mergerfs/src/fuse_create.cpp

/*
  Copyright (c) 2016, Antonio SJ Musumeci <trapexit@spawn.link>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#include "config.hpp"
#include "errno.hpp"
#include "fileinfo.hpp"
#include "fs_acl.hpp"
#include "fs_clonepath.hpp"
#include "fs_open.hpp"
#include "fs_path.hpp"
#include "ugid.hpp"

#include "fuse.h"

#include <string>
#include <vector>

using std::string;
using std::vector;


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
  void
  tweak_flags_writeback_cache(int *flags_)
  {
    if((*flags_ & O_ACCMODE) == O_WRONLY)
      *flags_ = ((*flags_ & ~O_ACCMODE) | O_RDWR);
    if(*flags_ & O_APPEND)
      *flags_ &= ~O_APPEND;
  }

  static
  void
  config_to_ffi_flags(Config::Read     &cfg_,
                      fuse_file_info_t *ffi_)
  {
    switch(cfg_->cache_files)
      {
      case CacheFiles::ENUM::LIBFUSE:
        ffi_->direct_io  = cfg_->direct_io;
        ffi_->keep_cache = cfg_->kernel_cache;
        ffi_->auto_cache = cfg_->auto_cache;
        break;
      case CacheFiles::ENUM::OFF:
        ffi_->direct_io  = 1;
        ffi_->keep_cache = 0;
        ffi_->auto_cache = 0;
        break;
      case CacheFiles::ENUM::PARTIAL:
        ffi_->direct_io  = 0;
        ffi_->keep_cache = 0;
        ffi_->auto_cache = 0;
        break;
      case CacheFiles::ENUM::FULL:
        ffi_->direct_io  = 0;
        ffi_->keep_cache = 1;
        ffi_->auto_cache = 0;
        break;
      case CacheFiles::ENUM::AUTO_FULL:
        ffi_->direct_io  = 0;
        ffi_->keep_cache = 0;
        ffi_->auto_cache = 1;
        break;
      }
  }

  static
  int
  create_core(const string &fullpath_,
              mode_t        mode_,
              const mode_t  umask_,
              const int     flags_)
  {
    if(!fs::acl::dir_has_defaults(fullpath_))
      mode_ &= ~umask_;

    return fs::open(fullpath_,flags_,mode_);
  }

  static
  int
  create_core(const string &createpath_,
              const char   *fusepath_,
              const mode_t  mode_,
              const mode_t  umask_,
              const int     flags_,
              uint64_t     *fh_)
  {
    int rv;
    string fullpath;

    fullpath = fs::path::make(createpath_,fusepath_);

    rv = l::create_core(fullpath,mode_,umask_,flags_);
    if(rv == -1)
      return -errno;

    *fh_ = reinterpret_cast<uint64_t>(new FileInfo(rv,fusepath_));

    return 0;
  }

  static
  int
  create(const Policy::Search &searchFunc_,
         const Policy::Create &createFunc_,
         const Branches       &branches_,
         const char           *fusepath_,
         const mode_t          mode_,
         const mode_t          umask_,
         const int             flags_,
         uint64_t             *fh_)
  {
    int rv;
    string fullpath;
    string fusedirpath;
    StrVec createpaths;
    StrVec existingpaths;

    fusedirpath = fs::path::dirname(fusepath_);

    rv = searchFunc_(branches_,fusedirpath,&existingpaths);
    if(rv == -1)
      return -errno;

    rv = createFunc_(branches_,fusedirpath,&createpaths);
    if(rv == -1)
      return -errno;

    rv = fs::clonepath_as_root(existingpaths[0],createpaths[0],fusedirpath);
    if(rv == -1)
      return -errno;

    return l::create_core(createpaths[0],
                          fusepath_,
                          mode_,
                          umask_,
                          flags_,
                          fh_);
  }
}

namespace FUSE
{
  int
  create(const char       *fusepath_,
         mode_t            mode_,
         fuse_file_info_t *ffi_)
  {
    Config::Read cfg;
    const fuse_context *fc = fuse_get_context();
    const ugid::Set     ugid(fc->uid,fc->gid);

    l::config_to_ffi_flags(cfg,ffi_);

    if(cfg->writeback_cache)
      l::tweak_flags_writeback_cache(&ffi_->flags);

    return l::create(cfg->func.getattr.policy,
                     cfg->func.create.policy,
                     cfg->branches,
                     fusepath_,
                     mode_,
                     fc->umask,
                     ffi_->flags,
                     &ffi_->fh);
  }
}