Merge pull request #710 from trapexit/writeback-xattr

add cache.writeback to xattrs

src/fuse_create.cpp

@@ -45,18 +45,48 @@ namespace l
     true of any caching.
   */
   static
-  int
-  tweak_flags_writeback_cache(const int flags_)
+  void
+  tweak_flags_writeback_cache(int *flags_)
   {
-    int flags;
-
-    flags = flags_;
-    if((flags & O_ACCMODE) == O_WRONLY)
-      flags = ((flags & ~O_ACCMODE) | O_RDWR);
-    if(flags & O_APPEND)
-      flags &= ~O_APPEND;
+    if((*flags_ & O_ACCMODE) == O_WRONLY)
+      *flags_ = ((*flags_ & ~O_ACCMODE) | O_RDWR);
+    if(*flags_ & O_APPEND)
+      *flags_ &= ~O_APPEND;
+  }
 
-    return flags;
+  static
+  void
+  config_to_ffi_flags(const Config   &config_,
+                      fuse_file_info *ffi_)
+  {
+    switch(config_.cache_files)
+      {
+      case CacheFiles::LIBFUSE:
+        ffi_->direct_io  = config_.direct_io;
+        ffi_->keep_cache = config_.kernel_cache;
+        ffi_->auto_cache = config_.auto_cache;
+        break;
+      case CacheFiles::OFF:
+        ffi_->direct_io  = 1;
+        ffi_->keep_cache = 0;
+        ffi_->auto_cache = 0;
+        break;
+      case CacheFiles::PARTIAL:
+        ffi_->direct_io  = 0;
+        ffi_->keep_cache = 0;
+        ffi_->auto_cache = 0;
+        break;
+      case CacheFiles::FULL:
+        ffi_->direct_io  = 0;
+        ffi_->keep_cache = 1;
+        ffi_->auto_cache = 0;
+        break;
+      case CacheFiles::AUTO_FULL:
+        ffi_->direct_io  = 0;
+        ffi_->keep_cache = 0;
+        ffi_->auto_cache = 1;
+        break;
+      }
   }
 
   static
@@ -148,37 +178,10 @@ namespace FUSE
     const ugid::Set          ugid(fc->uid,fc->gid);
     const rwlock::ReadGuard  readlock(&config.branches_lock);
 
-    switch(config.cache_files)
-      {
-      case CacheFiles::LIBFUSE:
-        ffi_->direct_io  = config.direct_io;
-        ffi_->keep_cache = config.kernel_cache;
-        ffi_->auto_cache = config.auto_cache;
-        break;
-      case CacheFiles::OFF:
-        ffi_->direct_io  = 1;
-        ffi_->keep_cache = 0;
-        ffi_->auto_cache = 0;
-        break;
-      case CacheFiles::PARTIAL:
-        ffi_->direct_io  = 0;
-        ffi_->keep_cache = 0;
-        ffi_->auto_cache = 0;
-        break;
-      case CacheFiles::FULL:
-        ffi_->direct_io  = 0;
-        ffi_->keep_cache = 1;
-        ffi_->auto_cache = 0;
-        break;
-      case CacheFiles::AUTO_FULL:
-        ffi_->direct_io  = 0;
-        ffi_->keep_cache = 0;
-        ffi_->auto_cache = 1;
-        break;
-      }
+    l::config_to_ffi_flags(config,ffi_);
 
     if(config.writeback_cache)
-      ffi_->flags = l::tweak_flags_writeback_cache(ffi_->flags);
+      l::tweak_flags_writeback_cache(&ffi_->flags);
 
     return l::create(config.getattr,
                      config.create,

src/fuse_getxattr.cpp

@@ -395,6 +395,8 @@ namespace l
           l::getxattr_controlfile_bool(config.cache_readdir,attrvalue);
         else if((attr[2] == "cache") && (attr[3] == "files"))
           l::getxattr_controlfile(config.cache_files,attrvalue);
+        else if((attr[2] == "cache") && (attr[3] == "writeback"))
+          l::getxattr_controlfile_bool(config.writeback_cache,attrvalue);
         break;
       }
 

