IOCTL-XFS-GETPARENTS(2)       System Calls Manual      IOCTL-XFS-GETPARENTS(2)

NAME
       ioctl_xfs_getparents - query XFS directory parent information

SYNOPSIS
       #include <xfs/xfs_fs.h>

       int ioctl(int fd, XFS_IOC_GETPARENTS, struct xfs_getparents *arg);

       int ioctl(int fd, XFS_IOC_GETPARENTS_BY_HANDLE, struct
       xfs_getparents_by_handle *arg);

DESCRIPTION
       This command is used to retrieve the directory parent pointers of
       either the currently opened file or a file handle.  Parent pointers
       point upwards in the directory tree from a child file towards a parent
       directories.  Each entry in a parent directory must have a
       corresponding parent pointer in the child.

       Calling programs should allocate a large memory buffer and initialize a
       header of the following form:

           struct xfs_getparents {
                struct xfs_attrlist_cursor  gp_cursor;
                __u16                       gp_iflags;
                __u16                       gp_oflags;
                __u32                       gp_bufsize;
                __u64                       __pad;
                __u64                       gp_buffer;
           };

           struct xfs_getparents {
                struct xfs_handle           gph_handle;
                struct xfs_getparents       gph_request;
           };


       The field gp_cursor tracks the progress of iterating through the parent
       pointers.  Calling programs must initialize this to zero before the
       first system call and must not touch it after that.


       The field gp_iflags control the behavior of the query operation and
       provide more information about the outcome of the operation.  There are
       no input flags currently defined; this field must be zero.


       The field gp_oflags contains information about the query itself.
       Possibly output flags are:

           XFS_GETPARENTS_OFLAG_ROOT
                  The file queried was the root directory.

           XFS_GETPARENTS_OFLAG_DONE
                  There are no more parent pointers to query.


       The field __pad must be zero.


       The field gp_bufsize should be set to the size of the buffer, in bytes.


       The field gp_buffer should point to an output buffer for the parent
       pointer records.

       Parent pointer records are returned in the following form:


           struct xfs_getparents_rec {
                struct xfs_handle           gpr_parent;
                __u16                       gpr_reclen;
                char                        gpr_name[];
           };


       The field gpr_parent is a file handle that can be used to open the
       parent directory.


       The field gpr_reclen will be set to the number of bytes used by this
       parent record.


       The array gpr_name will be set to a NULL-terminated byte sequence
       representing the filename stored in the parent pointer.  If the name is
       a zero-length string, the file queried has no parents.


SAMPLE PROGRAM
       Calling programs should allocate a large memory buffer, initialize the
       head structure to zeroes, set gp_bufsize to the size of the buffer, and
       call the ioctl.  The XFS_GETPARENTS_OFLAG_DONE flag will be set in
       gp_flags when there are no more parent pointers to be read.  The below
       code is an example of XFS_IOC_GETPARENTS usage:

       #include <stdio.h>
       #include <string.h>
       #include <errno.h>
       #include <xfs/linux.h>
       #include <xfs/xfs.h>
       #include <xfs/xfs_types.h>
       #include <xfs/xfs_fs.h>

       int main() {
            struct xfs_getparents gp = { };
            struct xfs_getparents_rec *gpr;
            int error, fd;

            gp.gp_buffer = (uintptr_t)malloc(65536);
            if (!gp.gp_buffer) {
                 perror("malloc");
                 return 1;
            }
            gp->gp_bufsize = 65536;

            fd = open("/mnt/test/foo.txt", O_RDONLY | O_CREAT);
            if (fd  == -1)
                 return errno;

            do {
                 error = ioctl(fd, XFS_IOC_GETPARENTS, gp);
                 if (error)
                      return error;

                 for (gpr = xfs_getparents_first_rec(&gp);
                      gpr != NULL;
                      gpr = xfs_getparents_next_rec(&gp, gpr)) {
                      if (gpr->gpr_name[0] == 0)
                           break;

                      printf("inode       = %llu\n",
                                gpr->gpr_parent.ha_fid.fid_ino);
                      printf("generation  = %u\n",
                                gpr->gpr_parent.ha_fid.fid_gen);
                      printf("name        = \"%s\"\n\n",
                                gpr->gpr_name);
                 }
            } while (!(gp.gp_flags & XFS_GETPARENTS_OFLAG_DONE));

            return 0;
       }


RETURN VALUE
       On error, -1 is returned, and errno is set to indicate the error.

ERRORS
       Error codes can be one of, but are not limited to, the following:

       EFSBADCRC
              Metadata checksum validation failed while performing the query.

       EFSCORRUPTED
              Metadata corruption was encountered while performing the query.

       EINVAL One or more of the arguments specified is invalid.

       EMSGSIZE
              The record buffer was not large enough to store even a single
              record.

       ENOMEM Not enough memory to retrieve parent pointers.

       EOPNOTSUPP
              Repairs of the requested metadata object are not supported.

       EROFS  Filesystem is read-only and a repair was requested.

       ESHUTDOWN
              Filesystem is shut down due to previous errors.

       EIO    An I/O error was encountered while performing the query.

CONFORMING TO
       This API is specific to XFS filesystem on the Linux kernel.

SEE ALSO
       ioctl(2)

XFS                               2024-04-09           IOCTL-XFS-GETPARENTS(2)