Messages in this thread | | | Date | Sat, 18 Apr 2015 00:02:52 +0100 | From | Al Viro <> | Subject | Re: [RFC PATCH] fs: use a sequence counter instead of file_lock in fd_install |
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On Sat, Apr 18, 2015 at 12:16:48AM +0200, Mateusz Guzik wrote:
> I would say this makes the use of seq counter impossible. Even if we > decided to fall back to a lock on retry, we cannot know what to do if > the slot is reserved - it very well could be that something called > close, and something else reserved the slot, so putting the file inside > could be really bad. In fact we would be putting a file for which we > don't have a reference anymore. > > However, not all hope is lost and I still think we can speed things up. > > A locking primitive which only locks stuff for current cpu and has > another mode where it locks stuff for all cpus would do the trick just > fine. I'm not a linux guy, quick search suggests 'lglock' would do what > I want. > > table reallocation is an extremely rare operation, so this should be > fine. It would take the lock 'globally' for given table.
It would also mean percpu_alloc() for each descriptor table...
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