Re: [PATCH 1/3] fs: Introduce buffered_write_operations

[Christoph Hellwig <hch@lst.de>]

> +struct buffered_write_operations {
> +	int (*write_begin)(struct file *, struct address_space *mapping,
> +			loff_t pos, size_t len, struct folio **foliop,
> +			void **fsdata);
> +	int (*write_end)(struct file *, struct address_space *mapping,
> +			loff_t pos, size_t len, size_t copied,
> +			struct folio *folio, void **fsdata);
> +};

Should write_begin simply return the folio or an ERR_PTR instead of
the return by reference?

I also wonder if the fsdata paramter should go away - if a fs needs
to pass forth and back fsdata, generic/filemap_perform_write is
probably the wrong abstraction for it.

Otherwise this looks sane to me.