locks: make locks_mandatory_area check for file-private locks (29723ade) · Commits · 戴 / test

Allow locks_mandatory_area() to handle file-private locks correctly. If there is a file-private lock set on an open file and we're doing I/O via the same, then that should not cause anything to block. Handle this by first doing a non-blocking FL_ACCESS check for a file-private lock, and then fall back to checking for a classic POSIX lock (and possibly blocking). Note that this approach is subject to the same races that have always plagued mandatory locking on Linux. Reported-by:

Trond Myklebust <trond.myklebust@primarydata.com> Signed-off-by:

Jeff Layton <jlayton@redhat.com>

fs/locks.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -1199,19 +1199,30 @@ int locks_mandatory_area(int read_write, struct inode *inode,
		{
		struct file_lock fl;
		int error;
		bool sleep = false;

		locks_init_lock(&fl);
		fl.fl_owner = current->files;
		fl.fl_pid = current->tgid;
		fl.fl_file = filp;
		fl.fl_flags = FL_POSIX \| FL_ACCESS;
		if (filp && !(filp->f_flags & O_NONBLOCK))
		fl.fl_flags \|= FL_SLEEP;
		sleep = true;
		fl.fl_type = (read_write == FLOCK_VERIFY_WRITE) ? F_WRLCK : F_RDLCK;
		fl.fl_start = offset;
		fl.fl_end = offset + count - 1;

		for (;;) {
		if (filp) {
		fl.fl_owner = (fl_owner_t)filp;
		fl.fl_flags &= ~FL_SLEEP;
		error = __posix_lock_file(inode, &fl, NULL);
		if (!error)
		break;
		}

		if (sleep)
		fl.fl_flags \|= FL_SLEEP;
		fl.fl_owner = current->files;
		error = __posix_lock_file(inode, &fl, NULL);
		if (error != FILE_LOCK_DEFERRED)
		break;

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