I had an idea in the bath yesterday :-)
I had the idea of the 'virtual mount'. Basically you mount with -o virtual, and the vfs records
the mount details, then returns immediately. When the first non-stat operation is done on the mount
point, the mount actually happens.
I mostly implemented it last night... however I thought I'd better put my ideas down here so I can be shot down in
flames (or even encouraged) for having the idea in the first place. (It turned out to be much simpler than I thought,
although I haven't acctually attempted the mount-from-vfs yet...)
I have some questions:
What is best for allocating memory? vmalloc or kmalloc? I am storing the details in a linked list and each element is a couple of dozen bytes.
Where would be the best reference for implementing a /proc interface? (I envisige a client daemon that reads this to check how long each virtual mount has been 'idle' and triggers an unmount after a user-specified time. Actually this could just be a perl script....)
At the moment it's implemented like this... When the virtual mount is attempted it records the parameters to do_mount, and the dentry (after doing a dget()) of the mount point. It then marks the dentry. Then in lookup_dentry I check whether this is a virtual mount (the d_mounted entry is set to a magic value) and printk an 'I would do a mount here...' message.
This is the first time I've done anything 'big' to the Kernel, so I may have missed a lot of rather obvious stuff (anyway it was 2am and I was tired...)
Tony
--"Now you too can enjoy having babies... start collecting today" (Recent advert)
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This archive was generated by hypermail 2b29 : Wed Feb 23 2000 - 21:00:28 EST