On Wed, May 10, 2023 at 08:19:58AM +1000, Dave Chinner wrote: > On Tue, May 09, 2023 at 03:35:01PM +0200, Christoph Hellwig wrote: > > On Fri, May 05, 2023 at 11:51:19AM -0700, Darrick J. Wong wrote: > > > Fun question: What happens when the swap disk falls off the bus? > > > > Your system is toast. > > > > > > - if (IS_ERR(blkdev_get_by_dev(bdev->bd_dev, mode | FMODE_EXCL, &bdev))) > > > > + if (IS_ERR(blkdev_get_by_dev(bdev->bd_dev, mode | FMODE_EXCL, &bdev, > > > > + NULL))) > > > > return -EBUSY; > > > > ret = set_blocksize(bdev, n); > > > > blkdev_put(bdev, mode | FMODE_EXCL); > > > > > > Somewhat related question: Should we allow userspace to initiate a fs > > > shutdown through the block device? Let's say you're preparing to yank > > > /dev/sda and want to kill anything attached to it or its partitions? > > > Without having to walk through however many mount namespaces there are > > > to find the mountpoints? > > > > That's kinda what we're doing here. Or do you mean even more advanced > > notice by having another callout before stopping I/O so that we could > > write out all log buffers? It's probably doable, but I'm not convinced > > that this use case is worth maintaining and testing the kernel code for > > it. > > The userspace shutdown code already does this by default - it > actually calls freeze_bdev() to cause the filesystem to be made > consistent on the block device before it executes the shutdown. > So, in effect, we already have the "shutdown before turning off > block device" paths in the filesystems and extremely well tested. > > Indeed, if the device is being removed, why not call freeze_bdev() > before doing anything else? It guarantees that applications will be > quiesced and the filesystem will stabilise and not try to change > anything until the shutdown occurs when the device is pulled... I think I want everything -- I want freeze_bdev on a device /before/ we pull it out so that we can try to flush dirty everything to the disk; I want that to work for the log/rt devices; and I want a final shutdown notification when the kernel drops the bdev so that we can offline the fs and shortcut/start returning EIO. --D > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx
