diff mbox series

[04/10] iomap: split bios to zone append limits in the submission handlers

Message ID 20241219173954.22546-5-hch@lst.de (mailing list archive)
State New
Headers show
Series [01/10] iomap: allow the file system to submit the writeback bios | expand

Commit Message

Christoph Hellwig Dec. 19, 2024, 5:39 p.m. UTC 
Provide helpers for file systems to split bios in the direct I/O and
writeback I/O submission handlers.

This Follows btrfs' lead and don't try to build bios to hardware limits
for zone append commands, but instead build them as normal unconstrained
bios and split them to the hardware limits in the I/O submission handler.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/Makefile      |  1 +
 fs/iomap/buffered-io.c | 49 ++++++++++++++----------
 fs/iomap/ioend.c       | 86 ++++++++++++++++++++++++++++++++++++++++++
 include/linux/iomap.h  |  9 +++++
 4 files changed, 125 insertions(+), 20 deletions(-)
 create mode 100644 fs/iomap/ioend.c

Comments

Darrick J. Wong Dec. 19, 2024, 6:17 p.m. UTC | #1 
On Thu, Dec 19, 2024 at 05:39:09PM +0000, Christoph Hellwig wrote:
> Provide helpers for file systems to split bios in the direct I/O and
> writeback I/O submission handlers.
> 
> This Follows btrfs' lead and don't try to build bios to hardware limits
> for zone append commands, but instead build them as normal unconstrained
> bios and split them to the hardware limits in the I/O submission handler.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

I wonder what iomap_split_ioend callsites look like now that the
alloc_len outparam from the previous version is gone, but I guess I'll
have to wait to see that.

> ---
>  fs/iomap/Makefile      |  1 +
>  fs/iomap/buffered-io.c | 49 ++++++++++++++----------
>  fs/iomap/ioend.c       | 86 ++++++++++++++++++++++++++++++++++++++++++
>  include/linux/iomap.h  |  9 +++++
>  4 files changed, 125 insertions(+), 20 deletions(-)
>  create mode 100644 fs/iomap/ioend.c
> 
> diff --git a/fs/iomap/Makefile b/fs/iomap/Makefile
> index 381d76c5c232..69e8ebb41302 100644
> --- a/fs/iomap/Makefile
> +++ b/fs/iomap/Makefile
> @@ -12,6 +12,7 @@ iomap-y				+= trace.o \
>  				   iter.o
>  iomap-$(CONFIG_BLOCK)		+= buffered-io.o \
>  				   direct-io.o \
> +				   ioend.o \
>  				   fiemap.o \
>  				   seek.o
>  iomap-$(CONFIG_SWAP)		+= swapfile.o
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 8c18fb2a82e0..0b68c9584a7f 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -40,7 +40,8 @@ struct iomap_folio_state {
>  	unsigned long		state[];
>  };
>  
> -static struct bio_set iomap_ioend_bioset;
> +struct bio_set iomap_ioend_bioset;
> +EXPORT_SYMBOL_GPL(iomap_ioend_bioset);
>  
>  static inline bool ifs_is_fully_uptodate(struct folio *folio,
>  		struct iomap_folio_state *ifs)
> @@ -1539,15 +1540,15 @@ static void iomap_finish_folio_write(struct inode *inode, struct folio *folio,
>   * ioend after this.
>   */
>  static u32
> -iomap_finish_ioend(struct iomap_ioend *ioend, int error)
> +iomap_finish_ioend_buffered(struct iomap_ioend *ioend)
>  {
>  	struct inode *inode = ioend->io_inode;
>  	struct bio *bio = &ioend->io_bio;
>  	struct folio_iter fi;
>  	u32 folio_count = 0;
>  
> -	if (error) {
> -		mapping_set_error(inode->i_mapping, error);
> +	if (ioend->io_error) {
> +		mapping_set_error(inode->i_mapping, ioend->io_error);
>  		if (!bio_flagged(bio, BIO_QUIET)) {
>  			pr_err_ratelimited(
>  "%s: writeback error on inode %lu, offset %lld, sector %llu",
> @@ -1566,6 +1567,24 @@ iomap_finish_ioend(struct iomap_ioend *ioend, int error)
>  	return folio_count;
>  }
>  
> +static u32
> +iomap_finish_ioend(struct iomap_ioend *ioend, int error)
> +{
> +	if (ioend->io_parent) {
> +		struct bio *bio = &ioend->io_bio;
> +
> +		ioend = ioend->io_parent;
> +		bio_put(bio);
> +	}
> +
> +	if (error)
> +		cmpxchg(&ioend->io_error, 0, error);
> +
> +	if (!atomic_dec_and_test(&ioend->io_remaining))
> +		return 0;
> +	return iomap_finish_ioend_buffered(ioend);
> +}
> +
>  /*
>   * Ioend completion routine for merged bios. This can only be called from task
>   * contexts as merged ioends can be of unbound length. Hence we have to break up
> @@ -1667,8 +1686,10 @@ EXPORT_SYMBOL_GPL(iomap_sort_ioends);
>  
>  static void iomap_writepage_end_bio(struct bio *bio)
>  {
> -	iomap_finish_ioend(iomap_ioend_from_bio(bio),
> -			blk_status_to_errno(bio->bi_status));
> +	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
> +
> +	ioend->io_error = blk_status_to_errno(bio->bi_status);
> +	iomap_finish_ioend_buffered(ioend);

