[Devel] Re: [PATCH 02/10] Per-mount allocated_ptys

[Serge E. Hallyn]

Quoting sukadev at us.ibm.com (sukadev at us.ibm.com):
> 
> >From bdba42b68e2b6765615618fce7eb7d4c6f75685d Mon Sep 17 00:00:00 2001
> From: Sukadev Bhattiprolu <sukadev at us.ibm.com>
> Date: Tue, 9 Sep 2008 10:22:11 -0700
> Subject: [PATCH 02/10] Per-mount allocated_ptys
> 
> To enable multiple mounts of devpts, 'allocated_ptys' must be a per-mount
> variable rather than a global variable.  Move 'allocated_ptys' into the
> super_block's s_fs_info.
> 
> Changelog[v2]:
> 	Define and use DEVPTS_SB() wrapper.
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev at us.ibm.com>
> ---
>  fs/devpts/inode.c |   55 ++++++++++++++++++++++++++++++++++++++++++++++------
>  1 files changed, 48 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c
> index ec33833..6e63db7 100644
> --- a/fs/devpts/inode.c
> +++ b/fs/devpts/inode.c
> @@ -30,7 +30,6 @@
>  #define PTMX_MINOR	2
> 
>  extern int pty_limit;			/* Config limit on Unix98 ptys */
> -static DEFINE_IDA(allocated_ptys);
>  static DEFINE_MUTEX(allocated_ptys_lock);
> 
>  static struct vfsmount *devpts_mnt;
> @@ -55,6 +54,15 @@ static match_table_t tokens = {
>  	{Opt_err, NULL}
>  };
> 
> +struct pts_fs_info {
> +	struct ida allocated_ptys;
> +};
> +
> +static inline struct pts_fs_info *DEVPTS_SB(struct super_block *sb)

This is an odd name...  how about DEVPTS_SBINFO or DEVPTS_SB_IDA?

> +{
> +	return sb->s_fs_info;
> +}
> +
>  static inline struct super_block *pts_sb_from_inode(struct inode *inode)
>  {
>  	if (inode->i_sb->s_magic == DEVPTS_SUPER_MAGIC)
> @@ -126,6 +134,19 @@ static const struct super_operations devpts_sops = {
>  	.show_options	= devpts_show_options,
>  };
> 
> +static void *new_pts_fs_info(void)
> +{
> +	struct pts_fs_info *fsi;
> +
> +	fsi = kzalloc(sizeof(struct pts_fs_info), GFP_KERNEL);
> +	if (!fsi)
> +		return NULL;
> +
> +	ida_init(&fsi->allocated_ptys);
> +
> +	return fsi;
> +}
> +
>  static int
>  devpts_fill_super(struct super_block *s, void *data, int silent)
>  {
> @@ -137,9 +158,13 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
>  	s->s_op = &devpts_sops;
>  	s->s_time_gran = 1;
> 
> +	s->s_fs_info = new_pts_fs_info();
> +	if (!s->s_fs_info)
> +		goto fail;
> +
>  	inode = new_inode(s);
>  	if (!inode)
> -		goto fail;
> +		goto free_fsi;
>  	inode->i_ino = 1;
>  	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;
>  	inode->i_blocks = 0;
> @@ -155,6 +180,9 @@ devpts_fill_super(struct super_block *s, void *data, int silent)
>  	
>  	printk("devpts: get root dentry failed\n");
>  	iput(inode);
> +
> +free_fsi:
> +	kfree(s->s_fs_info);
>  fail:
>  	return -ENOMEM;
>  }
> @@ -165,11 +193,19 @@ static int devpts_get_sb(struct file_system_type *fs_type,
>  	return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt);
>  }
> 
> +static void devpts_kill_sb(struct super_block *sb)
> +{
> +	struct pts_fs_info *fsi = DEVPTS_SB(sb);
> +

don't you need to ida_destroy(fsi->allocated_ptys) ?

> +	kfree(fsi);
> +	kill_anon_super(sb);
> +}
> +
>  static struct file_system_type devpts_fs_type = {
>  	.owner		= THIS_MODULE,
>  	.name		= "devpts",
>  	.get_sb		= devpts_get_sb,
> -	.kill_sb	= kill_anon_super,
> +	.kill_sb	= devpts_kill_sb,
>  };
> 
>  /*
> @@ -179,16 +215,18 @@ static struct file_system_type devpts_fs_type = {
> 
>  int devpts_new_index(struct inode *ptmx_inode)
>  {
> +	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
> +	struct pts_fs_info *fsi = DEVPTS_SB(sb);
>  	int index;
>  	int ida_ret;
> 
>  retry:
> -	if (!ida_pre_get(&allocated_ptys, GFP_KERNEL)) {
> +	if (!ida_pre_get(&fsi->allocated_ptys, GFP_KERNEL)) {
>  		return -ENOMEM;
>  	}
> 
>  	mutex_lock(&allocated_ptys_lock);
> -	ida_ret = ida_get_new(&allocated_ptys, &index);
> +	ida_ret = ida_get_new(&fsi->allocated_ptys, &index);
>  	if (ida_ret < 0) {
>  		mutex_unlock(&allocated_ptys_lock);
>  		if (ida_ret == -EAGAIN)
> @@ -197,7 +235,7 @@ retry:
>  	}
> 
>  	if (index >= pty_limit) {
> -		ida_remove(&allocated_ptys, index);
> +		ida_remove(&fsi->allocated_ptys, index);
>  		mutex_unlock(&allocated_ptys_lock);
>  		return -EIO;
>  	}
> @@ -207,8 +245,11 @@ retry:
> 
>  void devpts_kill_index(struct inode *ptmx_inode, int idx)
>  {
> +	struct super_block *sb = pts_sb_from_inode(ptmx_inode);
> +	struct pts_fs_info *fsi = DEVPTS_SB(sb);
> +
>  	mutex_lock(&allocated_ptys_lock);
> -	ida_remove(&allocated_ptys, idx);
> +	ida_remove(&fsi->allocated_ptys, idx);
>  	mutex_unlock(&allocated_ptys_lock);
>  }
> 
> -- 
> 1.5.2.5
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