotzfs_name[4] = ".zfs";
           vnode_t *dvp;
           int error;
   
           if (*ap->a_buflen < sizeof (dotzfs_name))
                   return (SET_ERROR(ENOMEM));
   
           error = vn_vget_ino_gen(ap->a_vp, zfsctl_fs_root_vnode, NULL,
               LK_SHARED, &dvp);
           if (error != 0)
                   return (SET_ERROR(error));
   
           VOP_UNLOCK1(dvp);
           *ap->a_vpp = dvp;
           *ap->a_buflen -= sizeof (dotzfs_name);
           memcpy(ap->a_buf + *ap->a_buflen, dotzfs_name, sizeof (dotzfs_name));
           return (0);
   }
   
   static int
   zfsctl_common_pathconf(struct vop_pathconf_args *ap)
   {
           /*
            * We care about ACL variables so that user land utilities like ls
            * can display them correctly.  Since the ctldir's st_dev is set to be
            * the same as the parent dataset, we must support all variables that
            * it supports.
            */
           switch (ap->a_name) {
           case _PC_LINK_MAX:
                   *ap->a_retval = MIN(LONG_MAX, ZFS_LINK_MAX);
                   return (0);
   
           case _PC_FILESIZEBITS:
                   *ap->a_retval = 64;
                   return (0);
   
           case _PC_MIN_HOLE_SIZE:
                   *ap->a_retval = (int)SPA_MINBLOCKSIZE;
                   return (0);
   
           case _PC_ACL_EXTENDED:
                   *ap->a_retval = 0;
                   return (0);
   
           case _PC_ACL_NFS4:
                   *ap->a_retval = 1;
                   return (0);
   
           case _PC_ACL_PATH_MAX:
                   *ap->a_retval = ACL_MAX_ENTRIES;
                   return (0);
   
           case _PC_NAME_MAX:
                   *ap->a_retval = NAME_MAX;
                   return (0);
   
           default:
                   return (vop_stdpathconf(ap));
           }
   }
   
   /*
    * Returns a trivial ACL
    */
   static int
   zfsctl_common_getacl(struct vop_getacl_args *ap)
   {
           int i;
   
           if (ap->a_type != ACL_TYPE_NFS4)
                   return (EINVAL);
   
           acl_nfs4_sync_acl_from_mode(ap->a_aclp, zfsctl_ctldir_mode, 0);
           /*
            * acl_nfs4_sync_acl_from_mode assumes that the owner can always modify
            * attributes.  That is not the case for the ctldir, so we must clear
            * those bits.  We also must clear ACL_READ_NAMED_ATTRS, because xattrs
            * aren't supported by the ctldir.
            */
           for (i = 0; i < ap->a_aclp->acl_cnt; i++) {
                   struct acl_entry *entry;
                   entry = &(ap->a_aclp->acl_entry[i]);
                   entry->ae_perm &= ~(ACL_WRITE_ACL | ACL_WRITE_OWNER |
                       ACL_WRITE_ATTRIBUTES | ACL_WRITE_NAMED_ATTRS |
                       ACL_READ_NAMED_ATTRS);
           }
   
           return (0);
   }
   
   static struct vop_vector zfsctl_ops_root = {
           .vop_default =  &default_vnodeops,
   #if __FreeBSD_version >= 1300121
           .vop_fplookup_vexec = VOP_EAGAIN,
   #endif
           .vop_open =     zfsctl_common_open,
           .vop_close =    zfsctl_common_close,
           .vop_ioctl =    VOP_EINVAL,
           .vop_getattr =  zfsctl_root_getattr,
           .vop_access =   zfsctl_common_access,
           .vop_readdir =  zfsctl_root_readdir,
           .vop_lookup =   zfsctl_root_lookup,
           .vop_inactive = VOP_NULL,
           .vop_reclaim =  zfsctl_common_reclaim,
           .vop_fid =      zfsctl_common_fid,
           .vop_print =    zfsctl_common_print,
           .vop_vptocnp =  zfsctl_root_vptocnp,
           .vop_pathconf = zfsctl_common_pathconf,
           .vop_getacl =   zfsctl_common_getacl,
   #if __FreeBSD_version >= 1400043
           .vop_add_writecount =   vop_stdadd_writecount_nomsync,
   #endif
   };
   VFS_VOP_VECTOR_REGISTER(zfsctl_ops_root);
   
   static int
   zfsctl_snapshot_zname(vnode_t *vp, const char *name, int len, char *zname)
   {
           objset_t *os = ((zfsvfs_t *)((vp)->v_vfsp->vfs_data))->z_os;
   
           dmu_objset_name(os, zname);
           if (strlen(zname) + 1 + strlen(name) >= len)
                   return (SET_ERROR(ENAMETOOLONG));
           (void) strcat(zname, "@");
           (void) strcat(zname, name);
           return (0);
   }
   
   static int
   zfsctl_snapshot_lookup(vnode_t *vp, const char *name, uint64_t *id)
   {
           objset_t *os = ((zfsvfs_t *)((vp)->v_vfsp->vfs_data))->z_os;
           int err;
   
           err = dsl_dataset_snap_lookup(dmu_objset_ds(os), name, id);
           return (err);
   }
   
   /*
    * Given a vnode get a root vnode of a filesystem mounted on top of
    * the vnode, if any.  The root vnode is referenced and locked.
    * If no filesystem is mounted then the orinal vnode remains referenced
    * and locked.  If any error happens the orinal vnode is unlocked and
    * released.
    */
   static int
   zfsctl_mounted_here(vnode_t **vpp, int flags)
   {
           struct mount *mp;
           int err;
   
           ASSERT_VOP_LOCKED(*vpp, __func__);
           ASSERT3S((*vpp)->v_type, ==, VDIR);
   
           if ((mp = (*vpp)->v_mountedhere) != NULL) {
                   err = vfs_busy(mp, 0);
                   KASSERT(err == 0, ("vfs_busy(mp, 0) failed with %d", err));
                   KASSERT(vrefcnt(*vpp) > 1, ("unreferenced mountpoint"));
                   vput(*vpp);
                   err = VFS_ROOT(mp, flags, vpp);
                   vfs_unbusy(mp);
                   return (err);
           }
           return (EJUSTRETURN);
   }
   
   typedef struct {
           const char *snap_name;
           uint64_t    snap_id;
   } snapshot_setup_arg_t;
   
   static void
   zfsctl_snapshot_vnode_setup(vnode_t *vp, void *arg)
   {
           snapshot_setup_arg_t *ssa = arg;
           sfs_node_t *node;
   
           ASSERT_VOP_ELOCKED(vp, __func__);
   
           node = sfs_alloc_node(sizeof (sfs_node_t),
               ssa->snap_name, ZFSCTL_INO_SNAPDIR, ssa->snap_id);
           zfsctl_common_vnode_setup(vp, node);
   
           /* We have to support recursive locking. */
           VN_LOCK_AREC(vp);
   }
   
   /*
    * Lookup entry point for the 'snapshot' directory.  Try to open the
    * snapshot if it exist, creating the pseudo filesystem vnode as necessary.
    * Perform a mount of the associated dataset on top of the vnode.
    * There are four possibilities:
    * - the snapshot node and vnode do not exist
    * - the snapshot vnode is covered by the mounted snapshot
    * - the snapshot vnode is not covered yet, the mount operation is in progress
    * - the snapshot vnode is not covered, because the snapshot has been unmounted
    * The last two states are transient and should be relatively short-lived.
    */
   static int
   zfsctl_snapdir_lookup(struct vop_lookup_args *ap)
   {
           vnode_t *dvp = ap->a_dvp;
           vnode_t **vpp = ap->a_vpp;
           struct componentname *cnp = ap->a_cnp;
           char name[NAME_MAX + 1];
           char fullname[ZFS_MAX_DATASET_NAME_LEN];
           char *mountpoint;
           size_t mountpoint_len;
           zfsvfs_t *zfsvfs = dvp->v_vfsp->vfs_data;
           uint64_t snap_id;
           int nameiop = cnp->cn_nameiop;
           int lkflags = cnp->cn_lkflags;
           int flags = cnp->cn_flags;
           int err;
   
