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.

1 files changed, 8 insertions, 2 deletions

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)
     {