On Tue, Feb 02, 2016 at 04:11:42PM -0700, Ross Zwisler wrote: > However, for raw block devices and for XFS with a real-time device, the > value in inode->i_sb->s_bdev is not correct. With the code as it is > currently written, an fsync or msync to a DAX enabled raw block device will > cause a NULL pointer dereference kernel BUG. For this to work correctly we > need to ask the block device or filesystem what struct block_device is > appropriate for our inode. > > To that end, add a get_bdev(struct inode *) entry point to struct > super_operations. If this function pointer is non-NULL, this notifies DAX > that it needs to use it to look up the correct block_device. If > i_sb->get_bdev() is NULL DAX will default to inode->i_sb->s_bdev.
Umm... It assumes that bdev will stay pinned for as long as inode is referenced, presumably? If so, that needs to be documented (and verified for existing fs instances). In principle, multi-disk fs might want to support things like "silently move the inodes backed by that disk to other ones"...
