Re: [PATCH 10/12] xfs: use vmalloc instead of vm_map_area for buffer backing memory

[Christoph Hellwig <hch@lst.de>]

On Wed, Feb 26, 2025 at 10:02:34AM -0800, Darrick J. Wong wrote:
> >  		if (!bp->b_error && is_vmalloc_addr(bp->b_addr))
> >  			invalidate_kernel_vmap_range(bp->b_addr,
> > -					xfs_buf_vmap_len(bp));
> > +					DIV_ROUND_UP(BBTOB(bp->b_length),
> > +							PAGE_SIZE));
> 
> The second argument to invalidate_kernel_vmap_range is the number of
> bytes, right?

Yes.

> Isn't this BBTOB() without the DIV_ROUND_UP?  Or do you
> actually want roundup(BBTOB(b_length), PAGE_SIZE) here?

Yes.

> > -	if (bp->b_page_count == 1) {
> > -		__bio_add_page(bio, virt_to_page(bp->b_addr), size,
> > -				offset_in_page(bp->b_addr));
> > -	} else {
> > -		for (p = 0; p < bp->b_page_count; p++)
> > -			__bio_add_page(bio, bp->b_pages[p], PAGE_SIZE, 0);
> > -		bio->bi_iter.bi_size = size; /* limit to the actual size used */
> > +		bio = bio_alloc(bp->b_target->bt_bdev, size >> PAGE_SHIFT,
> 
> Is the second argument (size >> PAGE_SHIFT) supposed to be the number of
> pages that we're going to __bio_add_page to the bio?

Yes.

> In which case, shouldn't it be alloc_size ?

Yes.

> > +		} while (size);
> >  
> > -		if (is_vmalloc_addr(bp->b_addr))
> > -			flush_kernel_vmap_range(bp->b_addr,
> > -					xfs_buf_vmap_len(bp));
> > +		flush_kernel_vmap_range(bp->b_addr, alloc_size);
> 
> ...and this one is roundup(size, PAGE_SIZE) isn't it?

Yes.