[Libguestfs] [nbdkit PATCH] ext2: Disable .can_multi_conn

Although passing through the plugin's multi-conn status happens to be safe due to our current .thread_model forbidding parallel connections, explicitly overriding it now will help us remember to think about the issue if we later improve the filter to allow parallelism. --- filters/ext2/ext2.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/filters/ext2/ext2.c b/filters/ext2/ext2.c index 549ef5ed..05ff634e 100644 --- a/filters/ext2/ext2.c +++ b/filters/ext2/ext2.c @@ -1,5 +1,5 @@ /* nbdkit - * Copyright (C) 2017-2020 Red Hat Inc. + * Copyright (C) 2017-2021 Red Hat Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are @@ -305,6 +305,20 @@ ext2_can_cache (struct nbdkit_next_ops *next_ops, void *nxdata, void *handle) return NBDKIT_CACHE_EMULATE; } +static int +ext2_can_multi_conn (struct nbdkit_next_ops *next_ops, void *nxdata, + void *handle) +{ + /* Since we do not permit parallel connections, it does not matter + * what we advertise here, and we could just as easily inherit the + * plugin's .can_multi_conn for now. But realistically, if we + * adjust .thread_model, we cannot advertise support unless .flush + * is consistent, and that would require inspecting the ext2 source + * code, so for now, we hard-code a safe answer. + */ + return 0; +} + /* It might be possible to relax this, but it's complicated. * * It's desirable for ‘nbdkit -r’ to behave the same way as @@ -470,6 +484,7 @@ static struct nbdkit_filter filter = { .close = ext2_close, .can_fua = ext2_can_fua, .can_cache = ext2_can_cache, + .can_multi_conn = ext2_can_multi_conn, .export_description = ext2_export_description, .get_size = ext2_get_size, .pread = ext2_pread, -- 2.30.1