Hmm.  This wasn't in the previous version of the patch.  But my guess is
that anyone using the io_parent chaining has its own ->submit_ioend
function and therefore set its own bi_end_io function?  IOWs, letting
iomap submit the bio itself is not compatible with io_parent != NULL.

If so, then you might want to note that in the declaration of io_parent
in iomap.h; and with that,

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

>  }
>  
>  /*
> @@ -1713,7 +1734,6 @@ static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
>  		struct writeback_control *wbc, struct inode *inode, loff_t pos,
>  		u16 ioend_flags)
>  {
> -	struct iomap_ioend *ioend;
>  	struct bio *bio;
>  
>  	bio = bio_alloc_bioset(wpc->iomap.bdev, BIO_MAX_VECS,
> @@ -1721,21 +1741,10 @@ static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
>  			       GFP_NOFS, &iomap_ioend_bioset);
>  	bio->bi_iter.bi_sector = iomap_sector(&wpc->iomap, pos);
>  	bio->bi_end_io = iomap_writepage_end_bio;
> -	wbc_init_bio(wbc, bio);
>  	bio->bi_write_hint = inode->i_write_hint;
> -
> -	ioend = iomap_ioend_from_bio(bio);
> -	INIT_LIST_HEAD(&ioend->io_list);
> -	ioend->io_flags = ioend_flags;
> -	if (pos > wpc->iomap.offset)
> -		wpc->iomap.flags &= ~IOMAP_F_BOUNDARY;
> -	ioend->io_inode = inode;
> -	ioend->io_size = 0;
> -	ioend->io_offset = pos;
> -	ioend->io_sector = bio->bi_iter.bi_sector;
> -
> +	wbc_init_bio(wbc, bio);
>  	wpc->nr_folios = 0;
> -	return ioend;
> +	return iomap_init_ioend(inode, bio, pos, ioend_flags);
>  }
>  
>  static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos,
> diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
> new file mode 100644
> index 000000000000..1b032323ee4e
> --- /dev/null
> +++ b/fs/iomap/ioend.c
> @@ -0,0 +1,86 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c) 2024 Christoph Hellwig.
> + */
> +#include <linux/iomap.h>
> +
> +struct iomap_ioend *iomap_init_ioend(struct inode *inode,
> +		struct bio *bio, loff_t file_offset, u16 ioend_flags)
> +{
> +	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
> +
> +	atomic_set(&ioend->io_remaining, 1);
> +	ioend->io_error = 0;
> +	ioend->io_parent = NULL;
> +	INIT_LIST_HEAD(&ioend->io_list);
> +	ioend->io_flags = ioend_flags;
> +	ioend->io_inode = inode;
> +	ioend->io_offset = file_offset;
> +	ioend->io_size = bio->bi_iter.bi_size;
> +	ioend->io_sector = bio->bi_iter.bi_sector;
> +	return ioend;
> +}
> +EXPORT_SYMBOL_GPL(iomap_init_ioend);
> +
> +/*
> + * Split up to the first @max_len bytes from @ioend if the ioend covers more
> + * than @max_len bytes.
> + *
> + * If @is_append is set, the split will be based on the hardware limits for
> + * REQ_OP_ZONE_APPEND commands and can be less than @max_len if the hardware
> + * limits don't allow the entire @max_len length.
> + *
> + * The bio embedded into @ioend must be a REQ_OP_WRITE because the block layer
> + * does not allow splitting REQ_OP_ZONE_APPEND bios.  The file systems has to
> + * switch the operation after this call, but before submitting the bio.
> + */
> +struct iomap_ioend *iomap_split_ioend(struct iomap_ioend *ioend,
> +		unsigned int max_len, bool is_append)
> +{
> +	struct bio *bio = &ioend->io_bio;
> +	struct iomap_ioend *split_ioend;
> +	unsigned int nr_segs;
> +	int sector_offset;
> +	struct bio *split;
> +
> +	if (is_append) {
> +		struct queue_limits *lim = bdev_limits(bio->bi_bdev);
> +
> +		max_len = min(max_len,
> +			      lim->max_zone_append_sectors << SECTOR_SHIFT);
