Topic       : TOS - The Operating System
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View Ref-File11.5.16.9  xfs_ddelete                                             TOS

 Name:        »xfs_ddelete« - Delete a directory.

 Parameters:

               a0 =     DD *
               -> d0 =  long errcode

 Description: The call xfs_ddelete had to be altered as of MagiC 
              Version 4.01.

              For MagiC < 4.01 (kernel version < 3) the following 
              applies:
              During deletion one must ensure that no directory may be 
              referenced by the kernel except by the call itself (i.e. 
              dd_refcnt must == 1). In addition one must ensure that 
              there are no files in the directory. ELINK may not be 
              returned, symbolic links may not be processed. The 
              access rights (if they exist) must be tested by the XFS.

              For MagiC < 4.01 (kernel version >= 3) the following 
              applies:
              Reentrance problems gave rise to some changes, whereby 
              the kernel takes over access control from the XFS and 
              furthermore the kernel releases the DD, not the XFS: The 
              kernel first of all opens the parent of the directory to 
              be deleted with xfs_path2DD, then it tests with 
              xfs_xattr whether it is dealing with a symlink, and if 
              appropriate deletes it with xfs_fdelete.

              If it is dealing with a directory, the kernel opens this 
              again with xfs_path2DD (mode 1) and releases the parent 
              again with xfs_freeDD. The check of dd_refcnt is 
              performed by the kernel, hence the counter can and must 
              be ignored by the XFS. The XFS must now ensure that the 
              directory to be deleted or the DD cannot be opened or 
              used by others (important for reentrant XFSs). The XFS 
              then deletes the directory, but does not (!) release the 
              DD, so that the kernel if successful (return value E_OK) 
              can release its standard paths beforehand. The kernel 
              then calls xfs_freeDD. As usual the XFS must check that 
              the directory is empty, or if access rights exist if 
              appropriate.

              Again in context:

                 . The kernel ascertains the DD to be deleted, tests 
                   the reference counter

                 . xfs_ddelete locks the DD. If this does not work 
                   then EACCDN is returned

                 . xfs_ddelete deletes the directory, provided it is 
                   empty; here the DD acts as a lock for parallel- 
                   runnning attempts to use the newly deleted 
                   directory

                 . xfs_ddelete leaves the now invalid (but still 
                   serving as a lock) DD still valid (in contrast to 
                   the old concept)

                 . On success the kernel makes its standard paths 
                   invalid

                 . The kernel releases the DD

 Group:       Make-up of an XFS

 See also:    MagiC's XFS-concept   Ddelete