Method _read_sync

src/client/Client.cc:11968–12087

}

int Client::_read_sync(Fh *f, uint64_t off, uint64_t len, bufferlist *bl,
		       bool *checkeof)
{
  ceph_assert(ceph_mutex_is_locked_by_me(client_lock));
  if (len == 0) {
    // zero byte read is not supported by OSD
    return 0;
  }

  Inode *in = f->inode.get();

  auto effective_size = in->effective_size();
  auto target_len = std::min(len, effective_size - off);
uint64_t read_start;
  uint64_t read_len;

#if defined(__linux__)
  FSCryptFDataDencRef fscrypt_denc;
  fscrypt->prepare_data_read(in->fscrypt_ctx,
                             &in->fscrypt_key_validator,
                             off, len, in->size,
                             &read_start, &read_len,
                             &fscrypt_denc);
#else
  read_start = off;
  read_len = len;
#endif
  uint64_t pos = read_start;
  int left = read_len;
  int read = 0;

  bufferlist encbl;
#if defined(__linux__) 
  bufferlist *pbl = (fscrypt_denc ? &encbl : bl);
#else
  bufferlist *pbl = bl;
#endif
  ldout(cct, 10) << __func__ << " " << *in << " " << off << "~" << len << dendl;

  // 0 success, 1 continue and < 0 error happen.
  auto wait_and_copy = [&](C_SaferCond &onfinish, bufferlist &tbl, int wanted) {
    int r = onfinish.wait();

    // if we get ENOENT from OSD, assume 0 bytes returned
    if (r == -ENOENT)
      r = 0;
    if (r < 0)
      return r;

    if (tbl.length()) {
      r = tbl.length();

      read += r;
      pos += r;
      left -= r;
      pbl->claim_append(tbl);
    }