Provided by:
linux-doc-2.6.15_2.6.15-23.39_all 
NAME
lock_may_write - checks that the region is free of locks
SYNOPSIS
int lock_may_write (struct inode * inode, loff_t start,
unsigned long len);
ARGUMENTS
inode the inode that is being written
start the first byte to write
len the number of bytes to write
DESCRIPTION
Emulates Windows locking requirements. Whole-file mandatory locks
(share modes) can prohibit a write and byte-range POSIX locks can
prohibit a write if they overlap.
N.B. this function is only ever called from knfsd and ownership of
locks is never checked.