On Wed, Oct 26, 2016 at 09:48:39AM -0700, Linus Torvalds wrote: > On Wed, Oct 26, 2016 at 9:30 AM, Dave Jones <da...@codemonkey.org.uk> wrote: > > > > I gave this a go last thing last night. It crashed within 5 minutes, > > but it was one we've already seen (the bad page map trace) with nothing > > additional that looked interesting. > > Did the bad page map trace have any registers that looked like they > had 0xd0d0d0d0d0d0 in them? > > I assume not, but worth checking. sadly not. In case I did overlook something, here's last nights..
BUG: Bad page state in process kworker/u8:13 pfn:4dae31 page:ffffea00136b8c40 count:0 mapcount:0 mapping:ffff8804f011d6e0 index:0xd1530 flags: 0x400000000000000c(referenced|uptodate) page dumped because: non-NULL mapping CPU: 3 PID: 1207 Comm: kworker/u8:13 Not tainted 4.9.0-rc2-think+ #3 Workqueue: writeback wb_workfn (flush-btrfs-1) ffffc900006fb870 ffffffff8130cf3c ffffea00136b8c40 ffffffff819ff54c ffffc900006fb898 ffffffff811511af 0000000000000000 ffffea00136b8c40 400000000000000c ffffc900006fb8a8 ffffffff8115126a ffffc900006fb8f0 Call Trace: [<ffffffff8130cf3c>] dump_stack+0x4f/0x73 [<ffffffff811511af>] bad_page+0xbf/0x120 [<ffffffff8115126a>] free_pages_check_bad+0x5a/0x70 [<ffffffff81153b68>] free_hot_cold_page+0x248/0x290 [<ffffffff81153e6b>] free_hot_cold_page_list+0x2b/0x50 [<ffffffff8115c87d>] release_pages+0x2bd/0x350 [<ffffffff8115ddb2>] __pagevec_release+0x22/0x30 [<ffffffffa00a0d4e>] extent_write_cache_pages.isra.48.constprop.63+0x32e/0x400 [btrfs] [<ffffffffa00a1199>] extent_writepages+0x49/0x60 [btrfs] [<ffffffffa0081840>] ? btrfs_releasepage+0x40/0x40 [btrfs] [<ffffffffa007e993>] btrfs_writepages+0x23/0x30 [btrfs] [<ffffffff8115af9c>] do_writepages+0x1c/0x30 [<ffffffff811f6d73>] __writeback_single_inode+0x33/0x180 [<ffffffff811f7568>] writeback_sb_inodes+0x2a8/0x5b0 [<ffffffff811f7abb>] wb_writeback+0xeb/0x1f0 [<ffffffff811f80f2>] wb_workfn+0xd2/0x280 [<ffffffff810908a5>] process_one_work+0x1d5/0x490 [<ffffffff81090845>] ? process_one_work+0x175/0x490 [<ffffffff81090ba9>] worker_thread+0x49/0x490 [<ffffffff81090b60>] ? process_one_work+0x490/0x490 [<ffffffff81095d1e>] kthread+0xee/0x110 [<ffffffff81095c30>] ? kthread_park+0x60/0x60 [<ffffffff81790a52>] ret_from_fork+0x22/0x30 > > Heisenbugs man, literally the worst. > > I know you already had this in some email, but I lost it. I think you > narrowed it down to a specific set of system calls that seems to > trigger this best. fallocate and xattrs or something? I did. Or so I thought. Then iirc, it ran for a really long time with those. I'll revisit that just to be sure. Something else I tried: Trinity is very heavily stressing the fork path, with new children forking off and doing crazy shit all the time, segfaulting, repeat. I wrote a small test app that models all of that sans the "do crazy shit with syscalls", and that didn't do anything useful in terms of reproducing this. I hoped that had panned out, because I could totally see the relationship between reusing vmap'ing stacks and heavy fork() use. Perhaps I'm still missing something non-obvious. Dave