Messages in this thread | | | Date | Wed, 9 Jun 2010 00:48:14 +0100 | From | Al Viro <> | Subject | Re: 2.6.35-rc2 module reference counting broken |
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On Mon, Jun 07, 2010 at 07:44:12AM +0100, Al Viro wrote: > On Mon, Jun 07, 2010 at 08:20:30AM +0300, Jari Ruusu wrote: > > Someone broke block device module reference counting. Problem occours when a > > modular block device is mounted and unmounted. Not when it is directly read. > > 2.6.34 kernel works OK, but 2.6.35-rc2 kernel seems to increase usage count > > by one for each mount + umount pair. > > Very interesting... Looks like mount() bumps refcount by 2. umount() after > that drops refcount by 1, so it's not leaking superblocks. > > Which probably means that open_bdev_exclusive() is fscked. Interesting... > FWIW, quick look through the history seems to point to this: > commit 6b4517a7913a09d3259bb1d21c9cb300f12294bd > Author: Tejun Heo <tj@kernel.org> > Date: Wed Apr 7 18:53:59 2010 +0900 > > block: implement bd_claiming and claiming block > > I'm far too sleepy right now, but I'd start with reviewing what that > thing is doing to module refcounting...
Yeah... bd_start_claiming() grabs a reference to gendisk and we never let it go. There's your leak...
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