[PATCH 6.4 517/800] dax/kmem: Pass valid argument to memory_group_register_static

Greg Kroah-Hartman
2023-07-16T20:17:04Z

From: Tarun Sahu <tsahu@linux.ibm.com>

[ Upstream commit 46e66dab8565f742374e9cc4ff7d35f344d774e2 ]

memory_group_register_static takes maximum number of pages as the argument
while dev_dax_kmem_probe passes total_len (in bytes) as the argument.

IIUC, I don't see any crash/panic impact as such. As,
memory_group_register_static just set the max_pages limit which is used in
auto_movable_zone_for_pfn to determine the zone.

which might cause these condition to behave differently,

This will be true always so jump will happen to kernel_zone
...
if (!auto_movable_can_online_movable(NUMA_NO_NODE, group, nr_pages))
goto kernel_zone;

...
kernel_zone:
return default_kernel_zone_for_pfn(nid, pfn, nr_pages);

Here, In below, zone_intersects compare range will be larger as nr_pages
will be higher (derived from total_len passed in dev_dax_kmem_probe).

...
static struct zone *default_kernel_zone_for_pfn(int nid, unsigned long start_pfn,
unsigned long nr_pages)
{
struct pglist_data *pgdat = NODE_DATA(nid);
int zid;

for (zid = 0; zid < ZONE_NORMAL; zid++) {
struct zone *zone = &pgdat->node_zones[zid];

if (zone_intersects(zone, start_pfn, nr_pages))
return zone;
}

return &pgdat->node_zones[ZONE_NORMAL];
}

Incorrect zone will be returned here, which in later time might cause bigger
problem.

Fixes: eedf634aac3b ("dax/kmem: use a single static memory group for a single probed unit")
Signed-off-by: Tarun Sahu <tsahu@linux.ibm.com>
Link: https://lore.kernel.org/r/20230621155025.370672-1-tsahu@linux.ibm.com
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/dax/kmem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index 7b36db6f1cbdc..898ca95057547 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -99,7 +99,7 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
if (!data->res_name)
goto err_res_name;

- rc = memory_group_register_static(numa_node, total_len);
+ rc = memory_group_register_static(numa_node, PFN_UP(total_len));
if (rc < 0)
goto err_reg_mgid;
data->mgid = rc;
--
2.39.2