mm/mglru: only clear kswapd_failures if reclaimable

lru_gen_shrink_node() unconditionally clears kswapd_failures, which can
prevent kswapd from sleeping and cause 100% kswapd cpu usage even when
kswapd repeatedly fails to make progress in reclaim.

Only clear kswap_failures in lru_gen_shrink_node() if reclaim makes some
progress, similar to shrink_node().

I happened to run into this problem in one of my tests recently.  It
requires a combination of several conditions: The allocator needs to
allocate a right amount of pages such that it can wake up kswapd
without itself being OOM killed; there is no memory for kswapd to
reclaim (My test disables swap and cleans page cache first); no other
process frees enough memory at the same time.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: e4dde56cd208 ("mm: multi-gen LRU: per-node lru_gen_folio lists")
Signed-off-by: Wei Xu <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: Brian Geffon <[email protected]>
Cc: Jan Alexander Steffens <[email protected]>
Cc: Suleiman Souhlal <[email protected]>
Cc: Yu Zhao <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions