Re: [PATCH v2 20/29] migration/multifd: Add incoming QIOChannelFile support

[Fabiano Rosas <farosas@suse.de>]

Daniel P. Berrangé <berrange@redhat.com> writes:

> On Mon, Oct 23, 2023 at 05:35:59PM -0300, Fabiano Rosas wrote:
>> On the receiving side we don't need to differentiate between main
>> channel and threads, so whichever channel is defined first gets to be
>> the main one. And since there are no packets, use the atomic channel
>> count to index into the params array.
>> 
>> Signed-off-by: Fabiano Rosas <farosas@suse.de>
>> ---
>>  migration/file.c      | 39 +++++++++++++++++++++++++++++----------
>>  migration/migration.c |  2 ++
>>  migration/multifd.c   |  7 ++++++-
>>  migration/multifd.h   |  1 +
>>  4 files changed, 38 insertions(+), 11 deletions(-)
>> 
>> diff --git a/migration/file.c b/migration/file.c
>> index 93b9b7bf5d..ad75225f43 100644
>> --- a/migration/file.c
>> +++ b/migration/file.c
>> @@ -6,13 +6,15 @@
>>   */
>>  
>>  #include "qemu/osdep.h"
>> -#include "qemu/cutils.h"
>>  #include "qapi/error.h"
>> +#include "qemu/cutils.h"
>> +#include "qemu/error-report.h"
>>  #include "channel.h"
>>  #include "file.h"
>>  #include "migration.h"
>>  #include "io/channel-file.h"
>>  #include "io/channel-util.h"
>> +#include "options.h"
>>  #include "trace.h"
>>  
>>  #define OFFSET_OPTION ",offset="
>> @@ -136,7 +138,8 @@ void file_start_incoming_migration(const char *filespec, Error **errp)
>>      g_autofree char *filename = g_strdup(filespec);
>>      QIOChannelFile *fioc = NULL;
>>      uint64_t offset = 0;
>> -    QIOChannel *ioc;
>> +    int channels = 1;
>> +    int i = 0, fd;
>>  
>>      trace_migration_file_incoming(filename);
>>  
>> @@ -146,16 +149,32 @@ void file_start_incoming_migration(const char *filespec, Error **errp)
>>  
>>      fioc = qio_channel_file_new_path(filename, O_RDONLY, 0, errp);
>>      if (!fioc) {
>> -        return;
>> +        goto out;
>> +    }
>> +
>> +    if (migrate_multifd()) {
>> +        channels += migrate_multifd_channels();
>>      }
>>  
>> -    ioc = QIO_CHANNEL(fioc);
>> -    if (offset && qio_channel_io_seek(ioc, offset, SEEK_SET, errp) < 0) {
>> +    fd = fioc->fd;
>> +
>> +    do {
>> +        QIOChannel *ioc = QIO_CHANNEL(fioc);
>> +
>> +        if (offset && qio_channel_io_seek(ioc, offset, SEEK_SET, errp) < 0) {
>> +            return;
>> +        }
>> +
>> +        qio_channel_set_name(ioc, "migration-file-incoming");
>> +        qio_channel_add_watch_full(ioc, G_IO_IN,
>> +                                   file_accept_incoming_migration,
>> +                                   NULL, NULL,
>> +                                   g_main_context_get_thread_default());
>> +    } while (++i < channels && (fioc = qio_channel_file_new_fd(fd)));
>
> IIUC, this loop is failing to call qio_channel_io_seek to set
> the offset on the last 'fioc' that is created.
>

Ah, this is actually bogus. We don't need to offset the secondary
channels. That does nothing since we carry pointers to everything in the
fixed-ram header. This should be out of the loop.