> +
> +		sector_offset = bio_split_rw_at(bio, lim, &nr_segs, max_len);
> +		if (unlikely(sector_offset < 0))
> +			return ERR_PTR(sector_offset);
> +		if (!sector_offset)
> +			return NULL;
> +	} else {
> +		if (bio->bi_iter.bi_size <= max_len)
> +			return NULL;
> +		sector_offset = max_len >> SECTOR_SHIFT;
> +	}
> +
> +	/* ensure the split ioend is still block size aligned */
> +	sector_offset = ALIGN_DOWN(sector_offset << SECTOR_SHIFT,
> +			i_blocksize(ioend->io_inode)) >> SECTOR_SHIFT;
> +
> +	split = bio_split(bio, sector_offset, GFP_NOFS, &iomap_ioend_bioset);
> +	if (IS_ERR_OR_NULL(split))
> +		return ERR_CAST(split);
> +	split->bi_private = bio->bi_private;
> +	split->bi_end_io = bio->bi_end_io;
> +
> +	split_ioend = iomap_init_ioend(ioend->io_inode, split, ioend->io_offset,
> +			ioend->io_flags);
> +	split_ioend->io_parent = ioend;
> +
> +	atomic_inc(&ioend->io_remaining);
> +	ioend->io_offset += split_ioend->io_size;
> +	ioend->io_size -= split_ioend->io_size;
> +
> +	split_ioend->io_sector = ioend->io_sector;
> +	if (!is_append)
> +		ioend->io_sector += (split_ioend->io_size >> SECTOR_SHIFT);
> +	return split_ioend;
> +}
> +EXPORT_SYMBOL_GPL(iomap_split_ioend);
> diff --git a/include/linux/iomap.h b/include/linux/iomap.h
> index 36a7298b6cea..0d221fbe0eb3 100644
> --- a/include/linux/iomap.h
> +++ b/include/linux/iomap.h
> @@ -358,6 +358,9 @@ struct iomap_ioend {
>  	struct list_head	io_list;	/* next ioend in chain */
>  	u16			io_flags;	/* IOMAP_IOEND_* */
>  	struct inode		*io_inode;	/* file being written to */
> +	atomic_t		io_remaining;	/* completetion defer count */
> +	int			io_error;	/* stashed away status */
> +	struct iomap_ioend	*io_parent;	/* parent for completions */
>  	size_t			io_size;	/* size of the extent */
>  	loff_t			io_offset;	/* offset in the file */
>  	sector_t		io_sector;	/* start sector of ioend */
> @@ -408,6 +411,10 @@ struct iomap_writepage_ctx {
>  	u32			nr_folios;	/* folios added to the ioend */
>  };
>  
> +struct iomap_ioend *iomap_init_ioend(struct inode *inode, struct bio *bio,
> +		loff_t file_offset, u16 ioend_flags);
> +struct iomap_ioend *iomap_split_ioend(struct iomap_ioend *ioend,
> +		unsigned int max_len, bool is_append);
>  void iomap_finish_ioends(struct iomap_ioend *ioend, int error);
>  void iomap_ioend_try_merge(struct iomap_ioend *ioend,
>  		struct list_head *more_ioends);
> @@ -479,4 +486,6 @@ int iomap_swapfile_activate(struct swap_info_struct *sis,
>  # define iomap_swapfile_activate(sis, swapfile, pagespan, ops)	(-EIO)
>  #endif /* CONFIG_SWAP */
>  
> +extern struct bio_set iomap_ioend_bioset;
> +
>  #endif /* LINUX_IOMAP_H */
> -- 
> 2.45.2
> 
>
Christoph Hellwig Dec. 19, 2024, 6:19 p.m. UTC | #2 
On Thu, Dec 19, 2024 at 10:17:25AM -0800, Darrick J. Wong wrote:
> On Thu, Dec 19, 2024 at 05:39:09PM +0000, Christoph Hellwig wrote:
> > Provide helpers for file systems to split bios in the direct I/O and
> > writeback I/O submission handlers.
> > 
> > This Follows btrfs' lead and don't try to build bios to hardware limits
> > for zone append commands, but instead build them as normal unconstrained
> > bios and split them to the hardware limits in the I/O submission handler.
> > 
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> I wonder what iomap_split_ioend callsites look like now that the
> alloc_len outparam from the previous version is gone, but I guess I'll
> have to wait to see that.

The initial callsite in XFS looks like this now:

http://git.infradead.org/?p=users/hch/xfs.git;a=blob;f=fs/xfs/xfs_zone_alloc.c;h=00b4df1e628f5d65c7aba44326e5f62306ffbd98;hb=refs/heads/xfs-zoned-rebase#l790
diff mbox series

Patch

diff --git a/fs/iomap/Makefile b/fs/iomap/Makefile
index 381d76c5c232..69e8ebb41302 100644
--- a/fs/iomap/Makefile
+++ b/fs/iomap/Makefile
@@ -12,6 +12,7 @@  iomap-y				+= trace.o \
 				   iter.o
 iomap-$(CONFIG_BLOCK)		+= buffered-io.o \
 				   direct-io.o \
+				   ioend.o \
 				   fiemap.o \
 				   seek.o
 iomap-$(CONFIG_SWAP)		+= swapfile.o
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 8c18fb2a82e0..0b68c9584a7f 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -40,7 +40,8 @@  struct iomap_folio_state {
 	unsigned long		state[];
 };
 
-static struct bio_set iomap_ioend_bioset;
+struct bio_set iomap_ioend_bioset;
+EXPORT_SYMBOL_GPL(iomap_ioend_bioset);
 
 static inline bool ifs_is_fully_uptodate(struct folio *folio,
 		struct iomap_folio_state *ifs)
@@ -1539,15 +1540,15 @@  static void iomap_finish_folio_write(struct inode *inode, struct folio *folio,
  * ioend after this.
  */
 static u32
-iomap_finish_ioend(struct iomap_ioend *ioend, int error)
+iomap_finish_ioend_buffered(struct iomap_ioend *ioend)
 {
 	struct inode *inode = ioend->io_inode;
 	struct bio *bio = &ioend->io_bio;
 	struct folio_iter fi;
 	u32 folio_count = 0;
 
