diff options
| -rw-r--r-- | docs/devel/migration/main.rst | 3 | ||||
| -rw-r--r-- | io/channel-file.c | 5 | ||||
| -rw-r--r-- | migration/multifd.c | 28 |
3 files changed, 21 insertions, 15 deletions
diff --git a/docs/devel/migration/main.rst b/docs/devel/migration/main.rst index 8024275d6d..54385a23e5 100644 --- a/docs/devel/migration/main.rst +++ b/docs/devel/migration/main.rst @@ -44,7 +44,8 @@ over any transport. - file migration: do the migration using a file that is passed to QEMU by path. A file offset option is supported to allow a management application to add its own metadata to the start of the file without - QEMU interference. + QEMU interference. Note that QEMU does not flush cached file + data/metadata at the end of migration. In addition, support is included for migration using RDMA, which transports the page data using ``RDMA``, where the hardware takes care of diff --git a/io/channel-file.c b/io/channel-file.c index d4706fa592..a6ad7770c6 100644 --- a/io/channel-file.c +++ b/io/channel-file.c @@ -242,11 +242,6 @@ static int qio_channel_file_close(QIOChannel *ioc, { QIOChannelFile *fioc = QIO_CHANNEL_FILE(ioc); - if (qemu_fdatasync(fioc->fd) < 0) { - error_setg_errno(errp, errno, - "Unable to synchronize file data with storage device"); - return -1; - } if (qemu_close(fioc->fd) < 0) { error_setg_errno(errp, errno, "Unable to close file"); diff --git a/migration/multifd.c b/migration/multifd.c index d4a44da559..bf9d483f7a 100644 --- a/migration/multifd.c +++ b/migration/multifd.c @@ -710,16 +710,26 @@ static bool multifd_send_cleanup_channel(MultiFDSendParams *p, Error **errp) if (p->c) { migration_ioc_unregister_yank(p->c); /* - * An explicit close() on the channel here is normally not - * required, but can be helpful for "file:" iochannels, where it - * will include fdatasync() to make sure the data is flushed to the - * disk backend. + * The object_unref() cannot guarantee the fd will always be + * released because finalize() of the iochannel is only + * triggered on the last reference and it's not guaranteed + * that we always hold the last refcount when reaching here. * - * The object_unref() cannot guarantee that because: (1) finalize() - * of the iochannel is only triggered on the last reference, and - * it's not guaranteed that we always hold the last refcount when - * reaching here, and, (2) even if finalize() is invoked, it only - * does a close(fd) without data flush. + * Closing the fd explicitly has the benefit that if there is any + * registered I/O handler callbacks on such fd, that will get a + * POLLNVAL event and will further trigger the cleanup to finally + * release the IOC. + * + * FIXME: It should logically be guaranteed that all multifd + * channels have no I/O handler callback registered when reaching + * here, because migration thread will wait for all multifd channel + * establishments to complete during setup. Since + * migrate_fd_cleanup() will be scheduled in main thread too, all + * previous callbacks should guarantee to be completed when + * reaching here. See multifd_send_state.channels_created and its + * usage. In the future, we could replace this with an assert + * making sure we're the last reference, or simply drop it if above + * is more clear to be justified. */ qio_channel_close(p->c, &error_abort); object_unref(OBJECT(p->c)); |