linux-kernel - [PATCH 4.9 30/71] btrfs: Remove redundant extent_buffer_get in get_old

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Date:   Fri, 11 Sep 2020 14:46:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Nikolay Borisov <nborisov@...e.com>,
        David Sterba <dsterba@...e.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 30/71] btrfs: Remove redundant extent_buffer_get in get_old_root

From: Nikolay Borisov <nborisov@...e.com>

[ Upstream commit 6c122e2a0c515cfb3f3a9cefb5dad4cb62109c78 ]

get_old_root used used only by btrfs_search_old_slot to initialise the
path structure. The old root is always a cloned buffer (either via alloc
dummy or via btrfs_clone_extent_buffer) and its reference count is 2: 1
from allocation, 1 from extent_buffer_get call in get_old_root.

This latter explicit ref count acquire operation is in fact unnecessary
since the semantic is such that the newly allocated buffer is handed
over to the btrfs_path for lifetime management. Considering this just
remove the extra extent_buffer_get in get_old_root.

Signed-off-by: Nikolay Borisov <nborisov@...e.com>
Reviewed-by: David Sterba <dsterba@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/btrfs/ctree.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index b5ebb43b1824f..78d4c8c22b4ac 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1430,7 +1430,6 @@ get_old_root(struct btrfs_root *root, u64 time_seq)

 	if (!eb)
 		return NULL;
-	extent_buffer_get(eb);
 	btrfs_tree_read_lock(eb);
 	if (old_root) {
 		btrfs_set_header_bytenr(eb, eb->start);
-- 
2.25.1