-	if (error) {
-		mapping_set_error(inode->i_mapping, error);
+	if (ioend->io_error) {
+		mapping_set_error(inode->i_mapping, ioend->io_error);
 		if (!bio_flagged(bio, BIO_QUIET)) {
 			pr_err_ratelimited(
 "%s: writeback error on inode %lu, offset %lld, sector %llu",
@@ -1566,6 +1567,24 @@  iomap_finish_ioend(struct iomap_ioend *ioend, int error)
 	return folio_count;
 }
 
+static u32
+iomap_finish_ioend(struct iomap_ioend *ioend, int error)
+{
+	if (ioend->io_parent) {
+		struct bio *bio = &ioend->io_bio;
+
+		ioend = ioend->io_parent;
+		bio_put(bio);
+	}
+
+	if (error)
+		cmpxchg(&ioend->io_error, 0, error);
+
+	if (!atomic_dec_and_test(&ioend->io_remaining))
+		return 0;
+	return iomap_finish_ioend_buffered(ioend);
+}
+
 /*
  * Ioend completion routine for merged bios. This can only be called from task
  * contexts as merged ioends can be of unbound length. Hence we have to break up
@@ -1667,8 +1686,10 @@  EXPORT_SYMBOL_GPL(iomap_sort_ioends);
 
 static void iomap_writepage_end_bio(struct bio *bio)
 {
-	iomap_finish_ioend(iomap_ioend_from_bio(bio),
-			blk_status_to_errno(bio->bi_status));
+	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
+
+	ioend->io_error = blk_status_to_errno(bio->bi_status);
+	iomap_finish_ioend_buffered(ioend);
 }
 
 /*
@@ -1713,7 +1734,6 @@  static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
 		struct writeback_control *wbc, struct inode *inode, loff_t pos,
 		u16 ioend_flags)
 {
-	struct iomap_ioend *ioend;
 	struct bio *bio;
 
 	bio = bio_alloc_bioset(wpc->iomap.bdev, BIO_MAX_VECS,
@@ -1721,21 +1741,10 @@  static struct iomap_ioend *iomap_alloc_ioend(struct iomap_writepage_ctx *wpc,
 			       GFP_NOFS, &iomap_ioend_bioset);
 	bio->bi_iter.bi_sector = iomap_sector(&wpc->iomap, pos);
 	bio->bi_end_io = iomap_writepage_end_bio;
-	wbc_init_bio(wbc, bio);
 	bio->bi_write_hint = inode->i_write_hint;
-
-	ioend = iomap_ioend_from_bio(bio);
-	INIT_LIST_HEAD(&ioend->io_list);
-	ioend->io_flags = ioend_flags;
-	if (pos > wpc->iomap.offset)
-		wpc->iomap.flags &= ~IOMAP_F_BOUNDARY;
-	ioend->io_inode = inode;
-	ioend->io_size = 0;
-	ioend->io_offset = pos;
-	ioend->io_sector = bio->bi_iter.bi_sector;
-
+	wbc_init_bio(wbc, bio);
 	wpc->nr_folios = 0;
-	return ioend;
+	return iomap_init_ioend(inode, bio, pos, ioend_flags);
 }
 
