Let -object memory-backend-file work on read-only files when the readonly=on option is given. This can be used to share the contents of a file between multiple guests while preventing them from consuming Copy-on-Write memory if guests dirty the pages, for example. Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com> Reviewed-by: Liam Merwick <liam.merwick@oracle.com> Acked-by: Michael S. Tsirkin <mst@redhat.com> Message-Id: <20210104171320.575838-3-stefanha@redhat.com> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
234 lines
6.6 KiB
C
234 lines
6.6 KiB
C
/*
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* QEMU Host Memory Backend for hugetlbfs
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*
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* Copyright (C) 2013-2014 Red Hat Inc
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*
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* Authors:
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* Paolo Bonzini <pbonzini@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#include "qemu/osdep.h"
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#include "qapi/error.h"
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#include "qemu/error-report.h"
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#include "qemu/module.h"
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#include "sysemu/hostmem.h"
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#include "sysemu/sysemu.h"
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#include "qom/object_interfaces.h"
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#include "qom/object.h"
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OBJECT_DECLARE_SIMPLE_TYPE(HostMemoryBackendFile, MEMORY_BACKEND_FILE)
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struct HostMemoryBackendFile {
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HostMemoryBackend parent_obj;
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char *mem_path;
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uint64_t align;
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bool discard_data;
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bool is_pmem;
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bool readonly;
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};
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static void
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file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
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{
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#ifndef CONFIG_POSIX
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error_setg(errp, "backend '%s' not supported on this host",
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object_get_typename(OBJECT(backend)));
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#else
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
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gchar *name;
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if (!backend->size) {
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error_setg(errp, "can't create backend with size 0");
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return;
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}
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if (!fb->mem_path) {
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error_setg(errp, "mem-path property not set");
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return;
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}
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name = host_memory_backend_get_name(backend);
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memory_region_init_ram_from_file(&backend->mr, OBJECT(backend),
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name,
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backend->size, fb->align,
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(backend->share ? RAM_SHARED : 0) |
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(fb->is_pmem ? RAM_PMEM : 0),
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fb->mem_path, fb->readonly, errp);
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g_free(name);
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#endif
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}
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static char *get_mem_path(Object *o, Error **errp)
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{
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
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return g_strdup(fb->mem_path);
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}
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static void set_mem_path(Object *o, const char *str, Error **errp)
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{
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HostMemoryBackend *backend = MEMORY_BACKEND(o);
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
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if (host_memory_backend_mr_inited(backend)) {
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error_setg(errp, "cannot change property 'mem-path' of %s",
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object_get_typename(o));
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return;
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}
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g_free(fb->mem_path);
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fb->mem_path = g_strdup(str);
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}
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static bool file_memory_backend_get_discard_data(Object *o, Error **errp)
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{
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return MEMORY_BACKEND_FILE(o)->discard_data;
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}
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static void file_memory_backend_set_discard_data(Object *o, bool value,
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Error **errp)
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{
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MEMORY_BACKEND_FILE(o)->discard_data = value;
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}
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static void file_memory_backend_get_align(Object *o, Visitor *v,
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const char *name, void *opaque,
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Error **errp)
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{
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
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uint64_t val = fb->align;
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visit_type_size(v, name, &val, errp);
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}
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static void file_memory_backend_set_align(Object *o, Visitor *v,
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const char *name, void *opaque,
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Error **errp)
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{
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HostMemoryBackend *backend = MEMORY_BACKEND(o);
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
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uint64_t val;
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if (host_memory_backend_mr_inited(backend)) {
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error_setg(errp, "cannot change property '%s' of %s", name,
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object_get_typename(o));
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return;
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}
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if (!visit_type_size(v, name, &val, errp)) {
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return;
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}
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fb->align = val;
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}
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static bool file_memory_backend_get_pmem(Object *o, Error **errp)
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{
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return MEMORY_BACKEND_FILE(o)->is_pmem;
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}
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static void file_memory_backend_set_pmem(Object *o, bool value, Error **errp)
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{
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HostMemoryBackend *backend = MEMORY_BACKEND(o);
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
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if (host_memory_backend_mr_inited(backend)) {
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error_setg(errp, "cannot change property 'pmem' of %s.",
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object_get_typename(o));
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return;
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}
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#ifndef CONFIG_LIBPMEM
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if (value) {
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error_setg(errp, "Lack of libpmem support while setting the 'pmem=on'"
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" of %s. We can't ensure data persistence.",
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object_get_typename(o));
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return;
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}
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#endif
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fb->is_pmem = value;
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}
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static bool file_memory_backend_get_readonly(Object *obj, Error **errp)
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{
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
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return fb->readonly;
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}
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static void file_memory_backend_set_readonly(Object *obj, bool value,
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Error **errp)
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{
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HostMemoryBackend *backend = MEMORY_BACKEND(obj);
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
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if (host_memory_backend_mr_inited(backend)) {
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error_setg(errp, "cannot change property 'readonly' of %s.",
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object_get_typename(obj));
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return;
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}
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fb->readonly = value;
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}
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static void file_backend_unparent(Object *obj)
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{
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HostMemoryBackend *backend = MEMORY_BACKEND(obj);
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(obj);
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if (host_memory_backend_mr_inited(backend) && fb->discard_data) {
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void *ptr = memory_region_get_ram_ptr(&backend->mr);
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uint64_t sz = memory_region_size(&backend->mr);
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qemu_madvise(ptr, sz, QEMU_MADV_REMOVE);
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}
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}
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static void
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file_backend_class_init(ObjectClass *oc, void *data)
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{
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HostMemoryBackendClass *bc = MEMORY_BACKEND_CLASS(oc);
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bc->alloc = file_backend_memory_alloc;
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oc->unparent = file_backend_unparent;
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object_class_property_add_bool(oc, "discard-data",
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file_memory_backend_get_discard_data, file_memory_backend_set_discard_data);
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object_class_property_add_str(oc, "mem-path",
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get_mem_path, set_mem_path);
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object_class_property_add(oc, "align", "int",
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file_memory_backend_get_align,
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file_memory_backend_set_align,
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NULL, NULL);
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object_class_property_add_bool(oc, "pmem",
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file_memory_backend_get_pmem, file_memory_backend_set_pmem);
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object_class_property_add_bool(oc, "readonly",
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file_memory_backend_get_readonly,
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file_memory_backend_set_readonly);
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}
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static void file_backend_instance_finalize(Object *o)
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{
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HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(o);
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g_free(fb->mem_path);
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}
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static const TypeInfo file_backend_info = {
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.name = TYPE_MEMORY_BACKEND_FILE,
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.parent = TYPE_MEMORY_BACKEND,
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.class_init = file_backend_class_init,
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.instance_finalize = file_backend_instance_finalize,
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.instance_size = sizeof(HostMemoryBackendFile),
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};
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static void register_types(void)
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{
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type_register_static(&file_backend_info);
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}
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type_init(register_types);
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