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SubjectRe: disk write cache and poweroff


Please use the latest patches found at


Andre Hedrick
CEO/President, LAD Storage Consulting Group
Linux ATA Development
Linux Disk Certification Project

On Mon, 12 Nov 2001, Miquel van Smoorenburg wrote:

> Hello Andre,
> A few users of the debian sysvinit package have complained that on
> their laptop, shutdown + poweroff is too fast. The disk is turned
> off before the write-cache on the disk is completely written,
> resulting in some filesystem corruption.
> After some experimentation with turning off the write cache before
> shutdown etc, I found out that a side-effect of putting the IDE
> disk in standby mode is that the write cache is flushed. So now
> halt(8) has an extra option to put all IDE disks it can find
> (through /proc/ide/hd*) in standby mode just before it calls
> reboot(LINUX_REBOOT_CMD_POWER_OFF). Thus flag is used in the
> /etc/rc0.d/S90halt script, and appears to fix the problem. I think
> windows does the same :|
> Anyway this should probably be done in the kernel. Perhaps the
> IDE driver should register a reboot notifier with
> register_reboot_notifier() that puts all IDE disks on the
> system in standby mode on SYS_HALT and SYS_POWER_OFF ?
> Many other drivers do this too, grep for SYS_HALT in linux/drivers/*/*.c
> Hmm I just noticed that a lot of driver check for SYS_DOWN (which
> is the same as SYS_RESTART: reboot) and SYS_HALT but not for
> SYS_POWEROFF, which is a bug in those drivers. Ugh.
> Mike.
> --
> "Only two things are infinite, the universe and human stupidity,
> and I'm not sure about the former" -- Albert Einstein.

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