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Subject[PATCH 4.14 09/48] Blktrace: bail out early if block debugfs is not configured
Date
From: Liu Bo <bo.liu@linux.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@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
[bwh: Cherry-picked for 4.14 to ease backporting a later fix]
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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);

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