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AJvYcCUbQ8jhqALy9oSeqH2h7z8QUPm4D7X5/TbY0vE9vOAP/+VCs3AzEX/dsiwBOpVyQuGs4KCFEwp2RWvjsas=@vger.kernel.org X-Gm-Message-State: AOJu0YwHCeVGE8JjxOFTbyO5eAxTR3rwAbaZ+Iat8Jl4PjvQCcu1sG6O MtBLxcuU/QnKNeBQOKaEf967vLyMPB34SrsaaFUVjc30RsChgc9Ca9PD8TpWt3rH4esW/RkUJJA ecuVSuA== X-Received: from dlbvg11.prod.google.com ([2002:a05:7022:7f0b:b0:127:bd1:76f0]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7022:6897:b0:127:337e:3301 with SMTP id a92af1059eb24-12741b6fd42mr4785616c88.12.1771345977912; Tue, 17 Feb 2026 08:32:57 -0800 (PST) Date: Tue, 17 Feb 2026 08:32:49 -0800 In-Reply-To: <20260217163250.2326001-1-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260217163250.2326001-1-surenb@google.com> X-Mailer: git-send-email 2.53.0.273.g2a3d683680-goog Message-ID: <20260217163250.2326001-3-surenb@google.com> Subject: [PATCH v2 2/3] mm: replace vma_start_write() with vma_start_write_killable() From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: willy@infradead.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, lorenzo.stoakes@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, vbabka@suse.cz, jannh@google.com, rppt@kernel.org, mhocko@suse.com, pfalcato@suse.de, kees@kernel.org, maddy@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au, chleroy@kernel.org, borntraeger@linux.ibm.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com, gerald.schaefer@linux.ibm.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, surenb@google.com, "Ritesh Harjani (IBM)" Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Now that we have vma_start_write_killable() we can replace most of the vma_start_write() calls with it, improving reaction time to the kill signal. There are several places which are left untouched by this patch: 1. free_pgtables() because function should free page tables even if a fatal signal is pending. 2. process_vma_walk_lock(), which requires changes in its callers and will be handled in the next patch. 3. userfaultd code, where some paths calling vma_start_write() can handle EINTR and some can't without a deeper code refactoring. 4. vm_flags_{set|mod|clear} require refactoring that involves moving vma_start_write() out of these functions and replacing it with vma_assert_write_locked(), then callers of these functions should lock the vma themselves using vma_start_write_killable() whenever possible. Suggested-by: Matthew Wilcox Signed-off-by: Suren Baghdasaryan Reviewed-by: Ritesh Harjani (IBM) # powerpc --- arch/powerpc/kvm/book3s_hv_uvmem.c | 5 +- include/linux/mempolicy.h | 5 +- mm/khugepaged.c | 5 +- mm/madvise.c | 4 +- mm/memory.c | 2 + mm/mempolicy.c | 23 ++++++-- mm/mlock.c | 20 +++++-- mm/mprotect.c | 4 +- mm/mremap.c | 4 +- mm/vma.c | 93 +++++++++++++++++++++--------- mm/vma_exec.c | 6 +- 11 files changed, 123 insertions(+), 48 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_h= v_uvmem.c index 7cf9310de0ec..69750edcf8d5 100644 --- a/arch/powerpc/kvm/book3s_hv_uvmem.c +++ b/arch/powerpc/kvm/book3s_hv_uvmem.c @@ -410,7 +410,10 @@ static int kvmppc_memslot_page_merge(struct kvm *kvm, ret =3D H_STATE; break; } - vma_start_write(vma); + if (vma_start_write_killable(vma)) { + ret =3D H_STATE; + break; + } /* Copy vm_flags to avoid partial modifications in ksm_madvise */ vm_flags =3D vma->vm_flags; ret =3D ksm_madvise(vma, vma->vm_start, vma->vm_end, diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h index 0fe96f3ab3ef..762930edde5a 100644 --- a/include/linux/mempolicy.h +++ b/include/linux/mempolicy.h @@ -137,7 +137,7 @@ bool vma_policy_mof(struct vm_area_struct *vma); extern void numa_default_policy(void); extern void numa_policy_init(void); extern void mpol_rebind_task(struct task_struct *tsk, const nodemask_t *ne= w); -extern void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new); +extern int mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new); =20 extern int huge_node(struct vm_area_struct *vma, unsigned long addr, gfp_t gfp_flags, @@ -251,8 +251,9 @@ static inline void mpol_rebind_task(struct task_struct = *tsk, { } =20 -static inline void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) +static inline int mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) { + return 0; } =20 static inline int huge_node(struct vm_area_struct *vma, diff --git a/mm/khugepaged.c b/mm/khugepaged.c index fa1e57fd2c46..392dde66fa86 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1150,7 +1150,10 @@ static enum scan_result collapse_huge_page(struct mm= _struct *mm, unsigned long a if (result !=3D SCAN_SUCCEED) goto out_up_write; /* check if the pmd is still valid */ - vma_start_write(vma); + if (vma_start_write_killable(vma)) { + result =3D SCAN_FAIL; + goto out_up_write; + } result =3D check_pmd_still_valid(mm, address, pmd); if (result !=3D SCAN_SUCCEED) goto out_up_write; diff --git a/mm/madvise.c b/mm/madvise.c index 8debb2d434aa..b41e64231c31 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -173,7 +173,9 @@ static int madvise_update_vma(vm_flags_t new_flags, madv_behavior->vma =3D vma; =20 /* vm_flags is protected by the mmap_lock held in write mode. */ - vma_start_write(vma); + if (vma_start_write_killable(vma)) + return -EINTR; + vm_flags_reset(vma, new_flags); if (set_new_anon_name) return replace_anon_vma_name(vma, anon_name); diff --git a/mm/memory.c b/mm/memory.c index dc0e5da70cdc..29e12f063c7b 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -379,6 +379,8 @@ void free_pgd_range(struct mmu_gather *tlb, * page tables that should be removed. This can differ from the vma mappi= ngs on * some archs that may have mappings that need to be removed outside the v= mas. * Note that the prev->vm_end and next->vm_start are often used. + * We don't use vma_start_write_killable() because page tables should be f= reed + * even if the task is being killed. * * The vma_end differs from the pg_end when a dup_mmap() failed and the tr= ee has * unrelated data to the mm_struct being torn down. diff --git a/mm/mempolicy.c b/mm/mempolicy.c index dbd48502ac24..5f6302d227f5 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -556,17 +556,25 @@ void mpol_rebind_task(struct task_struct *tsk, const = nodemask_t *new) * * Call holding a reference to mm. Takes mm->mmap_lock during call. */ -void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) +int mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new) { struct vm_area_struct *vma; VMA_ITERATOR(vmi, mm, 0); + int ret =3D 0; + + if (mmap_write_lock_killable(mm)) + return -EINTR; =20 - mmap_write_lock(mm); for_each_vma(vmi, vma) { - vma_start_write(vma); + if (vma_start_write_killable(vma)) { + ret =3D -EINTR; + break; + } mpol_rebind_policy(vma->vm_policy, new); } mmap_write_unlock(mm); + + return ret; } =20 static const struct mempolicy_operations mpol_ops[MPOL_MAX] =3D { @@ -1785,9 +1793,15 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned lo= ng, start, unsigned long, le return -EINVAL; if (end =3D=3D start) return 0; - mmap_write_lock(mm); + if (mmap_write_lock_killable(mm)) + return -EINTR; prev =3D vma_prev(&vmi); for_each_vma_range(vmi, vma, end) { + if (vma_start_write_killable(vma)) { + err =3D -EINTR; + break; + } + /* * If any vma in the range got policy other than MPOL_BIND * or MPOL_PREFERRED_MANY we return error. We don't reset @@ -1808,7 +1822,6 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned lon= g, start, unsigned long, le break; } =20 - vma_start_write(vma); new->home_node =3D home_node; err =3D mbind_range(&vmi, vma, &prev, start, end, new); mpol_put(new); diff --git a/mm/mlock.c b/mm/mlock.c index 2f699c3497a5..2885b858aa0f 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -420,7 +420,7 @@ static int mlock_pte_range(pmd_t *pmd, unsigned long ad= dr, * Called for mlock(), mlock2() and mlockall(), to set @vma VM_LOCKED; * called for munlock() and munlockall(), to clear VM_LOCKED from @vma. */ -static void mlock_vma_pages_range(struct vm_area_struct *vma, +static int mlock_vma_pages_range(struct vm_area_struct *vma, unsigned long start, unsigned long end, vm_flags_t newflags) { static const struct mm_walk_ops mlock_walk_ops =3D { @@ -441,7 +441,9 @@ static void mlock_vma_pages_range(struct vm_area_struct= *vma, */ if (newflags & VM_LOCKED) newflags |=3D VM_IO; - vma_start_write(vma); + if (vma_start_write_killable(vma)) + return -EINTR; + vm_flags_reset_once(vma, newflags); =20 lru_add_drain(); @@ -452,6 +454,7 @@ static void mlock_vma_pages_range(struct vm_area_struct= *vma, newflags &=3D ~VM_IO; vm_flags_reset_once(vma, newflags); } + return 0; } =20 /* @@ -501,10 +504,12 @@ static int mlock_fixup(struct vma_iterator *vmi, stru= ct vm_area_struct *vma, */ if ((newflags & VM_LOCKED) && (oldflags & VM_LOCKED)) { /* No work to do, and mlocking twice would be wrong */ - vma_start_write(vma); + ret =3D vma_start_write_killable(vma); + if (ret) + goto out; vm_flags_reset(vma, newflags); } else { - mlock_vma_pages_range(vma, start, end, newflags); + ret =3D mlock_vma_pages_range(vma, start, end, newflags); } out: *prev =3D vma; @@ -733,9 +738,12 @@ static int apply_mlockall_flags(int flags) =20 error =3D mlock_fixup(&vmi, vma, &prev, vma->vm_start, vma->vm_end, newflags); - /* Ignore errors, but prev needs fixing up. */ - if (error) + /* Ignore errors except EINTR, but prev needs fixing up. */ + if (error) { + if (error =3D=3D -EINTR) + break; prev =3D vma; + } cond_resched(); } out: diff --git a/mm/mprotect.c b/mm/mprotect.c index c0571445bef7..49dbb7156936 100644 --- a/mm/mprotect.c +++ b/mm/mprotect.c @@ -765,7 +765,9 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gat= her *tlb, * vm_flags and vm_page_prot are protected by the mmap_lock * held in write mode. */ - vma_start_write(vma); + error =3D vma_start_write_killable(vma); + if (error < 0) + goto fail; vm_flags_reset_once(vma, newflags); if (vma_wants_manual_pte_write_upgrade(vma)) mm_cp_flags |=3D MM_CP_TRY_CHANGE_WRITABLE; diff --git a/mm/mremap.c b/mm/mremap.c index 2be876a70cc0..aef1e5f373c7 100644 --- a/mm/mremap.c +++ b/mm/mremap.c @@ -1286,7 +1286,9 @@ static unsigned long move_vma(struct vma_remap_struct= *vrm) return -ENOMEM; =20 /* We don't want racing faults. */ - vma_start_write(vrm->vma); + err =3D vma_start_write_killable(vrm->vma); + if (err) + return err; =20 /* Perform copy step. */ err =3D copy_vma_and_data(vrm, &new_vma); diff --git a/mm/vma.c b/mm/vma.c index bb4d0326fecb..1d21351282cf 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -530,6 +530,13 @@ __split_vma(struct vma_iterator *vmi, struct vm_area_s= truct *vma, if (err) goto out_free_vmi; =20 + err =3D vma_start_write_killable(vma); + if (err) + goto out_free_mpol; + err =3D vma_start_write_killable(new); + if (err) + goto out_free_mpol; + err =3D anon_vma_clone(new, vma, VMA_OP_SPLIT); if (err) goto out_free_mpol; @@ -540,9 +547,6 @@ __split_vma(struct vma_iterator *vmi, struct vm_area_st= ruct *vma, if (new->vm_ops && new->vm_ops->open) new->vm_ops->open(new); =20 - vma_start_write(vma); - vma_start_write(new); - init_vma_prep(&vp, vma); vp.insert =3D new; vma_prepare(&vp); @@ -895,16 +899,22 @@ static __must_check struct vm_area_struct *vma_merge_= existing_range( } =20 /* No matter what