CHROMIUM: low-mem: add "on" command and fix error case

Stephan noticed that the code was not behaving correctly on invalid input,
and requested an "on" command to undo the effect of the "off" command.
Thanks Stephan!

BUG=chromium-os:29645
TEST=played around with "on", "off", valid and invalid input.

Change-Id: I73f9cf62e2571af250aa88340fc3186b0672a26d
Signed-off-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/21004
Reviewed-by: Stephan Uphoff <ups@chromium.org>

diff --git a/mm/low-mem-notify.c b/mm/low-mem-notify.c
index af0134c..c6729b2 100644 (file)
--- a/mm/low-mem-notify.c
+++ b/mm/low-mem-notify.c
@@ -135,17 +135,22 @@ static ssize_t low_mem_margin_store(struct kobject *kobj,
                low_mem_margin_enabled = false;
                return count;
        }
+       if (strncmp("on", buf, 2) == 0) {
+               printk(KERN_INFO "low_mem: enabling notifier\n");
+               low_mem_margin_enabled = true;
+               return count;
+       }
 
        err = strict_strtoul(buf, 10, &margin);
        if (err)
                return -EINVAL;
+       if (margin * ((1024 * 1024) / PAGE_SIZE) > totalram_pages)
+               return -EINVAL;
        /* Notify when the "free" memory is below margin megabytes. */
        low_mem_margin_enabled = true;
        low_mem_margin_mb = (unsigned int) margin;
        /* Convert to pages outside the allocator fast path. */
        low_mem_minfree = low_mem_margin_to_minfree(low_mem_margin_mb);
-       if (low_mem_minfree < 0 || low_mem_minfree > totalram_pages)
-               return -EINVAL;
        printk(KERN_INFO "low_mem: setting minfree to %lu kB\n",
               low_mem_minfree * (PAGE_SIZE / 1024));
        return count;