linux-kernel - [PATCH v5 3/4] mm/vmalloc.c: get rid of one single unlink

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Date:   Thu,  6 Jun 2019 14:04:10 +0200
From:   "Uladzislau Rezki (Sony)" <urezki@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
        Roman Gushchin <guro@...com>,
        Uladzislau Rezki <urezki@...il.com>,
        Hillf Danton <hdanton@...a.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH v5 3/4] mm/vmalloc.c: get rid of one single unlink_va() when merge

It does not make sense to try to "unlink" the node that is definitely not
linked with a list nor tree.  On the first merge step VA just points to
the previously disconnected busy area.

On the second step, check if the node has been merged and do "unlink" if
so, because now it points to an object that must be linked.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Acked-by: Hillf Danton <hdanton@...a.com>
Reviewed-by: Roman Gushchin <guro@...com>
---
 mm/vmalloc.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index fcda966589a6..a4bdf5fc3512 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -719,9 +719,6 @@ merge_or_add_vmap_area(struct vmap_area *va,
 			/* Check and update the tree if needed. */
 			augment_tree_propagate_from(sibling);
 
-			/* Remove this VA, it has been merged. */
-			unlink_va(va, root);
-
 			/* Free vmap_area object. */
 			kmem_cache_free(vmap_area_cachep, va);
 
@@ -746,12 +743,11 @@ merge_or_add_vmap_area(struct vmap_area *va,
 			/* Check and update the tree if needed. */
 			augment_tree_propagate_from(sibling);
 
-			/* Remove this VA, it has been merged. */
-			unlink_va(va, root);
+			if (merged)
+				unlink_va(va, root);
 
 			/* Free vmap_area object. */
 			kmem_cache_free(vmap_area_cachep, va);
-
 			return;
 		}
 	}
-- 
2.11.0