Re: [TOME] Re: [PATCH 1/1] Add check for dirty_writeback_interval inbdi_wakeup_thread_delayed

From: Raghavendra D Prabhu
Date: Mon Apr 18 2011 - 03:09:33 EST

* On Mon, Apr 18, 2011 at 10:02:04AM +1000, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
On Sun, Apr 17, 2011 at 09:53:08PM +0530, Raghavendra D Prabhu wrote:
In the function bdi_wakeup_thread_delayed, no checks are performed on
dirty_writeback_interval unlike other places and timeout is being set to
zero as result, thus defeating the purpose. So, I have changed it to be
passed default value of interval which is 500 centiseconds, when it is
set to zero.
I have also verified this and tested it.

Signed-off-by: Raghavendra D Prabhu <rprabhu@xxxxxxxxxxx>
---
mm/backing-dev.c | 5 ++++-
1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index befc875..d06533c 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -336,7 +336,10 @@ void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
{
unsigned long timeout;
- timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
+ if (dirty_writeback_interval)
+ timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
+ else
+ timeout = msecs_to_jiffies(5000);
mod_timer(&bdi->wb.wakeup_timer, jiffies + timeout);
}

Isn't the problem that the sysctl handler does not have a min/max
valid value set? I.e. to prevent invalid values from being set in
the first place?

Cheers,

Dave.
0 is a valid value for dirty_writeback_interval which according to the
definition/documentation is disabled when set to 0. In other places, a constraint
check is done on that value except here.

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