On Mon, Nov 27, 2023 at 05:25:55PM -0300, Fabiano Rosas wrote:
> Allow multifd to open file-backed channels. This will be used when
> enabling the fixed-ram migration stream format which expects a
> seekable transport.
>
> The QIOChannel read and write methods will use the preadv/pwritev
> versions which don't update the file offset at each call so we can
> reuse the fd without re-opening for every channel.
>
> Note that this is just setup code and multifd cannot yet make use of
> the file channels.
>
> Signed-off-by: Fabiano Rosas <faro...@suse.de>
> ---
> - open multifd channels with O_WRONLY and no mode
> - stop cancelling migration and propagate error via qio_task
> ---
> migration/file.c | 47 +++++++++++++++++++++++++++++++++++++++++--
> migration/file.h | 5 +++++
> migration/multifd.c | 14 +++++++++++--
> migration/options.c | 7 +++++++
> migration/options.h | 1 +
> migration/qemu-file.h | 1 -
> 6 files changed, 70 insertions(+), 5 deletions(-)
>
> diff --git a/migration/file.c b/migration/file.c
> index 5d4975f43e..67d6f42da7 100644
> --- a/migration/file.c
> +++ b/migration/file.c
> @@ -17,6 +17,10 @@
>
> #define OFFSET_OPTION ",offset="
>
> +static struct FileOutgoingArgs {
> + char *fname;
> +} outgoing_args;
> +
> /* Remove the offset option from @filespec and return it in @offsetp. */
>
> int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp)
> @@ -36,6 +40,42 @@ int file_parse_offset(char *filespec, uint64_t *offsetp,
> Error **errp)
> return 0;
> }
>
> +static void qio_channel_file_connect_worker(QIOTask *task, gpointer opaque)
> +{
> + /* noop */
> +}
> +
> +int file_send_channel_destroy(QIOChannel *ioc)
> +{
> + if (ioc) {
> + qio_channel_close(ioc, NULL);
> + object_unref(OBJECT(ioc));
> + }
> + g_free(outgoing_args.fname);
> + outgoing_args.fname = NULL;
> +
> + return 0;
> +}
> +
> +void file_send_channel_create(QIOTaskFunc f, void *data)
> +{
> + QIOChannelFile *ioc;
> + QIOTask *task;
> + Error *err = NULL;
> + int flags = O_WRONLY;
> +
> + ioc = qio_channel_file_new_path(outgoing_args.fname, flags, 0, &err);
> +
> + task = qio_task_new(OBJECT(ioc), f, (gpointer)data, NULL);
> + if (!ioc) {
> + qio_task_set_error(task, err);
> + return;
> + }
> +
> + qio_task_run_in_thread(task, qio_channel_file_connect_worker,
> + (gpointer)data, NULL, NULL);
This is pretty weird. This invokes a thread, but it'll run a noop. It
seems meaningless to me.
I assume you wanted to keep using the same async model as the socket typed
multifd, but I don't think that works anyway, because file open blocks at
qio_channel_file_new_path() so it's sync anyway.
AFAICT we still share the code, as long as the file path properly invokes
multifd_channel_connect() after the iochannel is setup.
