Re: [PATCH mm] vmalloc: back off when the current task is OOM-killed

[Tetsuo Handa]

On 2021/09/20 8:31, Andrew Morton wrote:
> On Fri, 17 Sep 2021 11:06:49 +0300 Vasily Averin <vvs@xxxxxxxxxxxxx> wrote:
> 
>> Huge vmalloc allocation on heavy loaded node can lead to a global
>> memory shortage. A task called vmalloc can have the worst badness
>> and be chosen by OOM-killer, however received fatal signal and
>> oom victim mark does not interrupt allocation cycle. Vmalloc will
>> continue allocating pages over and over again, exacerbating the crisis
>> and consuming the memory freed up by another killed tasks.
>>
>> This patch allows OOM-killer to break vmalloc cycle, makes OOM more
>> effective and avoid host panic.
>>
>> Unfortunately it is not 100% safe. Previous attempt to break vmalloc
>> cycle was reverted by commit b8c8a338f75e ("Revert "vmalloc: back off when
>> the current task is killed"") due to some vmalloc callers did not handled
>> failures properly. Found issues was resolved, however, there may
>> be other similar places.
> 
> Well that was lame of us.
> 
> I believe that at least one of the kernel testbots can utilize fault
> injection.  If we were to wire up vmalloc (as we have done with slab
> and pagealloc) then this will help to locate such buggy vmalloc callers.

__alloc_pages_bulk() has three callers.

  alloc_pages_bulk_list() => No in-tree users.

  alloc_pages_bulk_array() => Used by xfs_buf_alloc_pages(), __page_pool_alloc_pages_slow(), svc_alloc_arg().

    xfs_buf_alloc_pages() => Might retry forever until all pages are allocated (i.e. effectively __GFP_NOFAIL). This patch can cause infinite loop problem.

    __page_pool_alloc_pages_slow() => Will not retry if allocation failed. This patch might help.

    svc_alloc_arg() => Will not retry if signal pending. This patch might help only if allocating a lot of pages.

  alloc_pages_bulk_array_node() => Used by vm_area_alloc_pages().

vm_area_alloc_pages() => Used by __vmalloc_area_node() from __vmalloc_node_range() from vmalloc functions. Needs !__GFP_NOFAIL check?