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Fri, 25 Jul 2025 09:23:04 -0700 (PDT) From: Usama Arif To: Andrew Morton , david@redhat.com, linux-mm@kvack.org Cc: linux-fsdevel@vger.kernel.org, corbet@lwn.net, rppt@kernel.org, surenb@google.com, mhocko@suse.com, hannes@cmpxchg.org, baohua@kernel.org, shakeel.butt@linux.dev, riel@surriel.com, ziy@nvidia.com, laoar.shao@gmail.com, dev.jain@arm.com, baolin.wang@linux.alibaba.com, npache@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, vbabka@suse.cz, jannh@google.com, Arnd Bergmann , sj@kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@meta.com, Usama Arif Subject: [PATCH 3/5] mm/huge_memory: treat MADV_COLLAPSE as an advise with PR_THP_DISABLE_EXCEPT_ADVISED Date: Fri, 25 Jul 2025 17:22:42 +0100 Message-ID: <20250725162258.1043176-4-usamaarif642@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20250725162258.1043176-1-usamaarif642@gmail.com> References: <20250725162258.1043176-1-usamaarif642@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: David Hildenbrand Let's allow for making MADV_COLLAPSE succeed on areas that neither have VM_HUGEPAGE nor VM_NOHUGEPAGE when we have THP disabled unless explicitly advised (PR_THP_DISABLE_EXCEPT_ADVISED). MADV_COLLAPSE is a clear advise that we want to collapse. Note that we still respect the VM_NOHUGEPAGE flag, just like MADV_COLLAPSE always does. So consequently, MADV_COLLAPSE is now only refused on VM_NOHUGEPAGE with PR_THP_DISABLE_EXCEPT_ADVISED. Co-developed-by: Usama Arif Signed-off-by: Usama Arif Signed-off-by: David Hildenbrand --- include/linux/huge_mm.h | 8 +++++++- include/uapi/linux/prctl.h | 2 +- mm/huge_memory.c | 5 +++-- mm/memory.c | 6 ++++-- mm/shmem.c | 2 +- 5 files changed, 16 insertions(+), 7 deletions(-) diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index b0ff54eee81c..aeaf93f8ac2e 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -329,7 +329,7 @@ struct thpsize { * through madvise or prctl. */ static inline bool vma_thp_disabled(struct vm_area_struct *vma, - vm_flags_t vm_flags) + vm_flags_t vm_flags, bool forced_collapse) { /* Are THPs disabled for this VMA? */ if (vm_flags & VM_NOHUGEPAGE) @@ -343,6 +343,12 @@ static inline bool vma_thp_disabled(struct vm_area_str= uct *vma, */ if (vm_flags & VM_HUGEPAGE) return false; + /* + * Forcing a collapse (e.g., madv_collapse), is a clear advise to + * use THPs. + */ + if (forced_collapse) + return false; return test_bit(MMF_DISABLE_THP_EXCEPT_ADVISED, &vma->vm_mm->flags); } =20 diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 9c1d6e49b8a9..ee4165738779 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -185,7 +185,7 @@ struct prctl_mm_map { #define PR_SET_THP_DISABLE 41 /* * Don't disable THPs when explicitly advised (e.g., MADV_HUGEPAGE / - * VM_HUGEPAGE). + * VM_HUGEPAGE / MADV_COLLAPSE). */ # define PR_THP_DISABLE_EXCEPT_ADVISED (1 << 1) #define PR_GET_THP_DISABLE 42 diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 85252b468f80..ef5ccb0ec5d5 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -104,7 +104,8 @@ unsigned long __thp_vma_allowable_orders(struct vm_area= _struct *vma, { const bool smaps =3D type =3D=3D TVA_SMAPS; const bool in_pf =3D type =3D=3D TVA_PAGEFAULT; - const bool enforce_sysfs =3D type !=3D TVA_FORCED_COLLAPSE; + const bool forced_collapse =3D type =3D=3D TVA_FORCED_COLLAPSE; + const bool enforce_sysfs =3D !forced_collapse; unsigned long supported_orders; =20 /* Check the intersection of requested and supported orders. */ @@ -122,7 +123,7 @@ unsigned long __thp_vma_allowable_orders(struct vm_area= _struct *vma, if (!vma->vm_mm) /* vdso */ return 0; =20 - if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags)) + if (thp_disabled_by_hw() || vma_thp_disabled(vma, vm_flags, forced_collap= se)) return 0; =20 /* khugepaged doesn't collapse DAX vma, but page fault is fine. */ diff --git a/mm/memory.c b/mm/memory.c index be761753f240..bd04212d6f79 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -5186,9 +5186,11 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct f= olio *folio, struct page *pa * It is too late to allocate a small folio, we already have a large * folio in the pagecache: especially s390 KVM cannot tolerate any * PMD mappings, but PTE-mapped THP are fine. So let's simply refuse any - * PMD mappings if THPs are disabled. + * PMD mappings if THPs are disabled. As we already have a THP ... + * behave as if we are forcing a collapse. */ - if (thp_disabled_by_hw() || vma_thp_disabled(vma, vma->vm_flags)) + if (thp_disabled_by_hw() || vma_thp_disabled(vma, vma->vm_flags, + /* forced_collapse=3D*/ true)) return ret; =20 if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER)) diff --git a/mm/shmem.c b/mm/shmem.c index e6cdfda08aed..30609197a266 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1816,7 +1816,7 @@ unsigned long shmem_allowable_huge_orders(struct inod= e *inode, vm_flags_t vm_flags =3D vma ? vma->vm_flags : 0; unsigned int global_orders; =20 - if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags))) + if (thp_disabled_by_hw() || (vma && vma_thp_disabled(vma, vm_flags, shmem= _huge_force))) return 0; =20 global_orders =3D shmem_huge_global_enabled(inode, index, write_end, --=20 2.47.3