Re: [PATCH v3 11/28] iomap: pass readpage operation to read path

Darrick J. Wong
2023-10-11T18:31:21Z

On Fri, Oct 06, 2023 at 08:49:05PM +0200, Andrey Albershteyn wrote:
> Preparation for allowing filesystems to provide bio_set and
> ->submit_io() for read path. This will allow fs to do an additional
> processing of ioend on ioend completion.
>
> Make iomap_read_end_io() exportable, so, it can be called back from
> filesystem callout after verification is done.
>
> Signed-off-by: Andrey Albershteyn <aalbersh@redhat.com>
> ---
> fs/erofs/data.c | 4 ++--
> fs/gfs2/aops.c | 4 ++--
> fs/iomap/buffered-io.c | 13 ++++++++++---
> fs/xfs/xfs_aops.c | 4 ++--
> fs/zonefs/file.c | 4 ++--
> include/linux/iomap.h | 21 +++++++++++++++++++--
> 6 files changed, 37 insertions(+), 13 deletions(-)
>
> diff --git a/fs/erofs/data.c b/fs/erofs/data.c
> index 0c2c99c58b5e..3f5482d6cedb 100644
> --- a/fs/erofs/data.c
> +++ b/fs/erofs/data.c
> @@ -357,12 +357,12 @@ int erofs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
> */
> static int erofs_read_folio(struct file *file, struct folio *folio)
> {
> - return iomap_read_folio(folio, &erofs_iomap_ops);
> + return iomap_read_folio(folio, &erofs_iomap_ops, NULL);
> }
>
> static void erofs_readahead(struct readahead_control *rac)
> {
> - return iomap_readahead(rac, &erofs_iomap_ops);
> + return iomap_readahead(rac, &erofs_iomap_ops, NULL);
> }
>
> static sector_t erofs_bmap(struct address_space *mapping, sector_t block)
> diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
> index c26d48355cc2..9c09ff75e586 100644
> --- a/fs/gfs2/aops.c
> +++ b/fs/gfs2/aops.c
> @@ -456,7 +456,7 @@ static int gfs2_read_folio(struct file *file, struct folio *folio)
>
> if (!gfs2_is_jdata(ip) ||
> (i_blocksize(inode) == PAGE_SIZE && !folio_buffers(folio))) {
> - error = iomap_read_folio(folio, &gfs2_iomap_ops);
> + error = iomap_read_folio(folio, &gfs2_iomap_ops, NULL);
> } else if (gfs2_is_stuffed(ip)) {
> error = stuffed_readpage(ip, &folio->page);
> folio_unlock(folio);
> @@ -534,7 +534,7 @@ static void gfs2_readahead(struct readahead_control *rac)
> else if (gfs2_is_jdata(ip))
> mpage_readahead(rac, gfs2_block_map);
> else
> - iomap_readahead(rac, &gfs2_iomap_ops);
> + iomap_readahead(rac, &gfs2_iomap_ops, NULL);
> }
>
> /**
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 644479ccefbd..ca78c7f62527 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -264,7 +264,7 @@ static void iomap_finish_folio_read(struct folio *folio, size_t offset,
> folio_unlock(folio);
> }
>
> -static void iomap_read_end_io(struct bio *bio)
> +void iomap_read_end_io(struct bio *bio)
> {
> int error = blk_status_to_errno(bio->bi_status);
> struct folio_iter fi;
> @@ -273,12 +273,14 @@ static void iomap_read_end_io(struct bio *bio)
> iomap_finish_folio_read(fi.folio, fi.offset, fi.length, error);
> bio_put(bio);
> }
> +EXPORT_SYMBOL_GPL(iomap_read_end_io);
>
> struct iomap_readpage_ctx {
> struct folio *cur_folio;
> bool cur_folio_in_bio;
> struct bio *bio;
> struct readahead_control *rac;
> + const struct iomap_readpage_ops *ops;
> };
>
> /**
> @@ -402,7 +404,8 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
> return pos - orig_pos + plen;
> }
>
> -int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
> +int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops,
> + const struct iomap_readpage_ops *readpage_ops)
> {
> struct iomap_iter iter = {
> .inode = folio->mapping->host,
> @@ -411,6 +414,7 @@ int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops)
> };
> struct iomap_readpage_ctx ctx = {
> .cur_folio = folio,
> + .ops = readpage_ops,
> };
> int ret;
>
> @@ -468,6 +472,7 @@ static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
> * iomap_readahead - Attempt to read pages from a file.
