mm/swap: pull the CPU conditional out of __lru_add_drain_all()

The function is too long, so pull this complicated conditional out into
cpu_needs_drain().  This ends up shrinking the text by 14 bytes,
by allowing GCC to cache the result of calling per_cpu() instead of
relocating each lookup individually.

Link: https://lkml.kernel.org/r/20220617175020.717127-11-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/swap.c b/mm/swap.c
index 01e4e9c7d7a30239e16b06900d7b3f8a2f4fc56b..df78c4c4dbeb5627926674f2f3fd539dff28fa65 100644 (file)
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -765,6 +765,21 @@ static void lru_add_drain_per_cpu(struct work_struct *dummy)
        lru_add_and_bh_lrus_drain();
 }
 
+static bool cpu_needs_drain(unsigned int cpu)
+{
+       struct cpu_fbatches *fbatches = &per_cpu(cpu_fbatches, cpu);
+
+       /* Check these in order of likelihood that they're not zero */
+       return folio_batch_count(&fbatches->lru_add) ||
+               data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) ||
+               folio_batch_count(&fbatches->lru_deactivate_file) ||
+               folio_batch_count(&fbatches->lru_deactivate) ||
+               folio_batch_count(&fbatches->lru_lazyfree) ||
+               folio_batch_count(&fbatches->activate) ||
+               need_mlock_page_drain(cpu) ||
+               has_bh_in_lru(cpu, NULL);
+}
+
 /*
  * Doesn't need any cpu hotplug locking because we do rely on per-cpu
  * kworkers being shut down before our page_alloc_cpu_dead callback is
@@ -849,14 +864,7 @@ static inline void __lru_add_drain_all(bool force_all_cpus)
        for_each_online_cpu(cpu) {
                struct work_struct *work = &per_cpu(lru_add_drain_work, cpu);
 
-               if (folio_batch_count(&per_cpu(cpu_fbatches.lru_add, cpu)) ||
-                   data_race(folio_batch_count(&per_cpu(lru_rotate.fbatch, cpu))) ||
-                   folio_batch_count(&per_cpu(cpu_fbatches.lru_deactivate_file, cpu)) ||
-                   folio_batch_count(&per_cpu(cpu_fbatches.lru_deactivate, cpu)) ||
-                   folio_batch_count(&per_cpu(cpu_fbatches.lru_lazyfree, cpu)) ||
-                   folio_batch_count(&per_cpu(cpu_fbatches.activate, cpu)) ||
-                   need_mlock_page_drain(cpu) ||
-                   has_bh_in_lru(cpu, NULL)) {
+               if (cpu_needs_drain(cpu)) {
                        INIT_WORK(work, lru_add_drain_per_cpu);
                        queue_work_on(cpu, mm_percpu_wq, work);
                        __cpumask_set_cpu(cpu, &has_work);