On Thu, Feb 29, 2024 at 11:27:44AM -0300, Fabiano Rosas wrote:
> Peter Xu <pet...@redhat.com> writes:
>
> > 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 <faro...@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.
> >
>
> We need it so the fsync happens. The finalize() will be a noop because
> the qio_channel_file_close() will clear the fd. Not the cleanest, but it
> works.
It is always wise to explicitly call 'close'.
If something still has a GSource watch registered against
the QIOChannel, that GSource will be holding a reference
on the QIOChannel and will thus prevent finalize() ever
running.
By calling close() you guarantee the channel is closed,
even if you've mistakenly leaked a GSource somewhere.
Finalize still won't run in that case, but at least the
FD is gone, and the HUP might cause the GSource callback
to trigger correct cleanup;
With regards,
Daniel
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