diskfs: Fix rename_dir(excl=1) for source directories

Starting from coreutils 8.30 which uses
renameat2(flag=RENAME_NOREPLACE), we need to have excl=1 to behave
correctly, notably in this case:

$ mkdir a
$ mkdir b
$ touch b/t
$ mv b a

diskfs_rename("b", "a", excl=1) called by mv shall return EEXIST.

* libdiskfs/diskfs.h (diskfs_rename_dir): Add `excl' parameter.
* doc/hurd.texi (diskfs_rename_dir): Document `excl' parameter.
* libdiskfs/dir-renamed.c (diskfs_rename_dir): Add `excl' parameter.
Return EEXIST when target exists and `excl' is not 0.
* libdiskfs/dir-rename.c (diskfs_S_dir_rename): Pass `excl' to
diskfs_rename_dir.

4 files changed, 16 insertions, 7 deletions

diff --git a/doc/hurd.texi b/doc/hurd.texi
index 7ad798a9..e74ad2d4 100644
--- a/doc/hurd.texi
+++ b/doc/hurd.texi
@@ -4442,14 +4442,16 @@ file data) is used.  If it returns any other error, it is returned to
 the user.
 @end deftypefn
 
-@deftypefun error_t diskfs_rename_dir (@w{struct node *@var{fdp}}, @w{struct node *@var{fnp}}, @w{char *@var{fromname}}, @w{struct node *@var{tdp}}, @w{char *@var{toname}}, @w{struct protid *@var{fromcred}}, @w{struct protid *@var{tocred}})
+@deftypefun error_t diskfs_rename_dir (@w{struct node *@var{fdp}}, @w{struct node *@var{fnp}}, @w{char *@var{fromname}}, @w{struct node *@var{tdp}}, @w{char *@var{toname}}, @w{struct protid *@var{fromcred}}, @w{struct protid *@var{tocred}}, @w{int @var{excl}})
 Rename directory node @var{fnp} (whose parent is @var{fdp}, and which
 has name @var{fromname} in that directory) to have name @var{toname}
 inside directory @var{tdp}.  None of these nodes are locked, and none
 should be locked upon return.  This routine is serialized, so it doesn't
 have to be reentrant.  Directories will never be renamed except by this
 routine.  @var{fromcred} is the user responsible for @var{fdp} and
-@var{fnp}.  @var{tocred} is the user responsible for @var{tdp}.  This
+@var{fnp}.  @var{tocred} is the user responsible for @var{tdp}.
+If @var{excl} is set, then fail if @var{toname} already exists inside
+directory @var{tdp}. This
 routine assumes the usual convention where @file{.}  and @file{..} are
 represented by ordinary links; if that is not true for your format, you
 have to redefine this function.
diff --git a/libdiskfs/dir-rename.c b/libdiskfs/dir-rename.c
index 9ac48398..90f7c683 100644
--- a/libdiskfs/dir-rename.c
+++ b/libdiskfs/dir-rename.c
@@ -80,7 +80,7 @@ diskfs_S_dir_rename (struct protid *fromcred,
 	  goto try_again;
 	}
       err = diskfs_rename_dir (fdp, fnp, fromname, tdp, toname, fromcred,
-			       tocred);
+			       tocred, excl);
       if (diskfs_synchronous)
 	{
 	  pthread_mutex_lock (&fdp->lock);
diff --git a/libdiskfs/dir-renamed.c b/libdiskfs/dir-renamed.c
index 772258d2..69fd7fe3 100644
--- a/libdiskfs/dir-renamed.c
+++ b/libdiskfs/dir-renamed.c
@@ -64,11 +64,12 @@ checkpath(struct node *source,
    upon return.  This routine is serialized, so it doesn't have to be
    reentrant.  Directories will never be renamed except by this
    routine.  FROMCRED and TOCRED are the users responsible for
-   FDP/FNP and TDP respectively.  */
+   FDP/FNP and TDP respectively.  If EXCL is set, then fail if TONAME
+   already exists inside directory TDP. */
 error_t
 diskfs_rename_dir (struct node *fdp, struct node *fnp, const char *fromname,
 		   struct node *tdp, const char *toname,
-		   struct protid *fromcred, struct protid *tocred)
+		   struct protid *fromcred, struct protid *tocred, int excl)
 {
   error_t err;
   struct node *tnp, *tmpnp;
@@ -96,6 +97,11 @@ diskfs_rename_dir (struct node *fdp, struct node *fnp, const char *fromname,
   assert_backtrace (err != EAGAIN);	/* <-> assert_backtrace (TONAME != "..") */
   if (err && err != ENOENT)
     goto out;
+  if (tnp && excl)
+    {
+      err = EEXIST;
+      goto out;
+    }
 
   if (tnp == fnp)
     {
diff --git a/libdiskfs/diskfs.h b/libdiskfs/diskfs.h
index 40af37a9..f04b163a 100644
--- a/libdiskfs/diskfs.h
+++ b/libdiskfs/diskfs.h
@@ -1017,14 +1017,15 @@ struct node *diskfs_check_lookup_cache (struct node *dir, const char *name);
    upon return.  This routine is serialized, so it doesn't have to be
    reentrant.  Directories will never be renamed except by this
    routine.  FROMCRED and TOCRED are the users responsible for
-   FDP/FNP and TDP respectively.  This routine assumes the usual
+   FDP/FNP and TDP respectively. If EXCL is set, then fail if TONAME
+   already exists inside directory TDP. This routine assumes the usual
    convention where `.' and `..' are represented by ordinary links;
    if that is not true for your format, you have to redefine this
    function.*/
 error_t
 diskfs_rename_dir (struct node *fdp, struct node *fnp, const char *fromname,
 		   struct node *tdp, const char *toname,
-		   struct protid *fromcred, struct protid *tocred);
+		   struct protid *fromcred, struct protid *tocred, int excl);
 
 /* Clear the `.' and `..' entries from directory DP.  Its parent is
    PDP, and the user responsible for this is identified by CRED.  Both