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

[sukadev at linux.vnet.ibm.com]

Serge E. Hallyn [serue at us.ibm.com] wrote:
| 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?

I was just following established tradition :-)

	EXT4_SB(), EXT3_SB(), EXT2_SB(), REISERFS_SB(), NFS_SB()

I don't mind DEVPTS_SBINFO(), but since this will soon have more than
just an ida, DEVPTS_SB_IDA() may not work.

| 
| > +{
| > +	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) ?

I had it before, but since all ptys must be destroyed, and ida_remove()
frees the pages as necessary and ida_init() does not alloc memory, I had
commented it out and later removed it. Let me check again.

| 
| > +	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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