mergerfs/src/fuse_link.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 "fs_clonepath.hpp"
#include "fs_link.hpp"
#include "fs_path.hpp"
#include "ugid.hpp"

#include <fuse.h>

#include <string>
#include <vector>

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

namespace error
{
  static
  inline
  int
  calc(const int rv_,
       const int prev_,
       const int cur_)
  {
    if(rv_ == -1)
      {
        if(prev_ == 0)
          return 0;
        return cur_;
      }

    return 0;
  }
}

namespace l
{
  static
  int
  link_create_path_core(const string &oldbasepath_,
                        const string &newbasepath_,
                        const char   *oldfusepath_,
                        const char   *newfusepath_,
                        const int     error_)
  {
    int rv;
    string oldfullpath;
    string newfullpath;

    oldfullpath = fs::path::make(oldbasepath_,oldfusepath_);
    newfullpath = fs::path::make(oldbasepath_,newfusepath_);

    rv = fs::link(oldfullpath,newfullpath);

    return error::calc(rv,error_,errno);
  }

  static
  int
  link_create_path_loop(const vector<string> &oldbasepaths_,
                        const string         &newbasepath_,
                        const char           *oldfusepath_,
                        const char           *newfusepath_,
                        const string         &newfusedirpath_)
  {
    int rv;
    int error;

    error = -1;
    for(size_t i = 0, ei = oldbasepaths_.size(); i != ei; i++)
      {
        rv = fs::clonepath_as_root(newbasepath_,oldbasepaths_[i],newfusedirpath_);
        if(rv == -1)
          error = error::calc(rv,error,errno);
        else
          error = l::link_create_path_core(oldbasepaths_[i],newbasepath_,
                                           oldfusepath_,newfusepath_,
                                           error);
      }

    return -error;
  }

  static
  int
  link_create_path(Policy::Func::Search  searchFunc_,
                   Policy::Func::Action  actionFunc_,
                   const Branches       &branches_,
                   const char           *oldfusepath_,
                   const char           *newfusepath_)
  {
    int rv;
    string newfusedirpath;
    vector<string> oldbasepaths;
    vector<string> newbasepaths;

    rv = actionFunc_(branches_,oldfusepath_,&oldbasepaths);
    if(rv == -1)
      return -errno;

    newfusedirpath = fs::path::dirname(newfusepath_);

    rv = searchFunc_(branches_,newfusedirpath,&newbasepaths);
    if(rv == -1)
      return -errno;

    return l::link_create_path_loop(oldbasepaths,newbasepaths[0],
                                    oldfusepath_,newfusepath_,
                                    newfusedirpath);
  }

  static
  int
  clonepath_if_would_create(Policy::Func::Search  searchFunc_,
                            Policy::Func::Create  createFunc_,
                            const Branches       &branches_,
                            const string         &oldbasepath_,
                            const char           *oldfusepath_,
                            const char           *newfusepath_)
  {
    int rv;
    string newfusedirpath;
    vector<string> newbasepath;

    newfusedirpath = fs::path::dirname(newfusepath_);

    rv = createFunc_(branches_,newfusedirpath,&newbasepath);
    if(rv == -1)
      return -1;

    if(oldbasepath_ != newbasepath[0])
      return (errno=EXDEV,-1);

    rv = searchFunc_(branches_,newfusedirpath,&newbasepath);
    if(rv == -1)
      return -1;

    return fs::clonepath_as_root(newbasepath[0],oldbasepath_,newfusedirpath);
  }

  static
  int
  link_preserve_path_core(Policy::Func::Search  searchFunc_,
                          Policy::Func::Create  createFunc_,
                          const Branches       &branches_,
                          const string         &oldbasepath_,
                          const char           *oldfusepath_,
                          const char           *newfusepath_,
                          const int             error_)
  {
    int rv;
    string oldfullpath;
    string newfullpath;

    oldfullpath = fs::path::make(oldbasepath_,oldfusepath_);
    newfullpath = fs::path::make(oldbasepath_,newfusepath_);

    rv = fs::link(oldfullpath,newfullpath);
    if((rv == -1) && (errno == ENOENT))
      {
        rv = l::clonepath_if_would_create(searchFunc_,createFunc_,
                                          branches_,
                                          oldbasepath_,
                                          oldfusepath_,newfusepath_);
        if(rv != -1)
          rv = fs::link(oldfullpath,newfullpath);
      }

    return error::calc(rv,error_,errno);
  }

  static
  int
  link_preserve_path_loop(Policy::Func::Search  searchFunc_,
                          Policy::Func::Create  createFunc_,
                          const Branches       &branches_,
                          const char           *oldfusepath_,
                          const char           *newfusepath_,
                          const vector<string> &oldbasepaths_)
  {
    int error;

    error = -1;
    for(size_t i = 0, ei = oldbasepaths_.size(); i != ei; i++)
      {
        error = l::link_preserve_path_core(searchFunc_,createFunc_,
                                           branches_,
                                           oldbasepaths_[i],
                                           oldfusepath_,newfusepath_,
                                           error);
      }

    return -error;
  }

  static
  int
  link_preserve_path(Policy::Func::Search  searchFunc_,
                     Policy::Func::Action  actionFunc_,
                     Policy::Func::Create  createFunc_,
                     const Branches       &branches_,
                     const char           *oldfusepath_,
                     const char           *newfusepath_)
  {
    int rv;
    vector<string> oldbasepaths;

    rv = actionFunc_(branches_,oldfusepath_,&oldbasepaths);
    if(rv == -1)
      return -errno;

    return l::link_preserve_path_loop(searchFunc_,createFunc_,
                                      branches_,
                                      oldfusepath_,newfusepath_,
                                      oldbasepaths);
  }
}

namespace FUSE
{
  int
  link(const char *from_,
       const char *to_)
  {
    const fuse_context *fc     = fuse_get_context();
    const Config       &config = Config::ro();
    const ugid::Set     ugid(fc->uid,fc->gid);

    if(config.func.create.policy->path_preserving() && !config.ignorepponrename)
      return l::link_preserve_path(config.func.getattr.policy,
                                   config.func.link.policy,
                                   config.func.create.policy,
                                   config.branches,
                                   from_,
                                   to_);

    return l::link_create_path(config.func.link.policy,
                               config.func.create.policy,
                               config.branches,
                               from_,
                               to_);
  }
}