happens, we will be adjusting middle. */ - vma_start_write(middle); + err =3D vma_start_write_killable(middle); + if (err) + goto abort; =20 if (merge_right) { - vma_start_write(next); + err =3D vma_start_write_killable(next); + if (err) + goto abort; vmg->target =3D next; sticky_flags |=3D (next->vm_flags & VM_STICKY); } =20 if (merge_left) { - vma_start_write(prev); + err =3D vma_start_write_killable(prev); + if (err) + goto abort; vmg->target =3D prev; sticky_flags |=3D (prev->vm_flags & VM_STICKY); } @@ -1155,10 +1165,12 @@ int vma_expand(struct vma_merge_struct *vmg) struct vm_area_struct *next =3D vmg->next; bool remove_next =3D false; vm_flags_t sticky_flags; - int ret =3D 0; + int ret; =20 mmap_assert_write_locked(vmg->mm); - vma_start_write(target); + ret =3D vma_start_write_killable(target); + if (ret) + return ret; =20 if (next && target !=3D next && vmg->end =3D=3D next->vm_end) remove_next =3D true; @@ -1187,6 +1199,9 @@ int vma_expand(struct vma_merge_struct *vmg) * we don't need to account for vmg->give_up_on_mm here. */ if (remove_next) { + ret =3D vma_start_write_killable(next); + if (ret) + return ret; ret =3D dup_anon_vma(target, next, &anon_dup); if (ret) return ret; @@ -1197,10 +1212,8 @@ int vma_expand(struct vma_merge_struct *vmg) return ret; } =20 - if (remove_next) { - vma_start_write(next); + if (remove_next) vmg->__remove_next =3D true; - } if (commit_merge(vmg)) goto nomem; =20 @@ -1233,6 +1246,7 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_ar= ea_struct *vma, unsigned long start, unsigned long end, pgoff_t pgoff) { struct vma_prepare vp; + int err; =20 WARN_ON((vma->vm_start !=3D start) && (vma->vm_end !=3D end)); =20 @@ -1244,7 +1258,11 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_a= rea_struct *vma, if (vma_iter_prealloc(vmi, NULL)) return -ENOMEM; =20 - vma_start_write(vma); + err =3D vma_start_write_killable(vma); + if (err) { + vma_iter_free(vmi); + return err; + } =20 init_vma_prep(&vp, vma); vma_prepare(&vp); @@ -1434,7 +1452,9 @@ static int vms_gather_munmap_vmas(struct vma_munmap_s= truct *vms, if (error) goto end_split_failed; } - vma_start_write(next); + error =3D vma_start_write_killable(next); + if (error) + goto munmap_gather_failed; mas_set(mas_detach, vms->vma_count++); error =3D mas_store_gfp(mas_detach, next, GFP_KERNEL); if (error) @@ -1828,12 +1848,17 @@ static void vma_link_file(struct vm_area_struct *vm= a, bool hold_rmap_lock) static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma) { VMA_ITERATOR(vmi, mm, 0); + int err; =20 vma_iter_config(&vmi, vma->vm_start, vma->vm_end); if (vma_iter_prealloc(&vmi, vma)) return -ENOMEM; =20 - vma_start_write(vma); + err =3D vma_start_write_killable(vma); + if (err) { + vma_iter_free(&vmi); + return err; + } vma_iter_store_new(&vmi, vma); vma_link_file(vma, /* hold_rmap_lock=3D */false); mm->map_count++; @@ -2215,9 +2240,8 @@ int mm_take_all_locks(struct mm_struct *mm) * is reached. */ for_each_vma(vmi, vma) { - if (signal_pending(current)) + if (signal_pending(current) || vma_start_write_killable(vma)) goto out_unlock; - vma_start_write(vma); } =20 vma_iter_init(&vmi, mm, 0); @@ -2532,6 +2556,11 @@ static int __mmap_new_vma(struct mmap_state *map, st= ruct vm_area_struct **vmap) goto free_vma; } =20 + /* Lock the VMA since it is modified after insertion into VMA tree */ + error =3D vma_start_write_killable(vma); + if (error) + goto free_iter_vma; + if (map->file) error =3D __mmap_new_file_vma(map, vma); else if (map->vm_flags & VM_SHARED) @@ -2552,8 +2581,6 @@ static int __mmap_new_vma(struct mmap_state *map, str= uct vm_area_struct **vmap) WARN_ON_ONCE(!arch_validate_flags(map->vm_flags)); #endif =20 - /* Lock the VMA since it is modified after insertion into VMA