[PATCH] Represent dirty_*_centisecs as jiffies internally

Make that the internal values for:

/proc/sys/vm/dirty_writeback_centisecs
/proc/sys/vm/dirty_expire_centisecs

are stored as jiffies instead of centiseconds.  Let the sysctl interface do
the conversions with full precision using clock_t_to_jiffies, instead of
doing overflow-sensitive on-the-fly conversions every time the values are
used.

Cons: apparent precision loss if HZ is not a multiple of 100, because of
conversion back and forth.  This is a common problem for all sysctl values
that use proc_dointvec_userhz_jiffies.  (There is only one other in-tree
use, in net/core/neighbour.c.)

Signed-off-by: Bart Samwel <bart@samwel.tk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 32b48e8ee36e..817ba25517eb 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -742,18 +742,18 @@ static ctl_table vm_table[] = {
         {
                 .ctl_name       = VM_DIRTY_WB_CS,
                 .procname       = "dirty_writeback_centisecs",
-                .data           = &dirty_writeback_centisecs,
-                .maxlen         = sizeof(dirty_writeback_centisecs),
+                .data           = &dirty_writeback_interval,
+                .maxlen         = sizeof(dirty_writeback_interval),
                 .mode           = 0644,
                 .proc_handler   = &dirty_writeback_centisecs_handler,
         },
         {
                 .ctl_name       = VM_DIRTY_EXPIRE_CS,
                 .procname       = "dirty_expire_centisecs",
-                .data           = &dirty_expire_centisecs,
-                .maxlen         = sizeof(dirty_expire_centisecs),
+                .data           = &dirty_expire_interval,
+                .maxlen         = sizeof(dirty_expire_interval),
                 .mode           = 0644,
-                .proc_handler   = &proc_dointvec,
+                .proc_handler   = &proc_dointvec_userhz_jiffies,
         },
         {
                 .ctl_name       = VM_NR_PDFLUSH_THREADS,