On Mon, May 15, 2023 at 01:55:59PM +0200, Juan Quintela wrote: > Het Gala <het.g...@nutanix.com> wrote: > v> Just so that, there is a wider attention, I will try to address and > > discuss the comments from Daniel and Juan both here, as many of them > > seems to be overlapping. I hope that is fine with the maintainers. > > > > On 15/05/23 3:42 pm, Daniel P. Berrangé wrote: > >> On Fri, May 12, 2023 at 02:32:34PM +0000, Het Gala wrote: > >>> This patch introduces code that can parse 'uri' string parameter and > >>> spit out 'MigrateAddress' struct. All the required migration parameters > >>> are stored in the struct. > >>> > >>> Suggested-by: Aravind Retnakaran <aravind.retnaka...@nutanix.com> > >>> Signed-off-by: Het Gala <het.g...@nutanix.com> > >>> --- > >>> migration/migration.c | 63 +++++++++++++++++++++++++++++++++++++++++-- > >>> 1 file changed, 61 insertions(+), 2 deletions(-) > >>> > >>> diff --git a/migration/migration.c b/migration/migration.c > >>> index 0ee07802a5..a7e4e286aa 100644 > >>> --- a/migration/migration.c > >>> +++ b/migration/migration.c > >>> @@ -64,6 +64,7 @@ > >>> #include "yank_functions.h" > >>> #include "sysemu/qtest.h" > >>> #include "options.h" > >>> +#include "qemu/sockets.h" > >>> static NotifierList migration_state_notifiers = > >>> NOTIFIER_LIST_INITIALIZER(migration_state_notifiers); > >>> @@ -408,13 +409,58 @@ void migrate_add_address(SocketAddress *address) > >>> QAPI_CLONE(SocketAddress, address)); > >>> } > >>> +static bool migrate_uri_parse(const char *uri, > >>> + MigrateAddress **channel, > >>> + Error **errp) > >>> +{ > >>> + Error *local_err = NULL; > >>> + MigrateAddress *addrs = g_new0(MigrateAddress, 1); > >>> + SocketAddress *saddr; > >>> + InetSocketAddress *isock = &addrs->u.rdma; > >>> + strList **tail = &addrs->u.exec.args; > >>> + > >>> + if (strstart(uri, "exec:", NULL)) { > >>> + addrs->transport = MIGRATE_TRANSPORT_EXEC; > >>> + QAPI_LIST_APPEND(tail, g_strdup("/bin/sh")); > >>> + QAPI_LIST_APPEND(tail, g_strdup("-c")); > >>> + QAPI_LIST_APPEND(tail, g_strdup(uri + strlen("exec:"))); > >>> + } else if (strstart(uri, "rdma:", NULL) && > >>> + !inet_parse(isock, uri + strlen("rdma:"), errp)) { > >>> + addrs->transport = MIGRATE_TRANSPORT_RDMA; > >> I would have this as > >> > >> } else if (strstart(uri, "rdma:", NULL)) { > >> if (inet_parse(isock, uri + strlen("rdma:"), errp)) { > >> addrs->transport = MIGRATE_TRANSPORT_RDMA; > >> } > >> > >> as IMHO it is bad practice to have control pass to the next > >> else if clause when inet_parse() fails, as we know this is > >> only an RDMA addr > > Ack. I will change in the next patch. > >> Also you need to use '&local_err' not 'errp' in the inet_parse > >> call, otherwise the later code block for cleanup won't run. > > > > Yes, thanks for pointing it out Daniel. Will modify that. > > > > Also, Juan is of the opinion that we could omit 'local_error' variable > > and try to address and free the memory there itself. For ex: > > > > if (saddr == NULL) { > > qapi_free_MigrateAddress(addrs); > > return false; > > } > > > > Or, Daniel, can I also define here the variables like you suggested > > down in the patch ? or is it used in some special case or I am missing > > something ? > > > > g_autoptr(MigrateAddress) addrs = g_new0(MigrateAddress, 1); > > > > So we would not have to worry to free MigrateAddress struct. > > https://blogs.gnome.org/desrt/2015/01/30/g_autoptr/ > > Yes, but that only happens for the cases where you want to always remove > them. > > >>> + } else if (strstart(uri, "tcp:", NULL) || > >>> + strstart(uri, "unix:", NULL) || > >>> + strstart(uri, "vsock:", NULL) || > >>> + strstart(uri, "fd:", NULL)) { > >>> + addrs->transport = MIGRATE_TRANSPORT_SOCKET; > >>> + saddr = socket_parse(uri, &local_err); > >>> + addrs->u.socket = *saddr; > >> Protect with > >> > >> if (saddr != NULL) { > >> addrs->u.socket = *saddr; > >> } > >> > >>> + } > >>> + > >>> + if (local_err) { > >>> + qapi_free_MigrateAddress(addrs); > >>> + qapi_free_SocketAddress(saddr); > >>> + qapi_free_InetSocketAddress(isock); > >>> + error_propagate(errp, local_err); > >>> + return false; > >>> + } > >>> + > >>> + *channel = addrs; > >>> + return true; > >>> +} > >>> + > >>> static void qemu_start_incoming_migration(const char *uri, Error **errp) > >>> { > >>> const char *p = NULL; > >>> + MigrateAddress *channel = g_new0(MigrateAddress, 1); > >> Avoid the later 'out:' cleanup block by using: > >> > >> g_autoptr(MigrateAddress) channel = g_new0(MigrateAddress, 1); > > Ack. I think this also solves the doubt raised by Juan "I wish, I > > really wish, that there was a way to free things on error". Am I right > > ? > > No, that was the case where we have something like: > > Thing *foo(void) > { > OtherThing *bar = g_new0(OtherThing, 1) > > if (whatever) { > goto error; > } > if (whatever_else) { > goto error; > } > return bar; > error: > g_free(bad); > return NULL; > } [> > See, we have to put the goto because we have to free it in all error > paths. Not in the non-error path. > > If it is a pure local variable, i.e. never used after the function > finishes, then g_autoptr is the right thing to do.
It is still better to use g_autoptr even in that case. You just need to add in a call to g_steal_pointer in the success path. eg Thing *foo(void) { g_autoptr(OtherThing) bar = g_new0(OtherThing, 1) if (whatever) { return NULL; } if (whatever_else) { return NULL; } return g_steal_pointer(&bar); } g_steal_pointer(&bar) is the equivalent of doing OtherThing *tmp = bar; bar = NULL; return tmp; thus avoiding free'ing the pointer you're returning With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|