On 2021/09/20 8:31, Andrew Morton wrote:

On Fri, 17 Sep 2021 11:06:49 +0300 Vasily Averin [off-list ref] wrote:

quoted

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?