linux-kernel - [PATCH 3/4] mm/vmap: get rid of one single unlink

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Message-Id: <20190522150939.24605-3-urezki@gmail.com>
Date:   Wed, 22 May 2019 17:09:38 +0200
From:   "Uladzislau Rezki (Sony)" <urezki@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Roman Gushchin <guro@...com>, Uladzislau Rezki <urezki@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>
Subject: [PATCH 3/4] mm/vmap: 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>
---
 mm/vmalloc.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5302e1b79c7b..89b8f44e8837 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -718,9 +718,6 @@ 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);
 
@@ -745,12 +742,12 @@ 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);
+			/* Remove this VA, if it has been merged. */
+			if (merged)
+				unlink_va(va, root);
 
 			/* Free vmap_area object. */
 			kmem_cache_free(vmap_area_cachep, va);
-
 			return;
 		}
 	}
-- 
2.11.0