FreeBSD/Linux Kernel Cross Reference
sys/fs/msdosfs/msdosfs_vnops.c

     /* $FreeBSD: releng/11.0/sys/fs/msdosfs/msdosfs_vnops.c 298806 2016-04-29 20:51:24Z pfg $ */
     /*      $NetBSD: msdosfs_vnops.c,v 1.68 1998/02/10 14:10:04 mrg Exp $   */
     
     /*-
      * Copyright (C) 1994, 1995, 1997 Wolfgang Solfrank.
      * Copyright (C) 1994, 1995, 1997 TooLs GmbH.
      * All rights reserved.
      * Original code by Paul Popelka (paulp@uts.amdahl.com) (see below).
      *
     * 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 TooLs GmbH.
     * 4. The name of TooLs GmbH may not be used to endorse or promote products
     *    derived from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``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 TOOLS GMBH 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.
     */
    /*-
     * Written by Paul Popelka (paulp@uts.amdahl.com)
     *
     * You can do anything you want with this software, just don't say you wrote
     * it, and don't remove this notice.
     *
     * This software is provided "as is".
     *
     * The author supplies this software to be publicly redistributed on the
     * understanding that the author is not responsible for the correct
     * functioning of this software in any circumstances and is not liable for
     * any damages caused by this software.
     *
     * October 1992
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/bio.h>
    #include <sys/buf.h>
    #include <sys/clock.h>
    #include <sys/dirent.h>
    #include <sys/lock.h>
    #include <sys/lockf.h>
    #include <sys/malloc.h>
    #include <sys/mount.h>
    #include <sys/mutex.h>
    #include <sys/namei.h>
    #include <sys/priv.h>
    #include <sys/stat.h>
    #include <sys/unistd.h>
    #include <sys/vnode.h>
    
    #include <vm/vm.h>
    #include <vm/vm_extern.h>
    
    #include <fs/msdosfs/bpb.h>
    #include <fs/msdosfs/direntry.h>
    #include <fs/msdosfs/denode.h>
    #include <fs/msdosfs/fat.h>
    #include <fs/msdosfs/msdosfsmount.h>
    
    #define DOS_FILESIZE_MAX        0xffffffff
    
    /*
     * Prototypes for MSDOSFS vnode operations
     */
    static vop_create_t     msdosfs_create;
    static vop_mknod_t      msdosfs_mknod;
    static vop_open_t       msdosfs_open;
    static vop_close_t      msdosfs_close;
    static vop_access_t     msdosfs_access;
    static vop_getattr_t    msdosfs_getattr;
    static vop_setattr_t    msdosfs_setattr;
    static vop_read_t       msdosfs_read;
    static vop_write_t      msdosfs_write;
    static vop_fsync_t      msdosfs_fsync;
    static vop_remove_t     msdosfs_remove;
    static vop_link_t       msdosfs_link;
    static vop_rename_t     msdosfs_rename;
    static vop_mkdir_t      msdosfs_mkdir;
    static vop_rmdir_t      msdosfs_rmdir;
    static vop_symlink_t    msdosfs_symlink;
    static vop_readdir_t    msdosfs_readdir;
    static vop_bmap_t       msdosfs_bmap;
   static vop_strategy_t   msdosfs_strategy;
   static vop_print_t      msdosfs_print;
   static vop_pathconf_t   msdosfs_pathconf;
   static vop_vptofh_t     msdosfs_vptofh;
   
   /*
    * Some general notes:
    *
    * In the ufs filesystem the inodes, superblocks, and indirect blocks are
    * read/written using the vnode for the filesystem. Blocks that represent
    * the contents of a file are read/written using the vnode for the file
    * (including directories when they are read/written as files). This
    * presents problems for the dos filesystem because data that should be in
    * an inode (if dos had them) resides in the directory itself.  Since we
    * must update directory entries without the benefit of having the vnode
    * for the directory we must use the vnode for the filesystem.  This means
    * that when a directory is actually read/written (via read, write, or
    * readdir, or seek) we must use the vnode for the filesystem instead of
    * the vnode for the directory as would happen in ufs. This is to insure we
    * retrieve the correct block from the buffer cache since the hash value is
    * based upon the vnode address and the desired block number.
    */
   
   /*
    * Create a regular file. On entry the directory to contain the file being
    * created is locked.  We must release before we return. We must also free
    * the pathname buffer pointed at by cnp->cn_pnbuf, always on error, or
    * only if the SAVESTART bit in cn_flags is clear on success.
    */
   static int
   msdosfs_create(struct vop_create_args *ap)
   {
           struct componentname *cnp = ap->a_cnp;
           struct denode ndirent;
           struct denode *dep;
           struct denode *pdep = VTODE(ap->a_dvp);
           struct timespec ts;
           int error;
   
   #ifdef MSDOSFS_DEBUG
           printf("msdosfs_create(cnp %p, vap %p\n", cnp, ap->a_vap);
   #endif
   
           /*
            * If this is the root directory and there is no space left we
            * can't do anything.  This is because the root directory can not
            * change size.
            */
           if (pdep->de_StartCluster == MSDOSFSROOT
               && pdep->de_fndoffset >= pdep->de_FileSize) {
                   error = ENOSPC;
                   goto bad;
           }
   
           /*
            * Create a directory entry for the file, then call createde() to
            * have it installed. NOTE: DOS files are always executable.  We
            * use the absence of the owner write bit to make the file
            * readonly.
            */
   #ifdef DIAGNOSTIC
           if ((cnp->cn_flags & HASBUF) == 0)
                   panic("msdosfs_create: no name");
   #endif
           bzero(&ndirent, sizeof(ndirent));
           error = uniqdosname(pdep, cnp, ndirent.de_Name);
           if (error)
                   goto bad;
   
           ndirent.de_Attributes = ATTR_ARCHIVE;
           ndirent.de_LowerCase = 0;
           ndirent.de_StartCluster = 0;
           ndirent.de_FileSize = 0;
           ndirent.de_pmp = pdep->de_pmp;
           ndirent.de_flag = DE_ACCESS | DE_CREATE | DE_UPDATE;
           getnanotime(&ts);
           DETIMES(&ndirent, &ts, &ts, &ts);
           error = createde(&ndirent, pdep, &dep, cnp);
           if (error)
                   goto bad;
           *ap->a_vpp = DETOV(dep);
           if ((cnp->cn_flags & MAKEENTRY) != 0)
                   cache_enter(ap->a_dvp, *ap->a_vpp, cnp);
           return (0);
   
   bad:
           return (error);
   }
   
   static int
   msdosfs_mknod(struct vop_mknod_args *ap)
   {
   
       return (EINVAL);
   }
   
   static int
   msdosfs_open(struct vop_open_args *ap)
   {
           struct denode *dep = VTODE(ap->a_vp);
           vnode_create_vobject(ap->a_vp, dep->de_FileSize, ap->a_td);
           return 0;
   }
   
   static int
   msdosfs_close(struct vop_close_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           struct denode *dep = VTODE(vp);
           struct timespec ts;
   
           VI_LOCK(vp);
           if (vp->v_usecount > 1) {
                   getnanotime(&ts);
                   DETIMES(dep, &ts, &ts, &ts);
           }
           VI_UNLOCK(vp);
           return 0;
   }
   
   static int
   msdosfs_access(struct vop_access_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           struct denode *dep = VTODE(ap->a_vp);
           struct msdosfsmount *pmp = dep->de_pmp;
           mode_t file_mode;
           accmode_t accmode = ap->a_accmode;
   
           file_mode = S_IRWXU|S_IRWXG|S_IRWXO;
           file_mode &= (vp->v_type == VDIR ? pmp->pm_dirmask : pmp->pm_mask);
   
