[PATCH 6/6] blktrace: use existing disk debugfs directory

[Omar Sandoval]

From: Omar Sandoval <osan...@fb.com>

We may already have a directory to put the blktrace stuff in if

1. The disk uses blk-mq
2. CONFIG_BLK_DEBUG_FS is enabled
3. We are tracing the whole disk and not a partition

Instead of hardcoding this very specific case, let's use the new
debugfs_lookup(). If the directory exists, we use it, otherwise we
create one and clean it up later.

Fixes: 07e4fead45e6 ("blk-mq: create debugfs directory tree")
Signed-off-by: Omar Sandoval <osan...@fb.com>
---
 kernel/trace/blktrace.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 38052f625a0f..cc9d23692a35 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -470,12 +470,12 @@ static int do_blk_trace_setup(struct request_queue *q, 
char *name, dev_t dev,
        if (!blk_debugfs_root)
                goto err;
 
-       dir = debugfs_create_dir(buts->name, blk_debugfs_root);
-
+       dir = debugfs_lookup(buts->name, blk_debugfs_root);
+       if (!dir)
+               bt->dir = dir = debugfs_create_dir(buts->name, 
blk_debugfs_root);
        if (!dir)
                goto err;
 
-       bt->dir = dir;
        bt->dev = dev;
        atomic_set(&bt->dropped, 0);
        INIT_LIST_HEAD(&bt->running_list);
@@ -517,9 +517,12 @@ static int do_blk_trace_setup(struct request_queue *q, 
char *name, dev_t dev,
        if (atomic_inc_return(&blk_probes_ref) == 1)
                blk_register_tracepoints();
 
-       return 0;
+       ret = 0;
 err:
-       blk_trace_free(bt);
+       if (dir && !bt->dir)
+               dput(dir);
+       if (ret)
+               blk_trace_free(bt);
        return ret;
 }
 
-- 
2.11.0

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