On 23 Sep 2003, James Bottomley wrote: > On Tue, 2003-09-23 at 09:37, [EMAIL PROTECTED] wrote: > > > Pulling out a device while it is actively reading or writing > > will probably break something. But if a device is hot-pluggable > > it should be OK to pull it out when it has been inactive for > > a second or so. > > > > But if that is really true, then it should not be necessary > > to send the device any "synchronise cache" commands when we > > shut down. > > For a FC array, suprise unplug would be caveat emptor (possibly because > fibre connection transience is going to cause it to come back), but > notified unplug would still want to flush the cache on the assumption > the next action might be to power down the array.
Is there any way to notify the system that you are about to unplug a drive? It seems to me that the best approach is to flush the cache on an unmount. People naturally assume that it's safe to unplug a device once it has been unmounted, and they also realize that it's unsafe to unplug a device containing a mounted filesystem. That doesn't address the problem of raw device access, but perhaps whatever ioctl is used by blockdev --flushbufs can also flush the cache. Is there any harm in sending a SYNCHRONIZE command to a device that doesn't need it (write-through cache)? Maybe doing that is less dangerous than trying to read mode-sense page 8 on these buggy USB devices. (Although I'm not aware of anyone who has tried the experiment.) Alan Stern ------------------------------------------------------- This sf.net email is sponsored by:ThinkGeek Welcome to geek heaven. http://thinkgeek.com/sf _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