           /*
            * Disallow writing to directories and regular files if the
            * filesystem is read-only.
            */
           if (accmode & VWRITE) {
                   switch (vp->v_type) {
                   case VREG:
                   case VDIR:
                           if (vp->v_mount->mnt_flag & MNT_RDONLY)
                                   return (EROFS);
                           break;
                   default:
                           break;
                   }
           }
   
           return (vaccess(vp->v_type, file_mode, pmp->pm_uid, pmp->pm_gid,
               ap->a_accmode, ap->a_cred, NULL));
   }
   
   static int
   msdosfs_getattr(struct vop_getattr_args *ap)
   {
           struct denode *dep = VTODE(ap->a_vp);
           struct msdosfsmount *pmp = dep->de_pmp;
           struct vattr *vap = ap->a_vap;
           mode_t mode;
           struct timespec ts;
           u_long dirsperblk = pmp->pm_BytesPerSec / sizeof(struct direntry);
           uint64_t fileid;
   
           getnanotime(&ts);
           DETIMES(dep, &ts, &ts, &ts);
           vap->va_fsid = dev2udev(pmp->pm_dev);
           /*
            * The following computation of the fileid must be the same as that
            * used in msdosfs_readdir() to compute d_fileno. If not, pwd
            * doesn't work.
            */
           if (dep->de_Attributes & ATTR_DIRECTORY) {
                   fileid = (uint64_t)cntobn(pmp, dep->de_StartCluster) *
                       dirsperblk;
                   if (dep->de_StartCluster == MSDOSFSROOT)
                           fileid = 1;
           } else {
                   fileid = (uint64_t)cntobn(pmp, dep->de_dirclust) *
                       dirsperblk;
                   if (dep->de_dirclust == MSDOSFSROOT)
                           fileid = (uint64_t)roottobn(pmp, 0) * dirsperblk;
                   fileid += (uoff_t)dep->de_diroffset / sizeof(struct direntry);
           }
   
           if (pmp->pm_flags & MSDOSFS_LARGEFS)
                   vap->va_fileid = msdosfs_fileno_map(pmp->pm_mountp, fileid);
           else
                   vap->va_fileid = (long)fileid;
   
           mode = S_IRWXU|S_IRWXG|S_IRWXO;
           vap->va_mode = mode & 
               (ap->a_vp->v_type == VDIR ? pmp->pm_dirmask : pmp->pm_mask);
           vap->va_uid = pmp->pm_uid;
           vap->va_gid = pmp->pm_gid;
           vap->va_nlink = 1;
           vap->va_rdev = NODEV;
           vap->va_size = dep->de_FileSize;
           fattime2timespec(dep->de_MDate, dep->de_MTime, 0, 0, &vap->va_mtime);
           vap->va_ctime = vap->va_mtime;
           if (pmp->pm_flags & MSDOSFSMNT_LONGNAME) {
                   fattime2timespec(dep->de_ADate, 0, 0, 0, &vap->va_atime);
                   fattime2timespec(dep->de_CDate, dep->de_CTime, dep->de_CHun,
                       0, &vap->va_birthtime);
           } else {
                   vap->va_atime = vap->va_mtime;
                   vap->va_birthtime.tv_sec = -1;
                   vap->va_birthtime.tv_nsec = 0;
           }
           vap->va_flags = 0;
           if (dep->de_Attributes & ATTR_ARCHIVE)
                   vap->va_flags |= UF_ARCHIVE;
           if (dep->de_Attributes & ATTR_HIDDEN)
                   vap->va_flags |= UF_HIDDEN;
           if (dep->de_Attributes & ATTR_READONLY)
                   vap->va_flags |= UF_READONLY;
           if (dep->de_Attributes & ATTR_SYSTEM)
                   vap->va_flags |= UF_SYSTEM;
           vap->va_gen = 0;
           vap->va_blocksize = pmp->pm_bpcluster;
           vap->va_bytes =
               (dep->de_FileSize + pmp->pm_crbomask) & ~pmp->pm_crbomask;
           vap->va_type = ap->a_vp->v_type;
           vap->va_filerev = dep->de_modrev;
           return (0);
   }
   
   static int
   msdosfs_setattr(struct vop_setattr_args *ap)
   {
           struct vnode *vp = ap->a_vp;
           struct denode *dep = VTODE(ap->a_vp);
           struct msdosfsmount *pmp = dep->de_pmp;
           struct vattr *vap = ap->a_vap;
           struct ucred *cred = ap->a_cred;
           struct thread *td = curthread;
           int error = 0;
   
   #ifdef MSDOSFS_DEBUG
           printf("msdosfs_setattr(): vp %p, vap %p, cred %p\n",
               ap->a_vp, vap, cred);
   #endif
   
           /*
            * Check for unsettable attributes.
            */
           if ((vap->va_type != VNON) || (vap->va_nlink != VNOVAL) ||
               (vap->va_fsid != VNOVAL) || (vap->va_fileid != VNOVAL) ||
               (vap->va_blocksize != VNOVAL) || (vap->va_rdev != VNOVAL) ||
               (vap->va_bytes != VNOVAL) || (vap->va_gen != VNOVAL)) {
   #ifdef MSDOSFS_DEBUG
                   printf("msdosfs_setattr(): returning EINVAL\n");
                   printf("    va_type %d, va_nlink %x, va_fsid %lx, va_fileid %lx\n",
                       vap->va_type, vap->va_nlink, vap->va_fsid, vap->va_fileid);
                   printf("    va_blocksize %lx, va_rdev %x, va_bytes %qx, va_gen %lx\n",
                       vap->va_blocksize, vap->va_rdev, vap->va_bytes, vap->va_gen);
                   printf("    va_uid %x, va_gid %x\n",
                       vap->va_uid, vap->va_gid);
   #endif
                   return (EINVAL);
           }
   
           /*
            * We don't allow setting attributes on the root directory.
            * The special case for the root directory is because before
            * FAT32, the root directory didn't have an entry for itself
            * (and was otherwise special).  With FAT32, the root
            * directory is not so special, but still doesn't have an
            * entry for itself.
            */
           if (vp->v_vflag & VV_ROOT)
                   return (EINVAL);
   
           if (vap->va_flags != VNOVAL) {
                   if (vp->v_mount->mnt_flag & MNT_RDONLY)
                           return (EROFS);
                   if (cred->cr_uid != pmp->pm_uid) {
                           error = priv_check_cred(cred, PRIV_VFS_ADMIN, 0);
                           if (error)
                                   return (error);
                   }
                   /*
                    * We are very inconsistent about handling unsupported
                    * attributes.  We ignored the access time and the
                    * read and execute bits.  We were strict for the other
                    * attributes.
                    */
                   if (vap->va_flags & ~(UF_ARCHIVE | UF_HIDDEN | UF_READONLY |
                       UF_SYSTEM))
                           return EOPNOTSUPP;
                   if (vap->va_flags & UF_ARCHIVE)
                           dep->de_Attributes |= ATTR_ARCHIVE;
                   else
                           dep->de_Attributes &= ~ATTR_ARCHIVE;
                   if (vap->va_flags & UF_HIDDEN)
                           dep->de_Attributes |= ATTR_HIDDEN;
                   else
                           dep->de_Attributes &= ~ATTR_HIDDEN;
                   /* We don't allow changing the readonly bit on directories. */
                   if (vp->v_type != VDIR) {
                           if (vap->va_flags & UF_READONLY)
                                   dep->de_Attributes |= ATTR_READONLY;
                           else
                                   dep->de_Attributes &= ~ATTR_READONLY;
                   }
                   if (vap->va_flags & UF_SYSTEM)
                           dep->de_Attributes |= ATTR_SYSTEM;
                   else
                           dep->de_Attributes &= ~ATTR_SYSTEM;
                   dep->de_flag |= DE_MODIFIED;
           }
   
           if (vap->va_uid != (uid_t)VNOVAL || vap->va_gid != (gid_t)VNOVAL) {
                   uid_t uid;
                   gid_t gid;
   
                   if (vp->v_mount->mnt_flag & MNT_RDONLY)
                           return (EROFS);
                   uid = vap->va_uid;
                   if (uid == (uid_t)VNOVAL)
                           uid = pmp->pm_uid;
                   gid = vap->va_gid;
                   if (gid == (gid_t)VNOVAL)
                           gid = pmp->pm_gid;
                   if (cred->cr_uid != pmp->pm_uid || uid != pmp->pm_uid ||
                       (gid != pmp->pm_gid && !groupmember(gid, cred))) {
                           error = priv_check_cred(cred, PRIV_VFS_CHOWN, 0);
                           if (error)
                                   return (error);
                   }
                   if (uid != pmp->pm_uid || gid != pmp->pm_gid)
                           return EINVAL;
           }
   
