[patch 125/173] mm/pmem: avoid inserting hugepage PTE entry with fsdax if hugepage support is disabled
STALE2045d
REVIEWED: 1 (0M)
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2021-02-24 20:07:36
Also in:
mm-commits
1 review trailer.
From: "Aneesh Kumar K.V" <redacted> Subject: mm/pmem: avoid inserting hugepage PTE entry with fsdax if hugepage support is disabled 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 <redacted> Reviewed-by: Dan Williams <redacted> Cc: "Kirill A . Shutemov" <redacted> Cc: Jan Kara <jack@suse.cz> Cc: David Hildenbrand <redacted> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- include/linux/huge_mm.h | 15 +++++++++------ mm/huge_memory.c | 6 +++++- 2 files changed, 14 insertions(+), 7 deletions(-)
--- a/include/linux/huge_mm.h~mm-pmem-avoid-inserting-hugepage-pte-entry-with-fsdax-if-hugepage-support-is-disabled
+++ a/include/linux/huge_mm.h@@ -78,6 +78,7 @@ static inline vm_fault_t vmf_insert_pfn_ } enum transparent_hugepage_flag { + TRANSPARENT_HUGEPAGE_NEVER_DAX, TRANSPARENT_HUGEPAGE_FLAG, TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG, TRANSPARENT_HUGEPAGE_DEFRAG_DIRECT_FLAG,
@@ -123,6 +124,13 @@ extern unsigned long transparent_hugepag */ 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;
@@ -134,12 +142,7 @@ static inline bool __transparent_hugepag 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; --- a/mm/huge_memory.c~mm-pmem-avoid-inserting-hugepage-pte-entry-with-fsdax-if-hugepage-support-is-disabled +++ a/mm/huge_memory.c
@@ -386,7 +386,11 @@ 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; }
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