           ASSERT3S(dvp->v_type, ==, VDIR);
   
           if ((flags & ISLASTCN) != 0 && nameiop != LOOKUP)
                   return (SET_ERROR(ENOTSUP));
   
           if (cnp->cn_namelen == 1 && *cnp->cn_nameptr == '.') {
                   err = zfsctl_relock_dot(dvp, lkflags & LK_TYPE_MASK);
                   if (err == 0)
                           *vpp = dvp;
                   return (err);
           }
           if (flags & ISDOTDOT) {
                   err = vn_vget_ino_gen(dvp, zfsctl_root_vnode, NULL, lkflags,
                       vpp);
                   return (err);
           }
   
           if (cnp->cn_namelen >= sizeof (name))
                   return (SET_ERROR(ENAMETOOLONG));
   
           strlcpy(name, ap->a_cnp->cn_nameptr, ap->a_cnp->cn_namelen + 1);
           err = zfsctl_snapshot_lookup(dvp, name, &snap_id);
           if (err != 0)
                   return (SET_ERROR(ENOENT));
   
           for (;;) {
                   snapshot_setup_arg_t ssa;
   
                   ssa.snap_name = name;
                   ssa.snap_id = snap_id;
                   err = sfs_vgetx(dvp->v_mount, LK_SHARED, ZFSCTL_INO_SNAPDIR,
                       snap_id, "zfs", &zfsctl_ops_snapshot,
                       zfsctl_snapshot_vnode_setup, &ssa, vpp);
                   if (err != 0)
                           return (err);
   
                   /* Check if a new vnode has just been created. */
                   if (VOP_ISLOCKED(*vpp) == LK_EXCLUSIVE)
                           break;
   
                   /*
                    * Check if a snapshot is already mounted on top of the vnode.
                    */
                   err = zfsctl_mounted_here(vpp, lkflags);
                   if (err != EJUSTRETURN)
                           return (err);
   
                   /*
                    * If the vnode is not covered, then either the mount operation
                    * is in progress or the snapshot has already been unmounted
                    * but the vnode hasn't been inactivated and reclaimed yet.
                    * We can try to re-use the vnode in the latter case.
                    */
                   VI_LOCK(*vpp);
                   if (((*vpp)->v_iflag & VI_MOUNT) == 0) {
                           VI_UNLOCK(*vpp);
                           /*
                            * Upgrade to exclusive lock in order to:
                            * - avoid race conditions
                            * - satisfy the contract of mount_snapshot()
                            */
                           err = VOP_LOCK(*vpp, LK_TRYUPGRADE);
                           if (err == 0)
                                   break;
                   } else {
                           VI_UNLOCK(*vpp);
                   }
   
                   /*
                    * In this state we can loop on uncontested locks and starve
                    * the thread doing the lengthy, non-trivial mount operation.
                    * So, yield to prevent that from happening.
                    */
                   vput(*vpp);
                   kern_yield(PRI_USER);
          }
  
          VERIFY0(zfsctl_snapshot_zname(dvp, name, sizeof (fullname), fullname));
  
          mountpoint_len = strlen(dvp->v_vfsp->mnt_stat.f_mntonname) +
              strlen("/" ZFS_CTLDIR_NAME "/snapshot/") + strlen(name) + 1;
          mountpoint = kmem_alloc(mountpoint_len, KM_SLEEP);
          (void) snprintf(mountpoint, mountpoint_len,
              "%s/" ZFS_CTLDIR_NAME "/snapshot/%s",
              dvp->v_vfsp->mnt_stat.f_mntonname, name);
  
          err = mount_snapshot(curthread, vpp, "zfs", mountpoint, fullname, 0);
          kmem_free(mountpoint, mountpoint_len);
          if (err == 0) {
                  /*
                   * Fix up the root vnode mounted on .zfs/snapshot/<snapname>.
                   *
                   * This is where we lie about our v_vfsp in order to
                   * make .zfs/snapshot/<snapname> accessible over NFS
                   * without requiring manual mounts of <snapname>.
                   */
                  ASSERT3P(VTOZ(*vpp)->z_zfsvfs, !=, zfsvfs);
                  VTOZ(*vpp)->z_zfsvfs->z_parent = zfsvfs;
  
