Re: [PATCH RFC] libfs: getdents() should return 0 after reaching EOD

[Chuck Lever <chuck.lever@oracle.com>]

On Tue, Nov 14, 2023 at 03:56:50PM +0000, Matthew Wilcox wrote:
> On Tue, Nov 14, 2023 at 10:49:37AM -0500, Chuck Lever wrote:
> > -static void offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
> > +static void *offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
> >  {
> >  	struct offset_ctx *so_ctx = inode->i_op->get_offset_ctx(inode);
> >  	XA_STATE(xas, &so_ctx->xa, ctx->pos);
> > @@ -437,7 +437,8 @@ static void offset_iterate_dir(struct inode *inode, struct dir_context *ctx)
> >  	while (true) {
> >  		dentry = offset_find_next(&xas);
> >  		if (!dentry)
> > -			break;
> > +			/* readdir has reached the current EOD */
> > +			return (void *)0x10;
> 
> Funny, you used the same bit pattern as ZERO_SIZE_PTR without using
> the macro ...

On purpose, it's an eye catcher because I didn't have a better idea.
It obviously worked!


> > @@ -479,7 +481,12 @@ static int offset_readdir(struct file *file, struct dir_context *ctx)
> >  	if (!dir_emit_dots(file, ctx))
> >  		return 0;
> >  
> > -	offset_iterate_dir(d_inode(dir), ctx);
> > +	if (ctx->pos == 2)
> > +		file->private_data = NULL;
> > +	else if (file->private_data == (void *)0x10)
> > +		return 0;
> > +
> > +	file->private_data = offset_iterate_dir(d_inode(dir), ctx);
> >  	return 0;
> >  }
> 
> It might make more sense to use ERR_PTR(-ENOENT) or ERANGE or something
> that's a more understandable sentinel value?

Yes, thanks. That's a better idea.

-- 
Chuck Lever