On Tue, May 24, 2016 at 10:55:07AM -0700, Jianjun Duan wrote: > A recursive structure has elements of the same type in itself. Currently > we cannot directly transfer a QTAILQ instance, or any recursive > structure such as lists in migration because of the limitation in the > migration code. Here we introduce a general approach to transfer such > structures. In our approach a recursive structure is tagged with VMS_CSTM. > We extend VMStateField with 3 fields: meta_data to store the meta data > about the recursive structure in question, extend_get to load the structure > from migration stream to memory, and extend_put to dump the structure into > the migration stream. This extension mirrors VMStateInfo. We then modify > vmstate_save_state and vmstate_load_state so that when VMS_CSTM is > encountered, extend_put and extend_get are called respectively with the > knowledge of the meta data.
All the talk about recursive structures just obscures the issue. The
point is you're building a way of migrating QTAILQs - just stick to
that.
> To make it work for QTAILQ in qemu/queue.h, we created the meta data
> format, extend_get and extend_put for it. We will use this approach to
> transfer pending_events and ccs_list in spapr state.
>
> We also create some macros in qemu/queue.h to get the layout information
> about QTAILQ. This ensures that we do not depend on the implementation
> details about QTAILQ in the migration code.
I'm interested to see what Juan and Dave Gilbert think about this.
>
> Signed-off-by: Jianjun Duan <du...@linux.vnet.ibm.com>
> ---
> include/migration/vmstate.h | 59 +++++++++++++++++++++++++++++++
> include/qemu/queue.h | 38 ++++++++++++++++++++
> migration/vmstate.c | 84
> +++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 181 insertions(+)
>
> diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h
> index 1622638..bf57b25 100644
> --- a/include/migration/vmstate.h
> +++ b/include/migration/vmstate.h
> @@ -183,6 +183,8 @@ enum VMStateFlags {
> * to determine the number of entries in the array. Only valid in
> * combination with one of VMS_VARRAY*. */
> VMS_MULTIPLY_ELEMENTS = 0x4000,
> + /* For fields which need customized handling, such as QTAILQ in queue.h*/
> + VMS_CSTM = 0x8000,
> };
>
> typedef struct {
> @@ -198,6 +200,14 @@ typedef struct {
> const VMStateDescription *vmsd;
> int version_id;
> bool (*field_exists)(void *opaque, int version_id);
> + /*
> + * Following 3 fields are for VMStateField which needs customized
> handling,
> + * such as QTAILQ in qemu/queue.h, lists, and tree.
> + */
> + const void *meta_data;
> + int (*extend_get)(QEMUFile *f, const void *metadata, void *opaque);
> + void (*extend_put)(QEMUFile *f, const void *metadata, void *opaque,
> + QJSON *vmdesc);
> } VMStateField;
>
> struct VMStateDescription {
> @@ -654,6 +664,18 @@ extern const VMStateInfo vmstate_info_bitmap;
> .offset = offsetof(_state, _field), \
> }
>
> +/* For fields that need customized handling, such as queue, list */
> +#define VMSTATE_CSTM_V(_field, _state, _version, _meta_data, _get, _put) \
