Re: KASAN-related VMAP allocation errors in debug kernels with many logical CPUS

[Uladzislau Rezki <urezki@gmail.com>]

> Hi,
> 
> we're currently hitting a weird vmap issue in debug kernels with KASAN enabled
> on fairly large VMs. I reproduced it on v5.19 (did not get the chance to
> try 6.0 yet because I don't have access to the machine right now, but
> I suspect it persists).
> 
> It seems to trigger when udev probes a massive amount of devices in parallel
> while the system is booting up. Once the system booted, I no longer see any
> such issues.
> 
> 
> [  165.818200] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.836622] vmap allocation for size 315392 failed: use vmalloc=<size> to increase size
> [  165.837461] vmap allocation for size 315392 failed: use vmalloc=<size> to increase size
> [  165.840573] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.841059] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.841428] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.841819] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.842123] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.843359] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.844894] vmap allocation for size 2498560 failed: use vmalloc=<size> to increase size
> [  165.847028] CPU: 253 PID: 4995 Comm: systemd-udevd Not tainted 5.19.0 #2
> [  165.935689] Hardware name: Lenovo ThinkSystem SR950 -[7X12ABC1WW]-/-[7X12ABC1WW]-, BIOS -[PSE130O-1.81]- 05/20/2020
> [  165.947343] Call Trace:
> [  165.950075]  <TASK>
> [  165.952425]  dump_stack_lvl+0x57/0x81
> [  165.956532]  warn_alloc.cold+0x95/0x18a
> [  165.960836]  ? zone_watermark_ok_safe+0x240/0x240
> [  165.966100]  ? slab_free_freelist_hook+0x11d/0x1d0
> [  165.971461]  ? __get_vm_area_node+0x2af/0x360
> [  165.976341]  ? __get_vm_area_node+0x2af/0x360
> [  165.981219]  __vmalloc_node_range+0x291/0x560
> [  165.986087]  ? __mutex_unlock_slowpath+0x161/0x5e0
> [  165.991447]  ? move_module+0x4c/0x630
> [  165.995547]  ? vfree_atomic+0xa0/0xa0
> [  165.999647]  ? move_module+0x4c/0x630
> [  166.003741]  module_alloc+0xe7/0x170
> [  166.007747]  ? move_module+0x4c/0x630
> [  166.011840]  move_module+0x4c/0x630
> [  166.015751]  layout_and_allocate+0x32c/0x560
> [  166.020519]  load_module+0x8e0/0x25c0
>
Can it be that we do not have enough "module section" size? I mean the
section size, which is MODULES_END - MODULES_VADDR is rather small so
some modules are not loaded due to no space.

CONFIG_RANDOMIZE_BASE also creates some offset overhead if enabled on
your box. But it looks it is rather negligible.

Maybe try to increase the module-section size to see if it solves the
problem.

--
Uladzislau Rezki