           if (vap->va_size != VNOVAL) {
                   switch (vp->v_type) {
                   case VDIR:
                           return (EISDIR);
                   case VREG:
                           /*
                            * Truncation is only supported for regular files,
                            * Disallow it if the filesystem is read-only.
                            */
                           if (vp->v_mount->mnt_flag & MNT_RDONLY)
                                   return (EROFS);
                           break;
                   default:
                           /*
                            * According to POSIX, the result is unspecified
                            * for file types other than regular files,
                            * directories and shared memory objects.  We
                            * don't support any file types except regular
                            * files and directories in this file system, so
                            * this (default) case is unreachable and can do
                            * anything.  Keep falling through to detrunc()
                            * for now.
                            */
                           break;
                   }
                   error = detrunc(dep, vap->va_size, 0, cred);
                   if (error)
                           return error;
           }
           if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
                   if (vp->v_mount->mnt_flag & MNT_RDONLY)
                           return (EROFS);
                   error = vn_utimes_perm(vp, vap, cred, td);
                   if (error != 0)
                           return (error);
                   if ((pmp->pm_flags & MSDOSFSMNT_NOWIN95) == 0 &&
                       vap->va_atime.tv_sec != VNOVAL) {
                           dep->de_flag &= ~DE_ACCESS;
                           timespec2fattime(&vap->va_atime, 0,
                               &dep->de_ADate, NULL, NULL);
                   }
                   if (vap->va_mtime.tv_sec != VNOVAL) {
                           dep->de_flag &= ~DE_UPDATE;
                           timespec2fattime(&vap->va_mtime, 0,
                               &dep->de_MDate, &dep->de_MTime, NULL);
                   }
                   /*
                    * We don't set the archive bit when modifying the time of
                    * a directory to emulate the Windows/DOS behavior.
                    */
                   if (vp->v_type != VDIR)
                           dep->de_Attributes |= ATTR_ARCHIVE;
                   dep->de_flag |= DE_MODIFIED;
           }
           /*
            * DOS files only have the ability to have their writability
            * attribute set, so we use the owner write bit to set the readonly
            * attribute.
            */
           if (vap->va_mode != (mode_t)VNOVAL) {
                   if (vp->v_mount->mnt_flag & MNT_RDONLY)
                           return (EROFS);
                   if (cred->cr_uid != pmp->pm_uid) {
                           error = priv_check_cred(cred, PRIV_VFS_ADMIN, 0);
                           if (error)
                                   return (error);
                   }
                   if (vp->v_type != VDIR) {
                           /* We ignore the read and execute bits. */
                           if (vap->va_mode & VWRITE)
                                   dep->de_Attributes &= ~ATTR_READONLY;
                           else
                                   dep->de_Attributes |= ATTR_READONLY;
                           dep->de_Attributes |= ATTR_ARCHIVE;
                           dep->de_flag |= DE_MODIFIED;
                   }
           }
           return (deupdat(dep, 0));
   }
   
   static int
   msdosfs_read(struct vop_read_args *ap)
   {
           int error = 0;
           int blsize;
           int isadir;
           ssize_t orig_resid;
           u_int n;
           u_long diff;
           u_long on;
           daddr_t lbn;
           daddr_t rablock;
           int rasize;
           int seqcount;
           struct buf *bp;
           struct vnode *vp = ap->a_vp;
           struct denode *dep = VTODE(vp);
           struct msdosfsmount *pmp = dep->de_pmp;
           struct uio *uio = ap->a_uio;
   
           /*
            * If they didn't ask for any data, then we are done.
            */
           orig_resid = uio->uio_resid;
           if (orig_resid == 0)
                   return (0);
   
           /*
            * The caller is supposed to ensure that
            * uio->uio_offset >= 0 and uio->uio_resid >= 0.
            * We don't need to check for large offsets as in ffs because
            * dep->de_FileSize <= DOS_FILESIZE_MAX < OFF_MAX, so large
            * offsets cannot cause overflow even in theory.
            */
   
           seqcount = ap->a_ioflag >> IO_SEQSHIFT;
   
           isadir = dep->de_Attributes & ATTR_DIRECTORY;
           do {
                   if (uio->uio_offset >= dep->de_FileSize)
                           break;
                   lbn = de_cluster(pmp, uio->uio_offset);
                   rablock = lbn + 1;
                   blsize = pmp->pm_bpcluster;
                   on = uio->uio_offset & pmp->pm_crbomask;
                   /*
                    * If we are operating on a directory file then be sure to
                    * do i/o with the vnode for the filesystem instead of the
                    * vnode for the directory.
                    */
                   if (isadir) {
                           /* convert cluster # to block # */
                           error = pcbmap(dep, lbn, &lbn, 0, &blsize);
                           if (error == E2BIG) {
                                   error = EINVAL;
                                   break;
                           } else if (error)
                                   break;
                           error = bread(pmp->pm_devvp, lbn, blsize, NOCRED, &bp);
                   } else if (de_cn2off(pmp, rablock) >= dep->de_FileSize) {
                           error = bread(vp, lbn, blsize, NOCRED, &bp);
                   } else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
                           error = cluster_read(vp, dep->de_FileSize, lbn, blsize,
                               NOCRED, on + uio->uio_resid, seqcount, 0, &bp);
                   } else if (seqcount > 1) {
                           rasize = blsize;
                           error = breadn(vp, lbn,
                               blsize, &rablock, &rasize, 1, NOCRED, &bp);
                   } else {
                           error = bread(vp, lbn, blsize, NOCRED, &bp);
                   }
                   if (error) {
                           brelse(bp);
                           break;
                   }
                   diff = pmp->pm_bpcluster - on;
                   n = diff > uio->uio_resid ? uio->uio_resid : diff;
                   diff = dep->de_FileSize - uio->uio_offset;
                   if (diff < n)
                           n = diff;
                   diff = blsize - bp->b_resid;
                   if (diff < n)
                           n = diff;
                   error = uiomove(bp->b_data + on, (int) n, uio);
                   brelse(bp);
           } while (error == 0 && uio->uio_resid > 0 && n != 0);
           if (!isadir && (error == 0 || uio->uio_resid != orig_resid) &&
               (vp->v_mount->mnt_flag & (MNT_NOATIME | MNT_RDONLY)) == 0)
                   dep->de_flag |= DE_ACCESS;
           return (error);
   }
   
   /*
    * Write data to a file or directory.
    */
   static int
   msdosfs_write(struct vop_write_args *ap)
   {
           int n;
           int croffset;
           ssize_t resid;
           u_long osize;
           int error = 0;
           u_long count;
           int seqcount;
           daddr_t bn, lastcn;
           struct buf *bp;
           int ioflag = ap->a_ioflag;
           struct uio *uio = ap->a_uio;
           struct vnode *vp = ap->a_vp;
           struct vnode *thisvp;
           struct denode *dep = VTODE(vp);
           struct msdosfsmount *pmp = dep->de_pmp;
           struct ucred *cred = ap->a_cred;
   
   #ifdef MSDOSFS_DEBUG
           printf("msdosfs_write(vp %p, uio %p, ioflag %x, cred %p\n",
               vp, uio, ioflag, cred);
           printf("msdosfs_write(): diroff %lu, dirclust %lu, startcluster %lu\n",
               dep->de_diroffset, dep->de_dirclust, dep->de_StartCluster);
   #endif
   
           switch (vp->v_type) {
           case VREG:
                   if (ioflag & IO_APPEND)
                           uio->uio_offset = dep->de_FileSize;
                   thisvp = vp;
                   break;
           case VDIR:
                   return EISDIR;
           default:
                   panic("msdosfs_write(): bad file type");
           }
   
           /*
            * This is needed (unlike in ffs_write()) because we extend the
            * file outside of the loop but we don't want to extend the file
            * for writes of 0 bytes.
            */
           if (uio->uio_resid == 0)
                   return (0);
   
           /*
            * The caller is supposed to ensure that
            * uio->uio_offset >= 0 and uio->uio_resid >= 0.
            */
           if ((uoff_t)uio->uio_offset + uio->uio_resid > DOS_FILESIZE_MAX)
                   return (EFBIG);
   
           /*
            * If they've exceeded their filesize limit, tell them about it.
            */
           if (vn_rlimit_fsize(vp, uio, uio->uio_td))
                   return (EFBIG);
   
           /*
            * If the offset we are starting the write at is beyond the end of
            * the file, then they've done a seek.  Unix filesystems allow
            * files with holes in them, DOS doesn't so we must fill the hole
            * with zeroed blocks.
            */
           if (uio->uio_offset > dep->de_FileSize) {
                   error = deextend(dep, uio->uio_offset, cred);
                   if (error)
                           return (error);
           }
   
           /*
            * Remember some values in case the write fails.
            */
           resid = uio->uio_resid;
           osize = dep->de_FileSize;
   
