On Fri, 23 Sep 2011 10:40:45 +0100 "Daniel P. Berrange" <berrange@xxxxxxxxxx>
wrote:
> From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
>
> The md_notify_reboot() method includes a call to mdelay(1000),
> to deal with "exotic SCSI devices" which are too volatile on
> reboot. The delay is unconditional. Even if the machine does
> not have any block devices, let alone MD devices, the kernel
> shutdown sequence is slowed down.
>
> 1 second does not matter much with physical hardware, but with
> certain virtualization use cases any wasted time in the bootup
> & shutdown sequence counts for alot.
>
> * drivers/md/md.c: md_notify_reboot() - only impose a delay if
> there was at least one MD device to be stopped during reboot
>
> Signed-off-by: Daniel P. Berrange <berrange@xxxxxxxxxx>
queued for next merge window .... or maybe even next -rc if I'm feeling
brave.
Thanks,
NeilBrown
> ---
> drivers/md/md.c | 8 ++++++--
> 1 files changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index 5404b22..ef7ad8d 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -8059,12 +8059,13 @@ static int md_notify_reboot(struct notifier_block *this,
> {
> struct list_head *tmp;
> mddev_t *mddev;
> + int need_delay = 0;
>
> if ((code == SYS_DOWN) || (code == SYS_HALT) || (code == SYS_POWER_OFF)) {
>
> printk(KERN_INFO "md: stopping all md devices.\n");
>
> - for_each_mddev(mddev, tmp)
> + for_each_mddev(mddev, tmp) {
> if (mddev_trylock(mddev)) {
> /* Force a switch to readonly even array
> * appears to still be in use. Hence
> @@ -8073,13 +8074,16 @@ static int md_notify_reboot(struct notifier_block *this,
> md_set_readonly(mddev, 100);
> mddev_unlock(mddev);
> }
> + need_delay = 1;
> + }
> /*
> * certain more exotic SCSI devices are known to be
> * volatile wrt too early system reboots. While the
> * right place to handle this issue is the given
> * driver, we do want to have a safe RAID driver ...
> */
> - mdelay(1000*1);
> + if (need_delay)
> + mdelay(1000*1);
> }
> return NOTIFY_DONE;
> }
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