Re: [PATCH v2] [RFC] mm: fs: Invalidate BH LRU during page migration
From: Matthew Wilcox <willy@infradead.org>
Date: 2021-02-11 14:13:51
Also in:
linux-mm, lkml
On Wed, Feb 10, 2021 at 09:35:40PM -0800, Chris Goldsworthy wrote:
+/* These are used to control the BH LRU invalidation during page migration */ +static struct cpumask lru_needs_invalidation; +static bool bh_lru_disabled = false;
As I asked before, what protects this on an SMP system?
quoted hunk ↗ jump to hunk
@@ -1292,7 +1296,9 @@ static inline void check_irqs_on(void) /* * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is * inserted at the front, and the buffer_head at the back if any is evicted. - * Or, if already in the LRU it is moved to the front. + * Or, if already in the LRU it is moved to the front. Note that if LRU is + * disabled because of an ongoing page migration, we won't insert bh into the + * LRU.
And also, why do we need to do this? The page LRU has no equivalent mechanism to prevent new pages being added to the per-CPU LRU lists. If a BH has just been used, isn't that a strong hint that this page is a bad candidate for migration?