> +{ \
> + .name = (stringify(_field)), \
> + .version_id = (_version), \
> + .flags = VMS_CSTM, \
> + .offset = offsetof(_state, _field), \
> + .meta_data = &(_meta_data), \
> + .extend_get = (_get), \
> + .extend_put = (_put), \
> +}
> +
> /* _f : field name
> _f_n : num of elements field_name
> _n : num of elements
> @@ -970,4 +992,41 @@ int64_t self_announce_delay(int round)
>
> void dump_vmstate_json_to_file(FILE *out_fp);
>
> +
> +/* Meta data for QTAILQ */
> +typedef struct QTAILQMetaData {
> + /* the offset of tqh_first in QTAILQ_HEAD */
> + size_t first;
> + /* the offset of tqh_last in QTAILQ_HEAD */
> + size_t last;
> + /* the offset of tqe_next in QTAILQ_ENTRY */
> + size_t next;
> + /* the offset of tqe_prev in QTAILQ_ENTRY */
> + size_t prev;
> + /* the offset of QTAILQ_ENTRY in a QTAILQ element*/
> + size_t entry;
> + /* size of a QTAILQ element */
> + size_t size;
> + /* vmsd of a QTAILQ element */
> + const VMStateDescription *vmsd;
> +} QTAILQMetaData;
> +
> +#define VMSTATE_QTAILQ_METADATA(_field, _state, _type, _next, _vmsd) { \
> + .first = QTAILQ_FIRST_OFFSET(typeof_field(_state, _field)), \
> + .last = QTAILQ_LAST_OFFSET(typeof_field(_state, _field)), \
> + .next = QTAILQ_NEXT_OFFSET(_type, _next), \
> + .prev = QTAILQ_PREV_OFFSET(_type, _next), \
> + .entry = offsetof(_type, _next), \
> + .size = sizeof(_type), \
> + .vmsd = &(_vmsd), \
> +}
> +
> +int vmstate_get_qtailq(QEMUFile *f, const void *metadata, void *opaque);
> +void vmstate_put_qtailq(QEMUFile *f, const void *metadata,
> + void *opaque, QJSON *vmdesc);
> +
> +/* VMStateField for QTAILQ field */
> +#define VMSTATE_QTAILQ_V(_field, _state, _version, _meta_data)
> \
> + VMSTATE_CSTM_V(_field, _state, _version, _meta_data, vmstate_get_qtailq,
> \
> + vmstate_put_qtailq)
> #endif
> diff --git a/include/qemu/queue.h b/include/qemu/queue.h
> index f781aa2..46962d7 100644
> --- a/include/qemu/queue.h
> +++ b/include/qemu/queue.h
> @@ -437,3 +437,41 @@ struct {
> \
> (*(((struct headname *)((elm)->field.tqe_prev))->tqh_last))
>
> #endif /* !QEMU_SYS_QUEUE_H_ */
> +
> +/*
> + * Offsets of layout of a tail queue head.
> + */
> +#define QTAILQ_FIRST_OFFSET(head_type) \
> + ((size_t) ((char *) &((head_type *)0)->tqh_first - (char *)0))
> +
> +#define QTAILQ_LAST_OFFSET(head_type) \
> + ((size_t) ((char *) &((head_type *)0)->tqh_last - (char *)0))
> +
> +/*
> + * Offsets of layout of a tail queue element.
> + */
> +#define QTAILQ_NEXT_OFFSET(ele_type, field) \
> + ((size_t) ((char *) &((ele_type *)0)->field.tqe_next - \
> + (char *) &((ele_type *)0)->field))
> +
> +#define QTAILQ_PREV_OFFSET(ele_type, field) \
> + ((size_t) ((char *) &((ele_type *)0)->field.tqe_prev - \
> + (char *) &((ele_type *)0)->field))
> +/*
> + * Tail queue tranversal using pointer arithmetic.
> + */
> +#define QTAILQ_RAW_FOREACH(elm, head, entry, first, next) \
> + for ((elm) = *((void **) ((char *) (head) + (first))); \
> + (elm); \
> + (elm) = *((void **) ((char *) (elm) + (entry) + (next))))
> +/*
> + * Tail queue insertion using pointer arithmetic.
