Add getdents based readdir functions for Linux (#1533)

src/fuse_readdir_cor.cpp

@@ -16,29 +16,13 @@
 
 #include "fuse_readdir_cor.hpp"
 
+#include "supported_getdents64.hpp"
+
 #include "config.hpp"
 #include "dirinfo.hpp"
-#include "errno.hpp"
-#include "fs_close.hpp"
-#include "fs_closedir.hpp"
-#include "fs_getdents64.hpp"
-#include "fs_inode.hpp"
-#include "fs_opendir.hpp"
-#include "fs_path.hpp"
-#include "fs_readdir.hpp"
-#include "hashset.hpp"
-#include "scope_guard.hpp"
+#include "error.hpp"
 #include "ugid.hpp"
 
-#include "fuse_dirents.h"
-#include "linux_dirent64.h"
-
-#include "int_types.h"
-
-#include <filesystem>
-
-#define MAX_ENTRIES_PER_LOOP 64
-
 
 FUSE::ReadDirCOR::ReadDirCOR(unsigned concurrency_,
                              unsigned max_queue_depth_)
@@ -52,113 +36,11 @@ FUSE::ReadDirCOR::~ReadDirCOR()
 
 }
 
-static
-u64
-_dirent_exact_namelen(const struct dirent *d_)
-{
-#ifdef _D_EXACT_NAMLEN
-  return _D_EXACT_NAMLEN(d_);
-#elif defined _DIRENT_HAVE_D_NAMLEN
-  return d_->d_namlen;
+#ifdef MERGERFS_SUPPORTED_GETDENTS64
+#include "fuse_readdir_cor_getdents.icpp"
 #else
-  return strlen(d_->d_name);
+#include "fuse_readdir_cor_readdir.icpp"
 #endif
-}
-
-struct Error
-{
-private:
-  int _err;
-
-public:
-  Error()
-    : _err(ENOENT)
-  {
-  }
-
-  operator int()
-  {
-    return _err;
-  }
-
-  Error&
-  operator=(int v_)
-  {
-    if(_err != 0)
-      _err = v_;
-
-    return *this;
-  }
-};
-
-static
-inline
-int
-_readdir(const fs::path &branch_path_,
-         const fs::path &rel_dirpath_,
-         HashSet        &names_,
-         fuse_dirents_t *buf_,
-         std::mutex     &mutex_)
-{
-  int rv;
-  DIR *dir;
-  fs::path rel_filepath;
-  fs::path abs_dirpath;
-
-  abs_dirpath = branch_path_ / rel_dirpath_;
-
-  errno = 0;
-  dir = fs::opendir(abs_dirpath);
-  if(dir == NULL)
-    return errno;
-
-  DEFER{ fs::closedir(dir); };
-
-  // The default buffer size in glibc is 32KB. 64 is based on a
-  // guess of an average size of 512B per entry. This is to limit
-  // contention on the lock when needing to request more data from
-  // the kernel. This could be handled better by using getdents but
-  // due to the differences between Linux and FreeBSD a more
-  // complicated abstraction needs to be created to handle them to
-  // make it easier to use across the codebase.
-  // * https://man7.org/linux/man-pages/man2/getdents.2.html
-  // * https://man.freebsd.org/cgi/man.cgi?query=getdents
-  rel_filepath = rel_dirpath_ / "dummy";
-  while(true)
-    {
-      std::lock_guard<std::mutex> lk(mutex_);
-      for(int i = 0; i < MAX_ENTRIES_PER_LOOP; i++)
-        {
-          dirent *de;
-          u64 namelen;
-
-          de = fs::readdir(dir);
-          if(de == NULL)
-            return 0;
-
-          namelen = ::_dirent_exact_namelen(de);
-
-          rv = names_.put(de->d_name,namelen);
-          if(rv == 0)
-            continue;
-
-          rel_filepath.replace_filename(de->d_name);
-
-          de->d_ino = fs::inode::calc(branch_path_,
-                                      rel_filepath,
-                                      DTTOIF(de->d_type),
-                                      de->d_ino);
-
-          rv = fuse_dirents_add(buf_,de,namelen);
-          if(rv >= 0)
-            continue;
-
-          return ENOMEM;
-        }
-    }
-
-  return 0;
-}
 
 static
 inline
@@ -166,7 +48,7 @@ int
 _concurrent_readdir(ThreadPool          &tp_,
                     const Branches::Ptr &branches_,
                     const fs::path      &rel_dirpath_,
-                    fuse_dirents_t      *buf_,
+                    fuse_dirents_t      *dirents_,
                     const uid_t          uid_,
                     const gid_t          gid_)
 {
@@ -174,20 +56,20 @@ _concurrent_readdir(ThreadPool          &tp_,
   std::mutex mutex;
   std::vector<std::future<int>> futures;
 
-  fuse_dirents_reset(buf_);
+  fuse_dirents_reset(dirents_);
   futures.reserve(branches_->size());
 
   for(const auto &branch : *branches_)
     {
       auto func =
-        [&,buf_,uid_,gid_]()
+        [&,dirents_,uid_,gid_]()
         {
           const ugid::Set ugid(uid_,gid_);
 
           return ::_readdir(branch.path,
                             rel_dirpath_,
                             names,
-                            buf_,
+                            dirents_,
                             mutex);
         };
 
@@ -196,16 +78,16 @@ _concurrent_readdir(ThreadPool          &tp_,
       futures.emplace_back(std::move(rv));
     }
 
-  Error error;
+  Err err;
   for(auto &future : futures)
-    error = future.get();
+    err = future.get();
 
-  return -error;
+  return err;
 }
 
 int
 FUSE::ReadDirCOR::operator()(const fuse_file_info_t *ffi_,
-                             fuse_dirents_t         *buf_)
+                             fuse_dirents_t         *dirents_)
 {
   DirInfo            *di = DirInfo::from_fh(ffi_->fh);
   const fuse_context *fc = fuse_get_context();
@@ -213,7 +95,7 @@ FUSE::ReadDirCOR::operator()(const fuse_file_info_t *ffi_,
   return ::_concurrent_readdir(_tp,
                                cfg.branches,
                                di->fusepath,
-                               buf_,
+                               dirents_,
                                fc->uid,
                                fc->gid);
 }