Re: [PATCH 18/20] Use FIEMAP for FIBMAP calls

[Christoph Hellwig <hch@lst.de>]

On Tue, Oct 30, 2018 at 02:18:21PM +0100, Carlos Maiolino wrote:
> +	if (inode->i_op->fiemap) {
> +		fextent.fe_logical = 0;
> +		fextent.fe_physical = 0;
> +		f_ctx.fc_extents_max = 1;
> +		f_ctx.fc_extents_mapped = 0;
> +		f_ctx.fc_data = &fextent;
> +		f_ctx.fc_start = start;
> +		f_ctx.fc_len = 1;
> +		f_ctx.fc_flags = 0;
> +		f_ctx.fc_cb = fiemap_fill_kernel_extent;
> +
> +		error = inode->i_op->fiemap(inode, &f_ctx);
> +
> +		if (error)
> +			goto out;
> +
> +		*block = (fextent.fe_physical +
> +			(start - fextent.fe_logical)) >> inode->i_blkbits;
> +

I think this code needs to be split into a helper.

Also we need to check for various "dangerous" flags and fail the
call, e.g. FIEMAP_EXTENT_ENCODED, FIEMAP_EXTENT_DELALLOC,
FIEMAP_EXTENT_DATA_ENCRYPTED, FIEMAP_EXTENT_DATA_INLINE,
FIEMAP_EXTENT_DATA_TAIL, FIEMAP_EXTENT_UNWRITTEN,
FIEMAP_EXTENT_SHARED.

> +	} else if (inode->i_mapping->a_ops->bmap) {
> +		*block = inode->i_mapping->a_ops->bmap(inode->i_mapping, *block);

Too long line.

> +		error = 0;
> +	}
> +out:
> +	return error;

No need for a goto label just to return an error.

> +		return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;

Plain old if statement, please.

> +	return (flags & FIEMAP_EXTENT_LAST) ? 1 : 0;

Same here.  But in this case we could actually use a goto to share
the code.