[PATCH 2/8] mm: add shrink page cache core

[Xishi Qiu <qiuxishi@huawei.com>]

Add a new function shrink_page_cache(), it will call do_try_to_free_pages()
to reclaim the page cache.

Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
---
 include/linux/swap.h |    2 ++
 mm/page_alloc.c      |   12 ++++++++++++
 mm/vmscan.c          |   24 ++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 0 deletions(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 7e362d7..dcbe1a3 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -363,6 +363,8 @@ extern int cache_limit_ratio_sysctl_handler(struct ctl_table *table, int write,
 			void __user *buffer, size_t *length, loff_t *ppos);
 extern int cache_limit_mbytes_sysctl_handler(struct ctl_table *table, int write,
 			void __user *buffer, size_t *length, loff_t *ppos);
+extern unsigned long page_cache_over_limit(void);
+extern void shrink_page_cache(gfp_t mask);
 
 #ifdef CONFIG_NUMA
 extern int zone_reclaim_mode;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index a9cc034..00707ef 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5829,6 +5829,18 @@ int cache_limit_mbytes_sysctl_handler(struct ctl_table *table, int write,
 	return 0;
 }
 
+unsigned long page_cache_over_limit(void)
+{
+	unsigned long lru_file, limit;
+
+	limit = vm_cache_limit_mbytes * ((1024 * 1024UL) / PAGE_SIZE);
+	lru_file = global_page_state(NR_ACTIVE_FILE)
+		+ global_page_state(NR_INACTIVE_FILE);
+	if (lru_file > limit)
+		return lru_file - limit;
+	return 0;
+}
+
 #ifdef CONFIG_NUMA
 int sysctl_min_unmapped_ratio_sysctl_handler(ctl_table *table, int write,
 	void __user *buffer, size_t *length, loff_t *ppos)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 37ea902..ad01ff4 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3389,6 +3389,30 @@ static void shrink_page_cache_init(void)
 	vm_cache_limit_mbytes_max = totalram_pages;
 }
 
+static unsigned long __shrink_page_cache(gfp_t mask)
+{
+	struct scan_control sc = {
+		.gfp_mask = (mask = memalloc_noio_flags(mask)),
+		.may_writepage = !laptop_mode,
+		.nr_to_reclaim = SWAP_CLUSTER_MAX,
+		.may_unmap = 1,
+		.may_swap = 1,
+		.order = 0,
+		.priority = DEF_PRIORITY,
+		.target_mem_cgroup = NULL,
+		.nodemask = NULL,
+	};
+	struct zonelist *zonelist = node_zonelist(numa_node_id(), mask);
+
+	return do_try_to_free_pages(zonelist, &sc);
+}
+
+void shrink_page_cache(gfp_t mask)
+{
+	/* We reclaim the highmem zone too, it is useful for 32bit arch */
+	__shrink_page_cache(mask | __GFP_HIGHMEM);
+}
+
 /* It's optimal to keep kswapds on the same CPUs as their memory, but
    not required for correctness.  So if the last cpu in a node goes
    away, we get changed to run anywhere: as the first one comes back,
-- 
1.6.0.2


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