fuse-adaptor:Add splice api for all loop mode

This patch adds splice I/O support to the fuse request receive process for all
three loop modes. Due to some invisible struct definitions in the libfuse code,
parts of the libfuse interfaces have to be rewritten, which are all placed in
fuse-compat.cpp. For the same reason, we cannot automatically switch between splice(2)
and read(2) as libfuse does internally, so currently only the forced splice method
and the normal read interface are supported.

Author: haolianglh

fs/fuse_adaptor/fuse_adaptor.cpp

@@ -86,16 +86,9 @@ int fuser_go_exportfs(IFileSystem *fs_, int argc, char *argv[]) {
     return 0;
 }
 
-static int fuse_session_loop_mpt(struct fuse_session *se,
-                                 uint64_t looptype = FUSE_SESSION_LOOP_EPOLL) {
-    auto loop = new_session_loop(se, looptype);
-    loop->run();
-    delete loop;
-    return 0;
-}
-
 struct user_config {
     int threads;
+    int force_splice_read;
     char *looptype;
 };
 
@@ -117,6 +110,7 @@ uint64_t find_looptype(const char *name) {
 
 #define USER_OPT(t, p, v) { t, offsetof(struct user_config, p), v }
 struct fuse_opt user_opts[] = { USER_OPT("threads=%d",  threads, 0),
+                                USER_OPT("force_splice_read=%d", force_splice_read, 0),
                                 USER_OPT("looptype=%s", looptype, 0),
                                 FUSE_OPT_END };
 struct fuse_handle {
@@ -126,6 +120,7 @@ struct fuse_handle {
     char *mountpoint = NULL;
     int multithreaded = 1;
     int threads = 4;
+    int force_splice_read = 0;
     void *userdata = NULL;
 
     int setup(
@@ -136,16 +131,18 @@ struct fuse_handle {
         struct fuse_args args = FUSE_ARGS_INIT(argc, argv);
         DEFER(fuse_opt_free_args(&args));
 
-        struct user_config cfg{ .threads = 4, .looptype = NULL};
+        struct user_config cfg{ .threads = 4, .force_splice_read = 0, .looptype = NULL};
         fuse_opt_parse(&args, &cfg, user_opts, NULL);
         threads = cfg.threads;
         if (cfg.looptype)
             looptype = find_looptype(cfg.looptype);
 #if FUSE_USE_VERSION < FUSE_MAKE_VERSION(3, 13)
         looptype = FUSE_SESSION_LOOP_EPOLL;
 #endif
+        force_splice_read = cfg.force_splice_read;
         LOG_INFO("session cfg loop type: `", VALUE(cfg.looptype),
-                 " loop type: `", VALUE(looptype));
+                 " loop type: `", VALUE(looptype),
+                 " splice_read: `", VALUE(cfg.force_splice_read));
 
 #if FUSE_USE_VERSION < FUSE_MAKE_VERSION(3, 0)
         if (!ops) {
@@ -238,6 +235,17 @@ struct fuse_handle {
     }
 };
 
+static int fuse_session_loop_mpt(struct fuse_session *se,
+                                 const struct fuse_handle &fh) {
+    loop_args args;
+    args.looptype = fh.looptype;
+    args.force_splice_read = fh.force_splice_read;
+    auto loop = new_session_loop(se, args);
+    loop->run();
+    delete loop;
+    return 0;
+}
+
 static int _run_fuse(int argc, char *argv[],
                      const struct ::fuse_operations *op,
                      const struct ::fuse_lowlevel_ops *llops,
@@ -265,13 +273,13 @@ static int _run_fuse(int argc, char *argv[],
           ths.emplace_back(std::thread([&]() {
               init(INIT_EVENT_EPOLL, INIT_IO_LIBAIO);
               DEFER(fini());
-              if (fuse_session_loop_mpt(se, fh.looptype) != 0) ret = -1;
+              if (fuse_session_loop_mpt(se, fh) != 0) ret = -1;
           }));
         }
         for (auto& th : ths) th.join();
         fuse_session_reset(se);
     } else {
-        ret = fuse_session_loop_mpt(se);
+        ret = fuse_session_loop_mpt(se, fh);
         fuse_session_reset(se);
     }