From: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com
[ Upstream commit bae84953815793f68ddd8edeadd3f4e32676a2c8 ]
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 --- include/linux/huge_mm.h | 15 +++++++++------ mm/huge_memory.c | 6 +++++- 2 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index ff55be011739..10c7a80a0394 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -84,6 +84,7 @@ static inline vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, }
enum transparent_hugepage_flag { + TRANSPARENT_HUGEPAGE_NEVER_DAX, TRANSPARENT_HUGEPAGE_FLAG, TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG, @@ -129,6 +130,13 @@ extern unsigned long transparent_hugepage_flags; */ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma) { + + /* + * If the hardware/firmware marked hugepage support disabled. + */ + if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_NEVER_DAX)) + return false; + if (vma->vm_flags & VM_NOHUGEPAGE) return false;
@@ -140,12 +148,7 @@ static inline bool __transparent_hugepage_enabled(struct vm_area_struct *vma)
if (transparent_hugepage_flags & (1 << TRANSPARENT_HUGEPAGE_FLAG)) return true; - /* - * For dax vmas, try to always use hugepage mappings. If the kernel does - * not support hugepages, fsdax mappings will fallback to PAGE_SIZE - * mappings, and device-dax namespaces, that try to guarantee a given - * mapping size, will fail to enable - */ + if (vma_is_dax(vma)) return true;
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 6301ecc1f679..f1432d4d81c7 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -375,7 +375,11 @@ static int __init hugepage_init(void) struct kobject *hugepage_kobj;
if (!has_transparent_hugepage()) { - transparent_hugepage_flags = 0; + /* + * Hardware doesn't support hugepages, hence disable + * DAX PMD support. + */ + transparent_hugepage_flags = 1 << TRANSPARENT_HUGEPAGE_NEVER_DAX; return -EINVAL; }