> + */
> +#define QTAILQ_RAW_INSERT_TAIL(head, elm, entry, first, last, next, prev) do
> { \
> + *((void **) ((char *) (elm) + (entry) + (next))) = NULL;
> \
> + *((void **) ((char *) (elm) + (entry) + (prev))) =
> \
> + *((void **) ((char *) (head) + (last)));
> \
> + **((void ***)((char *) (head) + (last))) = (elm);
> \
> + *((void **) ((char *) (head) + (last))) =
> \
> + (void *) ((char *) (elm) + (entry) + (next));
> \
> +} while (/*CONSTCOND*/0)
> diff --git a/migration/vmstate.c b/migration/vmstate.c
> index bf3d5db..47cd052 100644
> --- a/migration/vmstate.c
> +++ b/migration/vmstate.c
> @@ -5,6 +5,7 @@
> #include "migration/vmstate.h"
> #include "qemu/bitops.h"
> #include "qemu/error-report.h"
> +#include "qemu/queue.h"
> #include "trace.h"
> #include "qjson.h"
>
> @@ -121,6 +122,8 @@ int vmstate_load_state(QEMUFile *f, const
> VMStateDescription *vmsd,
> if (field->flags & VMS_STRUCT) {
> ret = vmstate_load_state(f, field->vmsd, addr,
> field->vmsd->version_id);
> + } else if (field->flags & VMS_CSTM) {
> + ret = field->extend_get(f, field->meta_data, addr);
> } else {
> ret = field->info->get(f, addr, size);
>
> @@ -193,6 +196,8 @@ static const char *vmfield_get_type_name(VMStateField
> *field)
>
> if (field->flags & VMS_STRUCT) {
> type = "struct";
> + } else if (field->flags & VMS_CSTM) {
> + type = "customized";
> } else if (field->info->name) {
> type = field->info->name;
> }
> @@ -327,6 +332,8 @@ void vmstate_save_state(QEMUFile *f, const
> VMStateDescription *vmsd,
> }
> if (field->flags & VMS_STRUCT) {
> vmstate_save_state(f, field->vmsd, addr, vmdesc_loop);
> + } else if (field->flags & VMS_CSTM) {
> + field->extend_put(f, field->meta_data, addr,
> vmdesc_loop);
> } else {
> field->info->put(f, addr, size);
> }
> @@ -916,3 +923,80 @@ const VMStateInfo vmstate_info_bitmap = {
> .get = get_bitmap,
> .put = put_bitmap,
> };
> +
> +/* extend_get for QTAILQ */
> +int vmstate_get_qtailq(QEMUFile *f, const void *metadata, void *opaque)
> +{
> + bool link;
> + int ret = 0;
> + size_t first, last, next, prev, entry, size;
> + QTAILQMetaData *data = (QTAILQMetaData *)metadata;
> + const VMStateDescription *vmsd = data->vmsd;
> + int version_id = vmsd->version_id;
> + void *elm;
> +
> + first = data->first;
> + last = data->last;
> + next = data->next;
> + prev = data->prev;
> + entry = data->entry;
> + size = data->size;
> +
> + trace_vmstate_load_state(vmsd->name, version_id);
> + if (version_id > vmsd->version_id) {
> + trace_vmstate_load_state_end(vmsd->name, "too new", -EINVAL);
> + return -EINVAL;
> + }
> + if (version_id < vmsd->minimum_version_id) {
> + trace_vmstate_load_state_end(vmsd->name, "too old", -EINVAL);
> + return -EINVAL;
> + }
> +
> + while (true) {
> + vmstate_info_bool.get(f, &link, sizeof(bool));
> + if (!link) {
> + break;
> + }
> +
> + elm = g_malloc(size);
> + ret = vmstate_load_state(f, vmsd, elm, version_id);
> + if (ret) {
> + return ret;
> + }
> + QTAILQ_RAW_INSERT_TAIL(opaque, elm, entry, first, last, next, prev);
> + }
> +
> + trace_vmstate_load_state_end(vmsd->name, "end", ret);
> + return ret;
> +}
> +
> +/* extend_get for QTAILQ */
> +void vmstate_put_qtailq(QEMUFile *f, const void *metadata, void *opaque,
> + QJSON *vmdesc)
> +{
> + bool link = true;
> + size_t first, next, entry;
> + QTAILQMetaData *data = (QTAILQMetaData *)metadata;
> + const VMStateDescription *vmsd = data->vmsd;
> + void *elm;
> +
> + first = data->first;
> + next = data->next;
> + entry = data->entry;
> +
> + if (vmdesc) {
> + json_prop_str(vmdesc, "vmsd_name", vmsd->name);
> + json_prop_int(vmdesc, "version", vmsd->version_id);
> + json_start_array(vmdesc, "fields");
> + }
> +
> + QTAILQ_RAW_FOREACH(elm, opaque, entry, first, next) {
> + vmstate_info_bool.put(f, &link, sizeof(bool));
> + vmstate_save_state(f, vmsd, elm, vmdesc);
> + }
> + link = false;
> + vmstate_info_bool.put(f, &link, sizeof(bool));
> + if (vmdesc) {
> + json_end_array(vmdesc);
> + }
> +}
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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