virtiofs does not have a block device but it has dax device. Modify bdev_dax_pgoff() to be able to handle that.
If there is no bdev, that means dax offset is 0. (It can't be a partition block device starting at an offset in dax device). This is little hackish. There have been discussions about getting rid of dax not supporting partitions. https://lore.kernel.org/linux-fsdevel/20200107125159.ga15...@infradead.org/ IMHO, this path can easily break exisitng users. For example ioctl(BLKPG_ADD_PARTITION) will start breaking on block devices supporting DAX. Also, I personally find it very useful to be able to partition dax devices and still be able to use DAX. Alternatively, I tried to store offset into dax device information in iomap interface, but that got NACKed. https://lore.kernel.org/linux-fsdevel/20200217133117.gb20...@infradead.org/ I can't think of a good path to solve this issue properly. So to make progress, it seems this patch is least bad option for now and I hope we can take it. Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> Signed-off-by: Vivek Goyal <vgo...@redhat.com> Cc: Christoph Hellwig <h...@infradead.org> Cc: Dan Williams <dan.j.willi...@intel.com> Cc: linux-nvd...@lists.01.org --- drivers/dax/super.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/dax/super.c b/drivers/dax/super.c index 8e32345be0f7..c4bec437e88b 100644 --- a/drivers/dax/super.c +++ b/drivers/dax/super.c @@ -46,7 +46,8 @@ EXPORT_SYMBOL_GPL(dax_read_unlock); int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size, pgoff_t *pgoff) { - phys_addr_t phys_off = (get_start_sect(bdev) + sector) * 512; + sector_t start_sect = bdev ? get_start_sect(bdev) : 0; + phys_addr_t phys_off = (start_sect + sector) * 512; if (pgoff) *pgoff = PHYS_PFN(phys_off); -- 2.25.4