src/fuse_listxattr.cpp

@@ -54,6 +54,7 @@ namespace l
       ("user.mergerfs.cache.readdir")
       ("user.mergerfs.cache.statfs")
       ("user.mergerfs.cache.symlinks")
+      ("user.mergerfs.cache.writeback")
       ("user.mergerfs.direct_io")
       ("user.mergerfs.dropcacheonclose")
       ("user.mergerfs.fuse_msg_size")

src/fuse_open.cpp

@@ -35,19 +35,58 @@ typedef Config::CacheFiles CacheFiles;
 
 namespace l
 {
+  /*
+    The kernel expects being able to issue read requests when running
+    with writeback caching enabled so we must change O_WRONLY to
+    O_RDWR.
+
+    With writeback caching enabled the kernel handles O_APPEND. Could
+    be an issue if the underlying file changes out of band but that is
+    true of any caching.
+  */
   static
-  int
-  tweak_flags_writeback_cache(const int flags_)
+  void
+  tweak_flags_writeback_cache(int *flags_)
   {
-    int flags;
-
-    flags = flags_;
-    if((flags & O_ACCMODE) == O_WRONLY)
-      flags = ((flags & ~O_ACCMODE) | O_RDWR);
-    if(flags & O_APPEND)
-      flags &= ~O_APPEND;
+    if((*flags_ & O_ACCMODE) == O_WRONLY)
+      *flags_ = ((*flags_ & ~O_ACCMODE) | O_RDWR);
+    if(*flags_ & O_APPEND)
+      *flags_ &= ~O_APPEND;
+  }
 
-    return flags;
+  static
+  void
+  config_to_ffi_flags(const Config   &config_,
+                      fuse_file_info *ffi_)
+  {
+    switch(config_.cache_files)
+      {
+      case CacheFiles::LIBFUSE:
+        ffi_->direct_io  = config_.direct_io;
+        ffi_->keep_cache = config_.kernel_cache;
+        ffi_->auto_cache = config_.auto_cache;
+        break;
+      case CacheFiles::OFF:
+        ffi_->direct_io  = 1;
+        ffi_->keep_cache = 0;
+        ffi_->auto_cache = 0;
+        break;
+      case CacheFiles::PARTIAL:
+        ffi_->direct_io  = 0;
+        ffi_->keep_cache = 0;
+        ffi_->auto_cache = 0;
+        break;
+      case CacheFiles::FULL:
+        ffi_->direct_io  = 0;
+        ffi_->keep_cache = 1;
+        ffi_->auto_cache = 0;
+        break;
+      case CacheFiles::AUTO_FULL:
+        ffi_->direct_io  = 0;
+        ffi_->keep_cache = 0;
+        ffi_->auto_cache = 1;
+        break;
+      }
   }
 
   static
@@ -108,37 +147,10 @@ namespace FUSE
     const ugid::Set          ugid(fc->uid,fc->gid);
     const rwlock::ReadGuard  readlock(&config.branches_lock);
 
-    switch(config.cache_files)
-      {
-      case CacheFiles::LIBFUSE:
-        ffi_->direct_io  = config.direct_io;
-        ffi_->keep_cache = config.kernel_cache;
-        ffi_->auto_cache = config.auto_cache;
-        break;
-      case CacheFiles::OFF:
-        ffi_->direct_io  = 1;
-        ffi_->keep_cache = 0;
-        ffi_->auto_cache = 0;
-        break;
-      case CacheFiles::PARTIAL:
-        ffi_->direct_io  = 0;
-        ffi_->keep_cache = 0;
-        ffi_->auto_cache = 0;
-        break;
-      case CacheFiles::FULL:
-        ffi_->direct_io  = 0;
-        ffi_->keep_cache = 1;
-        ffi_->auto_cache = 0;
-        break;
-      case CacheFiles::AUTO_FULL:
-        ffi_->direct_io  = 0;
-        ffi_->keep_cache = 0;
-        ffi_->auto_cache = 1;
-        break;
-      }
+    l::config_to_ffi_flags(config,ffi_);
 
     if(config.writeback_cache)
-      ffi_->flags = l::tweak_flags_writeback_cache(ffi_->flags);
+      l::tweak_flags_writeback_cache(&ffi_->flags);
 
     return l::open(config.open,
                    config.open_cache,