Messages in this thread | | | Date | Fri, 18 Sep 2009 19:36:08 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] nfs: fix bdi_unregister() before sb kill |
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On Fri, Sep 18 2009, Trond Myklebust wrote: > On Fri, 2009-09-18 at 17:02 +0200, Jens Axboe wrote: > > On Fri, Sep 18 2009, Jens Axboe wrote: > > > On Thu, Sep 17 2009, Trond Myklebust wrote: > > > > On Thu, 2009-09-17 at 21:40 +0200, Jens Axboe wrote: > > > > > On Thu, Sep 17 2009, Jens Axboe wrote: > > > > > > Hi, > > > > > > > > > > > > This can cause a hang on NFS umount, since the bdi gets pruned before we > > > > > > flush any pending dirty IO. Peter, can you check whether it fixes your > > > > > > issue? > > > > > > > > > > There's another problem with NFS && backing devices. NFS may call > > > > > bdi_destroy() on a bdi without ever called bdi_init(). This was always a > > > > > bad idea, now it's an issue. > > > > > > > > > > So, Trond, can I safely add a server->flags private flag to indicate > > > > > that we have called bdi_init()? Then nfs_free_server() knows when to > > > > > call bdi_destroy(). Seems like the safest fix, since error handling is > > > > > currently 'just call nfs_free_server()'. > > > > > > > > Urgh... Is there any reason why we can't just move the call to > > > > bdi_init() into nfs_bdi_register()? It seems bizarre to have to > > > > initialise the backing_dev_info twice like this... > > > > > > No reason at all, I don't know why it was implemented that way > > > originally. > > > > > > > If we do that, then we can just look at the BDI_registered state flag in > > > > order to figure out if we need to call bdi_unregister() > > > > > > That's not exactly pretty either, diving into internal bdi details to > > > find out if we did an init/register of the device. BDI_registered is > > > just a debug flag, it may even go away again shortly. > > > > Trond, we need to make some sort of decision on this very shortly. It > > definitely needs to be fixed for -rc1, it's causing NFS oopses. So lets > > make some sort of call on this and get it added, then you/we/I can > > always pretty it up later. > > > > OK... I think the solution is to move the call to bdi_init() into > nfs_bdi_register(), then move the calls to nfs_bdi_register() into > nfs_set_super() (with an appropriate call to bdi_destroy() if > set_anon_super() fails). > > Then we can put bdi_destroy() in place of the call to bdi_unregister() > in nfs_kill_super().
Yeah, that sounds cleaner.
> I'm not going to attempt a patch, since I don't have a copy of your > current tree to base it on, but does the above make sense to you?
My current tree in the NFS area is just a one liner to move the bdi_destroy() in nfs_kill_super(). I'll try and cut a patch later tonight.
-- Jens Axboe
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