Re: [PATCH 20/27] tools/libxl: Infrastructure for writing a v2 stream

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 16/06/15 15:57, Ian Campbell wrote:
> On Mon, 2015-06-15 at 14:44 +0100, Andrew Cooper wrote:
>> From: Ross Lagerwall <ross.lagerwall@citrix.com>
>>
>> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> CC: Ian Campbell <Ian.Campbell@citrix.com>
>> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
>> CC: Wei Liu <wei.liu2@citrix.com>
>> ---
>>  tools/libxl/Makefile             |    2 +-
>>  tools/libxl/libxl_internal.h     |   33 +++
>>  tools/libxl/libxl_stream_write.c |  536 ++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 570 insertions(+), 1 deletion(-)
>>  create mode 100644 tools/libxl/libxl_stream_write.c
>>
>> diff --git a/tools/libxl/Makefile b/tools/libxl/Makefile
>> index ca0ae3e..63e32f7 100644
>> --- a/tools/libxl/Makefile
>> +++ b/tools/libxl/Makefile
>> @@ -94,7 +94,7 @@ LIBXL_OBJS = flexarray.o libxl.o libxl_create.o libxl_dm.o libxl_pci.o \
>>  			libxl_dom.o libxl_exec.o libxl_xshelp.o libxl_device.o \
>>  			libxl_internal.o libxl_utils.o libxl_uuid.o \
>>  			libxl_json.o libxl_aoutils.o libxl_numa.o libxl_vnuma.o \
>> -			libxl_stream_read.o \
>> +			libxl_stream_read.o libxl_stream_write.o \
>>  			libxl_save_callout.o _libxl_save_msgs_callout.o \
>>  			libxl_convert_callout.o \
>>  			libxl_qmp.o libxl_event.o libxl_fork.o $(LIBXL_OBJS-y)
>> diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
>> index 5482950..82cd792 100644
>> --- a/tools/libxl/libxl_internal.h
>> +++ b/tools/libxl/libxl_internal.h
>> @@ -2868,6 +2868,38 @@ typedef void libxl__domain_suspend_cb(libxl__egc*,
>>  typedef void libxl__save_device_model_cb(libxl__egc*,
>>                                           libxl__domain_suspend_state*, int rc);
>>  
>> +/* State for writing a libxl migration v2 stream */
>> +typedef struct libxl__stream_write_state libxl__stream_write_state;
>> +
>> +struct libxl__stream_write_state {
>> +    /* filled by the user */
>> +    libxl__ao *ao;
>> +    int fd;
>> +    uint32_t domid;
>> +    void (*completion_callback)(libxl__egc *egc,
>> +                                libxl__domain_suspend_state *dss,
>> +                                int rc);
>> +    /* Private */
>> +    int rc;
>> +    int joined_rc;
>> +    size_t padding;
>> +    bool running;
>> +    libxl__datacopier_state dc;
>> +};
>> +
>> +_hidden void libxl__stream_write_start(libxl__egc *egc,
>> +                                       libxl__stream_write_state *stream);
>> +
>> +_hidden void libxl__stream_write_abort(libxl__egc *egc,
>> +                                       libxl__stream_write_state *stream,
>> +                                       int rc);
>> +
>> +static inline bool libxl__stream_write_inuse(
>> +    const libxl__stream_write_state *stream)
>> +{
>> +    return stream->running;
>> +}
>> +
>>  typedef struct libxl__logdirty_switch {
>>      const char *cmd;
>>      const char *cmd_path;
>> @@ -2907,6 +2939,7 @@ struct libxl__domain_suspend_state {
>>      /* private for libxl__domain_save_device_model */
>>      libxl__save_device_model_cb *save_dm_callback;
>>      libxl__datacopier_state save_dm_datacopier;
>> +    libxl__stream_write_state sws;
>>  };
>>  
>>
>> diff --git a/tools/libxl/libxl_stream_write.c b/tools/libxl/libxl_stream_write.c
>> new file mode 100644
>> index 0000000..856d72e
>> --- /dev/null
>> +++ b/tools/libxl/libxl_stream_write.c
>> @@ -0,0 +1,536 @@
>> +/*
>> + * Copyright (C) 2015      Citrix Ltd.
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU Lesser General Public License as published
>> + * by the Free Software Foundation; version 2.1 only. with the special
>> + * exception on linking described in file LICENSE.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU Lesser General Public License for more details.
>> + */
>> +
>> +#include "libxl_osdeps.h" /* must come before any other headers */
>> +
>> +#include "libxl_internal.h"
>> +
>> +/*
>> + * Infrastructure for writing a domain to a libxl migration v2 stream.
>> + *
>> + * Entry points from outside:
>> + *  - libxl__stream_write_start()
>> + *     - Start writing a stream from the start.
>> + *
>> + * In normal operation, there are two tasks running at once; this stream
>> + * processing, and the the libxl-save-helper.  check_stream_finished() is used
> "the the".
>
>> + * to join all the tasks in both success and error cases.
>> + *
>> + * Nomenclature for event callbacks:
>> + *  - $FOO_done(): Completion callback for $FOO
>> + *  - write_$FOO(): Set up writing a $FOO
> Set up or actually write?

Set up the dc to write $FOO

The write doesn't actually happen until we get the dc callback.

>
>> +
>> +void libxl__stream_write_start(libxl__egc *egc,
>> +                               libxl__stream_write_state *stream)
>> +{
>> +    libxl__datacopier_state *dc = &stream->dc;
>> +    STATE_AO_GC(stream->ao);
>> +    struct libxl_sr_hdr hdr = { 0 };
>> +    int ret = 0;
>> +
>> +    assert(!stream->running);
>> +    stream->running = true;
>> +
>> +    memset(dc, 0, sizeof(*dc));
> Please use the _init()

_init() is already called for us.

>
>
>> +static void check_stream_finished(libxl__egc *egc,
>> +                                  libxl__domain_suspend_state *dss,
>> +                                  int rc, const char *what)
>> +{
>> +    libxl__stream_write_state *stream = &dss->sws;
>> +    STATE_AO_GC(dss->ao);
>> +
>> +    LOG(INFO, "Task '%s' joining (rc %d)", what, rc);
>> +
>> +    if (rc && !stream->joined_rc) {
>> +        bool skip = false;
>> +        /* First reported failure from joining tasks.  Tear everything down */
>> +        stream->joined_rc = rc;
>
> This (not just this, but a bunch of the preceeding helpers) all looks
> rather familiar, can it be shared to some extent?

The types are all different, including the signature of the eventual
callback to use.  As COLO gets built on top, I expect these to diverge
further.

~Andrew