[PATCH 7.1 212/438] lib: test_hmm: use device devt for coherent device range selection

7.1-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stanislav Kinsburskii <[email protected]>

commit 4fc089235378d1f9ddb6bcbe67c192ffdcaae0ed upstream.

Commit af69016dab96 ("lib: test_hmm: implement a device release method")
moved the initial dmirror_allocate_chunk() call before cdev_device_add().
That means the struct cdev has not been added yet, so cdev_add() has not
initialized mdevice->cdevice.dev.

The coherent-device range selection uses the device minor to choose
between spm_addr_dev0 and spm_addr_dev1.  Reading
MINOR(mdevice->cdevice.dev) before cdev_add() therefore always sees an
uninitialized dev_t.  As a result, both coherent devices select the same
physical range, and adding the second device fails due to the overlapping
dev_pagemap range.

Use mdevice->device.devt instead.  It is initialized in
dmirror_device_init() before dmirror_allocate_chunk() is called and is the
same dev_t later passed to cdev_device_add().

Link: https://lore.kernel.org/178277581197.172200.16265155329935822153.stgit@skinsburskii
Fixes: af69016dab96 ("lib: test_hmm: implement a device release method")
Signed-off-by: Stanislav Kinsburskii <[email protected]>
Reviewed-by: Alistair Popple <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Zenghui Yu (Huawei) <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Leon Romanovsky <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 lib/test_hmm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index 9c59d1ceb5b5..c4adbf98fac7 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -581,7 +581,7 @@ static int dmirror_allocate_chunk(struct dmirror_device *mdevice,
 		devmem->pagemap.type = MEMORY_DEVICE_PRIVATE;
 		break;
 	case HMM_DMIRROR_MEMORY_DEVICE_COHERENT:
-		devmem->pagemap.range.start = (MINOR(mdevice->cdevice.dev) - 2) ?
+		devmem->pagemap.range.start = (MINOR(mdevice->device.devt) - 2) ?
 							spm_addr_dev0 :
 							spm_addr_dev1;
 		devmem->pagemap.range.end = devmem->pagemap.range.start +
-- 
2.55.0