From: Chandra Seetharaman page-writeback.c has a static local variable "total_pages", which is the total number of pages in the system. There is a global variable "vm_total_pages", which is the total number of pages the VM controls. Both are assigned from the return value of nr_free_pagecache_pages(). This patch removes the local variable and uses the global variable in that place. One more issue with the local static variable "total_pages" is that it is not updated when new pages are hot-added. Since vm_total_pages is updated when new pages are hot-added, this patch fixes that problem too. Signed-off-by: Chandra Seetharaman Signed-off-by: Andrew Morton --- mm/page-writeback.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) diff -puN mm/page-writeback.c~remove-static-variable-mm-page-writebackctotal_pages mm/page-writeback.c --- a/mm/page-writeback.c~remove-static-variable-mm-page-writebackctotal_pages +++ a/mm/page-writeback.c @@ -48,7 +48,6 @@ */ static long ratelimit_pages = 32; -static long total_pages; /* The total number of pages in the machine. */ static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */ /* @@ -128,7 +127,7 @@ get_dirty_limits(long *pbackground, long int unmapped_ratio; long background; long dirty; - unsigned long available_memory = total_pages; + unsigned long available_memory = vm_total_pages; struct task_struct *tsk; #ifdef CONFIG_HIGHMEM @@ -143,7 +142,7 @@ get_dirty_limits(long *pbackground, long unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) + global_page_state(NR_ANON_PAGES)) * 100) / - total_pages; + vm_total_pages; dirty_ratio = vm_dirty_ratio; if (dirty_ratio > unmapped_ratio / 2) @@ -506,7 +505,7 @@ void laptop_sync_completion(void) static void set_ratelimit(void) { - ratelimit_pages = total_pages / (num_online_cpus() * 32); + ratelimit_pages = vm_total_pages / (num_online_cpus() * 32); if (ratelimit_pages < 16) ratelimit_pages = 16; if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024) @@ -535,9 +534,7 @@ void __init page_writeback_init(void) long buffer_pages = nr_free_buffer_pages(); long correction; - total_pages = nr_free_pagecache_pages(); - - correction = (100 * 4 * buffer_pages) / total_pages; + correction = (100 * 4 * buffer_pages) / vm_total_pages; if (correction < 100) { dirty_background_ratio *= correction; _