Implement proper Linux /dev/fd and /proc/self/fd behavior by adding
Linux specific things to the native fdescfs file system. Unlike FreeBSD, the Linux fdescfs is a directory containing a symbolic links to the actual files, which the process has open. A readlink(2) call on this file returns a full path in case of regular file or a string in a special format (type:[inode], anon_inode:<file-type>, etc..). As well as in a FreeBSD, opening the file in the Linux fdescfs directory is equivalent to duplicating the corresponding file descriptor. Here we have mutually exclusive requirements: - in case of readlink(2) call fdescfs lookup() method should return VLNK vnode otherwise our kern_readlink() fail with EINVAL error; - in the other calls fdescfs lookup() method should return non VLNK vnode. For what new vnode v_flag VV_READLINK was added, which is set if fdescfs has beed mounted with linrdlnk option an modified kern_readlinkat() to properly handle it. For now For Linux ABI compatibility mount fdescfs volume with linrdlnk option: mount -t fdescfs -o linrdlnk null /compat/linux/dev/fd Reviewed by: kib@ MFC after: 1 week Relnotes: yes
This commit is contained in:
parent
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commit
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Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=321839
@ -24,7 +24,7 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd February 8, 2010
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.Dd August 1, 2017
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.Dt LINUX 4
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.Os
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.Sh NAME
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@ -127,9 +127,11 @@ regardless of whether the
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module is statically linked into the kernel
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or loaded as a module.
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.Sh FILES
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.Bl -tag -width /compat/linux/proc -compact
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.Bl -tag -width /compat/linux/dev/fd -compact
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.It Pa /compat/linux
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minimal Linux run-time environment
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.It Pa /compat/linux/dev/fd
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limited Linux file-descriptor file system
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.It Pa /compat/linux/proc
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limited Linux process file system
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.It Pa /compat/linux/sys
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@ -138,6 +140,7 @@ limited Linux system file system
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.Sh SEE ALSO
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.Xr brandelf 1 ,
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.Xr elf 5 ,
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.Xr fdescfs 5 ,
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.Xr linprocfs 5 ,
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.Xr linsysfs 5
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.Sh HISTORY
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@ -34,7 +34,7 @@
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.\"
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.\" $FreeBSD$
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.\"
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.Dd September 18, 2010
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.Dd August 1, 2017
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.Dt FDESCFS 5
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.Os
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.Sh NAME
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@ -92,6 +92,14 @@ and
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files are created by default when devfs alone is mounted.
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.Nm
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creates entries for all file descriptors opened by the process.
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.Pp
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For
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.Xr linux 4
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ABI compatibility mount
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.Nm
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volume with
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.Cm linrdlnk
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option.
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.Sh FILES
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.Bl -tag -width /dev/stderr -compact
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.It Pa /dev/fd/#
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@ -103,6 +111,12 @@ volume located on
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.Pa /dev/fd :
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.Pp
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.Dl "mount -t fdescfs null /dev/fd"
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.Pp
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For
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.Xr linux 4
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ABI compatibility:
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.Pp
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.Dl "mount -t fdescfs -o linrdlnk null /compat/linux/dev/fd"
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.Sh SEE ALSO
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.Xr devfs 5 ,
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.Xr mount 8
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@ -39,6 +39,8 @@
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/* Private mount flags for fdescfs. */
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#define FMNT_UNMOUNTF 0x01
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#define FMNT_LINRDLNKF 0x02
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struct fdescmount {
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struct vnode *f_root; /* Root node */
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int flags;
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@ -101,6 +101,8 @@ fdesc_mount(struct mount *mp)
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*/
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mp->mnt_data = fmp;
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fmp->flags = 0;
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if (vfs_getopt(mp->mnt_optnew, "linrdlnk", NULL, NULL) == 0)
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fmp->flags |= FMNT_LINRDLNKF;
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error = fdesc_allocvp(Froot, -1, FD_ROOT, mp, &rvp);
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if (error) {
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free(fmp, M_FDESCMNT);
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@ -69,6 +69,7 @@ static vop_getattr_t fdesc_getattr;
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static vop_lookup_t fdesc_lookup;
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static vop_open_t fdesc_open;
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static vop_readdir_t fdesc_readdir;
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static vop_readlink_t fdesc_readlink;
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static vop_reclaim_t fdesc_reclaim;
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static vop_setattr_t fdesc_setattr;
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@ -81,6 +82,7 @@ static struct vop_vector fdesc_vnodeops = {
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.vop_open = fdesc_open,
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.vop_pathconf = vop_stdpathconf,
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.vop_readdir = fdesc_readdir,
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.vop_readlink = fdesc_readlink,
