From 5dd7864094033a281aeffccaf9703468cbcfccfc Mon Sep 17 00:00:00 2001 From: "Uladzislau Rezki (Sony)" Date: Thu, 6 Aug 2020 23:24:09 -0700 Subject: [PATCH] mm/vmalloc: simplify merge_or_add_vmap_area() Currently when a VA is deallocated and is about to be placed back to the tree, it can be either: merged with next/prev neighbors or inserted if not coalesced. On those steps the tree can be populated several times. For example when both neighbors are merged. It can be avoided and simplified in fact. Therefore do it only once when VA points to final merged area, after all manipulations: merging/removing/inserting. Signed-off-by: Uladzislau Rezki (Sony) Signed-off-by: Andrew Morton Link: http://lkml.kernel.org/r/20200527205054.1696-1-urezki@gmail.com Signed-off-by: Linus Torvalds --- mm/vmalloc.c | 25 ++++++++++++++----------- 1 file changed, 14 insertions(+), 11 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index d496856..d0ec023 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -797,9 +797,6 @@ merge_or_add_vmap_area(struct vmap_area *va, if (sibling->va_start == va->va_end) { sibling->va_start = va->va_start; - /* Check and update the tree if needed. */ - augment_tree_propagate_from(sibling); - /* Free vmap_area object. */ kmem_cache_free(vmap_area_cachep, va); @@ -819,14 +816,18 @@ merge_or_add_vmap_area(struct vmap_area *va, if (next->prev != head) { sibling = list_entry(next->prev, struct vmap_area, list); if (sibling->va_end == va->va_start) { - sibling->va_end = va->va_end; - - /* Check and update the tree if needed. */ - augment_tree_propagate_from(sibling); - + /* + * If both neighbors are coalesced, it is important + * to unlink the "next" node first, followed by merging + * with "previous" one. Otherwise the tree might not be + * fully populated if a sibling's augmented value is + * "normalized" because of rotation operations. + */ if (merged) unlink_va(va, root); + sibling->va_end = va->va_end; + /* Free vmap_area object. */ kmem_cache_free(vmap_area_cachep, va); @@ -837,11 +838,13 @@ merge_or_add_vmap_area(struct vmap_area *va, } insert: - if (!merged) { + if (!merged) link_va(va, root, parent, link, head); - augment_tree_propagate_from(va); - } + /* + * Last step is to check and update the tree. + */ + augment_tree_propagate_from(va); return va; } -- 2.7.4