LOOKUP_DCOOKIE(2)         (2017-09-15)          LOOKUP_DCOOKIE(2)

     NAME
          lookup_dcookie - return a directory entry's path

     SYNOPSIS
          int lookup_dcookie(u64 cookie, char *buffer, size_t len

     DESCRIPTION
          Look up the full path of the directory entry specified by
          the value cookie. The cookie is an opaque identifier
          uniquely identifying a particular directory entry.  The
          buffer given is filled in with the full path of the direc-
          tory entry.

          For lookup_dcookie() to return successfully, the kernel must
          still hold a cookie reference to the directory entry.

     RETURN VALUE
          On success, lookup_dcookie() returns the length of the path
          string copied into the buffer.  On error, -1 is returned,
          and errno is set appropriately.

     ERRORS
          EFAULT
               The buffer was not valid.

          EINVAL
               The kernel has no registered cookie/directory entry
               mappings at the time of lookup, or the cookie does not
               refer to a valid directory entry.

          ENAMETOOLONG
               The name could not fit in the buffer.

          ENOMEM
               The kernel could not allocate memory for the temporary
               buffer holding the path.

          EPERM
               The process does not have the capability CAP_SYS_ADMIN
               required to look up cookie values.

          ERANGE
               The buffer was not large enough to hold the path of the
               directory entry.

     VERSIONS
          Available since Linux 2.5.43.  The ENAMETOOLONG error return
          was added in 2.5.70.

     CONFORMING TO

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     LOOKUP_DCOOKIE(2)         (2017-09-15)          LOOKUP_DCOOKIE(2)

          lookup_dcookie() is Linux-specific.

     NOTES
          lookup_dcookie() is a special-purpose system call, currently
          used only by the oprofile(1) profiler.  It relies on a ker-
          nel driver to register cookies for directory entries.

          The path returned may be suffixed by the string " (deleted)"
          if the directory entry has been removed.

     SEE ALSO
          oprofile(1)

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

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