On Fri, Jan 09, 2026 at 10:28:47AM +0000, Hongbo Li wrote:
> It's useful to get filesystem-specific information using the
> existing private field in the @iomap_iter passed to iomap_{begin,end}
> for advanced usage for iomap buffered reads, which is much like the
> current iomap DIO.
>
> For example, EROFS needs it to:
>
> - implement an efficient page cache sharing feature, since iomap
> needs to apply to anon inode page cache but we'd like to get the
> backing inode/fs instead, so filesystem-specific private data is
> needed to keep such information;
>
> - pass in both struct page * and void * for inline data to avoid
> kmap_to_page() usage (which is bogus).
>
> Signed-off-by: Hongbo Li <[email protected]>
> Reviewed-by: Gao Xiang <[email protected]>
This looks like a dead simple patch to allow iomap pagecache users to
set iomap_iter::private, so no objections here:
Reviewed-by: "Darrick J. Wong" <[email protected]>
--D
> ---
> fs/fuse/file.c | 4 ++--
> fs/iomap/buffered-io.c | 6 ++++--
> include/linux/iomap.h | 8 ++++----
> 3 files changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index 01bc894e9c2b..f5d8887c1922 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -979,7 +979,7 @@ static int fuse_read_folio(struct file *file, struct
> folio *folio)
> return -EIO;
> }
>
> - iomap_read_folio(&fuse_iomap_ops, &ctx);
> + iomap_read_folio(&fuse_iomap_ops, &ctx, NULL);
> fuse_invalidate_atime(inode);
> return 0;
> }
> @@ -1081,7 +1081,7 @@ static void fuse_readahead(struct readahead_control
> *rac)
> if (fuse_is_bad(inode))
> return;
>
> - iomap_readahead(&fuse_iomap_ops, &ctx);
> + iomap_readahead(&fuse_iomap_ops, &ctx, NULL);
> }
>
> static ssize_t fuse_cache_read_iter(struct kiocb *iocb, struct iov_iter *to)
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index e5c1ca440d93..5f7dcbabbda3 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -555,13 +555,14 @@ static int iomap_read_folio_iter(struct iomap_iter
> *iter,
> }
>
> void iomap_read_folio(const struct iomap_ops *ops,
> - struct iomap_read_folio_ctx *ctx)
> + struct iomap_read_folio_ctx *ctx, void *private)
> {
> struct folio *folio = ctx->cur_folio;
> struct iomap_iter iter = {
> .inode = folio->mapping->host,
> .pos = folio_pos(folio),
> .len = folio_size(folio),
> + .private = private,
> };
> size_t bytes_submitted = 0;
> int ret;
> @@ -620,13 +621,14 @@ static int iomap_readahead_iter(struct iomap_iter *iter,
> * the filesystem to be reentered.
> */
> void iomap_readahead(const struct iomap_ops *ops,
> - struct iomap_read_folio_ctx *ctx)
> + struct iomap_read_folio_ctx *ctx, void *private)
> {
> struct readahead_control *rac = ctx->rac;
> struct iomap_iter iter = {
> .inode = rac->mapping->host,
> .pos = readahead_pos(rac),
> .len = readahead_length(rac),
> + .private = private,
> };
> size_t cur_bytes_submitted;
>
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 520e967cb501..441d614e9fdf 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -341,9 +341,9 @@ ssize_t iomap_file_buffered_write(struct kiocb *iocb,
> struct iov_iter *from,
> const struct iomap_ops *ops,
> const struct iomap_write_ops *write_ops, void *private);
> void iomap_read_folio(const struct iomap_ops *ops,
> - struct iomap_read_folio_ctx *ctx);
> + struct iomap_read_folio_ctx *ctx, void *private);
> void iomap_readahead(const struct iomap_ops *ops,
> - struct iomap_read_folio_ctx *ctx);
> + struct iomap_read_folio_ctx *ctx, void *private);
> bool iomap_is_partially_uptodate(struct folio *, size_t from, size_t count);
> struct folio *iomap_get_folio(struct iomap_iter *iter, loff_t pos, size_t
> len);
> bool iomap_release_folio(struct folio *folio, gfp_t gfp_flags);
> @@ -595,7 +595,7 @@ static inline void iomap_bio_read_folio(struct folio
> *folio,
> .cur_folio = folio,
> };
>
> - iomap_read_folio(ops, &ctx);
> + iomap_read_folio(ops, &ctx, NULL);
> }
>
> static inline void iomap_bio_readahead(struct readahead_control *rac,
> @@ -606,7 +606,7 @@ static inline void iomap_bio_readahead(struct
> readahead_control *rac,
> .rac = rac,
> };
>
> - iomap_readahead(ops, &ctx);
> + iomap_readahead(ops, &ctx, NULL);
> }
> #endif /* CONFIG_BLOCK */
>
> --
> 2.22.0
>
>
