linux-kernel - [PATCH 4.14 09/48] Blktrace: bail out early if block debugfs is not configured

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Message-Id: <20201109125017.198494084@linuxfoundation.org>
Date:   Mon,  9 Nov 2020 13:55:18 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Liu Bo <bo.liu@...ux.alibaba.com>,
        Jens Axboe <axboe@...nel.dk>,
        Ben Hutchings <ben.hutchings@...ethink.co.uk>
Subject: [PATCH 4.14 09/48] Blktrace: bail out early if block debugfs is not configured

From: Liu Bo <bo.liu@...ux.alibaba.com>

commit e1a413245a564683697a3d02ec197b72cf009b89 upstream.

Since @blk_debugfs_root couldn't be configured dynamically, we can
save a few memory allocation if it's not there.

Signed-off-by: Liu Bo <bo.liu@...ux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@...nel.dk>
[bwh: Cherry-picked for 4.14 to ease backporting a later fix]
Signed-off-by: Ben Hutchings <ben.hutchings@...ethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 kernel/trace/blktrace.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -498,6 +498,9 @@ static int do_blk_trace_setup(struct req
 	if (!buts->buf_size || !buts->buf_nr)
 		return -EINVAL;
 
+	if (!blk_debugfs_root)
+		return -ENOENT;
+
 	strncpy(buts->name, name, BLKTRACE_BDEV_SIZE);
 	buts->name[BLKTRACE_BDEV_SIZE - 1] = '\0';
 
@@ -532,9 +535,6 @@ static int do_blk_trace_setup(struct req
 
 	ret = -ENOENT;
 
-	if (!blk_debugfs_root)
-		goto err;
-
 	dir = debugfs_lookup(buts->name, blk_debugfs_root);
 	if (!dir)
 		bt->dir = dir = debugfs_create_dir(buts->name, blk_debugfs_root);