> +}
> +
> void file_start_outgoing_migration(MigrationState *s,
> FileMigrationArgs *file_args, Error
> **errp)
> {
> @@ -43,15 +83,18 @@ void file_start_outgoing_migration(MigrationState *s,
> g_autofree char *filename = g_strdup(file_args->filename);
> uint64_t offset = file_args->offset;
> QIOChannel *ioc;
> + int flags = O_CREAT | O_TRUNC | O_WRONLY;
> + mode_t mode = 0660;
>
> trace_migration_file_outgoing(filename);
>
> - fioc = qio_channel_file_new_path(filename, O_CREAT | O_WRONLY | O_TRUNC,
> - 0600, errp);
> + fioc = qio_channel_file_new_path(filename, flags, mode, errp);
> if (!fioc) {
> return;
> }
>
> + outgoing_args.fname = g_strdup(filename);
> +
> ioc = QIO_CHANNEL(fioc);
> if (offset && qio_channel_io_seek(ioc, offset, SEEK_SET, errp) < 0) {
> return;
> diff --git a/migration/file.h b/migration/file.h
> index 37d6a08bfc..511019b319 100644
> --- a/migration/file.h
> +++ b/migration/file.h
> @@ -9,10 +9,15 @@
> #define QEMU_MIGRATION_FILE_H
>
> #include "qapi/qapi-types-migration.h"
> +#include "io/task.h"
> +#include "channel.h"
>
> void file_start_incoming_migration(FileMigrationArgs *file_args, Error
> **errp);
>
> void file_start_outgoing_migration(MigrationState *s,
> FileMigrationArgs *file_args, Error
> **errp);
> int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp);
> +
> +void file_send_channel_create(QIOTaskFunc f, void *data);
> +int file_send_channel_destroy(QIOChannel *ioc);
> #endif
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 123ff0dec0..427740aab6 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -17,6 +17,7 @@
> #include "exec/ramblock.h"
> #include "qemu/error-report.h"
> #include "qapi/error.h"
> +#include "file.h"
> #include "ram.h"
> #include "migration.h"
> #include "migration-stats.h"
> @@ -28,6 +29,7 @@
> #include "threadinfo.h"
> #include "options.h"
> #include "qemu/yank.h"
> +#include "io/channel-file.h"
> #include "io/channel-socket.h"
> #include "yank_functions.h"
>
> @@ -511,7 +513,11 @@ static void multifd_send_terminate_threads(Error *err)
>
> static int multifd_send_channel_destroy(QIOChannel *send)
> {
> - return socket_send_channel_destroy(send);
> + if (migrate_to_file()) {
> + return file_send_channel_destroy(send);
> + } else {
> + return socket_send_channel_destroy(send);
> + }
> }
>
> void multifd_save_cleanup(void)
> @@ -904,7 +910,11 @@ static void multifd_new_send_channel_async(QIOTask
> *task, gpointer opaque)
>
> static void multifd_new_send_channel_create(gpointer opaque)
> {
> - socket_send_channel_create(multifd_new_send_channel_async, opaque);
> + if (migrate_to_file()) {
> + file_send_channel_create(multifd_new_send_channel_async, opaque);
> + } else {
> + socket_send_channel_create(multifd_new_send_channel_async, opaque);
> + }
> }
>
> int multifd_save_setup(Error **errp)
> diff --git a/migration/options.c b/migration/options.c
> index 10730b13ba..f671e24758 100644
> --- a/migration/options.c
> +++ b/migration/options.c
> @@ -409,6 +409,13 @@ bool migrate_tls(void)
> return s->parameters.tls_creds && *s->parameters.tls_creds;
> }
>
> +bool migrate_to_file(void)
> +{
> + MigrationState *s = migrate_get_current();
> +
> + return qemu_file_is_seekable(s->to_dst_file);
> +}
Would this migrate_to_file() == migrate_multifd_packets()?
Maybe we can keep using the other one and drop migrate_to_file?
> +
> typedef enum WriteTrackingSupport {
> WT_SUPPORT_UNKNOWN = 0,
> WT_SUPPORT_ABSENT,
> diff --git a/migration/options.h b/migration/options.h
> index 8a19d6939c..84628a76e8 100644
> --- a/migration/options.h
> +++ b/migration/options.h
> @@ -60,6 +60,7 @@ bool migrate_multifd_packets(void);
> bool migrate_postcopy(void);
> bool migrate_rdma(void);
> bool migrate_tls(void);
> +bool migrate_to_file(void);
>
> /* capabilities helpers */
>
> diff --git a/migration/qemu-file.h b/migration/qemu-file.h
> index 32fd4a34fd..78ea21ab98 100644
> --- a/migration/qemu-file.h
> +++ b/migration/qemu-file.h
> @@ -83,5 +83,4 @@ size_t qemu_get_buffer_at(QEMUFile *f, const uint8_t *buf,
> size_t buflen,
> off_t pos);
>
> QIOChannel *qemu_file_get_ioc(QEMUFile *file);
> -
> #endif
> --
> 2.35.3
>
--
Peter Xu
