* Suren Baghdasaryan <[email protected]> [260226 02:06]: > 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 <[email protected]> > Signed-off-by: Suren Baghdasaryan <[email protected]> > Reviewed-by: Ritesh Harjani (IBM) <[email protected]> # powerpc
Some nits below, but lgtm. Reviewed-by: Liam R. Howlett <[email protected]> > --- > 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; > + } Could avoid allocating here by reordering the lock, but this is fine. > > 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; > + } Ditto here, ordering would mean no freeing. > 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; > + There's no way this is going to fail, right? > 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; > + } I'd rather have another label saying write lock failed. Really, this will never fail though (besides syzbot..) > 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 > >
