Quoting Oren Laadan ([email protected]): > When seeing a CR_FD_PIPE file type, we create a new pipe and thus > have two file pointers (read- and write- ends). We only use one of > them, depending on which side was checkpointed first. We register the > file pointer of the other end in the hash table, with the 'objref' > given for this pipe from the checkpoint, deposited for later use. At > this point we also restore the contents of the pipe buffers. > > When the other end arrives, it will have file type CR_FD_OBJREF. We > will then use the corresponding 'objref' to retrieve the file pointer > from the hash table, and attach it to the process. > > Note the difference from the checkpoint logic: during checkpoint we > placed the _inode_ of the pipe in the hash table, while during restart > we place the resulting _file_ in the hash table. > > We restore the pipe contents we manually allocation and attaching > buffers to the pipe; (alternatively we could read the data from the > image file and then write it into the pipe, or use splice() syscall). > > Changelog[v14]: > - Discard the 'h.parent' field > - Check whether calls to cr_hbuf_get() fail > > Signed-off-by: Oren Laadan <[email protected]>
Acked-by: Serge Hallyn <[email protected]> ... > +/* restore a pipe */ > +static int cr_read_fd_pipe(struct cr_ctx *ctx, struct cr_hdr_file *hh) > +{ > + struct file *file; > + int fds[2], which, ret; > + > + file = cr_obj_get_by_ref(ctx, hh->fd_objref, CR_OBJ_FILE); > + if (IS_ERR(file)) > + return PTR_ERR(file); > + else if (file) > + return cr_attach_get_file(file); I think the casual reader would be helped by a comment like: /* * if cr_obj_get_by_ref returned a file, then one end * of the pipe has been restored, so we have * cr_attach_get_file() attach the other end to a new * fd, and we return that fd. */ > + > + /* first encounter of this pipe: create it */ > + ret = do_pipe(fds); > + if (ret < 0) > + return ret; thanks, -serge _______________________________________________ Containers mailing list [email protected] https://lists.linux-foundation.org/mailman/listinfo/containers _______________________________________________ Devel mailing list [email protected] https://openvz.org/mailman/listinfo/devel
