Messages in this thread | | | From | Kenneth Preslan <> | Subject | Re: [Call For Testers][VFS] Rename stuff. | Date | Tue, 9 Feb 1999 12:34:11 -0600 (EST) |
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> coda: no rename/rename protection, no is_subdir. Mommy, server will do the > right thing, certainly it will not screw me up, why would it? ... > nfs: no checks, no nothing. Fixed.
I think you're missing a big point here. Rename serialization MUST be done at the server. The semaphore you're taking out protects against two different processes doing renames at the same time. It doesn't protect against two different processes on *different machines* renaming at the same time. Their thinking was: "All the is_subdir() stuff already happens on the server, so why do it twice?"
I work on GFS (http://gfs.lcse.umn.edu). Shifting the is_subdir() test into the VFS does nothing for me except make my file system slower.
The VFS layer grabs the rename semaphore, does the is_subdir() check, and calls my rename() i_op. Then I have to get the GFS inter-machine rename lock and do the is_subdir() check again. If I don't, I leave myself open to race conditions.
This patch your proposing doesn't hurt the functionality of any file system. In that respect it's ok. And the performance hit of walking the dcache to do the check isn't too bad, but I just wanted to point out what you're doing.
Ken Preslan
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