From 93278814d3590eba0ee360b8d69a35c7f2203ea8 Mon Sep 17 00:00:00 2001 From: Sasha Levin Date: Thu, 10 May 2012 13:01:44 -0700 Subject: mm: fix division by 0 in percpu_pagelist_fraction() percpu_pagelist_fraction_sysctl_handler() has only considered -EINVAL as a possible error from proc_dointvec_minmax(). If any other error is returned, it would proceed to divide by zero since percpu_pagelist_fraction wasn't getting initialized at any point. For example, writing 0 bytes into the proc file would trigger the issue. Signed-off-by: Sasha Levin Reviewed-by: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a712fb9e04ce..b21b3db15a7f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -105,7 +105,7 @@ unsigned long totalreserve_pages __read_mostly; */ unsigned long dirty_balance_reserve __read_mostly; -int percpu_pagelist_fraction; +int percpu_pagelist_fraction = 8; gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK; #ifdef CONFIG_PM_SLEEP @@ -5203,7 +5203,7 @@ int percpu_pagelist_fraction_sysctl_handler(ctl_table *table, int write, int ret; ret = proc_dointvec_minmax(table, write, buffer, length, ppos); - if (!write || (ret == -EINVAL)) + if (!write || (ret < 0)) return ret; for_each_populated_zone(zone) { for_each_possible_cpu(cpu) { -- cgit v1.2.3 From 1b76b02f15c70d5f392ee2e231fbd20a26063a77 Mon Sep 17 00:00:00 2001 From: Hugh Dickins Date: Fri, 11 May 2012 01:00:07 -0700 Subject: mm: raise MemFree by reverting percpu_pagelist_fraction to 0 Why is there less MemFree than there used to be? It perturbed a test, so I've just been bisecting linux-next, and now find the offender went upstream yesterday. Commit 93278814d359 "mm: fix division by 0 in percpu_pagelist_fraction()" mistakenly initialized percpu_pagelist_fraction to the sysctl's minimum 8, which leaves 1/8th of memory on percpu lists (on each cpu??); but most of us expect it to be left unset at 0 (and it's not then used as a divisor). MemTotal: 8061476kB 8061476kB 8061476kB 8061476kB 8061476kB 8061476kB Repetitive test with percpu_pagelist_fraction 8: MemFree: 6948420kB 6237172kB 6949696kB 6840692kB 6949048kB 6862984kB Same test with percpu_pagelist_fraction back to 0: MemFree: 7945000kB 7944908kB 7948568kB 7949060kB 7948796kB 7948812kB Signed-off-by: Hugh Dickins [ We really should fix the crazy sysctl interface too, but that's a separate thing - Linus ] Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/page_alloc.c') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index b21b3db15a7f..918330f71dba 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -105,7 +105,7 @@ unsigned long totalreserve_pages __read_mostly; */ unsigned long dirty_balance_reserve __read_mostly; -int percpu_pagelist_fraction = 8; +int percpu_pagelist_fraction; gfp_t gfp_allowed_mask __read_mostly = GFP_BOOT_MASK; #ifdef CONFIG_PM_SLEEP -- cgit v1.2.3