From 05cafc5002360015a79484e6ee40c159b1c80958 Mon Sep 17 00:00:00 2001
From: Benjamin Barenblat <bbaren@mit.edu>
Date: Sun, 21 Feb 2016 19:22:01 -0500
Subject: Replace creat with mknod+open

Performance is not an immediate concern, so replace creat with mknod to
compact code.
---
 src/operations.cc   | 28 ++++++++++++++--------------
 src/posix_extras.cc | 11 +++++++++++
 src/posix_extras.h  |  4 ++++
 3 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/src/operations.cc b/src/operations.cc
index 2bded60..df12738 100644
--- a/src/operations.cc
+++ b/src/operations.cc
@@ -75,7 +75,7 @@ int Getattr(const char* const path, struct stat* output) noexcept {
 }
 
 template <typename T>
-int OpenResource(const char* const path, const int flags, const mode_t mode,
+int OpenResource(const char* const path, const int flags,
                  uint64_t* const handle) noexcept {
   try {
     std::unique_ptr<T> t(new T(
@@ -85,7 +85,7 @@ int OpenResource(const char* const path, const int flags, const mode_t mode,
             *root_
             :
             // Trim the leading slash so OpenAt will treat it relative to root_.
-            root_->OpenAt(path + 1, flags, mode)));
+            root_->OpenAt(path + 1, flags)));
 
     static_assert(sizeof(*handle) == sizeof(std::uintptr_t),
                   "FUSE file handles are a different size than pointers");
@@ -107,29 +107,29 @@ int ReleaseResource(const uint64_t handle) noexcept {
   return 0;
 }
 
-int Open(const char* const path, fuse_file_info* const file_info) noexcept {
-  return OpenResource<File>(path, file_info->flags, 0777, &file_info->fh);
-}
-
-int Create(const char* const path, const mode_t mode,
-           fuse_file_info* const file_info) noexcept {
+int Mknod(const char* const c_path, const mode_t mode,
+          const dev_t dev) noexcept {
   try {
     if (std::strcmp(path, "/") == 0) {
       // They're asking to create the mount point.  Huh?
       return -EEXIST;
     }
 
-    return OpenResource<File>(path,
-                              file_info->flags | O_CREAT | O_WRONLY | O_EXCL,
-                              mode, &file_info->fh);
+    // Trim the leading slash so OpenAt will treat it relative to root_.
+    root_->MkNod(path + 1, mode, dev);
+    return 0;
   } catch (const std::system_error& e) {
     return -e.code().value();
   } catch (...) {
-    LOG(ERROR) << "create: caught unexpected value";
+    LOG(ERROR) << "mknod: caught unexpected value";
     return -ENOTRECOVERABLE;
   }
 }
 
+int Open(const char* const path, fuse_file_info* const file_info) noexcept {
+  return OpenResource<File>(path, file_info->flags, &file_info->fh);
+}
+
 int Release(const char*, fuse_file_info* const file_info) noexcept {
   return ReleaseResource<File>(file_info->fh);
 }
@@ -153,7 +153,7 @@ int Unlink(const char* c_path) noexcept {
 }
 
 int Opendir(const char* const path, fuse_file_info* const file_info) noexcept {
-  return OpenResource<Directory>(path, O_DIRECTORY, 0777, &file_info->fh);
+  return OpenResource<Directory>(path, O_DIRECTORY, &file_info->fh);
 }
 
 int Readdir(const char*, void* const buffer, fuse_fill_dir_t filler,
@@ -209,8 +209,8 @@ fuse_operations FuseOperations(File* const root) {
 
   result.getattr = &Getattr;
 
+  result.mknod = &Mknod;
   result.open = &Open;
-  result.create = &Create;
   result.release = &Release;
   result.unlink = &Unlink;
 
diff --git a/src/posix_extras.cc b/src/posix_extras.cc
index 359240f..f8274fb 100644
--- a/src/posix_extras.cc
+++ b/src/posix_extras.cc
@@ -75,6 +75,17 @@ struct stat File::LinkStatAt(const char* const path) const {
   return result;
 }
 
+void File::MkNod(const char* const path, const mode_t mode,
+                 const dev_t dev) const {
+  if (path[0] == '/') {
+    throw std::invalid_argument("absolute path");
+  }
+
+  if (mknodat(fd_, path, mode, dev) == -1) {
+    throw SystemError();
+  }
+}
+
 File File::OpenAt(const char* const path, const int flags,
                   const mode_t mode) const {
   if (path[0] == '/') {
diff --git a/src/posix_extras.h b/src/posix_extras.h
index 9bcbe51..60b2284 100644
--- a/src/posix_extras.h
+++ b/src/posix_extras.h
@@ -66,6 +66,10 @@ class File {
   // indeed be relative (i.e., it must not start with '/').
   struct stat LinkStatAt(const char* path) const;
 
+  // Creates a file or directory at the path relative to the file descriptor.
+  // The path must indeed be relative (i.e., it must not start with '/').
+  void MkNod(const char* path, mode_t mode, dev_t dev) const;
+
   // Calls openat(2) on the path relative to the file descriptor.  The path must
   // indeed be relative (i.e., it must not start with '/').
   File OpenAt(const char* const path, const int flags) const {
-- 
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