                  /* Clear the root flag (set via VFS_ROOT) as well. */
                  (*vpp)->v_vflag &= ~VV_ROOT;
          }
  
          if (err != 0)
                  *vpp = NULL;
          return (err);
  }
  
  static int
  zfsctl_snapdir_readdir(struct vop_readdir_args *ap)
  {
          char snapname[ZFS_MAX_DATASET_NAME_LEN];
          struct dirent entry;
          vnode_t *vp = ap->a_vp;
          zfsvfs_t *zfsvfs = vp->v_vfsp->vfs_data;
          zfs_uio_t uio;
          int *eofp = ap->a_eofflag;
          off_t dots_offset;
          int error;
  
          zfs_uio_init(&uio, ap->a_uio);
  
          ASSERT3S(vp->v_type, ==, VDIR);
  
          error = sfs_readdir_common(ZFSCTL_INO_ROOT, ZFSCTL_INO_SNAPDIR, ap,
              &uio, &dots_offset);
          if (error != 0) {
                  if (error == ENAMETOOLONG) /* ran out of destination space */
                          error = 0;
                  return (error);
          }
  
          if ((error = zfs_enter(zfsvfs, FTAG)) != 0)
                  return (error);
          for (;;) {
                  uint64_t cookie;
                  uint64_t id;
  
                  cookie = zfs_uio_offset(&uio) - dots_offset;
  
                  dsl_pool_config_enter(dmu_objset_pool(zfsvfs->z_os), FTAG);
                  error = dmu_snapshot_list_next(zfsvfs->z_os, sizeof (snapname),
                      snapname, &id, &cookie, NULL);
                  dsl_pool_config_exit(dmu_objset_pool(zfsvfs->z_os), FTAG);
                  if (error != 0) {
                          if (error == ENOENT) {
                                  if (eofp != NULL)
                                          *eofp = 1;
                                  error = 0;
                          }
                          zfs_exit(zfsvfs, FTAG);
                          return (error);
                  }
  
                  entry.d_fileno = id;
                  entry.d_type = DT_DIR;
                  strcpy(entry.d_name, snapname);
                  entry.d_namlen = strlen(entry.d_name);
                  entry.d_reclen = sizeof (entry);
                  error = vfs_read_dirent(ap, &entry, zfs_uio_offset(&uio));
                  if (error != 0) {
                          if (error == ENAMETOOLONG)
                                  error = 0;
                          zfs_exit(zfsvfs, FTAG);
                          return (SET_ERROR(error));
                  }
                  zfs_uio_setoffset(&uio, cookie + dots_offset);
          }
          __builtin_unreachable();
  }
  
  static int
  zfsctl_snapdir_getattr(struct vop_getattr_args *ap)
  {
          vnode_t *vp = ap->a_vp;
          vattr_t *vap = ap->a_vap;
          zfsvfs_t *zfsvfs = vp->v_vfsp->vfs_data;
          dsl_dataset_t *ds;
          uint64_t snap_count;
          int err;
  
          if ((err = zfs_enter(zfsvfs, FTAG)) != 0)
                  return (err);
          ds = dmu_objset_ds(zfsvfs->z_os);
          zfsctl_common_getattr(vp, vap);
          vap->va_ctime = dmu_objset_snap_cmtime(zfsvfs->z_os);
          vap->va_mtime = vap->va_ctime;
          vap->va_birthtime = vap->va_ctime;
          if (dsl_dataset_phys(ds)->ds_snapnames_zapobj != 0) {
                  err = zap_count(dmu_objset_pool(ds->ds_objset)->dp_meta_objset,
                      dsl_dataset_phys(ds)->ds_snapnames_zapobj, &snap_count);
                  if (err != 0) {
                          zfs_exit(zfsvfs, FTAG);
                          return (err);
                  }
                  vap->va_nlink += snap_count;
          }
          vap->va_size = vap->va_nlink;
  
          zfs_exit(zfsvfs, FTAG);
          return (0);
  }
  
  static struct vop_vector zfsctl_ops_snapdir = {
          .vop_default =  &default_vnodeops,
  #if __FreeBSD_version >= 1300121
          .vop_fplookup_vexec = VOP_EAGAIN,
  #endif
          .vop_open =     zfsctl_common_open,
          .vop_close =    zfsctl_common_close,
          .vop_getattr =  zfsctl_snapdir_getattr,
          .vop_access =   zfsctl_common_access,
          .vop_readdir =  zfsctl_snapdir_readdir,
          .vop_lookup =   zfsctl_snapdir_lookup,
          .vop_reclaim =  zfsctl_common_reclaim,
          .vop_fid =      zfsctl_common_fid,
          .vop_print =    zfsctl_common_print,
          .vop_pathconf = zfsctl_common_pathconf,
          .vop_getacl =   zfsctl_common_getacl,
  #if __FreeBSD_version >= 1400043
          .vop_add_writecount =   vop_stdadd_writecount_nomsync,
  #endif
  };
  VFS_VOP_VECTOR_REGISTER(zfsctl_ops_snapdir);
  
