We support using O_DIRECT with multifd by isolating the main migration
channel which does unaligned IO from the multifd channels that do
aligned IO. When multifd is not enabled, we can still use O_DIRECT, if
we judiciously enable/disable the flag to avoid the unaligned IO.
Add helpers to enable/disable direct-io around the aligned parts.
Signed-off-by: Fabiano Rosas <faro...@suse.de>
---
migration/migration.c | 31 +++++++++++++++++++++++++++++++
migration/migration.h | 2 ++
migration/qemu-file.c | 29 +++++++++++++++++++++++++++++
migration/qemu-file.h | 2 +-
4 files changed, 63 insertions(+), 1 deletion(-)
diff --git a/migration/migration.c b/migration/migration.c
index e03c80b3aa..be128f95da 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -420,6 +420,37 @@ static void migrate_generate_event(int new_state)
}
}
+bool migration_direct_io_start(QEMUFile *file, Error **errp)
+{
+ if (!migrate_direct_io() || migrate_multifd()) {
+ return true;
+ }
+
+ /* flush any potentially unaligned IO before setting O_DIRECT */
+ qemu_fflush(file);
+
+ if (!qemu_file_set_direct_io(file, true)) {
+ error_setg(errp, "Failed to enable direct-io");
+ return false;
+ }
+
+ return true;
+}
+
+bool migration_direct_io_finish(QEMUFile *file, Error **errp)
+{
+ if (!migrate_direct_io() || migrate_multifd()) {
+ return true;
+ }
+
+ if (!qemu_file_set_direct_io(file, false)) {
+ error_setg(errp, "Failed to disable direct-io");
+ return false;
+ }
+
+ return true;
+}
+
/*
* Send a message on the return channel back to the source
* of the migration.
diff --git a/migration/migration.h b/migration/migration.h
index 6af01362d4..4d808563b5 100644
--- a/migration/migration.h
+++ b/migration/migration.h
@@ -536,4 +536,6 @@ int migration_rp_wait(MigrationState *s);
*/
void migration_rp_kick(MigrationState *s);
+bool migration_direct_io_start(QEMUFile *file, Error **errp);
+bool migration_direct_io_finish(QEMUFile *file, Error **errp);
#endif
diff --git a/migration/qemu-file.c b/migration/qemu-file.c
index 9ccbbb0099..4796be918f 100644
--- a/migration/qemu-file.c
+++ b/migration/qemu-file.c
@@ -52,6 +52,11 @@ struct QEMUFile {
int last_error;
Error *last_error_obj;
+ /*
+ * Whether O_DIRECT is in effect. Used to catch code attempting
+ * unaligned IO.
+ */
+ bool dio;
};
/*
@@ -281,6 +286,9 @@ int qemu_fflush(QEMUFile *f)
}
if (f->iovcnt > 0) {
Error *local_error = NULL;
+
+ assert(!f->dio);
+
if (qio_channel_writev_all(f->ioc,
f->iov, f->iovcnt,
&local_error) < 0) {
@@ -429,6 +437,8 @@ void qemu_put_buffer_async(QEMUFile *f, const uint8_t *buf,
size_t size,
return;
}
+ assert(!f->dio);
+
add_to_iovec(f, buf, size, may_free);
}
@@ -440,6 +450,8 @@ void qemu_put_buffer(QEMUFile *f, const uint8_t *buf,
size_t size)
return;
}
+ assert(!f->dio);
+
while (size > 0) {
l = IO_BUF_SIZE - f->buf_index;
if (l > size) {
@@ -558,6 +570,8 @@ off_t qemu_get_offset(QEMUFile *f)
void qemu_put_byte(QEMUFile *f, int v)
{
+ assert(!f->dio);
+
if (f->last_error) {
return;
}
@@ -865,3 +879,18 @@ int qemu_file_get_to_fd(QEMUFile *f, int fd, size_t size)
return 0;
}
+
+bool qemu_file_set_direct_io(QEMUFile *f, bool enabled)
+{
+ Error *local_err = NULL;
+
+ qio_channel_file_set_direct_io(f->ioc, enabled, &local_err);
+ if (local_err) {
+ qemu_file_set_error_obj(f, -EINVAL, local_err);
+ return false;
+ }
+
+ f->dio = enabled;
+
+ return true;
+}
diff --git a/migration/qemu-file.h b/migration/qemu-file.h
index 11c2120edd..118853b21c 100644
--- a/migration/qemu-file.h
+++ b/migration/qemu-file.h
@@ -79,5 +79,5 @@ 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);
-
+bool qemu_file_set_direct_io(QEMUFile *f, bool enabled);
#endif
--
2.35.3
