From: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Although struct dax_device itself is not tied to a block device, some
DAX code assumes there is a block device. Make block devices optional
by allowing bdev to be NULL in commonly used DAX APIs.
When there is no block device:
* Skip the partition offset calculation in bdev_dax_pgoff()
* Skip the blkdev_issue_zeroout() optimization
Note that more block device assumptions remain but I haven't reach those
code paths yet.
Signed-off-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
---
drivers/dax/super.c | 3 ++-
fs/dax.c | 7 ++++++-
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 0a339b85133e..cb44ec663991 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -53,7 +53,8 @@ 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);
diff --git a/fs/dax.c b/fs/dax.c
index e5e54da1715f..815bc32fd967 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1042,7 +1042,12 @@ static vm_fault_t dax_load_hole(struct xa_state *xas,
static bool dax_range_is_aligned(struct block_device *bdev,
unsigned int offset, unsigned int length)
{
- unsigned short sector_size = bdev_logical_block_size(bdev);
+ unsigned short sector_size;
+
+ if (!bdev)
+ return false;
+
+ sector_size = bdev_logical_block_size(bdev);
if (!IS_ALIGNED(offset, sector_size))
return false;
--
2.20.1
