[PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()

[PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()

[Suren Baghdasaryan]

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. userfaultd code, where some paths calling vma_start_write() can
handle EINTR and some can't without a deeper code refactoring.

3. 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 <willy@infradead.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
 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/pagewalk.c                      | 20 +++++--
 mm/vma.c                           | 94 +++++++++++++++++++++---------
 mm/vma_exec.c                      |  6 +-
 12 files changed, 139 insertions(+), 53 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_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 = 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/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 *new);
-extern void mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new);
+extern int mpol_rebind_mm(struct mm_struct *mm, nodemask_t *new);
 
 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,
 {
 }
 
-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;
 }
 
 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 != 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 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 = 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 d6d273eb2189..3831e3026615 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.
+ * Note: 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 dbd48502ac24..3de7ab4f4cee 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 = 0;
+
+	if (mmap_write_lock_killable(mm))
+		return -EINTR;
 
-	mmap_write_lock(mm);
 	for_each_vma(vmi, vma) {
-		vma_start_write(vma);
+		if (vma_start_write_killable(vma)) {
+			ret = -EINTR;
+			break;
+		}
 		mpol_rebind_policy(vma->vm_policy, new);
 	}
 	mmap_write_unlock(mm);
+
+	return ret;
 }
 
 static const struct mempolicy_operations mpol_ops[MPOL_MAX] = {
@@ -1785,7 +1793,8 @@ 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) {
 		/*
@@ -1808,7 +1817,11 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le
 			break;
 		}
 
-		vma_start_write(vma);
+		if (vma_start_write_killable(vma)) {
+			err = -EINTR;
+			break;
+		}
+
 		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..2885b858aa0f 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 +738,12 @@ 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)
+				break;
 			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/pagewalk.c b/mm/pagewalk.c
index a94c401ab2cf..dc9f7a7709c6 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -425,14 +425,13 @@ static inline void process_mm_walk_lock(struct mm_struct *mm,
 		mmap_assert_write_locked(mm);
 }
 
-static inline void process_vma_walk_lock(struct vm_area_struct *vma,
+static inline int process_vma_walk_lock(struct vm_area_struct *vma,
 					 enum page_walk_lock walk_lock)
 {
 #ifdef CONFIG_PER_VMA_LOCK
 	switch (walk_lock) {
 	case PGWALK_WRLOCK:
-		vma_start_write(vma);
-		break;
+		return vma_start_write_killable(vma);
 	case PGWALK_WRLOCK_VERIFY:
 		vma_assert_write_locked(vma);
 		break;
@@ -444,6 +443,7 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma,
 		break;
 	}
 #endif
+	return 0;
 }
 
 /*
@@ -487,7 +487,9 @@ int walk_page_range_mm_unsafe(struct mm_struct *mm, unsigned long start,
 			if (ops->pte_hole)
 				err = ops->pte_hole(start, next, -1, &walk);
 		} else { /* inside vma */
-			process_vma_walk_lock(vma, ops->walk_lock);
+			err = process_vma_walk_lock(vma, ops->walk_lock);
+			if (err)
+				break;
 			walk.vma = vma;
 			next = min(end, vma->vm_end);
 			vma = find_vma(mm, vma->vm_end);
@@ -704,6 +706,7 @@ int walk_page_range_vma_unsafe(struct vm_area_struct *vma, unsigned long start,
 		.vma		= vma,
 		.private	= private,
 	};
+	int err;
 
 	if (start >= end || !walk.mm)
 		return -EINVAL;
@@ -711,7 +714,9 @@ int walk_page_range_vma_unsafe(struct vm_area_struct *vma, unsigned long start,
 		return -EINVAL;
 
 	process_mm_walk_lock(walk.mm, ops->walk_lock);
-	process_vma_walk_lock(vma, ops->walk_lock);
+	err = process_vma_walk_lock(vma, ops->walk_lock);
+	if (err)
+		return err;
 	return __walk_page_range(start, end, &walk);
 }
 
