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// fsync.cpp
#include "mongo/db/d_concurrency.h"
#include "mongo/db/commands.h"
#include "mongo/db/dur.h"
namespace mongo {
/* see unlockFsync() for unlocking:
db.$cmd.sys.unlock.findOne()
*/
class FSyncCommand : public Command {
static const char* url() { return "http://www.mongodb.org/display/DOCS/fsync+Command"; }
public:
bool locked;
SimpleMutex m; // protects locked var above
FSyncCommand() : Command( "fsync" ), m("lockfsync") { locked=false; }
virtual LockType locktype() const { return NONE; }
virtual bool slaveOk() const { return true; }
virtual bool adminOnly() const { return true; }
virtual void help(stringstream& h) const { h << url(); }
virtual bool run(const string& dbname, BSONObj& cmdObj, int, string& errmsg, BSONObjBuilder& result, bool fromRepl) {
bool sync = !cmdObj["async"].trueValue(); // async means do an fsync, but return immediately
bool lock = cmdObj["lock"].trueValue();
log() << "CMD fsync: sync:" << sync << " lock:" << lock << endl;
if( lock ) {
Lock::ThreadSpanningOp::setWLockedNongreedy();
verify( !locked ); // impossible to get here if locked is true
try {
//uassert(12034, "fsync: can't lock while an unlock is pending", !unlockRequested);
uassert(12032, "fsync: sync option must be true when using lock", sync);
getDur().syncDataAndTruncateJournal();
} catch(...) {
Lock::ThreadSpanningOp::unsetW();
throw;
}
SimpleMutex::scoped_lock lk(m);
Lock::ThreadSpanningOp::W_to_R();
try {
MemoryMappedFile::flushAll(true);
}
catch(...) {
Lock::ThreadSpanningOp::unsetR();
throw;
}
verify( !locked );
locked = true;
log() << "db is now locked for snapshotting, no writes allowed. db.fsyncUnlock() to unlock" << endl;
log() << " For more info see " << FSyncCommand::url() << endl;
result.append("info", "now locked against writes, use db.fsyncUnlock() to unlock");
result.append("seeAlso", url());
Lock::ThreadSpanningOp::handoffR();
}
else {
// the simple fsync command case
if (sync) {
Lock::GlobalWrite w; // can this be GlobalRead? and if it can, it should be nongreedy.
getDur().commitNow();
}
// question : is it ok this is not in the dblock? i think so but this is a change from past behavior,
// please advise.
result.append( "numFiles" , MemoryMappedFile::flushAll( sync ) );
}
return 1;
}
} fsyncCmd;
bool lockedForWriting() { return fsyncCmd.locked; }
// @return true if unlocked
bool _unlockFsync() {
SimpleMutex::scoped_lock lk(fsyncCmd.m);
if( !fsyncCmd.locked ) {
return false;
}
fsyncCmd.locked = false;
Lock::ThreadSpanningOp::unsetR();
return true;
}
}
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