> If you are intrested in the design of aufs, please take a look at these > documents and let me know your impression or anything including my poor > English.
FMODE_EXEC and deny_write() ---------------------------------------------------------------------- Generally Unix prevents an executing file from writing its filedata. In linux it is implemented by deny_write() and allow_write(). When a file is executed by exec() family, open_exec() (and sys_uselib()) they opens the file and calls deny_write(). If the file is aufs's virtual one, it has no meaning. The file which deny_write() is really necessary is the file on a branch. But the FMODE_EXEC flag is not passed to ->open() operation. So aufs adopt a dirty trick. - in order to get FMODE_EXEC, aufs ->lookup() and ->d_revalidate() set nd->intent.open.file->private_data to nd->intent.open.flags temporary. - in aufs ->open(), when FMODE_EXEC is set in file->private_data, it calls deny_write() for the file on a branch. - when the aufs file is released, allow_write() for the file on a branch is called. ------------------------------------------------------------------------------ Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA -OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise -Strategies to boost innovation and cut costs with open source participation -Receive a $600 discount off the registration fee with the source code: SFAD http://p.sf.net/sfu/XcvMzF8H