  
  static int
  zfsctl_snapshot_inactive(struct vop_inactive_args *ap)
  {
          vnode_t *vp = ap->a_vp;
  
          VERIFY3S(vrecycle(vp), ==, 1);
          return (0);
  }
  
  static int
  zfsctl_snapshot_reclaim(struct vop_reclaim_args *ap)
  {
          vnode_t *vp = ap->a_vp;
          void *data = vp->v_data;
  
          sfs_reclaim_vnode(vp);
          sfs_destroy_node(data);
          return (0);
  }
  
  static int
  zfsctl_snapshot_vptocnp(struct vop_vptocnp_args *ap)
  {
          struct mount *mp;
          vnode_t *dvp;
          vnode_t *vp;
          sfs_node_t *node;
          size_t len;
          int locked;
          int error;
  
          vp = ap->a_vp;
          node = vp->v_data;
          len = strlen(node->sn_name);
          if (*ap->a_buflen < len)
                  return (SET_ERROR(ENOMEM));
  
          /*
           * Prevent unmounting of the snapshot while the vnode lock
           * is not held.  That is not strictly required, but allows
           * us to assert that an uncovered snapshot vnode is never
           * "leaked".
           */
          mp = vp->v_mountedhere;
          if (mp == NULL)
                  return (SET_ERROR(ENOENT));
          error = vfs_busy(mp, 0);
          KASSERT(error == 0, ("vfs_busy(mp, 0) failed with %d", error));
  
          /*
           * We can vput the vnode as we can now depend on the reference owned
           * by the busied mp.  But we also need to hold the vnode, because
           * the reference may go after vfs_unbusy() which has to be called
           * before we can lock the vnode again.
           */
          locked = VOP_ISLOCKED(vp);
  #if __FreeBSD_version >= 1300045
          enum vgetstate vs = vget_prep(vp);
  #else
          vhold(vp);
  #endif
          vput(vp);
  
          /* Look up .zfs/snapshot, our parent. */
          error = zfsctl_snapdir_vnode(vp->v_mount, NULL, LK_SHARED, &dvp);
          if (error == 0) {
                  VOP_UNLOCK1(dvp);
                  *ap->a_vpp = dvp;
                  *ap->a_buflen -= len;
                  memcpy(ap->a_buf + *ap->a_buflen, node->sn_name, len);
          }
          vfs_unbusy(mp);
  #if __FreeBSD_version >= 1300045
          vget_finish(vp, locked | LK_RETRY, vs);
  #else
          vget(vp, locked | LK_VNHELD | LK_RETRY, curthread);
  #endif
          return (error);
  }
  
  /*
   * These VP's should never see the light of day.  They should always
   * be covered.
   */
  static struct vop_vector zfsctl_ops_snapshot = {
          .vop_default =          NULL, /* ensure very restricted access */
  #if __FreeBSD_version >= 1300121
          .vop_fplookup_vexec =   VOP_EAGAIN,
  #endif
          .vop_inactive =         zfsctl_snapshot_inactive,
  #if __FreeBSD_version >= 1300045
          .vop_need_inactive = vop_stdneed_inactive,
  #endif
          .vop_reclaim =          zfsctl_snapshot_reclaim,
          .vop_vptocnp =          zfsctl_snapshot_vptocnp,
          .vop_lock1 =            vop_stdlock,
          .vop_unlock =           vop_stdunlock,
          .vop_islocked =         vop_stdislocked,
          .vop_advlockpurge =     vop_stdadvlockpurge, /* called by vgone */
          .vop_print =            zfsctl_common_print,
  #if __FreeBSD_version >= 1400043
          .vop_add_writecount =   vop_stdadd_writecount_nomsync,
  #endif
  };
  VFS_VOP_VECTOR_REGISTER(zfsctl_ops_snapshot);
  
  int
  zfsctl_lookup_objset(vfs_t *vfsp, uint64_t objsetid, zfsvfs_t **zfsvfsp)
  {
          zfsvfs_t *zfsvfs __unused = vfsp->vfs_data;
          vnode_t *vp;
          int error;
  
