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util: use fcntl instead of flock, for compatibility

in particular with NFS
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moneromooo-monero committed Dec 5, 2018
1 parent 1505dd3 commit 99cfb95edb55e3d4f8ab2d0b10dbff87e26bf1f1
Showing with 24 additions and 3 deletions.
  1. +24 −3 src/common/util.cpp
@@ -84,6 +84,27 @@ using namespace epee;
#undef MONERO_DEFAULT_LOG_CATEGORY
#define MONERO_DEFAULT_LOG_CATEGORY "util"
namespace
{
static int flock_exnb(int fd)
{
struct flock fl;
int ret;
memset(&fl, 0, sizeof(fl));
fl.l_type = F_WRLCK;
fl.l_whence = SEEK_SET;
fl.l_start = 0;
fl.l_len = 0;
ret = fcntl(fd, F_SETLK, &fl);
if (ret < 0)
MERROR("Error locking fd " << fd << ": " << errno << " (" << strerror(errno) << ")");
return ret;
}
}
namespace tools
{
std::function<void(int)> signal_handler::m_handler;
@@ -184,7 +205,7 @@ namespace tools
struct stat wstats = {};
if (fstat(fdw, std::addressof(wstats)) == 0 &&
rstats.st_dev == wstats.st_dev && rstats.st_ino == wstats.st_ino &&
flock(fdw, (LOCK_EX | LOCK_NB)) == 0 && ftruncate(fdw, 0) == 0)
flock_exnb(fdw) == 0 && ftruncate(fdw, 0) == 0)
{
std::FILE* file = fdopen(fdw, "w");
if (file) return {file, std::move(name)};
@@ -237,10 +258,10 @@ namespace tools
MERROR("Failed to open " << filename << ": " << std::error_code(GetLastError(), std::system_category()));
}
#else
m_fd = open(filename.c_str(), O_RDONLY | O_CREAT | O_CLOEXEC, 0666);
m_fd = open(filename.c_str(), O_RDWR | O_CREAT | O_CLOEXEC, 0666);
if (m_fd != -1)
{
if (flock(m_fd, LOCK_EX | LOCK_NB) == -1)
if (flock_exnb(m_fd) == -1)
{
MERROR("Failed to lock " << filename << ": " << std::strerror(errno));
close(m_fd);

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