On Wed 16-09-09 20:31:29, Jens Axboe wrote: > On Wed, Sep 16 2009, Jan Kara wrote: > > On Wed 16-09-09 15:21:08, Jens Axboe wrote: > > > On Wed, Sep 16 2009, Jan Kara wrote: > > > > On Tue 15-09-09 20:16:56, Jens Axboe wrote: > > > > > We cannot safely ensure that the inodes are all gone at this point > > > > > in time, and we must not destroy this bdi with inodes having off it. > > > > ^^^ hanging > > > > > > > > > So just splice our entries to the default bdi since that one will > > > > > always persist. > > > > BTW: Why can't we make sure all inodes on the BDI are clean when we > > > > destroy it? Common sence would suggest that we better should be able to do > > > > it :). > > > > Maybe it's because most users of private BDI do not call bdi_unregister > > > > but rather directly bdi_destroy? Is this correct behavior? > > > Not sure yet, it's on the TODO. This basically works around the problem > > > for now at least. With dm at least, I'm seeing inodes still hanging off > > > the bdi after we have done a sync_blockdev(bdev, 1);. > > Do you really mean sync_blockdev() or fsync_bdev()? Because the first one > > just synces the blockdev's mapping not the filesystem... > > Do we want a fsync_bdev() in __blkdev_put()? It's only doing No, we cannot call fsync_bdev() there because nothing really guarantees that there exists any filesystem on the device and that it is setup enough to handle IO - __blkdev_put() is called e.g. after the filesystem has been cleaned up in ->put_super(). You can have a look like code in generic_shutdown_super() looks like. The function is called when user has no chance of dirtying any more data. In particular sync_filesystem() call there should write everything to disk. If it does not, it's a bug. ->put_super() can dirty some data again, but only buffers of underlying blockdev (e.g. when writing bitmaps, superblock etc.). If ->put_super() method of some filesystem leaves some inodes dirty, it's a bug - we'd see "VFS: Busy inodes after unmount" message. > sync_blockdev() on last close, and dm wants to tear down the device at > that point. So either dm needs to really flush the device when going > readonly, or we need to strengthen the 'flush on last close'. Yes, but at the time __blkdev_put() is called, there should be no dirty inodes as I've argued above. So I still don't quite get how there could be any :) Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