           /*
            * If we write beyond the end of the file, extend it to its ultimate
            * size ahead of the time to hopefully get a contiguous area.
            */
           if (uio->uio_offset + resid > osize) {
                   count = de_clcount(pmp, uio->uio_offset + resid) -
                           de_clcount(pmp, osize);
                   error = extendfile(dep, count, NULL, NULL, 0);
                   if (error &&  (error != ENOSPC || (ioflag & IO_UNIT)))
                           goto errexit;
                   lastcn = dep->de_fc[FC_LASTFC].fc_frcn;
           } else
                   lastcn = de_clcount(pmp, osize) - 1;
   
           seqcount = ioflag >> IO_SEQSHIFT;
           do {
                   if (de_cluster(pmp, uio->uio_offset) > lastcn) {
                           error = ENOSPC;
                           break;
                   }
   
                   croffset = uio->uio_offset & pmp->pm_crbomask;
                   n = min(uio->uio_resid, pmp->pm_bpcluster - croffset);
                   if (uio->uio_offset + n > dep->de_FileSize) {
                           dep->de_FileSize = uio->uio_offset + n;
                           /* The object size needs to be set before buffer is allocated */
                           vnode_pager_setsize(vp, dep->de_FileSize);
                   }
   
                   bn = de_cluster(pmp, uio->uio_offset);
                   if ((uio->uio_offset & pmp->pm_crbomask) == 0
                       && (de_cluster(pmp, uio->uio_offset + uio->uio_resid)
                           > de_cluster(pmp, uio->uio_offset)
                           || uio->uio_offset + uio->uio_resid >= dep->de_FileSize)) {
                           /*
                            * If either the whole cluster gets written,
                            * or we write the cluster from its start beyond EOF,
                            * then no need to read data from disk.
                            */
                           bp = getblk(thisvp, bn, pmp->pm_bpcluster, 0, 0, 0);
                           vfs_bio_clrbuf(bp);
                           /*
                            * Do the bmap now, since pcbmap needs buffers
                            * for the fat table. (see msdosfs_strategy)
                            */
                           if (bp->b_blkno == bp->b_lblkno) {
                                   error = pcbmap(dep, bp->b_lblkno, &bn, 0, 0);
                                   if (error)
                                           bp->b_blkno = -1;
                                   else
                                           bp->b_blkno = bn;
                           }
                           if (bp->b_blkno == -1) {
                                   brelse(bp);
                                   if (!error)
                                           error = EIO;            /* XXX */
                                   break;
                           }
                   } else {
                           /*
                            * The block we need to write into exists, so read it in.
                            */
                           error = bread(thisvp, bn, pmp->pm_bpcluster, cred, &bp);
                           if (error) {
                                   brelse(bp);
                                   break;
                           }
                   }
   
                   /*
                    * Should these vnode_pager_* functions be done on dir
                    * files?
                    */
   
                   /*
                    * Copy the data from user space into the buf header.
                    */
                   error = uiomove(bp->b_data + croffset, n, uio);
                   if (error) {
                           brelse(bp);
                           break;
                   }
   
                   /* Prepare for clustered writes in some else clauses. */
                   if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0)
                           bp->b_flags |= B_CLUSTEROK;
   
                   /*
                    * If IO_SYNC, then each buffer is written synchronously.
                    * Otherwise, if we have a severe page deficiency then
                    * write the buffer asynchronously.  Otherwise, if on a
                    * cluster boundary then write the buffer asynchronously,
                    * combining it with contiguous clusters if permitted and
                    * possible, since we don't expect more writes into this
                    * buffer soon.  Otherwise, do a delayed write because we
                    * expect more writes into this buffer soon.
                    */
                   if (ioflag & IO_SYNC)
                           (void)bwrite(bp);
                   else if (vm_page_count_severe() || buf_dirty_count_severe())
                           bawrite(bp);
                   else if (n + croffset == pmp->pm_bpcluster) {
                           if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0)
                                   cluster_write(vp, bp, dep->de_FileSize,
                                       seqcount, 0);
                           else
                                   bawrite(bp);
                   } else
                           bdwrite(bp);
                   dep->de_flag |= DE_UPDATE;
           } while (error == 0 && uio->uio_resid > 0);
   
           /*
            * If the write failed and they want us to, truncate the file back
            * to the size it was before the write was attempted.
            */
   errexit:
           if (error) {
                   if (ioflag & IO_UNIT) {
                           detrunc(dep, osize, ioflag & IO_SYNC, NOCRED);
                           uio->uio_offset -= resid - uio->uio_resid;
                           uio->uio_resid = resid;
                   } else {
                           detrunc(dep, dep->de_FileSize, ioflag & IO_SYNC, NOCRED);
                           if (uio->uio_resid != resid)
                                   error = 0;
                   }
           } else if (ioflag & IO_SYNC)
                   error = deupdat(dep, 1);
           return (error);
   }
   
   /*
    * Flush the blocks of a file to disk.
    */
   static int
   msdosfs_fsync(struct vop_fsync_args *ap)
   {
           struct vnode *devvp;
           int allerror, error;
   
           vop_stdfsync(ap);
   
           /*
           * If the syncing request comes from fsync(2), sync the entire
           * FAT and any other metadata that happens to be on devvp.  We
           * need this mainly for the FAT.  We write the FAT sloppily, and
           * syncing it all now is the best we can easily do to get all
           * directory entries associated with the file (not just the file)
           * fully synced.  The other metadata includes critical metadata
           * for all directory entries, but only in the MNT_ASYNC case.  We
           * will soon sync all metadata in the file's directory entry.
           * Non-critical metadata for associated directory entries only
           * gets synced accidentally, as in most file systems.
           */
           if (ap->a_waitfor == MNT_WAIT) {
                   devvp = VTODE(ap->a_vp)->de_pmp->pm_devvp;
                   vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
                   allerror = VOP_FSYNC(devvp, MNT_WAIT, ap->a_td);
                   VOP_UNLOCK(devvp, 0);
           } else
                   allerror = 0;
   
           error = deupdat(VTODE(ap->a_vp), ap->a_waitfor == MNT_WAIT);
           if (allerror == 0)
                   allerror = error;
           return (allerror);
   }
   
   static int
   msdosfs_remove(struct vop_remove_args *ap)
   {
           struct denode *dep = VTODE(ap->a_vp);
           struct denode *ddep = VTODE(ap->a_dvp);
           int error;
   
           if (ap->a_vp->v_type == VDIR)
                   error = EPERM;
           else
                   error = removede(ddep, dep);
   #ifdef MSDOSFS_DEBUG
           printf("msdosfs_remove(), dep %p, v_usecount %d\n", dep, ap->a_vp->v_usecount);
   #endif
           return (error);
   }
   
   /*
    * DOS filesystems don't know what links are.
    */
   static int
   msdosfs_link(struct vop_link_args *ap)
   {
           return (EOPNOTSUPP);
   }
   
   /*
    * Renames on files require moving the denode to a new hash queue since the
    * denode's location is used to compute which hash queue to put the file
    * in. Unless it is a rename in place.  For example "mv a b".
    *
    * What follows is the basic algorithm:
    *
    * if (file move) {
    *      if (dest file exists) {
    *              remove dest file
    *      }
    *      if (dest and src in same directory) {
    *              rewrite name in existing directory slot
    *      } else {
    *              write new entry in dest directory
    *              update offset and dirclust in denode
    *              move denode to new hash chain
    *              clear old directory entry
    *      }
    * } else {
    *      directory move
    *      if (dest directory exists) {
    *              if (dest is not empty) {
    *                      return ENOTEMPTY
    *              }
    *              remove dest directory
    *      }
    *      if (dest and src in same directory) {
    *              rewrite name in existing entry
    *      } else {
    *              be sure dest is not a child of src directory
    *              write entry in dest directory
    *              update "." and ".." in moved directory
    *              clear old directory entry for moved directory
    *      }
    * }
    *
    * On entry:
    *      source's parent directory is unlocked
    *      source file or directory is unlocked
    *      destination's parent directory is locked
    *      destination file or directory is locked if it exists
    *
    * On exit:
    *      all denodes should be released
    */
   static int
   msdosfs_rename(struct vop_rename_args *ap)
   {
           struct vnode *tdvp = ap->a_tdvp;
           struct vnode *fvp = ap->a_fvp;
           struct vnode *fdvp = ap->a_fdvp;
           struct vnode *tvp = ap->a_tvp;
           struct componentname *tcnp = ap->a_tcnp;
           struct componentname *fcnp = ap->a_fcnp;
           struct denode *ip, *xp, *dp, *zp;
           u_char toname[12], oldname[11];
           u_long from_diroffset, to_diroffset;
           u_char to_count;
           int doingdirectory = 0, newparent = 0;
           int error;
           u_long cn, pcl;
           daddr_t bn;
           struct msdosfsmount *pmp;
           struct direntry *dotdotp;
           struct buf *bp;
   
           pmp = VFSTOMSDOSFS(fdvp->v_mount);
   
   #ifdef DIAGNOSTIC
           if ((tcnp->cn_flags & HASBUF) == 0 ||
               (fcnp->cn_flags & HASBUF) == 0)
                   panic("msdosfs_rename: no name");
   #endif
           /*
            * Check for cross-device rename.
            */
           if (fvp->v_mount != tdvp->v_mount ||
               (tvp && fvp->v_mount != tvp->v_mount)) {
                   error = EXDEV;
   abortit:
                   if (tdvp == tvp)
                           vrele(tdvp);
                   else
                           vput(tdvp);
                   if (tvp)
                           vput(tvp);
                   vrele(fdvp);
                   vrele(fvp);
                   return (error);
           }
   
           /*
            * If source and dest are the same, do nothing.
            */
           if (tvp == fvp) {
                   error = 0;
                   goto abortit;
           }
   
           error = vn_lock(fvp, LK_EXCLUSIVE);
           if (error)
                   goto abortit;
           dp = VTODE(fdvp);
           ip = VTODE(fvp);
   
           /*
            * Be sure we are not renaming ".", "..", or an alias of ".". This
            * leads to a crippled directory tree.  It's pretty tough to do a
            * "ls" or "pwd" with the "." directory entry missing, and "cd .."
            * doesn't work if the ".." entry is missing.
            */
           if (ip->de_Attributes & ATTR_DIRECTORY) {
                   /*
                    * Avoid ".", "..", and aliases of "." for obvious reasons.
                    */
                   if ((fcnp->cn_namelen == 1 && fcnp->cn_nameptr[0] == '.') ||
                       dp == ip ||
                       (fcnp->cn_flags & ISDOTDOT) ||
                      (tcnp->cn_flags & ISDOTDOT) ||
                      (ip->de_flag & DE_RENAME)) {
                          VOP_UNLOCK(fvp, 0);
                          error = EINVAL;
                          goto abortit;
                  }
                  ip->de_flag |= DE_RENAME;
                  doingdirectory++;
          }
  
          /*
           * When the target exists, both the directory
           * and target vnodes are returned locked.
           */
          dp = VTODE(tdvp);
          xp = tvp ? VTODE(tvp) : NULL;
          /*
           * Remember direntry place to use for destination
           */
          to_diroffset = dp->de_fndoffset;
          to_count = dp->de_fndcnt;
  
          /*
           * If ".." must be changed (ie the directory gets a new
           * parent) then the source directory must not be in the
           * directory hierarchy above the target, as this would
           * orphan everything below the source directory. Also
           * the user must have write permission in the source so
           * as to be able to change "..". We must repeat the call
           * to namei, as the parent directory is unlocked by the
           * call to doscheckpath().
           */
          error = VOP_ACCESS(fvp, VWRITE, tcnp->cn_cred, tcnp->cn_thread);
          VOP_UNLOCK(fvp, 0);
          if (VTODE(fdvp)->de_StartCluster != VTODE(tdvp)->de_StartCluster)
                  newparent = 1;
          if (doingdirectory && newparent) {
                  if (error)      /* write access check above */
                          goto bad;
                  if (xp != NULL)
                          vput(tvp);
                  /*
                   * doscheckpath() vput()'s dp,
                   * so we have to do a relookup afterwards
                   */
                  error = doscheckpath(ip, dp);
                  if (error)
                          goto out;
                  if ((tcnp->cn_flags & SAVESTART) == 0)
                          panic("msdosfs_rename: lost to startdir");
                  error = relookup(tdvp, &tvp, tcnp);
                  if (error)
                          goto out;
                  dp = VTODE(tdvp);
                  xp = tvp ? VTODE(tvp) : NULL;
          }
  
          if (xp != NULL) {
                  /*
                   * Target must be empty if a directory and have no links
                   * to it. Also, ensure source and target are compatible
                   * (both directories, or both not directories).
                   */
                  if (xp->de_Attributes & ATTR_DIRECTORY) {
                          if (!dosdirempty(xp)) {
                                  error = ENOTEMPTY;
                                  goto bad;
                          }
                          if (!doingdirectory) {
                                  error = ENOTDIR;
                                  goto bad;
                          }
                          cache_purge(tdvp);
                  } else if (doingdirectory) {
                          error = EISDIR;
                          goto bad;
                  }
                  error = removede(dp, xp);
                  if (error)
                          goto bad;
                  vput(tvp);
                  xp = NULL;
          }
  
          /*
           * Convert the filename in tcnp into a dos filename. We copy this
           * into the denode and directory entry for the destination
           * file/directory.
           */
          error = uniqdosname(VTODE(tdvp), tcnp, toname);
          if (error)
                  goto abortit;
  
          /*
           * Since from wasn't locked at various places above,
           * have to do a relookup here.
           */
          fcnp->cn_flags &= ~MODMASK;
          fcnp->cn_flags |= LOCKPARENT | LOCKLEAF;
          if ((fcnp->cn_flags & SAVESTART) == 0)
                  panic("msdosfs_rename: lost from startdir");
          if (!newparent)
                  VOP_UNLOCK(tdvp, 0);
          if (relookup(fdvp, &fvp, fcnp) == 0)
                  vrele(fdvp);
          if (fvp == NULL) {
                  /*
                   * From name has disappeared.
                   */
                  if (doingdirectory)
                          panic("rename: lost dir entry");
                  if (newparent)
                          VOP_UNLOCK(tdvp, 0);
                  vrele(tdvp);
                  vrele(ap->a_fvp);
                  return 0;
          }
          xp = VTODE(fvp);
          zp = VTODE(fdvp);
          from_diroffset = zp->de_fndoffset;
  
          /*
           * Ensure that the directory entry still exists and has not
           * changed till now. If the source is a file the entry may
           * have been unlinked or renamed. In either case there is
           * no further work to be done. If the source is a directory
           * then it cannot have been rmdir'ed or renamed; this is
           * prohibited by the DE_RENAME flag.
           */
          if (xp != ip) {
                  if (doingdirectory)
                          panic("rename: lost dir entry");
                  VOP_UNLOCK(fvp, 0);
                  if (newparent)
                          VOP_UNLOCK(fdvp, 0);
                  vrele(ap->a_fvp);
                  xp = NULL;
          } else {
                  vrele(fvp);
                  xp = NULL;
  
                  /*
                   * First write a new entry in the destination
                   * directory and mark the entry in the source directory
                   * as deleted.  Then move the denode to the correct hash
                   * chain for its new location in the filesystem.  And, if
                   * we moved a directory, then update its .. entry to point
                   * to the new parent directory.
                   */
                  bcopy(ip->de_Name, oldname, 11);
                  bcopy(toname, ip->de_Name, 11); /* update denode */
                  dp->de_fndoffset = to_diroffset;
                  dp->de_fndcnt = to_count;
                  error = createde(ip, dp, (struct denode **)0, tcnp);
                  if (error) {
                          bcopy(oldname, ip->de_Name, 11);
                          if (newparent)
                                  VOP_UNLOCK(fdvp, 0);
                          VOP_UNLOCK(fvp, 0);
                          goto bad;
                  }
                  /*
                   * If ip is for a directory, then its name should always
                   * be "." since it is for the directory entry in the
                   * directory itself (msdosfs_lookup() always translates
                   * to the "." entry so as to get a unique denode, except
                   * for the root directory there are different
                   * complications).  However, we just corrupted its name
                   * to pass the correct name to createde().  Undo this.
                   */
                  if ((ip->de_Attributes & ATTR_DIRECTORY) != 0)
                          bcopy(oldname, ip->de_Name, 11);
                  ip->de_refcnt++;
                  zp->de_fndoffset = from_diroffset;
                  error = removede(zp, ip);
                  if (error) {
                          /* XXX should downgrade to ro here, fs is corrupt */
                          if (newparent)
                                  VOP_UNLOCK(fdvp, 0);
                          VOP_UNLOCK(fvp, 0);
                          goto bad;
                  }
                  if (!doingdirectory) {
                          error = pcbmap(dp, de_cluster(pmp, to_diroffset), 0,
                                         &ip->de_dirclust, 0);
                          if (error) {
                                  /* XXX should downgrade to ro here, fs is corrupt */
                                  if (newparent)
                                          VOP_UNLOCK(fdvp, 0);
                                  VOP_UNLOCK(fvp, 0);
                                  goto bad;
                          }
                          if (ip->de_dirclust == MSDOSFSROOT)
                                  ip->de_diroffset = to_diroffset;
                          else
                                  ip->de_diroffset = to_diroffset & pmp->pm_crbomask;
                  }
                  reinsert(ip);
                  if (newparent)
                          VOP_UNLOCK(fdvp, 0);
          }
  
