On Thu, Jun 26, 2014 at 02:20:04PM -0400, Jeff Layton wrote: > While testing some knfsd patches on XFS today, I got this lockdep > splatter. The kernel is a stock -rc2 kernel with a pile of knfsd > patches on top. There are a couple of others in other areas, but > nothing that would affect this. > > Nothing crashed or seems to be hung, so I'm not sure if it's a real > problem or not... Known false positive. the problem is that lockdep is too stupid to realise you can't mmap a directory inode, but it sees unused directory inodes from memory reclaim in page faults (i.e. under the mmap_sem) and so therefore thinks that taking a page fault in readdir() while holding a directory inode lock on a referenced directory inode will deadlock.... Teaching lockdep the intricacies of locking heirarchies is difficult and painful. Fixing this one (and all the other stupidities lockdep reports because of this) can't be done through annotations - it requires rewriting a bunch of directory code to use different locks. And, well, it ain't actually broken right now and there's other more important issues to be fixed, so unless someone else beats me to rewriting the readdir readahead code, lockdep is going to remain unhappy about XFS. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
