Fix parts file i/o errors (#3110)

Since i/o operations are not synchronized, it is possible that one thread closes file handle, opened in another thread. With addition of `hidden` file attribute, an old bug in `part_file::open_file()` revealed both problems, causing a lot of random i/o errors in parts file. Fixing `open_file` bug should reduce the number of such errors back to 'normal'.
This commit is contained in:
d-komarov 2018-06-18 15:34:39 +03:00 committed by Arvid Norberg
parent af686a3819
commit 81ce7aa4ab
3 changed files with 23 additions and 38 deletions

View File

@ -1,4 +1,6 @@
* fix race condition during part_file export
* fix part_file open mode compatibility test
* fixed race condition in random number generator
* fix race condition in stat_cache (disk storage)
* improve error handling of failing to change file priority

View File

@ -73,8 +73,11 @@ namespace libtorrent
void open_file(int mode, error_code& ec);
void flush_metadata_impl(error_code& ec);
boost::int64_t slot_offset(boost::int64_t const slot) const
{ return m_header_size + slot * m_piece_size; }
std::string m_path;
std::string m_name;
std::string const m_name;
// allocate a slot and return the slot index
int allocate_slot(int piece);
@ -93,15 +96,15 @@ namespace libtorrent
// the max number of pieces in the torrent this part file is
// backing
int m_max_pieces;
int const m_max_pieces;
// number of bytes each piece contains
int m_piece_size;
int const m_piece_size;
// this is the size of the part_file header, it is added
// to offsets when calculating the offset to read and write
// payload data from
int m_header_size;
int const m_header_size;
// if this is true, the metadata in memory has changed since
// we last saved or read it from disk. It means that we

View File

@ -183,17 +183,11 @@ namespace libtorrent
open_file(file::read_write | file::attribute_hidden, ec);
if (ec) return -1;
int slot = -1;
boost::unordered_map<int, int>::iterator i = m_piece_map.find(piece);
if (i == m_piece_map.end())
slot = allocate_slot(piece);
else
slot = i->second;
boost::unordered_map<int, int>::iterator const i = m_piece_map.find(piece);
int const slot = i == m_piece_map.end() ? allocate_slot(piece) : i->second;
l.unlock();
boost::int64_t slot_offset = boost::int64_t(m_header_size) + boost::int64_t(slot) * m_piece_size;
return m_file.writev(slot_offset + offset, bufs, num_bufs, ec);
return m_file.writev(slot_offset(slot) + offset, bufs, num_bufs, ec);
}
int part_file::readv(file::iovec_t const* bufs, int num_bufs
@ -202,32 +196,29 @@ namespace libtorrent
TORRENT_ASSERT(offset >= 0);
mutex::scoped_lock l(m_mutex);
boost::unordered_map<int, int>::iterator i = m_piece_map.find(piece);
boost::unordered_map<int, int>::iterator const i = m_piece_map.find(piece);
if (i == m_piece_map.end())
{
ec = error_code(boost::system::errc::no_such_file_or_directory
, boost::system::generic_category());
ec = make_error_code(boost::system::errc::no_such_file_or_directory);
return -1;
}
int slot = i->second;
int const slot = i->second;
open_file(file::read_write | file::attribute_hidden, ec);
if (ec) return -1;
l.unlock();
boost::int64_t slot_offset = boost::int64_t(m_header_size) + boost::int64_t(slot) * m_piece_size;
return m_file.readv(slot_offset + offset, bufs, num_bufs, ec);
return m_file.readv(slot_offset(slot) + offset, bufs, num_bufs, ec);
}
void part_file::open_file(int mode, error_code& ec)
{
if (m_file.is_open()
&& ((m_file.open_mode() & file::rw_mask) == mode
|| mode == file::read_only)) return;
if (m_file.is_open() && ((mode & file::rw_mask) == file::read_only
|| (m_file.open_mode() & file::rw_mask) == file::read_write))
return;
std::string fn = combine_path(m_path, m_name);
std::string const fn = combine_path(m_path, m_name);
m_file.open(fn, mode, ec);
if (((mode & file::rw_mask) != file::read_only)
&& ec == boost::system::errc::no_such_file_or_directory)
@ -323,14 +314,8 @@ namespace libtorrent
if (!buf) buf.reset(new char[m_piece_size]);
boost::int64_t const slot_offset = boost::int64_t(m_header_size)
+ boost::int64_t(slot) * m_piece_size;
// don't hold the lock during disk I/O
l.unlock();
file::iovec_t v = { buf.get(), size_t(block_to_copy) };
v.iov_len = m_file.readv(slot_offset + piece_offset, &v, 1, ec);
v.iov_len = m_file.readv(slot_offset(slot) + piece_offset, &v, 1, ec);
TORRENT_ASSERT(!ec);
if (ec || v.iov_len == 0) return;
@ -338,10 +323,6 @@ namespace libtorrent
TORRENT_ASSERT(ec || ret == v.iov_len);
if (ec || ret != v.iov_len) return;
// we're done with the disk I/O, grab the lock again to update
// the slot map
l.lock();
if (block_to_copy == m_piece_size)
{
// since we released the lock, it's technically possible that
@ -423,4 +404,3 @@ namespace libtorrent
if (ec) return;
}
}