On Fri, Aug 29, 2025 at 04:56:18PM -0700, Joanne Koong wrote:
> Iterate through the entire folio in iomap_readpage_iter() in one go
> instead of in pieces. This will be needed for supporting user-provided
> async read folio callbacks (not yet added). This additionally makes the
> iomap_readahead_iter() logic simpler to follow.
This might be a good time to change the name since you're not otherwise
changing the function declaration, and there ought to be /some/
indication that the behavior isn't the same anymore.
Otherwise, this looks correct to me.
--D
> Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> ---
> fs/iomap/buffered-io.c | 76 ++++++++++++++++++------------------------
> 1 file changed, 33 insertions(+), 43 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index f26544fbcb36..75bbef386b62 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -452,6 +452,7 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
> loff_t length = iomap_length(iter);
> struct folio *folio = ctx->cur_folio;
> size_t poff, plen;
> + loff_t count;
> int ret;
>
> if (iomap->type == IOMAP_INLINE) {
> @@ -463,26 +464,30 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
>
> /* zero post-eof blocks as the page may be mapped */
> ifs_alloc(iter->inode, folio, iter->flags);
> - iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff, &plen);
> - if (plen == 0)
> - goto done;
>
> - if (iomap_block_needs_zeroing(iter, pos)) {
> - folio_zero_range(folio, poff, plen);
> - iomap_set_range_uptodate(folio, poff, plen);
> - } else {
> - iomap_read_folio_range_async(iter, ctx, pos, plen);
> - }
> + length = min_t(loff_t, length,
> + folio_size(folio) - offset_in_folio(folio, pos));
> + while (length) {
> + iomap_adjust_read_range(iter->inode, folio, &pos,
> + length, &poff, &plen);
> + count = pos - iter->pos + plen;
> + if (plen == 0)
> + return iomap_iter_advance(iter, &count);
>
> -done:
> - /*
> - * Move the caller beyond our range so that it keeps making progress.
> - * For that, we have to include any leading non-uptodate ranges, but
> - * we can skip trailing ones as they will be handled in the next
> - * iteration.
> - */
> - length = pos - iter->pos + plen;
> - return iomap_iter_advance(iter, &length);
> + if (iomap_block_needs_zeroing(iter, pos)) {
> + folio_zero_range(folio, poff, plen);
> + iomap_set_range_uptodate(folio, poff, plen);
> + } else {
> + iomap_read_folio_range_async(iter, ctx, pos, plen);
> + }
> +
> + length -= count;
> + ret = iomap_iter_advance(iter, &count);
> + if (ret)
> + return ret;
> + pos = iter->pos;
> + }
> + return 0;
> }
>
> static void iomap_readfolio_complete(const struct iomap_iter *iter,
> @@ -494,20 +499,6 @@ static void iomap_readfolio_complete(const struct iomap_iter *iter,
> folio_unlock(ctx->cur_folio);
> }
>
> -static int iomap_read_folio_iter(struct iomap_iter *iter,
> - struct iomap_readpage_ctx *ctx)
> -{
> - int ret;
> -
> - while (iomap_length(iter)) {
> - ret = iomap_readpage_iter(iter, ctx);
> - if (ret)
> - return ret;
> - }
> -
> - return 0;
> -}
> -
> int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
> {
> struct iomap_iter iter = {
> @@ -523,7 +514,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
> trace_iomap_readpage(iter.inode, 1);
>
> while ((ret = iomap_iter(&iter, ops)) > 0)
> - iter.status = iomap_read_folio_iter(&iter, &ctx);
> + iter.status = iomap_readpage_iter(&iter, &ctx);
>
> iomap_readfolio_complete(&iter, &ctx);
>
> @@ -537,16 +528,15 @@ static int iomap_readahead_iter(struct iomap_iter *iter,
> int ret;
>
> while (iomap_length(iter)) {
> - if (ctx->cur_folio &&
> - offset_in_folio(ctx->cur_folio, iter->pos) == 0) {
> - if (!ctx->folio_unlocked)
> - folio_unlock(ctx->cur_folio);
> - ctx->cur_folio = NULL;
> - }
> - if (!ctx->cur_folio) {
> - ctx->cur_folio = readahead_folio(ctx->rac);
> - ctx->folio_unlocked = false;
> - }
> + if (ctx->cur_folio && !ctx->folio_unlocked)
> + folio_unlock(ctx->cur_folio);
> + ctx->cur_folio = readahead_folio(ctx->rac);
> + /*
> + * We should never in practice hit this case since
> + * the iter length matches the readahead length.
> + */
> + WARN_ON(!ctx->cur_folio);
> + ctx->folio_unlocked = false;
> ret = iomap_readpage_iter(iter, ctx);
> if (ret)
> return ret;
> --
> 2.47.3
>
>
