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AJvYcCWB1xz1+kveb9wxzsWy1zaUZ9ZECSDQ9Z46E84s/eb8Jk49SvUPk//w/Dq3hZF7e9mlkPRvVEU+76v+@vger.kernel.org X-Gm-Message-State: AOJu0YxvNhl3J6UD3AAAFLAjHHKCf8eP3s9X0MAhG5YAWMu23hDWuunW F4zEptvcS81QRfGv4MXJmc0JDvfU0wkce0vx4pD614t0cqczmi5VcVkYK9bE9RrvnjttWKMV/7i uhRthxQ== X-Received: from dlbcy1.prod.google.com ([2002:a05:7022:b81:b0:123:3358:ca1c]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:7022:f00a:b0:124:a4cf:ce90 with SMTP id a92af1059eb24-1278693cf97mr1461760c88.1.1772089577435; Wed, 25 Feb 2026 23:06:17 -0800 (PST) Date: Wed, 25 Feb 2026 23:06:08 -0800 In-Reply-To: <20260226070609.3072570-1-surenb@google.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260226070609.3072570-1-surenb@google.com> X-Mailer: git-send-email 2.53.0.414.gf7e9f6c205-goog Message-ID: <20260226070609.3072570-3-surenb@google.com> Subject: [PATCH v3 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-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. mpol_rebind_mm() which is used by cpusset controller for migrations and operates on a remote mm. Incomplete operations here would result in an inconsistent cgroup state. 5. 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 +- mm/khugepaged.c | 5 +- mm/madvise.c | 4 +- mm/memory.c | 2 + mm/mempolicy.c | 8 ++- mm/mlock.c | 21 +++++-- mm/mprotect.c | 4 +- mm/mremap.c | 4 +- mm/vma.c | 93 +++++++++++++++++++++--------- mm/vma_exec.c | 6 +- 10 files changed, 109 insertions(+), 43 deletions(-) diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_uvmem.c index 5fbb95d90e99..0a28b48a46b8 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 = H_STATE; break; } - vma_start_write(vma); + if (vma_start_write_killable(vma)) { + ret = H_STATE; + break; + } /* Copy vm_flags to avoid partial modifications in ksm_madvise */ vm_flags = vma->vm_flags; ret = ksm_madvise(vma, vma->vm_start, vma->vm_end, diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 1dd3cfca610d..6c92e31ee5fb 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1141,7 +1141,10 @@ static enum scan_result collapse_huge_page(struct mm_struct *mm, unsigned long a if (result != SCAN_SUCCEED) goto out_up_write; /* check if the pmd is still valid */ - vma_start_write(vma); + if (vma_start_write_killable(vma)) { + result = SCAN_FAIL; + goto out_up_write; + } result = check_pmd_still_valid(mm, address, pmd); if (result != SCAN_SUCCEED) goto out_up_write; diff --git a/mm/madvise.c b/mm/madvise.c index c0370d9b4e23..ccdaea6b3b15 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 = vma; /* 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 07778814b4a8..691062154cf5 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 mappings on * some archs that may have mappings that need to be removed outside the vmas. * 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 freed + * even if the task is being killed. * * The vma_end differs from the pg_end when a dup_mmap() failed and the tree has * unrelated data to the mm_struct being torn down. diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 0e5175f1c767..90939f5bde02 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1784,7 +1784,8 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le return -EINVAL; if (end == start) return 0; - mmap_write_lock(mm); + if (mmap_write_lock_killable(mm)) + return -EINTR; prev = vma_prev(&vmi); for_each_vma_range(vmi, vma, end) { /* @@ -1801,13 +1802,16 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le err = -EOPNOTSUPP; break; } + if (vma_start_write_killable(vma)) { + err = -EINTR; + break; + } new = mpol_dup(old); if (IS_ERR(new)) { err = PTR_ERR(new); break; } - vma_start_write(vma); new->home_node = home_node; err = mbind_range(&vmi, vma, &prev, start, end, new); mpol_put(new); diff --git a/mm/mlock.c b/mm/mlock.c index 2f699c3497a5..c562c77c3ee0 100644 --- a/mm/mlock.c +++ b/mm/mlock.c @@ -420,7 +420,7 @@ static int mlock_pte_range(pmd_t *pmd, unsigned long addr, * 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 = { @@ -441,7 +441,9 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma, */ if (newflags & VM_LOCKED) newflags |= VM_IO; - vma_start_write(vma); + if (vma_start_write_killable(vma)) + return -EINTR; + vm_flags_reset_once(vma, newflags); lru_add_drain(); @@ -452,6 +454,7 @@ static void mlock_vma_pages_range(struct vm_area_struct *vma, newflags &= ~VM_IO; vm_flags_reset_once(vma, newflags); } + return 0; } /* @@ -501,10 +504,12 @@ static int mlock_fixup(struct vma_iterator *vmi, struct 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 = vma_start_write_killable(vma); + if (ret) + goto out; vm_flags_reset(vma, newflags); } else { - mlock_vma_pages_range(vma, start, end, newflags); + ret = mlock_vma_pages_range(vma, start, end, newflags); } out: *prev = vma; @@ -733,9 +738,13 @@ static int apply_mlockall_flags(int flags) error = 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 == -EINTR) + return error; + prev = 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_gather *tlb, * vm_flags and vm_page_prot are protected by the mmap_lock * held in write mode. */ - vma_start_write(vma); + error = 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 |= 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; /* We don't want racing faults. */ - vma_start_write(vrm->vma); + err = vma_start_write_killable(vrm->vma); + if (err) + return err; /* Perform copy step. */ err = copy_vma_and_data(vrm, &new_vma); diff --git a/mm/vma.c b/mm/vma.c index bb4d0326fecb..9f2664f1d078 100644 --- a/mm/vma.c +++ b/mm/vma.c @@ -530,6 +530,13 @@ __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma, if (err) goto out_free_vmi; + err = vma_start_write_killable(vma); + if (err) + goto out_free_mpol; + err = vma_start_write_killable(new); + if (err) + goto out_free_mpol; + err = 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_struct *vma, if (new->vm_ops && new->vm_ops->open) new->vm_ops->open(new); - vma_start_write(vma); - vma_start_write(new); - init_vma_prep(&vp, vma); vp.insert = new; vma_prepare(&vp); @@ -895,16 +899,22 @@ static __must_check struct vm_area_struct *vma_merge_existing_range( } /* No matter what happens, we will be adjusting middle. */ - vma_start_write(middle); + err = vma_start_write_killable(middle); + if (err) + goto abort; if (merge_right) { - vma_start_write(next); + err = vma_start_write_killable(next); + if (err) + goto abort; vmg->target = next; sticky_flags |= (next->vm_flags & VM_STICKY); } if (merge_left) { - vma_start_write(prev); + err = vma_start_write_killable(prev); + if (err) + goto abort; vmg->target = prev; sticky_flags |= (prev->vm_flags & VM_STICKY); } @@ -1155,10 +1165,12 @@ int vma_expand(struct vma_merge_struct *vmg) struct vm_area_struct *next = vmg->next; bool remove_next = false; vm_flags_t sticky_flags; - int ret = 0; + int ret; mmap_assert_write_locked(vmg->mm); - vma_start_write(target); + ret = vma_start_write_killable(target); + if (ret) + return ret; if (next && target != next && vmg->end == next->vm_end) remove_next = 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 = vma_start_write_killable(next); + if (ret) + return ret; ret = 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; } - if (remove_next) { - vma_start_write(next); + if (remove_next) vmg->__remove_next = true; - } if (commit_merge(vmg)) goto nomem; @@ -1233,6 +1246,7 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma, unsigned long start, unsigned long end, pgoff_t pgoff) { struct vma_prepare vp; + int err; WARN_ON((vma->vm_start != start) && (vma->vm_end != end)); @@ -1244,7 +1258,11 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma, if (vma_iter_prealloc(vmi, NULL)) return -ENOMEM; - vma_start_write(vma); + err = vma_start_write_killable(vma); + if (err) { + vma_iter_free(vmi); + return err; + } init_vma_prep(&vp, vma); vma_prepare(&vp); @@ -1434,7 +1452,9 