Subject: Re: [PATCH v9 vfio 4/7] vfio/pds: Add VFIO live migration support

From: Jason Gunthorpe <[email-masked]>
Date: Thu, 4 May 2023 14:34:28 -0300

On Fri, Apr 21, 2023 at 06:06:39PM -0700, Brett Creeley wrote:

> +static struct pds_vfio_lm_file *
> +pds_vfio_get_lm_file(const struct file_operations *fops, int flags, u64 size)
> +{
> +	struct pds_vfio_lm_file *lm_file = NULL;
> +	unsigned long long npages;
> +	struct page **pages;
> +	int err = 0;
> +
> +	if (!size)
> +		return NULL;
> +
> +	/* Alloc file structure */
> +	lm_file = kzalloc(sizeof(*lm_file), GFP_KERNEL);
> +	if (!lm_file)
> +		return NULL;
> +
> +	/* Create file */
> +	lm_file->filep = anon_inode_getfile("pds_vfio_lm", fops, lm_file, flags);
> +	if (!lm_file->filep)
> +		goto err_get_file;
> +
> +	stream_open(lm_file->filep->f_inode, lm_file->filep);
> +	mutex_init(&lm_file->lock);
> +
> +	lm_file->size = size;
> +
> +	/* Allocate memory for file pages */
> +	npages = DIV_ROUND_UP_ULL(lm_file->size, PAGE_SIZE);
> +
> +	pages = kcalloc(npages, sizeof(*pages), GFP_KERNEL);
> +	if (!pages)
> +		goto err_alloc_pages;
> +
> +	for (unsigned long long i = 0; i < npages; i++) {
> +		pages[i] = alloc_page(GFP_KERNEL);
> +		if (!pages[i])
> +			goto err_alloc_page;
> +	}
> +
> +	lm_file->pages = pages;
> +	lm_file->npages = npages;
> +	lm_file->alloc_size = npages * PAGE_SIZE;
> +
> +	/* Create scatterlist of file pages to use for DMA mapping later */
> +	err = sg_alloc_table_from_pages(&lm_file->sg_table, pages, npages,
> +					0, size, GFP_KERNEL);
> +	if (err)
> +		goto err_alloc_sg_table;
> +
> +	/* prevent file from being released before we are done with it */
> +	get_file(lm_file->filep);
> +
> +	return lm_file;
> +
> +err_alloc_sg_table:
> +err_alloc_page:

What is with these double error out labels? I see it in a few places,
that is not the kernel style.

In VFIO we have been trying to label the err outs based on what they
free, it is not a 'call from' scheme.

Jason