          ASSERT3P(zfsvfs->z_ctldir, !=, NULL);
          *zfsvfsp = NULL;
          error = sfs_vnode_get(vfsp, LK_EXCLUSIVE,
              ZFSCTL_INO_SNAPDIR, objsetid, &vp);
          if (error == 0 && vp != NULL) {
                  /*
                   * XXX Probably need to at least reference, if not busy, the mp.
                   */
                  if (vp->v_mountedhere != NULL)
                          *zfsvfsp = vp->v_mountedhere->mnt_data;
                  vput(vp);
          }
          if (*zfsvfsp == NULL)
                  return (SET_ERROR(EINVAL));
          return (0);
  }
  
  /*
   * Unmount any snapshots for the given filesystem.  This is called from
   * zfs_umount() - if we have a ctldir, then go through and unmount all the
   * snapshots.
   */
  int
  zfsctl_umount_snapshots(vfs_t *vfsp, int fflags, cred_t *cr)
  {
          char snapname[ZFS_MAX_DATASET_NAME_LEN];
          zfsvfs_t *zfsvfs = vfsp->vfs_data;
          struct mount *mp;
          vnode_t *vp;
          uint64_t cookie;
          int error;
  
          ASSERT3P(zfsvfs->z_ctldir, !=, NULL);
  
          cookie = 0;
          for (;;) {
                  uint64_t id;
  
                  dsl_pool_config_enter(dmu_objset_pool(zfsvfs->z_os), FTAG);
                  error = dmu_snapshot_list_next(zfsvfs->z_os, sizeof (snapname),
                      snapname, &id, &cookie, NULL);
                  dsl_pool_config_exit(dmu_objset_pool(zfsvfs->z_os), FTAG);
                  if (error != 0) {
                          if (error == ENOENT)
                                  error = 0;
                          break;
                  }
  
                  for (;;) {
                          error = sfs_vnode_get(vfsp, LK_EXCLUSIVE,
                              ZFSCTL_INO_SNAPDIR, id, &vp);
                          if (error != 0 || vp == NULL)
                                  break;
  
                          mp = vp->v_mountedhere;
  
                          /*
                           * v_mountedhere being NULL means that the
                           * (uncovered) vnode is in a transient state
                           * (mounting or unmounting), so loop until it
                           * settles down.
                           */
                          if (mp != NULL)
                                  break;
                          vput(vp);
                  }
                  if (error != 0)
                          break;
                  if (vp == NULL)
                          continue;       /* no mountpoint, nothing to do */
  
                  /*
                   * The mount-point vnode is kept locked to avoid spurious EBUSY
                   * from a concurrent umount.
                   * The vnode lock must have recursive locking enabled.
                   */
                  vfs_ref(mp);
                  error = dounmount(mp, fflags, curthread);
                  KASSERT_IMPLY(error == 0, vrefcnt(vp) == 1,
                      ("extra references after unmount"));
                  vput(vp);
                  if (error != 0)
                          break;
          }
          KASSERT_IMPLY((fflags & MS_FORCE) != 0, error == 0,
              ("force unmounting failed"));
          return (error);
  }
  
  int
  zfsctl_snapshot_unmount(const char *snapname, int flags __unused)
  {
          vfs_t *vfsp = NULL;
          zfsvfs_t *zfsvfs = NULL;
  
          if (strchr(snapname, '@') == NULL)
                  return (0);
  
          int err = getzfsvfs(snapname, &zfsvfs);
          if (err != 0) {
                  ASSERT3P(zfsvfs, ==, NULL);
                  return (0);
          }
          vfsp = zfsvfs->z_vfs;
  
          ASSERT(!dsl_pool_config_held(dmu_objset_pool(zfsvfs->z_os)));
  
          vfs_ref(vfsp);
          vfs_unbusy(vfsp);
          return (dounmount(vfsp, MS_FORCE, curthread));
  }

Cache object: baf6824aa79e9895b8414bbc4cfad4d5