          /*
           * If we moved a directory to a new parent directory, then we must
           * fixup the ".." entry in the moved directory.
           */
          if (doingdirectory && newparent) {
                  cn = ip->de_StartCluster;
                  if (cn == MSDOSFSROOT) {
                          /* this should never happen */
                          panic("msdosfs_rename(): updating .. in root directory?");
                  } else
                          bn = cntobn(pmp, cn);
                  error = bread(pmp->pm_devvp, bn, pmp->pm_bpcluster,
                                NOCRED, &bp);
                  if (error) {
                          /* XXX should downgrade to ro here, fs is corrupt */
                          brelse(bp);
                          VOP_UNLOCK(fvp, 0);
                          goto bad;
                  }
                  dotdotp = (struct direntry *)bp->b_data + 1;
                  pcl = dp->de_StartCluster;
                  if (FAT32(pmp) && pcl == pmp->pm_rootdirblk)
                          pcl = MSDOSFSROOT;
                  putushort(dotdotp->deStartCluster, pcl);
                  if (FAT32(pmp))
                          putushort(dotdotp->deHighClust, pcl >> 16);
                  if (DOINGASYNC(fvp))
                          bdwrite(bp);
                  else if ((error = bwrite(bp)) != 0) {
                          /* XXX should downgrade to ro here, fs is corrupt */
                          VOP_UNLOCK(fvp, 0);
                          goto bad;
                  }
          }
  
          /*
           * The msdosfs lookup is case insensitive. Several aliases may
           * be inserted for a single directory entry. As a consequnce,
           * name cache purge done by lookup for fvp when DELETE op for
           * namei is specified, might be not enough to expunge all
           * namecache entries that were installed for this direntry.
           */
          cache_purge(fvp);
          VOP_UNLOCK(fvp, 0);
  bad:
          if (xp)
                  vput(tvp);
          vput(tdvp);
  out:
          ip->de_flag &= ~DE_RENAME;
          vrele(fdvp);
          vrele(fvp);
          return (error);
  
  }
  
  static struct {
          struct direntry dot;
          struct direntry dotdot;
  } dosdirtemplate = {
          {       ".          ",                          /* the . entry */
                  ATTR_DIRECTORY,                         /* file attribute */
                  0,                                      /* reserved */
                  0, { 0, 0 }, { 0, 0 },                  /* create time & date */
                  { 0, 0 },                               /* access date */
                  { 0, 0 },                               /* high bits of start cluster */
                  { 210, 4 }, { 210, 4 },                 /* modify time & date */
                  { 0, 0 },                               /* startcluster */
                  { 0, 0, 0, 0 }                          /* filesize */
          },
          {       "..         ",                          /* the .. entry */
                  ATTR_DIRECTORY,                         /* file attribute */
                  0,                                      /* reserved */
                  0, { 0, 0 }, { 0, 0 },                  /* create time & date */
                  { 0, 0 },                               /* access date */
                  { 0, 0 },                               /* high bits of start cluster */
                  { 210, 4 }, { 210, 4 },                 /* modify time & date */
                  { 0, 0 },                               /* startcluster */
                  { 0, 0, 0, 0 }                          /* filesize */
          }
  };
  
  static int
  msdosfs_mkdir(struct vop_mkdir_args *ap)
  {
          struct componentname *cnp = ap->a_cnp;
          struct denode *dep;
          struct denode *pdep = VTODE(ap->a_dvp);
          struct direntry *denp;
          struct msdosfsmount *pmp = pdep->de_pmp;
          struct buf *bp;
          u_long newcluster, pcl;
          int bn;
          int error;
          struct denode ndirent;
          struct timespec ts;
  
          /*
           * If this is the root directory and there is no space left we
           * can't do anything.  This is because the root directory can not
           * change size.
           */
          if (pdep->de_StartCluster == MSDOSFSROOT
              && pdep->de_fndoffset >= pdep->de_FileSize) {
                  error = ENOSPC;
                  goto bad2;
          }
  
          /*
           * Allocate a cluster to hold the about to be created directory.
           */
          error = clusteralloc(pmp, 0, 1, CLUST_EOFE, &newcluster, NULL);
          if (error)
                  goto bad2;
  
          bzero(&ndirent, sizeof(ndirent));
          ndirent.de_pmp = pmp;
          ndirent.de_flag = DE_ACCESS | DE_CREATE | DE_UPDATE;
          getnanotime(&ts);
          DETIMES(&ndirent, &ts, &ts, &ts);
  
          /*
           * Now fill the cluster with the "." and ".." entries. And write
           * the cluster to disk.  This way it is there for the parent
           * directory to be pointing at if there were a crash.
           */
          bn = cntobn(pmp, newcluster);
          /* always succeeds */
          bp = getblk(pmp->pm_devvp, bn, pmp->pm_bpcluster, 0, 0, 0);
          bzero(bp->b_data, pmp->pm_bpcluster);
          bcopy(&dosdirtemplate, bp->b_data, sizeof dosdirtemplate);
          denp = (struct direntry *)bp->b_data;
          putushort(denp[0].deStartCluster, newcluster);
          putushort(denp[0].deCDate, ndirent.de_CDate);
          putushort(denp[0].deCTime, ndirent.de_CTime);
          denp[0].deCHundredth = ndirent.de_CHun;
          putushort(denp[0].deADate, ndirent.de_ADate);
          putushort(denp[0].deMDate, ndirent.de_MDate);
          putushort(denp[0].deMTime, ndirent.de_MTime);
          pcl = pdep->de_StartCluster;
          /*
           * Although the root directory has a non-magic starting cluster
           * number for FAT32, chkdsk and fsck_msdosfs still require
           * references to it in dotdot entries to be magic.
           */
          if (FAT32(pmp) && pcl == pmp->pm_rootdirblk)
                  pcl = MSDOSFSROOT;
          putushort(denp[1].deStartCluster, pcl);
          putushort(denp[1].deCDate, ndirent.de_CDate);
          putushort(denp[1].deCTime, ndirent.de_CTime);
          denp[1].deCHundredth = ndirent.de_CHun;
          putushort(denp[1].deADate, ndirent.de_ADate);
          putushort(denp[1].deMDate, ndirent.de_MDate);
          putushort(denp[1].deMTime, ndirent.de_MTime);
          if (FAT32(pmp)) {
                  putushort(denp[0].deHighClust, newcluster >> 16);
                  putushort(denp[1].deHighClust, pcl >> 16);
          }
  
          if (DOINGASYNC(ap->a_dvp))
                  bdwrite(bp);
          else if ((error = bwrite(bp)) != 0)
                  goto bad;
  
          /*
           * Now build up a directory entry pointing to the newly allocated
           * cluster.  This will be written to an empty slot in the parent
           * directory.
           */
  #ifdef DIAGNOSTIC
          if ((cnp->cn_flags & HASBUF) == 0)
                  panic("msdosfs_mkdir: no name");
  #endif
          error = uniqdosname(pdep, cnp, ndirent.de_Name);
          if (error)
                  goto bad;
  
          ndirent.de_Attributes = ATTR_DIRECTORY;
          ndirent.de_LowerCase = 0;
          ndirent.de_StartCluster = newcluster;
          ndirent.de_FileSize = 0;
          error = createde(&ndirent, pdep, &dep, cnp);
          if (error)
                  goto bad;
          *ap->a_vpp = DETOV(dep);
          return (0);
  
  bad:
          clusterfree(pmp, newcluster, NULL);
  bad2:
          return (error);
  }
  
  static int
  msdosfs_rmdir(struct vop_rmdir_args *ap)
  {
          struct vnode *vp = ap->a_vp;
          struct vnode *dvp = ap->a_dvp;
          struct componentname *cnp = ap->a_cnp;
          struct denode *ip, *dp;
          int error;
  
          ip = VTODE(vp);
          dp = VTODE(dvp);
  
