block: get rid of the manual directory counting in blktrace

It can result in a stuck blktrace system, if --kill is used.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 21 insertions, 51 deletions

diff --git a/block/blktrace.c b/block/blktrace.c
index b0a2cae886db..39cc3bfe56e4 100644
--- a/block/blktrace.c
+++ b/block/blktrace.c
@@ -187,59 +187,12 @@ static void __blk_add_trace(struct blk_trace *bt, sector_t sector, int bytes,
 
 static struct dentry *blk_tree_root;
 static DEFINE_MUTEX(blk_tree_mutex);
-static unsigned int root_users;
-
-static inline void blk_remove_root(void)
-{
-        if (blk_tree_root) {
-                debugfs_remove(blk_tree_root);
-                blk_tree_root = NULL;
-        }
-}
-
-static void blk_remove_tree(struct dentry *dir)
-{
-        mutex_lock(&blk_tree_mutex);
-        debugfs_remove(dir);
-        if (--root_users == 0)
-                blk_remove_root();
-        mutex_unlock(&blk_tree_mutex);
-}
-
-static struct dentry *blk_create_tree(const char *blk_name)
-{
-        struct dentry *dir = NULL;
-        int created = 0;
-
-        mutex_lock(&blk_tree_mutex);
-
-        if (!blk_tree_root) {
-                blk_tree_root = debugfs_create_dir("block", NULL);
-                if (!blk_tree_root)
-                        goto err;
-                created = 1;
-        }
-
-        dir = debugfs_create_dir(blk_name, blk_tree_root);
-        if (dir)
-                root_users++;
-        else {
-                /* Delete root only if we created it */
-                if (created)
-                        blk_remove_root();
-        }
-
-err:
-        mutex_unlock(&blk_tree_mutex);
-        return dir;
-}
 
 static void blk_trace_cleanup(struct blk_trace *bt)
 {
-        relay_close(bt->rchan);
         debugfs_remove(bt->msg_file);
         debugfs_remove(bt->dropped_file);
-        blk_remove_tree(bt->dir);
+        relay_close(bt->rchan);
         free_percpu(bt->sequence);
         free_percpu(bt->msg_data);
         kfree(bt);
@@ -346,7 +299,18 @@ static int blk_subbuf_start_callback(struct rchan_buf *buf, void *subbuf,
 
 static int blk_remove_buf_file_callback(struct dentry *dentry)
 {
+        struct dentry *parent = dentry->d_parent;
         debugfs_remove(dentry);
+
+        /*
+        * this will fail for all but the last file, but that is ok. what we
+        * care about is the top level buts->name directory going away, when
+        * the last trace file is gone. Then we don't have to rmdir() that
+        * manually on trace stop, so it nicely solves the issue with
+        * force killing of running traces.
+        */
+
+        debugfs_remove(parent);
         return 0;
 }
 
@@ -404,7 +368,15 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
                 goto err;
 
         ret = -ENOENT;
-        dir = blk_create_tree(buts->name);
+
+        if (!blk_tree_root) {
+                blk_tree_root = debugfs_create_dir("block", NULL);
+                if (!blk_tree_root)
+                        return -ENOMEM;
+        }
+
+        dir = debugfs_create_dir(buts->name, blk_tree_root);
+
         if (!dir)
                 goto err;
 
@@ -458,8 +430,6 @@ probe_err:
         atomic_dec(&blk_probes_ref);
         mutex_unlock(&blk_probe_mutex);
 err:
-        if (dir)
-                blk_remove_tree(dir);
         if (bt) {
                 if (bt->msg_file)
                         debugfs_remove(bt->msg_file);