From c9dbe82cb99db5b6029c6bc43fcf7881d3f50268 Mon Sep 17 00:00:00 2001 From: "Liam R. Howlett" Date: Tue, 6 Sep 2022 19:48:47 +0000 Subject: kernel/fork: use maple tree for dup_mmap() during forking The maple tree was already tracking VMAs in this function by an earlier commit, but the rbtree iterator was being used to iterate the list. Change the iterator to use a maple tree native iterator and switch to the maple tree advanced API to avoid multiple walks of the tree during insert operations. Unexport the now-unused vma_store() function. For performance reasons we bulk allocate the maple tree nodes. The node calculations are done internally to the tree and use the VMA count and assume the worst-case node requirements. The VM_DONT_COPY flag does not allow for the most efficient copy method of the tree and so a bulk loading algorithm is used. Link: https://lkml.kernel.org/r/20220906194824.2110408-15-Liam.Howlett@oracle.com Signed-off-by: Liam R. Howlett Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Vlastimil Babka Tested-by: Yu Zhao Cc: Catalin Marinas Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: SeongJae Park Cc: Sven Schnelle Cc: Will Deacon Signed-off-by: Andrew Morton --- kernel/fork.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) (limited to 'kernel/fork.c') diff --git a/kernel/fork.c b/kernel/fork.c index 273364207f17..16970c346b5b 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -583,8 +583,9 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, struct vm_area_struct *mpnt, *tmp, *prev, **pprev; struct rb_node **rb_link, *rb_parent; int retval; - unsigned long charge; + unsigned long charge = 0; LIST_HEAD(uf); + MA_STATE(old_mas, &oldmm->mm_mt, 0, 0); MA_STATE(mas, &mm->mm_mt, 0, 0); uprobe_start_dup_mmap(); @@ -620,7 +621,12 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, goto out; prev = NULL; - for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { + + retval = mas_expected_entries(&mas, oldmm->map_count); + if (retval) + goto out; + + mas_for_each(&old_mas, mpnt, ULONG_MAX) { struct file *file; if (mpnt->vm_flags & VM_DONTCOPY) { @@ -703,6 +709,8 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm, mas.index = tmp->vm_start; mas.last = tmp->vm_end - 1; mas_store(&mas, tmp); + if (mas_is_err(&mas)) + goto fail_nomem_mas_store; mm->map_count++; if (!(tmp->vm_flags & VM_WIPEONFORK)) @@ -726,6 +734,9 @@ out: fail_uprobe_end: uprobe_end_dup_mmap(); return retval; + +fail_nomem_mas_store: + unlink_anon_vmas(tmp); fail_nomem_anon_vma_fork: mpol_put(vma_policy(tmp)); fail_nomem_policy: -- cgit v1.2.3