tree */ - vma_start_write(vma); vma_iter_store_new(vmi, vma); map->mm->map_count++; vma_link_file(vma, map->hold_file_rmap_lock); @@ -2864,6 +2891,7 @@ int do_brk_flags(struct vma_iterator *vmi, struct vm_= area_struct *vma, unsigned long addr, unsigned long len, vm_flags_t vm_flags) { struct mm_struct *mm =3D current->mm; + int err =3D -ENOMEM; =20 /* * Check against address space limits by the changed size @@ -2908,7 +2936,10 @@ int do_brk_flags(struct vma_iterator *vmi, struct vm= _area_struct *vma, vma_set_range(vma, addr, addr + len, addr >> PAGE_SHIFT); vm_flags_init(vma, vm_flags); vma->vm_page_prot =3D vm_get_page_prot(vm_flags); - vma_start_write(vma); + if (vma_start_write_killable(vma)) { + err =3D -EINTR; + goto mas_store_fail; + } if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL)) goto mas_store_fail; =20 @@ -2928,7 +2959,7 @@ int do_brk_flags(struct vma_iterator *vmi, struct vm_= area_struct *vma, vm_area_free(vma); unacct_fail: vm_unacct_memory(len >> PAGE_SHIFT); - return -ENOMEM; + return err; } =20 /** @@ -3089,7 +3120,7 @@ int expand_upwards(struct vm_area_struct *vma, unsign= ed long address) struct mm_struct *mm =3D vma->vm_mm; struct vm_area_struct *next; unsigned long gap_addr; - int error =3D 0; + int error; VMA_ITERATOR(vmi, mm, vma->vm_start); =20 if (!(vma->vm_flags & VM_GROWSUP)) @@ -3126,12 +3157,14 @@ int expand_upwards(struct vm_area_struct *vma, unsi= gned long address) =20 /* We must make sure the anon_vma is allocated. */ if (unlikely(anon_vma_prepare(vma))) { - vma_iter_free(&vmi); - return -ENOMEM; + error =3D -ENOMEM; + goto free; } =20 /* Lock the VMA before expanding to prevent concurrent page faults */ - vma_start_write(vma); + error =3D vma_start_write_killable(vma); + if (error) + goto free; /* We update the anon VMA tree. */ anon_vma_lock_write(vma->anon_vma); =20 @@ -3160,6 +3193,7 @@ int expand_upwards(struct vm_area_struct *vma, unsign= ed long address) } } anon_vma_unlock_write(vma->anon_vma); +free: vma_iter_free(&vmi); validate_mm(mm); return error; @@ -3174,7 +3208,7 @@ int expand_downwards(struct vm_area_struct *vma, unsi= gned long address) { struct mm_struct *mm =3D vma->vm_mm; struct vm_area_struct *prev; - int error =3D 0; + int error; VMA_ITERATOR(vmi, mm, vma->vm_start); =20 if (!(vma->vm_flags & VM_GROWSDOWN)) @@ -3205,12 +3239,14 @@ int expand_downwards(struct vm_area_struct *vma, un= signed long address) =20 /* We must make sure the anon_vma is allocated. */ if (unlikely(anon_vma_prepare(vma))) { - vma_iter_free(&vmi); - return -ENOMEM; + error =3D -ENOMEM; + goto free; } =20 /* Lock the VMA before expanding to prevent concurrent page faults */ - vma_start_write(vma); + error =3D vma_start_write_killable(vma); + if (error) + goto free; /* We update the anon VMA tree. */ anon_vma_lock_write(vma->anon_vma); =20 @@ -3240,6 +3276,7 @@ int expand_downwards(struct vm_area_struct *vma, unsi= gned long address) } } anon_vma_unlock_write(vma->anon_vma); +free: vma_iter_free(&vmi); validate_mm(mm); return error; diff --git a/mm/vma_exec.c b/mm/vma_exec.c index 8134e1afca68..a4addc2a8480 100644 --- a/mm/vma_exec.c +++ b/mm/vma_exec.c @@ -40,6 +40,7 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigne= d long shift) struct vm_area_struct *next; struct mmu_gather tlb; PAGETABLE_MOVE(pmc, vma, vma, old_start, new_start, length); + int err; =20 BUG_ON(new_start > new_end); =20 @@ -55,8 +56,9 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigne= d long shift) * cover the whole range: [new_start, old_end) */ vmg.target =3D vma; - if (vma_expand(&vmg)) - return -ENOMEM; + err =3D vma_expand(&vmg); + if (err) + return err; =20 /* * move the page tables downwards, on failure we rely on --=20 2.53.0.273.g2a3d683680-goog