@@ -734,6 +739,7 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		.vma		= vma,
 		.private	= private,
 	};
+	int err;
 
 	if (!walk.mm)
 		return -EINVAL;
@@ -741,7 +747,9 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
 		return -EINVAL;
 
 	process_mm_walk_lock(walk.mm, ops->walk_lock);
-	process_vma_walk_lock(vma, ops->walk_lock);
+	err = process_vma_walk_lock(vma, ops->walk_lock);
+	if (err)
+		return err;
 	return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
 }
 
diff --git a/mm/vma.c b/mm/vma.c
index be64f781a3aa..3cfb81b3b7cf 100644
--- a/mm/vma.c
+++ b/mm/vma.c
@@ -540,8 +540,12 @@ __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);
+	err = vma_start_write_killable(vma);
+	if (err)
+		goto out_fput;
+	err = vma_start_write_killable(new);
+	if (err)
+		goto out_fput;
 
 	init_vma_prep(&vp, vma);
 	vp.insert = new;
@@ -574,6 +578,9 @@ __split_vma(struct vma_iterator *vmi, struct vm_area_struct *vma,
 
 	return 0;
 
+out_fput:
+	if (new->vm_file)
+		fput(new->vm_file);
 out_free_mpol:
 	mpol_put(vma_policy(new));
 out_free_vmi:
@@ -895,16 +902,22 @@ 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 +1168,12 @@ 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;
@@ -1186,17 +1201,19 @@ int vma_expand(struct vma_merge_struct *vmg)
 	 * Note that, by convention, callers ignore OOM for this case, so
 	 * we don't need to account for vmg->give_up_on_mm here.
 	 */
-	if (remove_next)
+	if (remove_next) {
+		ret = vma_start_write_killable(next);
+		if (ret)
+			return ret;
 		ret = dup_anon_vma(target, next, &anon_dup);
+	}
 	if (!ret && vmg->copied_from)
 		ret = dup_anon_vma(target, vmg->copied_from, &anon_dup);
 	if (ret)
 		return ret;
 
-	if (remove_next) {
-		vma_start_write(next);
+	if (remove_next)
 		vmg->__remove_next = true;
-	}
 	if (commit_merge(vmg))
 		goto nomem;
 
@@ -1229,6 +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));
 
@@ -1240,7 +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);
@@ -1430,7 +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)
@@ -1824,12 +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++;
@@ -2211,9 +2240,8 @@ int mm_take_all_locks(struct mm_struct *mm)
 	 * is reached.
 	 */
 	for_each_vma(vmi, vma) {
-		if (signal_pending(current))
+		if (vma_start_write_killable(vma))
 			goto out_unlock;
-		vma_start_write(vma);
 	}
 
 	vma_iter_init(&vmi, mm, 0);
@@ -2549,7 +2577,9 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
 #endif
 
 	/* Lock the VMA since it is modified after insertion into VMA tree */
-	vma_start_write(vma);
+	error = vma_start_write_killable(vma);
+	if (error)
+		goto free_iter_vma;
 	vma_iter_store_new(vmi, vma);
 	map->mm->map_count++;
 	vma_link_file(vma, map->hold_file_rmap_lock);
@@ -2860,6 +2890,7 @@ 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
@@ -2904,7 +2935,10 @@ 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;
 
@@ -2924,7 +2958,7 @@ 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;
 }
 
 /**
@@ -3085,7 +3119,7 @@ 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))
@@ -3122,12 +3156,14 @@ 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);
 
@@ -3156,6 +3192,7 @@ 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;
@@ -3170,7 +3207,7 @@ 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))
@@ -3201,12 +3238,14 @@ 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);
 
@@ -3236,6 +3275,7 @@ 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

base-commit: a1a876489abcc1e75b03bd3b2f6739ceeaaec8c5
-- 
2.53.0.rc2.204.g2597b5adb4-goog

Re: [PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()

[kernel test robot]

Hi Suren,

kernel test robot noticed the following build warnings:

[auto build test WARNING on a1a876489abcc1e75b03bd3b2f6739ceeaaec8c5]

url:    https://github.com/intel-lab-lkp/linux/commits/Suren-Baghdasaryan/mm-replace-vma_start_write-with-vma_start_write_killable/20260210-061104
base:   a1a876489abcc1e75b03bd3b2f6739ceeaaec8c5
patch link:    https://lore.kernel.org/r/20260209220849.2126486-1-surenb%40google.com
patch subject: [PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()
config: nios2-allnoconfig (https://download.01.org/0day-ci/archive/20260210/202602101205.7QyEq3MD-lkp@intel.com/config)
compiler: nios2-linux-gcc (GCC) 11.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260210/202602101205.7QyEq3MD-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602101205.7QyEq3MD-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: mm/memory.c:381 duplicate section name 'Note'
>> Warning: mm/memory.c:381 duplicate section name 'Note'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()

