Man page 9 : posix_lock_file

posix_lock_file - Apply a POSIX-style lock to a file

int posix_lock_file(struct file *  filp , struct file_lock *  fl , struct file_lock *  conflock );

filp
    The file to apply the lock to

fl
    The lock to be applied

conflock
    Place to return a copy of the conflicting lock, if found.

Add a POSIX style lock to a file. We merge adjacent & overlapping locks whenever possible. POSIX locks are sorted by owner task, then by starting address

Note that if called with an FL_EXISTS argument, the caller may determine whether or not a lock was successfully freed by testing the return value for -ENOENT.