          /*
           * Verify the directory is empty (and valid).
           * (Rmdir ".." won't be valid since
           *  ".." will contain a reference to
           *  the current directory and thus be
           *  non-empty.)
           */
          error = 0;
          if (!dosdirempty(ip) || ip->de_flag & DE_RENAME) {
                  error = ENOTEMPTY;
                  goto out;
          }
          /*
           * Delete the entry from the directory.  For dos filesystems this
           * gets rid of the directory entry on disk, the in memory copy
           * still exists but the de_refcnt is <= 0.  This prevents it from
           * being found by deget().  When the vput() on dep is done we give
           * up access and eventually msdosfs_reclaim() will be called which
           * will remove it from the denode cache.
           */
          error = removede(dp, ip);
          if (error)
                  goto out;
          /*
           * This is where we decrement the link count in the parent
           * directory.  Since dos filesystems don't do this we just purge
           * the name cache.
           */
          cache_purge(dvp);
          /*
           * Truncate the directory that is being deleted.
           */
          error = detrunc(ip, (u_long)0, IO_SYNC, cnp->cn_cred);
          cache_purge(vp);
  
  out:
          return (error);
  }
  
  /*
   * DOS filesystems don't know what symlinks are.
   */
  static int
  msdosfs_symlink(struct vop_symlink_args *ap)
  {
          return (EOPNOTSUPP);
  }
  
  static int
  msdosfs_readdir(struct vop_readdir_args *ap)
  {
          struct mbnambuf nb;
          int error = 0;
          int diff;
          long n;
          int blsize;
          long on;
          u_long cn;
          uint64_t fileno;
          u_long dirsperblk;
          long bias = 0;
          daddr_t bn, lbn;
          struct buf *bp;
          struct denode *dep = VTODE(ap->a_vp);
          struct msdosfsmount *pmp = dep->de_pmp;
          struct direntry *dentp;
          struct dirent dirbuf;
          struct uio *uio = ap->a_uio;
          u_long *cookies = NULL;
          int ncookies = 0;
          off_t offset, off;
          int chksum = -1;
  
  #ifdef MSDOSFS_DEBUG
          printf("msdosfs_readdir(): vp %p, uio %p, cred %p, eofflagp %p\n",
              ap->a_vp, uio, ap->a_cred, ap->a_eofflag);
  #endif
  
          /*
           * msdosfs_readdir() won't operate properly on regular files since
           * it does i/o only with the filesystem vnode, and hence can
           * retrieve the wrong block from the buffer cache for a plain file.
           * So, fail attempts to readdir() on a plain file.
           */
          if ((dep->de_Attributes & ATTR_DIRECTORY) == 0)
                  return (ENOTDIR);
  
          /*
           * To be safe, initialize dirbuf
           */
          bzero(dirbuf.d_name, sizeof(dirbuf.d_name));
  
          /*
           * If the user buffer is smaller than the size of one dos directory
           * entry or the file offset is not a multiple of the size of a
           * directory entry, then we fail the read.
           */
          off = offset = uio->uio_offset;
          if (uio->uio_resid < sizeof(struct direntry) ||
              (offset & (sizeof(struct direntry) - 1)))
                  return (EINVAL);
  
          if (ap->a_ncookies) {
                  ncookies = uio->uio_resid / 16;
                  cookies = malloc(ncookies * sizeof(u_long), M_TEMP,
                         M_WAITOK);
                  *ap->a_cookies = cookies;
                  *ap->a_ncookies = ncookies;
          }
  
          dirsperblk = pmp->pm_BytesPerSec / sizeof(struct direntry);
  
          /*
           * If they are reading from the root directory then, we simulate
           * the . and .. entries since these don't exist in the root
           * directory.  We also set the offset bias to make up for having to
           * simulate these entries. By this I mean that at file offset 64 we
           * read the first entry in the root directory that lives on disk.
           */
          if (dep->de_StartCluster == MSDOSFSROOT
              || (FAT32(pmp) && dep->de_StartCluster == pmp->pm_rootdirblk)) {
  #if 0
                  printf("msdosfs_readdir(): going after . or .. in root dir, offset %d\n",
                      offset);
  #endif
                  bias = 2 * sizeof(struct direntry);
                  if (offset < bias) {
                          for (n = (int)offset / sizeof(struct direntry);
                               n < 2; n++) {
                                  if (FAT32(pmp))
                                          fileno = (uint64_t)cntobn(pmp,
                                                                   pmp->pm_rootdirblk)
                                                            * dirsperblk;
                                  else
                                          fileno = 1;
                                  if (pmp->pm_flags & MSDOSFS_LARGEFS) {
                                          dirbuf.d_fileno =
                                              msdosfs_fileno_map(pmp->pm_mountp,
                                              fileno);
                                  } else {
  
                                          dirbuf.d_fileno = (uint32_t)fileno;
                                  }
                                  dirbuf.d_type = DT_DIR;
                                  switch (n) {
                                  case 0:
                                          dirbuf.d_namlen = 1;
                                          strcpy(dirbuf.d_name, ".");
                                          break;
                                  case 1:
                                          dirbuf.d_namlen = 2;
                                          strcpy(dirbuf.d_name, "..");
                                          break;
                                  }
                                  dirbuf.d_reclen = GENERIC_DIRSIZ(&dirbuf);
                                  if (uio->uio_resid < dirbuf.d_reclen)
                                          goto out;
                                  error = uiomove(&dirbuf, dirbuf.d_reclen, uio);
                                  if (error)
                                          goto out;
                                  offset += sizeof(struct direntry);
                                  off = offset;
                                  if (cookies) {
                                          *cookies++ = offset;
                                          if (--ncookies <= 0)
                                                  goto out;
                                  }
                          }
                  }
          }
  
          mbnambuf_init(&nb);
          off = offset;
          while (uio->uio_resid > 0) {
                  lbn = de_cluster(pmp, offset - bias);
                  on = (offset - bias) & pmp->pm_crbomask;
                  n = min(pmp->pm_bpcluster - on, uio->uio_resid);
                  diff = dep->de_FileSize - (offset - bias);
                  if (diff <= 0)
                          break;
                  n = min(n, diff);
                  error = pcbmap(dep, lbn, &bn, &cn, &blsize);
                  if (error)
                          break;
                  error = bread(pmp->pm_devvp, bn, blsize, NOCRED, &bp);
                  if (error) {
                          brelse(bp);
                          return (error);
                  }
                  n = min(n, blsize - bp->b_resid);
                  if (n == 0) {
                          brelse(bp);
                          return (EIO);
                  }
  
                  /*
                   * Convert from dos directory entries to fs-independent
                   * directory entries.
                   */
                  for (dentp = (struct direntry *)(bp->b_data + on);
                       (char *)dentp < bp->b_data + on + n;
                       dentp++, offset += sizeof(struct direntry)) {
  #if 0
                          printf("rd: dentp %08x prev %08x crnt %08x deName %02x attr %02x\n",
                              dentp, prev, crnt, dentp->deName[0], dentp->deAttributes);
  #endif
                          /*
                           * If this is an unused entry, we can stop.
                           */
                          if (dentp->deName[0] == SLOT_EMPTY) {
                                  brelse(bp);
                                  goto out;
                          }
                          /*
                           * Skip deleted entries.
                           */
                          if (dentp->deName[0] == SLOT_DELETED) {
                                  chksum = -1;
                                  mbnambuf_init(&nb);
                                  continue;
                          }
  
                          /*
                           * Handle Win95 long directory entries
                           */
                          if (dentp->deAttributes == ATTR_WIN95) {
                                  if (pmp->pm_flags & MSDOSFSMNT_SHORTNAME)
                                          continue;
                                  chksum = win2unixfn(&nb,
                                      (struct winentry *)dentp, chksum, pmp);
                                  continue;
                          }
  
                          /*
                           * Skip volume labels
                           */
                          if (dentp->deAttributes & ATTR_VOLUME) {
                                  chksum = -1;
                                  mbnambuf_init(&nb);
                                  continue;
                          }
                          /*
                           * This computation of d_fileno must match
                           * the computation of va_fileid in
                           * msdosfs_getattr.
                           */
                          if (dentp->deAttributes & ATTR_DIRECTORY) {
                                  fileno = getushort(dentp->deStartCluster);
                                  if (FAT32(pmp))
                                          fileno |= getushort(dentp->deHighClust) << 16;
                                  /* if this is the root directory */
                                  if (fileno == MSDOSFSROOT)
                                          if (FAT32(pmp))
                                                  fileno = (uint64_t)cntobn(pmp,
                                                                  pmp->pm_rootdirblk)
                                                           * dirsperblk;
                                          else
                                                  fileno = 1;
                                  else
                                          fileno = (uint64_t)cntobn(pmp, fileno) *
                                              dirsperblk;
                                  dirbuf.d_type = DT_DIR;
                          } else {
                                  fileno = (uoff_t)offset /
                                      sizeof(struct direntry);
                                  dirbuf.d_type = DT_REG;
                          }
                          if (pmp->pm_flags & MSDOSFS_LARGEFS) {
                                  dirbuf.d_fileno =
                                      msdosfs_fileno_map(pmp->pm_mountp, fileno);
                          } else
                                  dirbuf.d_fileno = (uint32_t)fileno;
  
