Hi Satyam, > From: Satyam Sharma <[EMAIL PROTECTED]> > > [9/9] netconsole: Support dynamic reconfiguration using configfs > > This patch introduces support for dynamic reconfiguration (adding, removing > and/or modifying parameters of netconsole targets at runtime) using a > userspace interface exported via configfs. Documentation is also updated > accordingly. > > Issues and brief design overview: > > (1) Kernel-initiated creation / destruction of kernel objects is not > possible with configfs -- the lifetimes of the "config items" is managed > exclusively from userspace. But netconsole must support boot/module params > too, and these are parsed in kernel and hence netpolls must be setup from > the kernel. Joel Becker suggested to separately manage the lifetimes of > the two kinds of netconsole_target objects -- those created via configfs > mkdir(2) from userspace and those specified from the boot/module option > string. This adds complexity and some redundancy here and also means that > boot/module param-created targets are not exposed through the configfs > namespace (and hence cannot be updated / destroyed dynamically). However, > this saves us from locking / refcounting complexities that would need to > be introduced in configfs to support kernel-initiated item creation / > destroy there. Also, this is similar to present behaviour in any case so > not really a problem. > > (2) In configfs, item creation takes place in the call chain of the mkdir(2) > syscall in the driver subsystem. If we used an ioctl(2) to create / destroy > objects from userspace, the special userspace program is able to fill out > the structure to be passed into the ioctl and hence specify attributes such > as local interface that are required at the time we set up the netpoll. > For configfs, this information is not available at the time of mkdir(2). > So, we keep all newly-created targets (via configfs) disabled by default. > The user is expected to set various attributes appropriately (including the > local network interface if required) and then write(2) "1" to the "enabled" > attribute. Thus, netpoll_setup() is then called on the set parameters in the > context of _this_ write(2) on the "enabled" attribute itself. This design > enables the user to reconfigure existing netconsole targets at runtime to > be attached to newly-come-up interfaces that may not have existed when > netconsole was loaded or when the targets were actually created. This all > enables us to get rid of custom ioctls. > > (3) Ultra-paranoid configfs attribute show() and store() operations, with > sanity and input range checking, using only safe string primitives, and > compliant with the recommendations in Documentation/filesystems/sysfs.txt. > > (4) A new function netpoll_print_options() is created in the netpoll API, > that just prints out the configured parameters for a netpoll structure. > netpoll_parse_options() is modified to use that and it is also exported to > be used from netconsole. > > Signed-off-by: Satyam Sharma <[EMAIL PROTECTED]> > Cc: Keiichi Kii <[EMAIL PROTECTED]> > Acked-by: Keiichi Kii <[EMAIL PROTECTED]>
Thanks -- Keiichi KII NEC Corporation OSS Platform Development Division E-mail: [EMAIL PROTECTED] - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