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms, if (error) goto end_split_failed; } - vma_start_write(next); + error = vma_start_write_killable(next); + if (error) + goto munmap_gather_failed; mas_set(mas_detach, vms->vma_count++); error = mas_store_gfp(mas_detach, next, GFP_KERNEL); if (error) @@ -1828,12 +1848,17 @@ static void vma_link_file(struct vm_area_struct *vma, bool hold_rmap_lock) static int vma_link(struct mm_struct *mm, struct vm_area_struct *vma) { VMA_ITERATOR(vmi, mm, 0); + int err; vma_iter_config(&vmi, vma->vm_start, vma->vm_end); if (vma_iter_prealloc(&vmi, vma)) return -ENOMEM; - vma_start_write(vma); + err = 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= */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); } vma_iter_init(&vmi, mm, 0); @@ -2522,6 +2546,11 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap) if (!vma) return -ENOMEM; + /* Lock the VMA since it is modified after insertion into VMA tree */ + error = vma_start_write_killable(vma); + if (error) + goto free_vma; + vma_iter_config(vmi, map->addr, map->end); vma_set_range(vma, map->addr, map->end, map->pgoff); vm_flags_init(vma, map->vm_flags); @@ -2552,8 +2581,6 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap) WARN_ON_ONCE(!arch_validate_flags(map->vm_flags)); #endif - /* 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 = current->mm; + int err = -ENOMEM; /* * 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 = vm_get_page_prot(vm_flags); - vma_start_write(vma); + if (vma_start_write_killable(vma)) { + err = -EINTR; + goto mas_store_fail; + } if (vma_iter_store_gfp(vmi, vma, GFP_KERNEL)) goto mas_store_fail; @@ -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; } /** @@ -3089,7 +3120,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) struct mm_struct *mm = vma->vm_mm; struct vm_area_struct *next; unsigned long gap_addr; - int error = 0; + int error; VMA_ITERATOR(vmi, mm, vma->vm_start); if (!(vma->vm_flags & VM_GROWSUP)) @@ -3126,12 +3157,14 @@ int expand_upwards(struct vm_area_struct *vma, unsigned long address) /* We must make sure the anon_vma is allocated. */ if (unlikely(anon_vma_prepare(vma))) { - vma_iter_free(&vmi); - return -ENOMEM; + error = -ENOMEM; + goto free; } /* Lock the VMA before expanding to prevent concurrent page faults */ - vma_start_write(vma); + error = vma_start_write_killable(vma); + if (error) + goto free; /* We update the anon VMA tree. */ anon_vma_lock_write(vma->anon_vma); @@ -3160,6 +3193,7 @@ int expand_upwards(struct vm_area_struct *vma, unsigned 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, unsigned long address) { struct mm_struct *mm = vma->vm_mm; struct vm_area_struct *prev; - int error = 0; + int error; VMA_ITERATOR(vmi, mm, vma->vm_start); if (!(vma->vm_flags & VM_GROWSDOWN)) @@ -3205,12 +3239,14 @@ int expand_downwards(struct vm_area_struct *vma, unsigned long address) /* We must make sure the anon_vma is allocated. */ if (unlikely(anon_vma_prepare(vma))) { - vma_iter_free(&vmi); - return -ENOMEM; + error = -ENOMEM; + goto free; } /* Lock the VMA before expanding to prevent concurrent page faults */ - vma_start_write(vma); + error = vma_start_write_killable(vma); + if (error) + goto free; /* We update the anon VMA tree. */ anon_vma_lock_write(vma->anon_vma); @@ -3240,6 +3276,7 @@ int expand_downwards(struct vm_area_struct *vma, unsigned 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, unsigned long shift) struct vm_area_struct *next; struct mmu_gather tlb; PAGETABLE_MOVE(pmc, vma, vma, old_start, new_start, length); + int err; BUG_ON(new_start > new_end); @@ -55,8 +56,9 @@ int relocate_vma_down(struct vm_area_struct *vma, unsigned long shift) * cover the whole range: [new_start, old_end) */ vmg.target = vma; - if (vma_expand(&vmg)) - return -ENOMEM; + err = vma_expand(&vmg); + if (err) + return err; /* * move the page tables downwards, on failure we rely on -- 2.53.0.414.gf7e9f6c205-goog