On Tue, Sep 15, 2020 at 08:34:41AM -0400, Mikulas Patocka wrote: > - when the fsck.nvfs tool mmaps the device /dev/pmem0, the kernel uses > buffer cache for the mapping. The buffer cache slows does fsck by a factor > of 5 to 10. Could it be possible to change the kernel so that it maps DAX > based block devices directly? Oh, because fs/block_dev.c has: .mmap = generic_file_mmap, I don't see why we shouldn't have a blkdev_mmap modelled after ext2_file_mmap() with the corresponding blkdev_dax_vm_ops.