Re: [PATCH v2 2/4] binder: Add stats, state and transactions files

[Christian Brauner]

On Thu, Aug 29, 2019 at 02:18:10PM -0700, Hridya Valsaraju wrote:
> The following binder stat files currently live in debugfs.
> 
> /sys/kernel/debug/binder/state
> /sys/kernel/debug/binder/stats
> /sys/kernel/debug/binder/transactions
> 
> This patch makes these files available in a binderfs instance
> mounted with the mount option 'stats=global'. For example, if a binderfs
> instance is mounted at path /dev/binderfs, the above files will be
> available at the following locations:
> 
> /dev/binderfs/binder_logs/state
> /dev/binderfs/binder_logs/stats
> /dev/binderfs/binder_logs/transactions
> 
> This provides a way to access them even when debugfs is not mounted.
> 
> Signed-off-by: Hridya Valsaraju <hridya@xxxxxxxxxx>

Just two comments below. If you have addressed them you can add my:

Acked-by: Christian Brauner <christian.brauner@xxxxxxxxxx>

> ---
> 
>  Changes in v2:
>  - Consistently name variables across functions as per Christian
>    Brauner.
>  - Improve check for binderfs device in binderfs_evict_inode()
>    as per Christian Brauner.
> 
>  drivers/android/binder.c          |  15 ++--
>  drivers/android/binder_internal.h |   8 ++
>  drivers/android/binderfs.c        | 140 +++++++++++++++++++++++++++++-
>  3 files changed, 153 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index ca6b21a53321..de795bd229c4 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -6055,7 +6055,7 @@ static void print_binder_proc_stats(struct seq_file *m,
>  }
>  
>  
> -static int state_show(struct seq_file *m, void *unused)
> +int binder_state_show(struct seq_file *m, void *unused)
>  {
>  	struct binder_proc *proc;
>  	struct binder_node *node;
> @@ -6094,7 +6094,7 @@ static int state_show(struct seq_file *m, void *unused)
>  	return 0;
>  }
>  
> -static int stats_show(struct seq_file *m, void *unused)
> +int binder_stats_show(struct seq_file *m, void *unused)
>  {
>  	struct binder_proc *proc;
>  
> @@ -6110,7 +6110,7 @@ static int stats_show(struct seq_file *m, void *unused)
>  	return 0;
>  }
>  
> -static int transactions_show(struct seq_file *m, void *unused)
> +int binder_transactions_show(struct seq_file *m, void *unused)
>  {
>  	struct binder_proc *proc;
>  
> @@ -6198,9 +6198,6 @@ const struct file_operations binder_fops = {
>  	.release = binder_release,
>  };
>  
> -DEFINE_SHOW_ATTRIBUTE(state);
> -DEFINE_SHOW_ATTRIBUTE(stats);
> -DEFINE_SHOW_ATTRIBUTE(transactions);
>  DEFINE_SHOW_ATTRIBUTE(transaction_log);
>  
>  static int __init init_binder_device(const char *name)
> @@ -6256,17 +6253,17 @@ static int __init binder_init(void)
>  				    0444,
>  				    binder_debugfs_dir_entry_root,
>  				    NULL,
> -				    &state_fops);
> +				    &binder_state_fops);
>  		debugfs_create_file("stats",
>  				    0444,
>  				    binder_debugfs_dir_entry_root,
>  				    NULL,
> -				    &stats_fops);
> +				    &binder_stats_fops);
>  		debugfs_create_file("transactions",
>  				    0444,
>  				    binder_debugfs_dir_entry_root,
>  				    NULL,
> -				    &transactions_fops);
> +				    &binder_transactions_fops);
>  		debugfs_create_file("transaction_log",
>  				    0444,
>  				    binder_debugfs_dir_entry_root,
> diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h
> index fe8c745dc8e0..12ef96f256c6 100644
> --- a/drivers/android/binder_internal.h
> +++ b/drivers/android/binder_internal.h
> @@ -57,4 +57,12 @@ static inline int __init init_binderfs(void)
>  }
>  #endif
>  
> +int binder_stats_show(struct seq_file *m, void *unused);
> +DEFINE_SHOW_ATTRIBUTE(binder_stats);
> +
> +int binder_state_show(struct seq_file *m, void *unused);
> +DEFINE_SHOW_ATTRIBUTE(binder_state);
> +
> +int binder_transactions_show(struct seq_file *m, void *unused);
> +DEFINE_SHOW_ATTRIBUTE(binder_transactions);
>  #endif /* _LINUX_BINDER_INTERNAL_H */
> diff --git a/drivers/android/binderfs.c b/drivers/android/binderfs.c
> index 7045bfe5b52b..0e1e7c87cd33 100644
> --- a/drivers/android/binderfs.c
> +++ b/drivers/android/binderfs.c
> @@ -280,7 +280,7 @@ static void binderfs_evict_inode(struct inode *inode)
>  
>  	clear_inode(inode);
>  
> -	if (!device)
> +	if (!S_ISCHR(inode->i_mode) || !device)
>  		return;
>  
>  	mutex_lock(&binderfs_minors_mutex);
> @@ -502,6 +502,141 @@ static const struct inode_operations binderfs_dir_inode_operations = {
>  	.unlink = binderfs_unlink,
>  };
>  
> +static struct inode *binderfs_make_inode(struct super_block *sb, int mode)
> +{
> +	struct inode *ret;
> +
> +	ret = new_inode(sb);
> +	if (ret) {
> +		ret->i_ino = iunique(sb, BINDERFS_MAX_MINOR + INODE_OFFSET);
> +		ret->i_mode = mode;
> +		ret->i_atime = ret->i_mtime = ret->i_ctime = current_time(ret);
> +	}
> +	return ret;
> +}
> +
> +static struct dentry *binderfs_create_dentry(struct dentry *parent,
> +					     const char *name)
> +{
> +	struct dentry *dentry;
> +
> +	dentry = lookup_one_len(name, parent, strlen(name));
> +	if (IS_ERR(dentry))
> +		return dentry;
> +
> +	/* Return error if the file/dir already exists. */
> +	if (d_really_is_positive(dentry)) {
> +		dput(dentry);
> +		return ERR_PTR(-EEXIST);
> +	}
> +
> +	return dentry;
> +}
> +
> +static struct dentry *binderfs_create_file(struct dentry *parent,
> +					   const char *name,
> +					   const struct file_operations *fops,
> +					   void *data)
> +{
> +	struct dentry *dentry;
> +	struct inode *new_inode, *parent_inode;
> +	struct super_block *sb;
> +
> +	parent_inode = parent->d_inode;