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.vop_reclaim = fdesc_reclaim,
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.vop_setattr = fdesc_setattr,
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};
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@ -195,6 +197,8 @@ fdesc_allocvp(fdntype ftype, unsigned fd_fd, int ix, struct mount *mp,
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fd->fd_type = ftype;
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fd->fd_fd = fd_fd;
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fd->fd_ix = ix;
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if (ftype == Fdesc && fmp->flags & FMNT_LINRDLNKF)
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vp->v_vflag |= VV_READLINK;
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error = insmntque1(vp, mp, fdesc_insmntque_dtr, NULL);
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if (error != 0) {
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*vpp = NULLVP;
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@ -420,7 +424,7 @@ fdesc_getattr(struct vop_getattr_args *ap)
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break;
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case Fdesc:
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vap->va_type = VCHR;
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vap->va_type = (vp->v_vflag & VV_READLINK) == 0 ? VCHR : VLNK;
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vap->va_nlink = 1;
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vap->va_size = 0;
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vap->va_rdev = makedev(0, vap->va_fileid);
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@ -490,6 +494,7 @@ fdesc_setattr(struct vop_setattr_args *ap)
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static int
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fdesc_readdir(struct vop_readdir_args *ap)
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{
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struct fdescmount *fmp;
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struct uio *uio = ap->a_uio;
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struct filedesc *fdp;
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struct dirent d;
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@ -499,6 +504,7 @@ fdesc_readdir(struct vop_readdir_args *ap)
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if (VTOFDESC(ap->a_vp)->fd_type != Froot)
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panic("fdesc_readdir: not dir");
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fmp = VFSTOFDESC(ap->a_vp->v_mount);
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if (ap->a_ncookies != NULL)
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*ap->a_ncookies = 0;
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@ -530,7 +536,8 @@ fdesc_readdir(struct vop_readdir_args *ap)
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break;
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dp->d_namlen = sprintf(dp->d_name, "%d", fcnt);
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dp->d_reclen = UIO_MX;
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dp->d_type = DT_CHR;
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dp->d_type = (fmp->flags & FMNT_LINRDLNKF) == 0 ?
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DT_CHR : DT_LNK;
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dp->d_fileno = i + FD_DESC;
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break;
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}
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@ -567,3 +574,52 @@ fdesc_reclaim(struct vop_reclaim_args *ap)
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vp->v_data = NULL;
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return (0);
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}
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static int
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fdesc_readlink(struct vop_readlink_args *va)
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{
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struct vnode *vp, *vn;
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cap_rights_t rights;
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struct thread *td;
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struct uio *uio;
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struct file *fp;
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char *freepath, *fullpath;
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size_t pathlen;
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int lockflags, fd_fd;
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int error;
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freepath = NULL;
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vn = va->a_vp;
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if (VTOFDESC(vn)->fd_type != Fdesc)
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panic("fdesc_readlink: not fdescfs link");
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fd_fd = ((struct fdescnode *)vn->v_data)->fd_fd;
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lockflags = VOP_ISLOCKED(vn);
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VOP_UNLOCK(vn, 0);
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td = curthread;
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error = fget_cap(td, fd_fd, cap_rights_init(&rights), &fp, NULL);
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if (error != 0)
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goto out;
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switch (fp->f_type) {
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case DTYPE_VNODE:
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vp = fp->f_vnode;
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error = vn_fullpath(td, vp, &fullpath, &freepath);
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break;
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default:
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fullpath = "anon_inode:[unknown]";
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break;
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}
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if (error == 0) {
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uio = va->a_uio;
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pathlen = strlen(fullpath);
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error = uiomove(fullpath, pathlen, uio);
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}
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if (freepath != NULL)
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free(freepath, M_TEMP);
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fdrop(fp, td);
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out:
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vn_lock(vn, lockflags | LK_RETRY);
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return (error);
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}
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return (error);
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}
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#endif
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if (vp->v_type != VLNK)
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if (vp->v_type != VLNK && (vp->v_vflag & VV_READLINK) == 0)
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error = EINVAL;
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else {
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aiov.iov_base = buf;
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#define VV_DELETED 0x0400 /* should be removed */
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#define VV_MD 0x0800 /* vnode backs the md device */
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#define VV_FORCEINSMQ 0x1000 /* force the insmntque to succeed */
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#define VV_READLINK 0x2000 /* fdescfs linux vnode */
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#define VMP_TMPMNTFREELIST 0x0001 /* Vnode is on mnt's tmp free list */
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