On Fri, Jun 22, 2018 at 03:33:35PM -0700, Guenter Roeck wrote: > On Fri, Jun 22, 2018 at 02:05:19PM -0700, Matthew Wilcox wrote: > > On Fri, Jun 22, 2018 at 11:42:46AM -0700, Guenter Roeck wrote: > > > Hi, > > > > > > a few days ago, m68k boot tests in linux-next started to crash. > > > I bisected the problem to commit 'xarray: Replace exceptional entries'. > > > Bisect and crash logs are attached below. > > > > Thank you! I was afraid something like this might happen. > > > > > ------------[ cut here ]------------ > > > WARNING: CPU: 0 PID: 1 at lib/idr.c:42 idr_alloc_u32+0x44/0xe8 > > > > Line 42 is: > > > > if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr))) > > return -EINVAL; > > > > The pointer passed in to idr_alloc() is not 4-byte aligned; it's aligned > > to a 2 byte boundary. I'm having a little trouble seeing who it is that's > > passing in what pointer ... > > > > > Call Trace: [<000180d6>] __warn+0xc0/0xc2 > > > [<000020e8>] do_one_initcall+0x0/0x140 > > > [<0001816a>] warn_slowpath_null+0x26/0x2c > > > [<002b50e4>] idr_alloc_u32+0x44/0xe8 > > > [<002b50e4>] idr_alloc_u32+0x44/0xe8 > > > [<002b51e4>] idr_alloc+0x5c/0x76 > > > [<00247160>] genl_register_family+0x14c/0x54c > > > > It makes sense to here (other than idr_alloc being listed twice) > > > > > [<000020e8>] do_one_initcall+0x0/0x140 > > > [<003f0f02>] genl_init+0x0/0x34 > > > > Assuming this is right, that would imply that genl_ctrl is not 4-byte > > aligned. Is that true? I'm not familiar with the m68k alignment rules, > > but it has a lot of 4-byte sized quantities in the struct, so I would > > assume it's 4-byte aligned. > > > > > [<003f0ce6>] bpf_lwt_init+0x10/0x14 > > > > I don't think this is the caller. > > > > Here is the culprit: > > genl_register_family(0x36dd7a) registering VFS_DQUOT > ------------[ cut here ]------------ > WARNING: CPU: 0 PID: 1 at lib/idr.c:42 idr_alloc_u32+0x44/0xe8 > > It may be odd that fs/quota/netlink.c:quota_genl_family is not word > aligned, but on the other side I don't think there is a rule that > the function parameter to genl_register_family() - or the second > parameter of idr_alloc() - must be word aligned. Am I missing > something ? After all, it could be a pointer to the nth element > of a string, or the caller could on purpose allocate IDRs for > (ptr), (ptr + 1), and so on.
There actually is a rule that pointers passed to the IDR be aligned. It might not be written down anywhere ;-) And I'm quite happy to lift that restriction; after all I don't want to force everybody to decorate definitions with __aligned(4). I'll see what I can do to fix it. I'm actually on holiday this week, so a fix may be delayed.
