Create a dedicated function for ensuring that cdir and rdir are populated.

Previously several places were doing it on its own, partially
incorrectly (e.g. without the filedesc locked) or even actively harmful
by populating jdir or assigning rootvnode without vrefing it.

Reviewed by:	kib

sys/cam/ctl/ctl_backend_block.c

@@ -2123,18 +2123,7 @@ ctl_be_block_open(struct ctl_be_block_softc *softc,
 		return (1);
 	}
 
-	if (!curthread->td_proc->p_fd->fd_cdir) {
-		curthread->td_proc->p_fd->fd_cdir = rootvnode;
-		VREF(rootvnode);
-	}
-	if (!curthread->td_proc->p_fd->fd_rdir) {
-		curthread->td_proc->p_fd->fd_rdir = rootvnode;
-		VREF(rootvnode);
-	}
-	if (!curthread->td_proc->p_fd->fd_jdir) {
-		curthread->td_proc->p_fd->fd_jdir = rootvnode;
-		VREF(rootvnode);
-	}
+	pwd_ensure_dirs();
 
  again:
 	NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, be_lun->dev_path, curthread);

sys/cddl/compat/opensolaris/kern/opensolaris_kobj.c

@@ -67,21 +67,10 @@ static void *
 kobj_open_file_vnode(const char *file)
 {
 	struct thread *td = curthread;
-	struct filedesc *fd;
 	struct nameidata nd;
 	int error, flags;
 
-	fd = td->td_proc->p_fd;
-	FILEDESC_XLOCK(fd);
-	if (fd->fd_rdir == NULL) {
-		fd->fd_rdir = rootvnode;
-		vref(fd->fd_rdir);
-	}
-	if (fd->fd_cdir == NULL) {
-		fd->fd_cdir = rootvnode;
-		vref(fd->fd_cdir);
-	}
-	FILEDESC_XUNLOCK(fd);
+	pwd_ensure_dirs();
 
 	flags = FREAD | O_NOFOLLOW;
 	NDINIT(&nd, LOOKUP, 0, UIO_SYSSPACE, file, td);

sys/cddl/compat/opensolaris/sys/vnode.h

@@ -162,7 +162,6 @@ vn_openat(char *pnamep, enum uio_seg seg, int filemode, int createmode,
     int fd)
 {
 	struct thread *td = curthread;
-	struct filedesc *fdc;
 	struct nameidata nd;
 	int error, operation;
 
@@ -179,17 +178,7 @@ vn_openat(char *pnamep, enum uio_seg seg, int filemode, int createmode,
 	}
 	ASSERT(umask == 0);
 
-	fdc = td->td_proc->p_fd;
-	FILEDESC_XLOCK(fdc);
-	if (fdc->fd_rdir == NULL) {
-		fdc->fd_rdir = rootvnode;
-		vref(fdc->fd_rdir);
-	}
-	if (fdc->fd_cdir == NULL) {
-		fdc->fd_cdir = rootvnode;
-		vref(fdc->fd_rdir);
-	}
-	FILEDESC_XUNLOCK(fdc);
+	pwd_ensure_dirs();
 
 	if (startvp != NULL)
 		vref(startvp);

sys/compat/ndis/subr_ndis.c

@@ -2817,10 +2817,7 @@ NdisOpenFile(status, filehandle, filelength, filename, highestaddr)
 
 	/* Some threads don't have a current working directory. */
 
-	if (td->td_proc->p_fd->fd_rdir == NULL)
-		td->td_proc->p_fd->fd_rdir = rootvnode;
-	if (td->td_proc->p_fd->fd_cdir == NULL)
-		td->td_proc->p_fd->fd_cdir = rootvnode;
+	pwd_ensure_dirs();
 
 	NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, path, td);
 

sys/dev/xen/blkback/blkback.c

@@ -2692,18 +2692,7 @@ xbb_open_backend(struct xbb_softc *xbb)
 	if ((xbb->flags & XBBF_READ_ONLY) == 0)
 		flags |= FWRITE;
 
-	if (!curthread->td_proc->p_fd->fd_cdir) {
-		curthread->td_proc->p_fd->fd_cdir = rootvnode;
-		VREF(rootvnode);
-	}
-	if (!curthread->td_proc->p_fd->fd_rdir) {
-		curthread->td_proc->p_fd->fd_rdir = rootvnode;
-		VREF(rootvnode);
-	}
-	if (!curthread->td_proc->p_fd->fd_jdir) {
-		curthread->td_proc->p_fd->fd_jdir = rootvnode;
-		VREF(rootvnode);
-	}
+	pwd_ensure_dirs();
 
  again:
 	NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, xbb->dev_name, curthread);

sys/kern/kern_descrip.c

@@ -68,6 +68,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sbuf.h>
 #include <sys/signalvar.h>
 #include <sys/socketvar.h>
+#include <sys/kdb.h>
 #include <sys/stat.h>
 #include <sys/sx.h>
 #include <sys/syscallsubr.h>
@@ -308,6 +309,24 @@ fdfree(struct filedesc *fdp, int fd)
 #endif
 }
 
+void
+pwd_ensure_dirs(void)
+{
+	struct filedesc *fdp;
+
+	fdp = curproc->p_fd;
+	FILEDESC_XLOCK(fdp);
+	if (fdp->fd_cdir == NULL) {
+		fdp->fd_cdir = rootvnode;
+		VREF(rootvnode);
+	}
+	if (fdp->fd_rdir == NULL) {
+		fdp->fd_rdir = rootvnode;
+		VREF(rootvnode);
+	}
+	FILEDESC_XUNLOCK(fdp);
+}
+
 /*
  * System calls on descriptors.
  */

sys/kern/subr_firmware.c

@@ -383,19 +383,8 @@ firmware_put(const struct firmware *p, int flags)
 static void
 set_rootvnode(void *arg, int npending)
 {
-	struct thread *td = curthread;
-	struct proc *p = td->td_proc;
 
-	FILEDESC_XLOCK(p->p_fd);
-	if (p->p_fd->fd_cdir == NULL) {
-		p->p_fd->fd_cdir = rootvnode;
-		VREF(rootvnode);
-	}
-	if (p->p_fd->fd_rdir == NULL) {
-		p->p_fd->fd_rdir = rootvnode;
-		VREF(rootvnode);
-	}
-	FILEDESC_XUNLOCK(p->p_fd);
+	pwd_ensure_dirs();
 
 	free(arg, M_TEMP);
 }

sys/sys/filedesc.h

@@ -208,6 +208,7 @@ fd_modified(struct filedesc *fdp, int fd, seq_t seq)
 /* cdir/rdir/jdir manipulation functions. */
 void	pwd_chdir(struct thread *td, struct vnode *vp);
 int	pwd_chroot(struct thread *td, struct vnode *vp);
+void	pwd_ensure_dirs(void);
 
 #endif /* _KERNEL */