mm: vmscan: restore high-cpu watermark safety in kswapd

Vlastimil points out that commit a211c6550efc ("mm: page_alloc:
defrag_mode kswapd/kcompactd watermarks") switched kswapd from
zone_watermark_ok_safe() to the standard, percpu-cached version of reading
free pages, thus dropping the watermark safety precautions for systems
with high CPU counts (e.g.  >212 cpus on 64G).  Restore them.

Since zone_watermark_ok_safe() is no longer the right interface, and this
was the last caller of the function anyway, open-code the
zone_page_state_snapshot() conditional and delete the function.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: a211c6550efc ("mm: page_alloc: defrag_mode kswapd/kcompactd watermarks")
Signed-off-by: Johannes Weiner <[email protected]>
Reported-by: Vlastimil Babka <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Brendan Jackman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions