assoc_array: Fix BUG_ON during garbage collect
commit d1dc8776 upstream. A rare BUG_ON triggered in assoc_array_gc: [3430308.818153] kernel BUG at lib/assoc_array.c:1609! Which corresponded to the statement currently at line 1593 upstream: BUG_ON(assoc_array_ptr_is_meta(p)); Using the data from the core dump, I was able to generate a userspace reproducer[1] and determine the cause of the bug. [1]: https://github.com/brenns10/kernel_stuff/tree/master/assoc_array_gc After running the iterator on the entire branch, an internal tree node looked like the following: NODE (nr_leaves_on_branch: 3) SLOT [0] NODE (2 leaves) SLOT [1] NODE (1 leaf) SLOT [2..f] NODE (empty) In the userspace reproducer, the pr_devel output when compressing this node was: -- compress node 0x5607cc089380 -- free=0, leaves=0 [0] retain node 2/1 [nx 0] [1] fold node 1/1 [nx 0] [2] fold node 0/1 [nx 2] [3] fold node 0/2 [nx 2] [4] fold node 0...
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