[PATCH V3 5/9] dax/fsdev: use __va(phys) for kaddr in direct_access

[John Groves]

From: John Groves <John@xxxxxxxxxx>

Use __va(phys) instead of virt_addr + linear_offset for the kaddr
return in __fsdev_dax_direct_access(). The previous code added a
device-linear byte offset to virt_addr (which is __va of ranges[0]),
but for multi-range devices with physical gaps between ranges, this
linear arithmetic crosses the gap and produces a wrong kernel virtual
address. Using __va(phys) where phys comes from dax_pgoff_to_phys()
is correct for any range layout because the direct map translates
each physical address independently.

Fixes: 759455848df0b ("dax: Save the kva from memremap")
Signed-off-by: John Groves <john@xxxxxxxxxx>
---
 drivers/dax/fsdev.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/dax/fsdev.c b/drivers/dax/fsdev.c
index 42aac7e952516..a2d2eb20fb4d0 100644
--- a/drivers/dax/fsdev.c
+++ b/drivers/dax/fsdev.c
@@ -51,9 +51,7 @@ static long __fsdev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
 	struct dev_dax *dev_dax = dax_get_private(dax_dev);
 	size_t size = nr_pages << PAGE_SHIFT;
 	size_t offset = pgoff << PAGE_SHIFT;
-	void *virt_addr = dev_dax->virt_addr + offset;
 	phys_addr_t phys;
-	unsigned long local_pfn;
 
 	phys = dax_pgoff_to_phys(dev_dax, pgoff, size);
 	if (phys == -1) {
@@ -63,11 +61,10 @@ static long __fsdev_dax_direct_access(struct dax_device *dax_dev, pgoff_t pgoff,
 	}
 
 	if (kaddr)
-		*kaddr = virt_addr;
+		*kaddr = __va(phys);
 
-	local_pfn = PHYS_PFN(phys);
 	if (pfn)
-		*pfn = local_pfn;
+		*pfn = PHYS_PFN(phys);
 
 	/*
 	 * Use cached_size which was computed at probe time. The size cannot
-- 
2.53.0