Patch series "Make khugepaged collapse readonly FS THP more consistent", v4. The readonly FS THP relies on khugepaged to collapse THP for suitable vmas. But the behavior is inconsistent for "always" mode (https://lore.kernel.org/linux-mm/00f195d4-d039-3cf2-d3a1-a2c88de397a0@suse.cz/). The "always" mode means THP allocation should be tried all the time and khugepaged should try to collapse THP all the time. Of course the allocation and collapse may fail due to other factors and conditions. Currently file THP may not be collapsed by khugepaged even though all the conditions are met. That does break the semantics of "always" mode. So make sure readonly FS vmas are registered to khugepaged to fix the break. Register suitable vmas in common mmap path, that could cover both readonly FS vmas and shmem vmas, so remove the khugepaged calls in shmem.c. The patch 1-7 are minor bug fixes, clean up and preparation patches. Patch 8 is the real meat. Tested with khugepaged test in selftests and the testcase provided by Vlastimil Babka in https://lore.kernel.org/lkml/df3b5d1c-a36b-2c73-3e27-99e74983de3a@suse.cz/ by commenting out MADV_HUGEPAGE call. This patch (of 8): MMF_VM_HUGEPAGE is set as long as the mm is available for khugepaged by khugepaged_enter(), not only when VM_HUGEPAGE is set on vma. Correct the comment to avoid confusion.
Unified · Split
| @@ -57,7 +57,8 @@ static inline int get_dumpable(struct mm_struct *mm) · 56 unmodified lines | |||
| 57 | #endif | 57 | #endif |
| 58 | /* leave room for more dump flags */ | 58 | /* leave room for more dump flags */ |
| 59 | #define MMF_VM_MERGEABLE 16 /* KSM may merge identical pages */ | 59 | #define MMF_VM_MERGEABLE 16 /* KSM may merge identical pages */ |
| 60 | #define MMF_VM_HUGEPAGE 17 /* set when VM_HUGEPAGE is set on vma */ | 60 | #define MMF_VM_HUGEPAGE 17 /* set when mm is available for |
| 61 | khugepaged */ | ||
| 61 | /* | 62 | /* |
| 62 | * This one-shot flag is dropped due to necessity of changing exe once again | 63 | * This one-shot flag is dropped due to necessity of changing exe once again |
| 63 | * on NFS restore | 64 | * on NFS restore |