On Fri, Aug 29, 2025 at 04:56:12PM -0700, Joanne Koong wrote:
> Move the iomap_readpage_iter() async bio read logic into a separate
> helper function. This is needed to make iomap read/readahead more
> generically usable, especially for filesystems that do not require
> CONFIG_BLOCK.
>
> Rename iomap_read_folio_range() to iomap_read_folio_range_sync() to
> diferentiate between the synchronous and asynchronous bio folio read
> calls.
Hrmm. Readahead is asynchronous, whereas reading in data as part of an
unaligned write to a file must be synchronous. How about naming it
iomap_readahead_folio_range() ?
Oh wait, iomap_read_folio also calls iomap_readpage_iter, which uses the
readahead paths to fill out a folio, but then waits for the folio lock
to drop, which effectively makes it ... a synchronous user of
asynchronous code.
Bleh, naming is hard. Though the code splitting seems fine...
--D
> Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> ---
> fs/iomap/buffered-io.c | 68 ++++++++++++++++++++++++------------------
> 1 file changed, 39 insertions(+), 29 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index fd827398afd2..f8bdb2428819 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -357,36 +357,15 @@ struct iomap_readpage_ctx {
> struct readahead_control *rac;
> };
>
> -static int iomap_readpage_iter(struct iomap_iter *iter,
> - struct iomap_readpage_ctx *ctx)
> +static void iomap_read_folio_range_async(const struct iomap_iter *iter,
> + struct iomap_readpage_ctx *ctx, loff_t pos, size_t plen)
> {
> + struct folio *folio = ctx->cur_folio;
> const struct iomap *iomap = &iter->iomap;
> - loff_t pos = iter->pos;
> + struct iomap_folio_state *ifs = folio->private;
> + size_t poff = offset_in_folio(folio, pos);
> loff_t length = iomap_length(iter);
> - struct folio *folio = ctx->cur_folio;
> - struct iomap_folio_state *ifs;
> - size_t poff, plen;
> sector_t sector;
> - int ret;
> -
> - if (iomap->type == IOMAP_INLINE) {
> - ret = iomap_read_inline_data(iter, folio);
> - if (ret)
> - return ret;
> - return iomap_iter_advance(iter, &length);
> - }
> -
> - /* zero post-eof blocks as the page may be mapped */
> - ifs = 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);
> - goto done;
> - }
>
> ctx->cur_folio_in_bio = true;
> if (ifs) {
> @@ -425,6 +404,37 @@ static int iomap_readpage_iter(struct iomap_iter *iter,
> ctx->bio->bi_end_io = iomap_read_end_io;
> bio_add_folio_nofail(ctx->bio, folio, plen, poff);
> }
> +}
> +
> +static int iomap_readpage_iter(struct iomap_iter *iter,
> + struct iomap_readpage_ctx *ctx)
> +{
> + const struct iomap *iomap = &iter->iomap;
> + loff_t pos = iter->pos;
> + loff_t length = iomap_length(iter);
> + struct folio *folio = ctx->cur_folio;
> + size_t poff, plen;
> + int ret;
> +
> + if (iomap->type == IOMAP_INLINE) {
> + ret = iomap_read_inline_data(iter, folio);
> + if (ret)
> + return ret;
> + return iomap_iter_advance(iter, &length);
> + }
> +
> + /* 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);
> + }
>
> done:
> /*
> @@ -549,7 +559,7 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
> }
> EXPORT_SYMBOL_GPL(iomap_readahead);
>
> -static int iomap_read_folio_range(const struct iomap_iter *iter,
> +static int iomap_read_folio_range_sync(const struct iomap_iter *iter,
> struct folio *folio, loff_t pos, size_t len)
> {
> const struct iomap *srcmap = iomap_iter_srcmap(iter);
> @@ -562,7 +572,7 @@ static int iomap_read_folio_range(const struct iomap_iter *iter,
> return submit_bio_wait(&bio);
> }
> #else
> -static int iomap_read_folio_range(const struct iomap_iter *iter,
> +static int iomap_read_folio_range_sync(const struct iomap_iter *iter,
> struct folio *folio, loff_t pos, size_t len)
> {
> WARN_ON_ONCE(1);
> @@ -739,7 +749,7 @@ static int __iomap_write_begin(const struct iomap_iter *iter,
> status = write_ops->read_folio_range(iter,
> folio, block_start, plen);
> else
> - status = iomap_read_folio_range(iter,
> + status = iomap_read_folio_range_sync(iter,
> folio, block_start, plen);
> if (status)
> return status;
> --
> 2.47.3
>
>