Note that you're using d_inode(parent) below but parent->d_inode here. :)

> +	inode_lock(parent_inode);
> +
> +	dentry = binderfs_create_dentry(parent, name);
> +	if (IS_ERR(dentry))
> +		goto out;
> +
> +	sb = parent_inode->i_sb;
> +	new_inode = binderfs_make_inode(sb, S_IFREG | 0444);
> +	if (!new_inode) {
> +		dput(dentry);
> +		dentry = ERR_PTR(-ENOMEM);
> +		goto out;
> +	}
> +
> +	new_inode->i_fop = fops;
> +	new_inode->i_private = data;
> +	d_instantiate(dentry, new_inode);
> +	fsnotify_create(parent_inode, dentry);
> +
> +out:
> +	inode_unlock(parent_inode);
> +	return dentry;
> +}
> +
> +static struct dentry *binderfs_create_dir(struct dentry *parent,
> +					  const char *name)
> +{
> +	struct dentry *dentry;
> +	struct inode *new_inode, *parent_inode;
> +	struct super_block *sb;
> +
> +	parent_inode = d_inode(parent);
> +	inode_lock(parent_inode);
> +
> +	dentry = binderfs_create_dentry(parent, name);
> +	if (IS_ERR(dentry))
> +		goto out;
> +
> +	sb = parent_inode->i_sb;
> +	new_inode = binderfs_make_inode(sb, S_IFDIR | 0755);
> +	if (!new_inode) {
> +		dput(dentry);
> +		dentry = ERR_PTR(-ENOMEM);
> +		goto out;
> +	}
> +
> +	new_inode->i_fop = &simple_dir_operations;
> +	new_inode->i_op = &simple_dir_inode_operations;
> +
> +	inc_nlink(new_inode);

This should be set_nlink(new_inode, 2) since noboby can modify it and
it's also clearer what's happening and what the expected count is.

> +	d_instantiate(dentry, new_inode);
> +	inc_nlink(parent_inode);
> +	fsnotify_mkdir(parent_inode, dentry);
> +
> +out:
> +	inode_unlock(parent_inode);
> +	return dentry;
> +}
> +
> +static int init_binder_logs(struct super_block *sb)
> +{
> +	struct dentry *binder_logs_root_dir, *dentry;
> +	int ret = 0;
> +
> +	binder_logs_root_dir = binderfs_create_dir(sb->s_root,
> +						   "binder_logs");
> +	if (IS_ERR(binder_logs_root_dir)) {
> +		ret = PTR_ERR(binder_logs_root_dir);
> +		goto out;
> +	}
> +
> +	dentry = binderfs_create_file(binder_logs_root_dir, "stats",
> +				      &binder_stats_fops, NULL);
> +	if (IS_ERR(dentry)) {
> +		ret = PTR_ERR(dentry);
> +		goto out;
> +	}
> +
> +	dentry = binderfs_create_file(binder_logs_root_dir, "state",
> +				      &binder_state_fops, NULL);
> +	if (IS_ERR(dentry)) {
> +		ret = PTR_ERR(dentry);
> +		goto out;
> +	}
> +
> +	dentry = binderfs_create_file(binder_logs_root_dir, "transactions",
> +				      &binder_transactions_fops, NULL);
> +	if (IS_ERR(dentry))
> +		ret = PTR_ERR(dentry);
> +
> +out:
> +	return ret;
> +}
> +
>  static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
>  {
>  	int ret;
> @@ -580,6 +715,9 @@ static int binderfs_fill_super(struct super_block *sb, void *data, int silent)
>  
>  	}
>  
> +	if (info->mount_opts.stats_mode == STATS_GLOBAL)
> +		return init_binder_logs(sb);
> +
>  	return 0;
>  }
>  
> -- 
> 2.23.0.187.g17f5b7556c-goog
>