> * @rac: Describes the pages to be read.
> * @ops: The operations vector for the filesystem.
> + * @readpage_ops: Filesystem supplied folio processiong operation
> *
> * This function is for filesystems to call to implement their readahead
> * address_space operation.
> @@ -479,7 +484,8 @@ static loff_t iomap_readahead_iter(const struct iomap_iter *iter,
> * function is called with memalloc_nofs set, so allocations will not cause
> * the filesystem to be reentered.
> */
> -void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
> +void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops,
> + const struct iomap_readpage_ops *readpage_ops)
> {
> struct iomap_iter iter = {
> .inode = rac->mapping->host,
> @@ -488,6 +494,7 @@ void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops)
> };
> struct iomap_readpage_ctx ctx = {
> .rac = rac,
> + .ops = readpage_ops,
> };
>
> trace_iomap_readahead(rac->mapping->host, readahead_count(rac));
> diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
> index 465d7630bb21..b413a2dbcc18 100644
> --- a/fs/xfs/xfs_aops.c
> +++ b/fs/xfs/xfs_aops.c
> @@ -553,14 +553,14 @@ xfs_vm_read_folio(
> struct file *unused,
> struct folio *folio)
> {
> - return iomap_read_folio(folio, &xfs_read_iomap_ops);
> + return iomap_read_folio(folio, &xfs_read_iomap_ops, NULL);
> }
>
> STATIC void
> xfs_vm_readahead(
> struct readahead_control *rac)
> {
> - iomap_readahead(rac, &xfs_read_iomap_ops);
> + iomap_readahead(rac, &xfs_read_iomap_ops, NULL);
> }
>
> static int
> diff --git a/fs/zonefs/file.c b/fs/zonefs/file.c
> index b2c9b35df8f7..29428c012150 100644
> --- a/fs/zonefs/file.c
> +++ b/fs/zonefs/file.c
> @@ -112,12 +112,12 @@ static const struct iomap_ops zonefs_write_iomap_ops = {
>
> static int zonefs_read_folio(struct file *unused, struct folio *folio)
> {
> - return iomap_read_folio(folio, &zonefs_read_iomap_ops);
> + return iomap_read_folio(folio, &zonefs_read_iomap_ops, NULL);
> }
>
> static void zonefs_readahead(struct readahead_control *rac)
> {
> - iomap_readahead(rac, &zonefs_read_iomap_ops);
> + iomap_readahead(rac, &zonefs_read_iomap_ops, NULL);
> }
>
> /*
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 96dd0acbba44..3565c449f3c9 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -262,8 +262,25 @@ int iomap_file_buffered_write_punch_delalloc(struct inode *inode,
> struct iomap *iomap, loff_t pos, loff_t length, ssize_t written,
> int (*punch)(struct inode *inode, loff_t pos, loff_t length));
>
> -int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops);
> -void iomap_readahead(struct readahead_control *, const struct iomap_ops *ops);
> +struct iomap_readpage_ops {
> + /*
> + * Filesystems wishing to attach private information to a direct io bio
> + * must provide a ->submit_io method that attaches the additional
> + * information to the bio and changes the ->bi_end_io callback to a
> + * custom function. This function should, at a minimum, perform any
> + * relevant post-processing of the bio and end with a call to
> + * iomap_read_end_io.
> + */
> + void (*submit_io)(const struct iomap_iter *iter, struct bio *bio,
> + loff_t file_offset);
> + struct bio_set *bio_set;

Needs a comment to mention that iomap will allocate bios from @bio_set
if non-null; or its own internal bioset if null.

> +};

It's odd that this patch adds this ops structure but doesn't actually
start using it until the next patch.

--D

> +
> +void iomap_read_end_io(struct bio *bio);
> +int iomap_read_folio(struct folio *folio, const struct iomap_ops *ops,
> + const struct iomap_readpage_ops *readpage_ops);
> +void iomap_readahead(struct readahead_control *, const struct iomap_ops *ops,
> + const struct iomap_readpage_ops *readpage_ops);
> 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);
> --
> 2.40.1
>