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SubjectRe: [PATCH mm] mm: fix BUG with kvzalloc+GFP_ATOMIC
On Fri 23-09-22 15:35:12, Florian Westphal wrote:
> Michal Hocko <mhocko@suse.com> wrote:
> > On Fri 23-09-22 12:38:58, Florian Westphal wrote:
> > > Martin Zaharinov reports BUG() in mm land for 5.19.10 kernel:
> > > kernel BUG at mm/vmalloc.c:2437!
> > > invalid opcode: 0000 [#1] SMP
> > > CPU: 28 PID: 0 Comm: swapper/28 Tainted: G W O 5.19.9 #1
> > > [..]
> > > RIP: 0010:__get_vm_area_node+0x120/0x130
> > > __vmalloc_node_range+0x96/0x1e0
> > > kvmalloc_node+0x92/0xb0
> > > bucket_table_alloc.isra.0+0x47/0x140
> > > rhashtable_try_insert+0x3a4/0x440
> > > rhashtable_insert_slow+0x1b/0x30
> > > [..]
> > >
> > > bucket_table_alloc uses kvzallocGPF_ATOMIC). If kmalloc fails, this now
> > > falls through to vmalloc and hits code paths that assume GFP_KERNEL.
> > >
> > > Revert the problematic change and stay with slab allocator.
> >
> > Why don't you simply fix the caller?
>
> Uh, not following?
>
> kvzalloc(GFP_ATOMIC) was perfectly fine, is this illegal again?

kvmalloc has never really supported GFP_ATOMIC semantic.

> I can revert 93f976b5190df32793908d49165f78e67fcb66cf instead
> but that change is from 2018.

Yeah I would just revert this one as it relies on internal details of
kvmalloc doing or not doing a fallback.
--
Michal Hocko
SUSE Labs

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