centos man page for lock_may_read

LOCK_MAY_READ(9)						   The Linux VFS						  LOCK_MAY_READ(9)

NAME
       lock_may_read - checks that the region is free of locks

SYNOPSIS
       int lock_may_read(struct inode * inode, loff_t start, unsigned long len);

ARGUMENTS
       inode
	   the inode that is being read

       start
	   the first byte to read

       len
	   the number of bytes to read

DESCRIPTION
       Emulates Windows locking requirements. Whole-file mandatory locks (share modes) can prohibit a read and byte-range POSIX locks can prohibit
       a read if they overlap.

       N.B. this function is only ever called from knfsd and ownership of locks is never checked.

COPYRIGHT
Kernel Hackers Manual 3.10					     June 2014							  LOCK_MAY_READ(9)