[kernel test robot]

Hi Suren,

kernel test robot noticed the following build warnings:

[auto build test WARNING on a1a876489abcc1e75b03bd3b2f6739ceeaaec8c5]

url:    https://github.com/intel-lab-lkp/linux/commits/Suren-Baghdasaryan/mm-replace-vma_start_write-with-vma_start_write_killable/20260210-061104
base:   a1a876489abcc1e75b03bd3b2f6739ceeaaec8c5
patch link:    https://lore.kernel.org/r/20260209220849.2126486-1-surenb%40google.com
patch subject: [PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260210/202602101014.tdhEXT8X-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260210/202602101014.tdhEXT8X-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602101014.tdhEXT8X-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: mm/memory.c:381 duplicate section name 'Note'
>> Warning: mm/memory.c:381 duplicate section name 'Note'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()

[Jann Horn]

On Mon, Feb 9, 2026 at 11:08 PM Suren Baghdasaryan <surenb@google.com> wrote:
> 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.
[...]
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index dbd48502ac24..3de7ab4f4cee 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
[...]
> @@ -1808,7 +1817,11 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le
>                         break;
>                 }
>
> -               vma_start_write(vma);
> +               if (vma_start_write_killable(vma)) {
> +                       err = -EINTR;

Doesn't this need mpol_put(new)? Or less complicated, move the
vma_start_write_killable() up to somewhere above the mpol_dup() call.

> +                       break;
> +               }
> +
>                 new->home_node = home_node;
>                 err = mbind_range(&vmi, vma, &prev, start, end, new);
>                 mpol_put(new);
[...]
> diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> index a94c401ab2cf..dc9f7a7709c6 100644
> --- a/mm/pagewalk.c
> +++ b/mm/pagewalk.c
> @@ -425,14 +425,13 @@ static inline void process_mm_walk_lock(struct mm_struct *mm,
>                 mmap_assert_write_locked(mm);
>  }
>
> -static inline void process_vma_walk_lock(struct vm_area_struct *vma,
> +static inline int process_vma_walk_lock(struct vm_area_struct *vma,
>                                          enum page_walk_lock walk_lock)
>  {
>  #ifdef CONFIG_PER_VMA_LOCK
>         switch (walk_lock) {
>         case PGWALK_WRLOCK:
> -               vma_start_write(vma);
> -               break;
> +               return vma_start_write_killable(vma);

There are two users of PGWALK_WRLOCK in arch/s390/mm/gmap.c code that
don't check pagewalk return values, have you checked that they are not
negatively affected by this new possible error return?

>         case PGWALK_WRLOCK_VERIFY:
>                 vma_assert_write_locked(vma);
>                 break;
[...]
> diff --git a/mm/vma.c b/mm/vma.c
> index be64f781a3aa..3cfb81b3b7cf 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -540,8 +540,12 @@ __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);
> +       err = vma_start_write_killable(vma);
> +       if (err)
> +               goto out_fput;
> +       err = vma_start_write_killable(new);
> +       if (err)
> +               goto out_fput;

What about the new->vm_ops->open() call and the anon_vma_clone()
above? I don't think the error path properly undoes either. These
calls should probably be moved further up, so that the point of no
return in this function stays where it was.

>         init_vma_prep(&vp, vma);
>         vp.insert = new;
[...]
> @@ -1155,10 +1168,12 @@ 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;
> @@ -1186,17 +1201,19 @@ int vma_expand(struct vma_merge_struct *vmg)
>          * Note that, by convention, callers ignore OOM for this case, so
>          * we don't need to account for vmg->give_up_on_mm here.
>          */
> -       if (remove_next)
> +       if (remove_next) {
> +               ret = vma_start_write_killable(next);
> +               if (ret)
> +                       return ret;
>                 ret = dup_anon_vma(target, next, &anon_dup);
> +       }
>         if (!ret && vmg->copied_from)
>                 ret = dup_anon_vma(target, vmg->copied_from, &anon_dup);
>         if (ret)
>                 return ret;

nit: the control flow here is kinda chaotic, with some "if (ret)
return ret;" mixed with "if (!ret && ...) ret = ...;".

