Messages in this thread | | | Date | Fri, 18 Sep 2009 08:40:07 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] nfs: fix bdi_unregister() before sb kill |
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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.
-- Jens Axboe
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