Re: [PATCH] drivers:md: Remove no longer needed fixme comment in raid5.c

Re: [PATCH] drivers:md: Remove no longer needed fixme comment in raid5.c

[NeilBrown]

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On Wed, 17 Dec 2014 10:49:33 -0500 Nicholas Krause <xerofoify@gmail.com>
wrote:

> Removes the no longer needed fix me comment related to not needing the agrument faster for the function,
> sync_request. Due to getting warnings when building without the agrument it seems that this fix me was
> wrong and we must keep this agrument in order to avoid build warnings when building without it.
> 
> Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
> ---
>  drivers/md/raid5.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
> index c1b0d52..c0fde2a 100644
> --- a/drivers/md/raid5.c
> +++ b/drivers/md/raid5.c
> @@ -4986,7 +4986,6 @@ ret:
>  	return reshape_sectors;
>  }
>  
> -/* FIXME go_faster isn't used */
>  static inline sector_t sync_request(struct mddev *mddev, sector_t sector_nr, int *skipped, int go_faster)
>  {
>  	struct r5conf *conf = mddev->private;


Why do you think the comment is no longer needed.  Is "go_faster" being used
now?  Is there a clear explanation somewhere of why "go_faster" should not be
used?

NeilBrown

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Re: [PATCH] drivers:md: Remove no longer needed fixme comment in raid5.c

[Valdis.Kletnieks]

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On Thu, 18 Dec 2014 10:19:06 +1100, NeilBrown said:
> On Wed, 17 Dec 2014 10:49:33 -0500 Nicholas Krause <xerofoify@gmail.com> wrote:
>
> > Removes the no longer needed fix me comment related to not needing the agrument faster for the function,
> > sync_request. Due to getting warnings when building without the agrument it seems that this fix me was
> > wrong and we must keep this agrument in order to avoid build warnings when building without it.

Examining raid1.c, which *does* use the go_faster parameter, I suspect
that the *real* meaning of the FIXME is that the code in raid5.c *should*
possibly be doing this that's done in raid1.c's sync_request():

        /*
         * If there is non-resync activity waiting for a turn,
         * and resync is going fast enough,
         * then let it though before starting on this new sync request.
         */
        if (!go_faster && conf->nr_waiting)
                msleep_interruptible(1000);

(Which is one of the few flow differences for the sync_request() code
in raid1.c versus raid5.c.  I'll however defer to actual RAID experts
on whether raid5 needs resync throttling, or if it's accomplished via
other means I'm not spotting.  Finding a FIXME outside of drivers/staging
is usually a "Here be fearsome and nasty dragons" comment....


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