Re: [PATCH v5 17/23] migration/multifd: Add outgoing QIOChannelFile support

[Peter Xu <peterx@redhat.com>]

On Thu, Feb 29, 2024 at 10:44:21AM +0800, Peter Xu wrote:
> On Wed, Feb 28, 2024 at 12:21:21PM -0300, Fabiano Rosas wrote:
> > Allow multifd to open file-backed channels. This will be used when
> > enabling the mapped-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.
> > 
> > Contrary to the socket migration, the file migration doesn't need an
> > asynchronous channel creation process, so expose
> > multifd_channel_connect() and call it directly.
> > 
> > Note that this is just setup code and multifd cannot yet make use of
> > the file channels.
> > 
> > Signed-off-by: Fabiano Rosas <farosas@suse.de>
> > ---
> > - moved flags change to another patch
> > - removed channels_created assert
> > ---
> >  migration/file.c    | 41 +++++++++++++++++++++++++++++++++++++++--
> >  migration/file.h    |  4 ++++
> >  migration/multifd.c | 18 +++++++++++++++---
> >  migration/multifd.h |  1 +
> >  4 files changed, 59 insertions(+), 5 deletions(-)
> > 
> > diff --git a/migration/file.c b/migration/file.c
> > index 22d052a71f..83328a7a1b 100644
> > --- a/migration/file.c
> > +++ b/migration/file.c
> > @@ -12,12 +12,17 @@
> >  #include "channel.h"
> >  #include "file.h"
> >  #include "migration.h"
> > +#include "multifd.h"
> >  #include "io/channel-file.h"
> >  #include "io/channel-util.h"
> >  #include "trace.h"
> >  
> >  #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)
> > @@ -37,6 +42,36 @@ int file_parse_offset(char *filespec, uint64_t *offsetp, Error **errp)
> >      return 0;
> >  }
> >  
> > +void file_cleanup_outgoing_migration(void)
> > +{
> > +    g_free(outgoing_args.fname);
> > +    outgoing_args.fname = NULL;
> > +}
> > +
> > +bool file_send_channel_create(gpointer opaque, Error **errp)
> > +{
> > +    QIOChannelFile *ioc;
> > +    int flags = O_WRONLY;
> > +    bool ret = true;
> > +
> > +    ioc = qio_channel_file_new_path(outgoing_args.fname, flags, 0, errp);
> > +    if (!ioc) {
> > +        ret = false;
> > +        goto out;
> > +    }
> > +
> > +    multifd_channel_connect(opaque, QIO_CHANNEL(ioc));
> > +
> > +out:
> > +    /*
> > +     * File channel creation is synchronous. However posting this
> > +     * semaphore here is simpler than adding a special case.
> > +     */
> > +    multifd_send_channel_created();
> > +
> > +    return ret;
> > +}
> > +
> >  void file_start_outgoing_migration(MigrationState *s,
> >                                     FileMigrationArgs *file_args, Error **errp)
> >  {
> > @@ -47,12 +82,14 @@ void file_start_outgoing_migration(MigrationState *s,
> >  
> >      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, O_CREAT | O_TRUNC | O_WRONLY,
> > +                                     0660, errp);
> 
> It seems this is still leftover?
> 
> >      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..4577f9efdd 100644
> > --- a/migration/file.h
> > +++ b/migration/file.h
> > @@ -9,10 +9,14 @@
> >  #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_cleanup_outgoing_migration(void);
> > +bool file_send_channel_create(gpointer opaque, Error **errp);
> >  #endif
> > diff --git a/migration/multifd.c b/migration/multifd.c
> > index 3574fd3953..f155223303 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"
> >  
> > @@ -694,6 +696,7 @@ static bool multifd_send_cleanup_channel(MultiFDSendParams *p, Error **errp)
> >  {
> >      if (p->c) {
> >          migration_ioc_unregister_yank(p->c);
> > +        qio_channel_close(p->c, NULL);
> 
> s/NULL/&error_abort/?

Or we can drop this line?  IIUC iochannel finalize() will always close it,
or it could be a separate bug.

> 
> >          object_unref(OBJECT(p->c));
> >          p->c = NULL;
> >      }
> > @@ -715,6 +718,7 @@ static bool multifd_send_cleanup_channel(MultiFDSendParams *p, Error **errp)
> >  
> >  static void multifd_send_cleanup_state(void)
> >  {
> > +    file_cleanup_outgoing_migration();
> >      socket_cleanup_outgoing_migration();
> >      qemu_sem_destroy(&multifd_send_state->channels_created);
> >      qemu_sem_destroy(&multifd_send_state->channels_ready);
> > @@ -977,7 +981,7 @@ static bool multifd_tls_channel_connect(MultiFDSendParams *p,
> >      return true;
> >  }
> >  
> > -static void multifd_channel_connect(MultiFDSendParams *p, QIOChannel *ioc)
> > +void multifd_channel_connect(MultiFDSendParams *p, QIOChannel *ioc)
> >  {
> >      qio_channel_set_delay(ioc, false);
> >  
> > @@ -1045,9 +1049,14 @@ out:
> >      error_free(local_err);
> >  }
> >  
> > -static void multifd_new_send_channel_create(gpointer opaque)
> > +static bool multifd_new_send_channel_create(gpointer opaque, Error **errp)
> >  {
> > +    if (!multifd_use_packets()) {
> > +        return file_send_channel_create(opaque, errp);
> > +    }
> > +
> >      socket_send_channel_create(multifd_new_send_channel_async, opaque);
> > +    return true;
> >  }
> >  
> >  bool multifd_send_setup(void)
> > @@ -1096,7 +1105,10 @@ bool multifd_send_setup(void)
> >          p->page_size = qemu_target_page_size();
> >          p->page_count = page_count;
> >          p->write_flags = 0;
> > -        multifd_new_send_channel_create(p);
> > +
> > +        if (!multifd_new_send_channel_create(p, &local_err)) {
> > +            return -1;
> 
> "-1" is unfortunately a "true"!..
> 
> > +        }
> >      }
> >  
> >      /*
> > diff --git a/migration/multifd.h b/migration/multifd.h
> > index 1d8bbaf96b..db8887f088 100644
> > --- a/migration/multifd.h
> > +++ b/migration/multifd.h
> > @@ -227,5 +227,6 @@ static inline void multifd_send_prepare_header(MultiFDSendParams *p)
> >      p->iovs_num++;
> >  }
> >  
> > +void multifd_channel_connect(MultiFDSendParams *p, QIOChannel *ioc);
> >  
> >  #endif
> > -- 
> > 2.35.3
> > 
> 
> -- 
> Peter Xu

-- 
Peter Xu