mm/vmscan: fix unexpected shrinking page cache with vm_cache_reclaim_enable disable

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SK3S
CVE: NA

-------------------------------------------------------

In function cache_limit_ratio_sysctl_handler and
cache_limit_mbytes_sysctl_handler, it will shrink
page cache even if vm_cache_reclaim_enable is false,
it is unexpected.
Signed-off-by: NChen Wandun <chenwandun@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

mm/page_alloc.c

@@ -8600,7 +8600,8 @@ int cache_limit_ratio_sysctl_handler(struct ctl_table *table, int write,
 				vm_cache_limit_ratio);
 		else
 			pr_warn("page cache limit off\n");
-		while (vm_cache_limit_mbytes && page_cache_over_limit())
+		while (vm_cache_limit_mbytes && page_cache_over_limit() &&
+				vm_cache_reclaim_enable)
 			shrink_page_cache(GFP_KERNEL);
 	}
 
@@ -8628,7 +8629,8 @@ int cache_limit_mbytes_sysctl_handler(struct ctl_table *table, int write,
 		else
 			pr_warn("page cache limit off\n");
 
-		while (vm_cache_limit_mbytes && page_cache_over_limit())
+		while (vm_cache_limit_mbytes && page_cache_over_limit() &&
+				vm_cache_reclaim_enable)
 			shrink_page_cache(GFP_KERNEL);
 	}
 

mm/vmscan.c

@@ -3562,7 +3562,8 @@ static int balance_pgdat(pg_data_t *pgdat, int order, int classzone_idx)
 	kernel_swap_check(&sc);
 
 #ifdef CONFIG_SHRINK_PAGECACHE
-	if (vm_cache_limit_mbytes && page_cache_over_limit())
+	if (vm_cache_limit_mbytes && page_cache_over_limit() &&
+	    vm_cache_reclaim_enable)
 		shrink_page_cache(GFP_KERNEL);
 #endif