mm/pmem: avoid inserting hugepage PTE entry with fsdax if hugepage support is disabled

stable inclusion
from stable-5.10.50
commit 9b0b9edea1d3a08bb448465b27569b1f378900e5
bugzilla: 174522 https://gitee.com/openeuler/kernel/issues/I4DNFY

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9b0b9edea1d3a08bb448465b27569b1f378900e5

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

[ Upstream commit bae84953 ]

Differentiate between hardware not supporting hugepages and user disabling
THP via 'echo never > /sys/kernel/mm/transparent_hugepage/enabled'

For the devdax namespace, the kernel handles the above via the
supported_alignment attribute and failing to initialize the namespace if
the namespace align value is not supported on the platform.

For the fsdax namespace, the kernel will continue to initialize the
namespace.  This can result in the kernel creating a huge pte entry even
though the hardware don't support the same.

We do want hugepage support with pmem even if the end-user disabled THP
via sysfs file (/sys/kernel/mm/transparent_hugepage/enabled).  Hence
differentiate between hardware/firmware lacking support vs user-controlled
disable of THP and prevent a huge fault if the hardware lacks hugepage
support.

Link: https://lkml.kernel.org/r/20210205023956.417587-1-aneesh.kumar@linux.ibm.com


Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Acked-by: Weilong Chen <chenweilong@huawei.com>
Signed-off-by: Chen Jun <chenjun102@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>