Messages in this thread | | | Date | Thu, 24 Oct 2002 13:46:39 -0400 | From | Jeff Garzik <> | Subject | Re: Switching from IOCTLs to a RAMFS |
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Mark Peloquin wrote: > Based on the feedback and comments regarding > the use of IOCTLs in EVMS, we are switching to > the more preferred method of using a ram based > fs. Since we are going through this effort, I > would like to get it right now, rather than > having to switch to another ramfs system later > on. The question I have is: should we roll our > own fs, (a.k.a. evmsfs) or should we use sysfs > for this purpose? My initial thoughts are that > sysfs should be used. However, recent discussions > about device mapper have suggested a custom ramfs. > Which is the *best* choice?
(cc'd viro and mochel, as I feel they are 'owners' in the subject area)
Let's jump back a bit, for a second. Why is procfs bad news? There are minor issues with the implementation of single-page output and lack of pure file operations, but the big issue is lack of a sane namespace. sysfs is no better than procfs if we keep heaving junk into it without thinking about proper namespace organization.
I personally prefer a separate filesystem for what you describe. That gives the EVMS team control over their own portion of the namespace, while giving complete flexibility. I do _not_ see sysfs as simply a procfs replacement -- sysfs IMO is more intended as a way to organize certain events and export internal kernel structure.
To tangent a bit, WRT a private evmsfs, make sure that (a) you prefer ASCII over binary interfaces where reasonable, and (b) any binary interfaces you have are fixed-endian and 64-bit safe from the get-go. Consider crazy cases like someone exporting evmsfs over NFS, from a 32-bit IA32 server to a big-endian 64-bit client.
Jeff
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