                          if (chksum != winChksum(dentp->deName)) {
                                  dirbuf.d_namlen = dos2unixfn(dentp->deName,
                                      (u_char *)dirbuf.d_name,
                                      dentp->deLowerCase |
                                          ((pmp->pm_flags & MSDOSFSMNT_SHORTNAME) ?
                                          (LCASE_BASE | LCASE_EXT) : 0),
                                      pmp);
                                  mbnambuf_init(&nb);
                          } else
                                  mbnambuf_flush(&nb, &dirbuf);
                          chksum = -1;
                          dirbuf.d_reclen = GENERIC_DIRSIZ(&dirbuf);
                          if (uio->uio_resid < dirbuf.d_reclen) {
                                  brelse(bp);
                                  goto out;
                          }
                          error = uiomove(&dirbuf, dirbuf.d_reclen, uio);
                          if (error) {
                                  brelse(bp);
                                  goto out;
                          }
                          if (cookies) {
                                  *cookies++ = offset + sizeof(struct direntry);
                                  if (--ncookies <= 0) {
                                          brelse(bp);
                                          goto out;
                                  }
                          }
                          off = offset + sizeof(struct direntry);
                  }
                  brelse(bp);
          }
  out:
          /* Subtract unused cookies */
          if (ap->a_ncookies)
                  *ap->a_ncookies -= ncookies;
  
          uio->uio_offset = off;
  
          /*
           * Set the eofflag (NFS uses it)
           */
          if (ap->a_eofflag) {
                  if (dep->de_FileSize - (offset - bias) <= 0)
                          *ap->a_eofflag = 1;
                  else
                          *ap->a_eofflag = 0;
          }
          return (error);
  }
  
  /*-
   * a_vp   - pointer to the file's vnode
   * a_bn   - logical block number within the file (cluster number for us)
   * a_bop  - where to return the bufobj of the special file containing the fs
   * a_bnp  - where to return the "physical" block number corresponding to a_bn
   *          (relative to the special file; units are blocks of size DEV_BSIZE)
   * a_runp - where to return the "run past" a_bn.  This is the count of logical
   *          blocks whose physical blocks (together with a_bn's physical block)
   *          are contiguous.
   * a_runb - where to return the "run before" a_bn.
   */
  static int
  msdosfs_bmap(struct vop_bmap_args *ap)
  {
          struct denode *dep;
          struct mount *mp;
          struct msdosfsmount *pmp;
          struct vnode *vp;
          daddr_t runbn;
          u_long cn;
          int bnpercn, error, maxio, maxrun, run;
  
          vp = ap->a_vp;
          dep = VTODE(vp);
          pmp = dep->de_pmp;
          if (ap->a_bop != NULL)
                  *ap->a_bop = &pmp->pm_devvp->v_bufobj;
          if (ap->a_bnp == NULL)
                  return (0);
          if (ap->a_runp != NULL)
                  *ap->a_runp = 0;
          if (ap->a_runb != NULL)
                  *ap->a_runb = 0;
          cn = ap->a_bn;
          if (cn != ap->a_bn)
                  return (EFBIG);
          error = pcbmap(dep, cn, ap->a_bnp, NULL, NULL);
          if (error != 0 || (ap->a_runp == NULL && ap->a_runb == NULL))
                  return (error);
  
          mp = vp->v_mount;
          maxio = mp->mnt_iosize_max / mp->mnt_stat.f_iosize;
          bnpercn = de_cn2bn(pmp, 1);
          if (ap->a_runp != NULL) {
                  maxrun = ulmin(maxio - 1, pmp->pm_maxcluster - cn);
                  for (run = 1; run <= maxrun; run++) {
                          if (pcbmap(dep, cn + run, &runbn, NULL, NULL) != 0 ||
                              runbn != *ap->a_bnp + run * bnpercn)
                                  break;
                  }
                  *ap->a_runp = run - 1;
          }
          if (ap->a_runb != NULL) {
                  maxrun = ulmin(maxio - 1, cn);
                  for (run = 1; run < maxrun; run++) {
                          if (pcbmap(dep, cn - run, &runbn, NULL, NULL) != 0 ||
                              runbn != *ap->a_bnp - run * bnpercn)
                                  break;
                  }
                  *ap->a_runb = run - 1;
          }
          return (0);
  }
  
  static int
  msdosfs_strategy(struct vop_strategy_args *ap)
  {
          struct buf *bp = ap->a_bp;
          struct denode *dep = VTODE(ap->a_vp);
          struct bufobj *bo;
          int error = 0;
          daddr_t blkno;
  
          /*
           * If we don't already know the filesystem relative block number
           * then get it using pcbmap().  If pcbmap() returns the block
           * number as -1 then we've got a hole in the file.  DOS filesystems
           * don't allow files with holes, so we shouldn't ever see this.
           */
          if (bp->b_blkno == bp->b_lblkno) {
                  error = pcbmap(dep, bp->b_lblkno, &blkno, 0, 0);
                  bp->b_blkno = blkno;
                  if (error) {
                          bp->b_error = error;
                          bp->b_ioflags |= BIO_ERROR;
                          bufdone(bp);
                          return (0);
                  }
                  if ((long)bp->b_blkno == -1)
                          vfs_bio_clrbuf(bp);
          }
          if (bp->b_blkno == -1) {
                  bufdone(bp);
                  return (0);
          }
          /*
           * Read/write the block from/to the disk that contains the desired
           * file block.
           */
          bp->b_iooffset = dbtob(bp->b_blkno);
          bo = dep->de_pmp->pm_bo;
          BO_STRATEGY(bo, bp);
          return (0);
  }
  
  static int
  msdosfs_print(struct vop_print_args *ap)
  {
          struct denode *dep = VTODE(ap->a_vp);
  
          printf("\tstartcluster %lu, dircluster %lu, diroffset %lu, ",
                 dep->de_StartCluster, dep->de_dirclust, dep->de_diroffset);
          printf("on dev %s\n", devtoname(dep->de_pmp->pm_dev));
          return (0);
  }
  
  static int
  msdosfs_pathconf(struct vop_pathconf_args *ap)
  {
          struct msdosfsmount *pmp = VTODE(ap->a_vp)->de_pmp;
  
          switch (ap->a_name) {
          case _PC_LINK_MAX:
                  *ap->a_retval = 1;
                  return (0);
          case _PC_NAME_MAX:
                  *ap->a_retval = pmp->pm_flags & MSDOSFSMNT_LONGNAME ? WIN_MAXLEN : 12;
                  return (0);
          case _PC_PATH_MAX:
                  *ap->a_retval = PATH_MAX;
                  return (0);
          case _PC_CHOWN_RESTRICTED:
                  *ap->a_retval = 1;
                  return (0);
          case _PC_NO_TRUNC:
                  *ap->a_retval = 0;
                  return (0);
          default:
                  return (EINVAL);
          }
          /* NOTREACHED */
  }
  
  static int
  msdosfs_vptofh(struct vop_vptofh_args *ap)
  {
          struct denode *dep;
          struct defid *defhp;
  
          dep = VTODE(ap->a_vp);
          defhp = (struct defid *)ap->a_fhp;
          defhp->defid_len = sizeof(struct defid);
          defhp->defid_dirclust = dep->de_dirclust;
          defhp->defid_dirofs = dep->de_diroffset;
          /* defhp->defid_gen = dep->de_gen; */
          return (0);
  }
  
  /* Global vfs data structures for msdosfs */
  struct vop_vector msdosfs_vnodeops = {
          .vop_default =          &default_vnodeops,
  
          .vop_access =           msdosfs_access,
          .vop_bmap =             msdosfs_bmap,
          .vop_cachedlookup =     msdosfs_lookup,
          .vop_open =             msdosfs_open,
          .vop_close =            msdosfs_close,
          .vop_create =           msdosfs_create,
          .vop_fsync =            msdosfs_fsync,
          .vop_getattr =          msdosfs_getattr,
          .vop_inactive =         msdosfs_inactive,
          .vop_link =             msdosfs_link,
          .vop_lookup =           vfs_cache_lookup,
          .vop_mkdir =            msdosfs_mkdir,
          .vop_mknod =            msdosfs_mknod,
          .vop_pathconf =         msdosfs_pathconf,
          .vop_print =            msdosfs_print,
          .vop_read =             msdosfs_read,
          .vop_readdir =          msdosfs_readdir,
          .vop_reclaim =          msdosfs_reclaim,
          .vop_remove =           msdosfs_remove,
          .vop_rename =           msdosfs_rename,
          .vop_rmdir =            msdosfs_rmdir,
          .vop_setattr =          msdosfs_setattr,
          .vop_strategy =         msdosfs_strategy,
          .vop_symlink =          msdosfs_symlink,
          .vop_write =            msdosfs_write,
          .vop_vptofh =           msdosfs_vptofh,
  };

Cache object: 19643b73a5cf21fb2429ec5a6cf4462f