Force a user visible low bound of 5% for the vm.dirty_ratio interface. Currently global_dirty_limits() applies a low bound of 5% for vm_dirty_ratio. This is not very user visible -- if the user sets vm.dirty_ratio=1, the operation seems to succeed but will be rounded up to 5% when used. Another problem is inconsistency: calc_period_shift() uses the plain vm_dirty_ratio value, which may be a problem when vm.dirty_ratio is set to < 5 by the user. CC: Peter Zijlstra Signed-off-by: Wu Fengguang --- kernel/sysctl.c | 3 ++- mm/page-writeback.c | 10 ++-------- 2 files changed, 4 insertions(+), 9 deletions(-) --- linux-next.orig/kernel/sysctl.c 2010-08-05 22:48:34.000000000 +0800 +++ linux-next/kernel/sysctl.c 2010-08-05 22:48:47.000000000 +0800 @@ -126,6 +126,7 @@ static int ten_thousand = 10000; /* this is needed for the proc_doulongvec_minmax of vm_dirty_bytes */ static unsigned long dirty_bytes_min = 2 * PAGE_SIZE; +static int dirty_ratio_min = 5; /* this is needed for the proc_dointvec_minmax for [fs_]overflow UID and GID */ static int maxolduid = 65535; @@ -1031,7 +1032,7 @@ static struct ctl_table vm_table[] = { .maxlen = sizeof(vm_dirty_ratio), .mode = 0644, .proc_handler = dirty_ratio_handler, - .extra1 = &zero, + .extra1 = &dirty_ratio_min, .extra2 = &one_hundred, }, { --- linux-next.orig/mm/page-writeback.c 2010-08-05 22:48:42.000000000 +0800 +++ linux-next/mm/page-writeback.c 2010-08-05 22:48:47.000000000 +0800 @@ -415,14 +415,8 @@ void global_dirty_limits(unsigned long * if (vm_dirty_bytes) dirty = DIV_ROUND_UP(vm_dirty_bytes, PAGE_SIZE); - else { - int dirty_ratio; - - dirty_ratio = vm_dirty_ratio; - if (dirty_ratio < 5) - dirty_ratio = 5; - dirty = (dirty_ratio * available_memory) / 100; - } + else + dirty = (vm_dirty_ratio * available_memory) / 100; if (dirty_background_bytes) background = DIV_ROUND_UP(dirty_background_bytes, PAGE_SIZE); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/