>
> -       if (remove_next) {
> -               vma_start_write(next);
> +       if (remove_next)
>                 vmg->__remove_next = true;
> -       }
>         if (commit_merge(vmg))
>                 goto nomem;
>
[...]
> @@ -2211,9 +2240,8 @@ int mm_take_all_locks(struct mm_struct *mm)
>          * is reached.
>          */
>         for_each_vma(vmi, vma) {
> -               if (signal_pending(current))
> +               if (vma_start_write_killable(vma))
>                         goto out_unlock;
> -               vma_start_write(vma);

nit: might want to keep the signal_pending() so that this can sort of
be interrupted by non-fatal signals, which seems to be the intention

>         }
>
>         vma_iter_init(&vmi, mm, 0);
> @@ -2549,7 +2577,9 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
>  #endif
>
>         /* Lock the VMA since it is modified after insertion into VMA tree */
> -       vma_start_write(vma);
> +       error = vma_start_write_killable(vma);
> +       if (error)
> +               goto free_iter_vma;

This seems way past the point of no return, we've already called the
->mmap() handler which I think means removing the VMA again would
require a ->close() call. The VMA should be locked further up if we
want to do it killably.

>         vma_iter_store_new(vmi, vma);
>         map->mm->map_count++;
>         vma_link_file(vma, map->hold_file_rmap_lock);
>

Re: [PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()

[Suren Baghdasaryan]

On Tue, Feb 10, 2026 at 1:19 PM Jann Horn <jannh@google.com> wrote:
>
> On Mon, Feb 9, 2026 at 11:08 PM Suren Baghdasaryan <surenb@google.com> wrote:
> > 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.
> [...]
> > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > index dbd48502ac24..3de7ab4f4cee 100644
> > --- a/mm/mempolicy.c
> > +++ b/mm/mempolicy.c
> [...]
> > @@ -1808,7 +1817,11 @@ SYSCALL_DEFINE4(set_mempolicy_home_node, unsigned long, start, unsigned long, le
> >                         break;
> >                 }
> >
> > -               vma_start_write(vma);
> > +               if (vma_start_write_killable(vma)) {
> > +                       err = -EINTR;
>
> Doesn't this need mpol_put(new)? Or less complicated, move the
> vma_start_write_killable() up to somewhere above the mpol_dup() call.

Thanks for the review, Jann!

Yes you are right. I'll move it before mpol_dup().

>
> > +                       break;
> > +               }
> > +
> >                 new->home_node = home_node;
> >                 err = mbind_range(&vmi, vma, &prev, start, end, new);
> >                 mpol_put(new);
> [...]
> > diff --git a/mm/pagewalk.c b/mm/pagewalk.c
> > index a94c401ab2cf..dc9f7a7709c6 100644
> > --- a/mm/pagewalk.c
> > +++ b/mm/pagewalk.c
> > @@ -425,14 +425,13 @@ static inline void process_mm_walk_lock(struct mm_struct *mm,
> >                 mmap_assert_write_locked(mm);
> >  }
> >
> > -static inline void process_vma_walk_lock(struct vm_area_struct *vma,
> > +static inline int process_vma_walk_lock(struct vm_area_struct *vma,
> >                                          enum page_walk_lock walk_lock)
> >  {
> >  #ifdef CONFIG_PER_VMA_LOCK
> >         switch (walk_lock) {
> >         case PGWALK_WRLOCK:
> > -               vma_start_write(vma);
> > -               break;
> > +               return vma_start_write_killable(vma);
>
> There are two users of PGWALK_WRLOCK in arch/s390/mm/gmap.c code that
> don't check pagewalk return values, have you checked that they are not
> negatively affected by this new possible error return?

Uh, even the ones which check for the error like queue_pages_range()
don't seem to handle it well. I'll split this part into a separate
patch as I think it will be sizable and will go over all users to
ensure they handle the new error.

