On Thu, 12 May 2011, James Bottomley wrote: > > I need someone from USB/SCSI camp to see if this approach makes sense. > > I don't really think so, because it's pretending the device cache has > flipped to write through. It's certainly possible to envisage removable > media where the cache is in the housing and we still need to preserve > the idea of it being write back. I don't follow your argument here. What difference does it make what kind of cache the drive has, if the media is gone? > Instinct tells me the correct set of fixes is to add a sync cache from > release (so we automatically sync on last close, which is usually when > an ordered remove happens), That certainly makes sense. Is there any reason why this isn't done already? > keep the one on shutdown, just in case the > system goes down with stuff still mounted and print a nasty message on > suspend for a write back device that's been removed. There's no need for a nasty message unless the cache is still dirty. Your suggested patch doesn't check for that -- in fact, I don't think the driver even knows whether the cache is dirty. (Not that this matters, seeing as how your patch doesn't print any nasty messages.) > I also think we shouldn't abort the suspend if the disk doesn't respond > correctly to start/stop ... the power is going to be disconnected > anyway, so it's no issue if the disk spins for a second or so longer. That's a good idea. On several occasions Linus has mentioned that almost nothing should stop a system suspend. It's even questionable whether a SYNC failure should stop a suspend ... but that's a separate matter. What happens if the medium was recently removed, meaning that sdkp->media_present hasn't yet had a chance to become 0? The patch needs to handle that case as well, perhaps by adding another check after sd_sync_cache() returns. > The problem this is going to cause is double sync on shutdown (once when > final unmount closes the device and once on shutdown) ... do people > agree that's a price worth paying? I don't think the price will be high. The second sync will have nothing to do, because the first sync will have cleaned out the cache. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
