On Fri, Mar 22, 2024 at 09:02:31AM +0100, Pankaj Raghav (Samsung) wrote:
> > * Bulk filling of pages can take multiple calls. Not filling the entire
> > @@ -426,7 +484,7 @@ _xfs_buf_map_folios(
> > {
> > ASSERT(bp->b_flags & _XBF_FOLIOS);
> > if (bp->b_folio_count == 1) {
> > - /* A single page buffer is always mappable */
> > + /* A single folio buffer is always mappable */
> > bp->b_addr = folio_address(bp->b_folios[0]);
> > } else if (flags & XBF_UNMAPPED) {
> > bp->b_addr = NULL;
> > @@ -1525,20 +1583,28 @@ xfs_buf_ioapply_map(
> > int *count,
> > blk_opf_t op)
> > {
> > - int page_index;
> > - unsigned int total_nr_pages = bp->b_folio_count;
> > - int nr_pages;
> > + int folio_index;
> > + unsigned int total_nr_folios = bp->b_folio_count;
> > + int nr_folios;
> > struct bio *bio;
> > sector_t sector = bp->b_maps[map].bm_bn;
> > int size;
> > int offset;
> >
> > - /* skip the pages in the buffer before the start offset */
> > - page_index = 0;
> > + /*
> > + * If the start offset if larger than a single page, we need to be
> > + * careful. We might have a high order folio, in which case the indexing
> > + * is from the start of the buffer. However, if we have more than one
> > + * folio single page folio in the buffer, we need to skip the folios in
> s/folio single page folio/single page folio/
>
> > + * the buffer before the start offset.
> > + */
> > + folio_index = 0;
> > offset = *buf_offset;
> > - while (offset >= PAGE_SIZE) {
> > - page_index++;
> > - offset -= PAGE_SIZE;
> > + if (bp->b_folio_count > 1) {
> > + while (offset >= PAGE_SIZE) {
> > + folio_index++;
> > + offset -= PAGE_SIZE;
>
> Can this be:
> folio_index = offset >> PAGE_SHIFT;
> offset = offset_in_page(offset);
>
> instead of a loop?
It could, but I'm not going to change it or even bother to fix the
comment as this code goes away later in the patch set.
See "[PATCH 7/9] xfs: walk b_addr for buffer I/O" later in the
series - once we can rely on bp->b_addr always being set for buffers
we convert this code to a simpler and more efficient folio based
iteration that is not reliant on pages or PAGE_SIZE at all.
-Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