>
> >         case PGWALK_WRLOCK_VERIFY:
> >                 vma_assert_write_locked(vma);
> >                 break;
> [...]
> > diff --git a/mm/vma.c b/mm/vma.c
> > index be64f781a3aa..3cfb81b3b7cf 100644
> > --- a/mm/vma.c
> > +++ b/mm/vma.c
> > @@ -540,8 +540,12 @@ __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);
> > +       err = vma_start_write_killable(vma);
> > +       if (err)
> > +               goto out_fput;
> > +       err = vma_start_write_killable(new);
> > +       if (err)
> > +               goto out_fput;
>
> What about the new->vm_ops->open() call and the anon_vma_clone()
> above? I don't think the error path properly undoes either. These
> calls should probably be moved further up, so that the point of no
> return in this function stays where it was.

Ack.

>
> >         init_vma_prep(&vp, vma);
> >         vp.insert = new;
> [...]
> > @@ -1155,10 +1168,12 @@ 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;
> > @@ -1186,17 +1201,19 @@ int vma_expand(struct vma_merge_struct *vmg)
> >          * Note that, by convention, callers ignore OOM for this case, so
> >          * we don't need to account for vmg->give_up_on_mm here.
> >          */
> > -       if (remove_next)
> > +       if (remove_next) {
> > +               ret = vma_start_write_killable(next);
> > +               if (ret)
> > +                       return ret;
> >                 ret = dup_anon_vma(target, next, &anon_dup);
> > +       }
> >         if (!ret && vmg->copied_from)
> >                 ret = dup_anon_vma(target, vmg->copied_from, &anon_dup);
> >         if (ret)
> >                 return ret;
>
> nit: the control flow here is kinda chaotic, with some "if (ret)
> return ret;" mixed with "if (!ret && ...) ret = ...;".

I'll see what I can do about it but probably as a separate patch.

>
> >
> > -       if (remove_next) {
> > -               vma_start_write(next);
> > +       if (remove_next)
> >                 vmg->__remove_next = true;
> > -       }
> >         if (commit_merge(vmg))
> >                 goto nomem;
> >
> [...]
> > @@ -2211,9 +2240,8 @@ int mm_take_all_locks(struct mm_struct *mm)
> >          * is reached.
> >          */
> >         for_each_vma(vmi, vma) {
> > -               if (signal_pending(current))
> > +               if (vma_start_write_killable(vma))
> >                         goto out_unlock;
> > -               vma_start_write(vma);
>
> nit: might want to keep the signal_pending() so that this can sort of
> be interrupted by non-fatal signals, which seems to be the intention

Yes, I will bring back that check.

>
> >         }
> >
> >         vma_iter_init(&vmi, mm, 0);
> > @@ -2549,7 +2577,9 @@ static int __mmap_new_vma(struct mmap_state *map, struct vm_area_struct **vmap)
> >  #endif
> >
> >         /* Lock the VMA since it is modified after insertion into VMA tree */
> > -       vma_start_write(vma);
> > +       error = vma_start_write_killable(vma);
> > +       if (error)
> > +               goto free_iter_vma;
>
> This seems way past the point of no return, we've already called the
> ->mmap() handler which I think means removing the VMA again would
> require a ->close() call. The VMA should be locked further up if we
> want to do it killably.

Yeah, I realized this big issue after posting the patch. Moving it up
seems possible, so I'll try that.

Thanks,
Suren.

>
> >         vma_iter_store_new(vmi, vma);
> >         map->mm->map_count++;
> >         vma_link_file(vma, map->hold_file_rmap_lock);
> >

Re: [PATCH 1/1] mm: replace vma_start_write() with vma_start_write_killable()

[Ritesh Harjani]

Suren Baghdasaryan <surenb@google.com> writes:

> 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. userfaultd code, where some paths calling vma_start_write() can
> handle EINTR and some can't without a deeper code refactoring.
>
> 3. 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 <willy@infradead.org>
> Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> ---
>  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/pagewalk.c                      | 20 +++++--
>  mm/vma.c                           | 94 +++++++++++++++++++++---------
>  mm/vma_exec.c                      |  6 +-
>  12 files changed, 139 insertions(+), 53 deletions(-)
>
> diff --git a/arch/powerpc/kvm/book3s_hv_uvmem.c b/arch/powerpc/kvm/book3s_hv_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 = 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,


The above change w.r.t. powerpc error handling in function
kvmppc_memslot_page_merge() looks good to me. 

Please feel free to add:
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> # powerpc

-ritesh