[PATCH v2] dax/kmem: account for partial dis-contiguous resource upon removal

[Davidlohr Bueso]

When dev_dax_kmem_probe() partially succeeds (at least one range
is mapped) but a subsequent range fails request_mem_region()
or add_memory_driver_managed(), the probe silently continues,
ultimately returning success, but with the corresponding range
resource NULL'ed out.

dev_dax_kmem_remove() iterates over all dax_device ranges regardless
of if the underlying resource exists. When remove_memory() is
called later, it returns 0 because the memory was never added which
causes dev_dax_kmem_remove() to incorrectly assume the (nonexistent)
resource can be removed and attempts cleanup on a NULL pointer.

Fix this by skipping these ranges altogether, noting that these
cases are considered success, such that the cleanup is still
reached when all actually-added ranges are successfully removed.

Reviewed-by: Ben Cheatham <benjamin.cheatham@xxxxxxx>
Fixes: 60e93dc097f7 ("device-dax: add dis-contiguous resource support")
Signed-off-by: Davidlohr Bueso <dave@xxxxxxxxxxxx>
---
Changes from v1: reword some of the changelog (Ben)

 drivers/dax/kmem.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index c036e4d0b610..edd62e68ffb7 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -227,6 +227,12 @@ static void dev_dax_kmem_remove(struct dev_dax *dev_dax)
 		if (rc)
 			continue;
 
+		/* range was never added during probe */
+		if (!data->res[i]) {
+			success++;
+			continue;
+		}
+
 		rc = remove_memory(range.start, range_len(&range));
 		if (rc == 0) {
 			remove_resource(data->res[i]);
-- 
2.39.5