Re: Boot failure with kernel BUG at mm/usercopy.c on next-20240325

[Andrew Morton]

On Tue, 26 Mar 2024 10:30:10 +0800 Feng Tang <feng.tang@xxxxxxxxx> wrote:

> Add Vlastimil for slab related topic.
> 
> On Tue, Mar 26, 2024 at 04:37:14AM +0800, Borislav Petkov wrote:
> > On Mon, Mar 25, 2024 at 11:34:33AM -0700, Andrew Morton wrote:
> > > Thanks, I'll just drop the patch.  It didn't receive a very favorable
> > > review reception anyway.
> > 
> > See here:
> > 
> > https://lore.kernel.org/all/DM4PR12MB5086B9BDBF32D53DF226CBF489362@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
> > 
> > folks still need to learn email. :-)
> > 
> > Anyway, apparently there's some fix there.
> 
> The original commit 328c801335d5 ("cpumask: create dedicated kmem
> cache for cpumask var") has some benefit, that there are CPU numbers
> which are not power of 8, like 144, 288 etc where it will save
> some memory. 
> 
> And 'slabtop' on a qemu-VM with 16 cpus shows it is surprisingly
> non-trivial and has the third largest number of objects: 
> 
> 22350   22350 100%    0.13K    745       30      2980K kernfs_node_cache
>  11172  10693   0%    0.19K    266       42      2128K dentry
>  10240   8222   0%    0.01K     20      512        80K cpumask
> 
> Andrew, if it is worth merging, you can folder my fix into the patch. 

I'll await a resend, please.