 static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx *wpc, loff_t pos,
diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
new file mode 100644
index 000000000000..1b032323ee4e
--- /dev/null
+++ b/fs/iomap/ioend.c
@@ -0,0 +1,86 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2024 Christoph Hellwig.
+ */
+#include <linux/iomap.h>
+
+struct iomap_ioend *iomap_init_ioend(struct inode *inode,
+		struct bio *bio, loff_t file_offset, u16 ioend_flags)
+{
+	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
+
+	atomic_set(&ioend->io_remaining, 1);
+	ioend->io_error = 0;
+	ioend->io_parent = NULL;
+	INIT_LIST_HEAD(&ioend->io_list);
+	ioend->io_flags = ioend_flags;
+	ioend->io_inode = inode;
+	ioend->io_offset = file_offset;
+	ioend->io_size = bio->bi_iter.bi_size;
+	ioend->io_sector = bio->bi_iter.bi_sector;
+	return ioend;
+}
+EXPORT_SYMBOL_GPL(iomap_init_ioend);
+
+/*
+ * Split up to the first @max_len bytes from @ioend if the ioend covers more
+ * than @max_len bytes.
+ *
+ * If @is_append is set, the split will be based on the hardware limits for
+ * REQ_OP_ZONE_APPEND commands and can be less than @max_len if the hardware
+ * limits don't allow the entire @max_len length.
+ *
+ * The bio embedded into @ioend must be a REQ_OP_WRITE because the block layer
+ * does not allow splitting REQ_OP_ZONE_APPEND bios.  The file systems has to
+ * switch the operation after this call, but before submitting the bio.
+ */
+struct iomap_ioend *iomap_split_ioend(struct iomap_ioend *ioend,
+		unsigned int max_len, bool is_append)
+{
+	struct bio *bio = &ioend->io_bio;
+	struct iomap_ioend *split_ioend;
+	unsigned int nr_segs;
+	int sector_offset;
+	struct bio *split;
+
+	if (is_append) {
+		struct queue_limits *lim = bdev_limits(bio->bi_bdev);
+
+		max_len = min(max_len,
+			      lim->max_zone_append_sectors << SECTOR_SHIFT);
+
+		sector_offset = bio_split_rw_at(bio, lim, &nr_segs, max_len);
+		if (unlikely(sector_offset < 0))
+			return ERR_PTR(sector_offset);
+		if (!sector_offset)
+			return NULL;
+	} else {
+		if (bio->bi_iter.bi_size <= max_len)
+			return NULL;
+		sector_offset = max_len >> SECTOR_SHIFT;
+	}
+
+	/* ensure the split ioend is still block size aligned */
+	sector_offset = ALIGN_DOWN(sector_offset << SECTOR_SHIFT,
+			i_blocksize(ioend->io_inode)) >> SECTOR_SHIFT;
+
+	split = bio_split(bio, sector_offset, GFP_NOFS, &iomap_ioend_bioset);
+	if (IS_ERR_OR_NULL(split))
+		return ERR_CAST(split);
+	split->bi_private = bio->bi_private;
+	split->bi_end_io = bio->bi_end_io;
+
+	split_ioend = iomap_init_ioend(ioend->io_inode, split, ioend->io_offset,
+			ioend->io_flags);
+	split_ioend->io_parent = ioend;
+
+	atomic_inc(&ioend->io_remaining);
+	ioend->io_offset += split_ioend->io_size;
+	ioend->io_size -= split_ioend->io_size;
+
+	split_ioend->io_sector = ioend->io_sector;
+	if (!is_append)
+		ioend->io_sector += (split_ioend->io_size >> SECTOR_SHIFT);
+	return split_ioend;
+}
+EXPORT_SYMBOL_GPL(iomap_split_ioend);
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 36a7298b6cea..0d221fbe0eb3 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -358,6 +358,9 @@  struct iomap_ioend {
 	struct list_head	io_list;	/* next ioend in chain */
 	u16			io_flags;	/* IOMAP_IOEND_* */
 	struct inode		*io_inode;	/* file being written to */
+	atomic_t		io_remaining;	/* completetion defer count */
+	int			io_error;	/* stashed away status */
+	struct iomap_ioend	*io_parent;	/* parent for completions */
 	size_t			io_size;	/* size of the extent */
 	loff_t			io_offset;	/* offset in the file */
 	sector_t		io_sector;	/* start sector of ioend */
@@ -408,6 +411,10 @@  struct iomap_writepage_ctx {
 	u32			nr_folios;	/* folios added to the ioend */
 };
 
+struct iomap_ioend *iomap_init_ioend(struct inode *inode, struct bio *bio,
+		loff_t file_offset, u16 ioend_flags);
+struct iomap_ioend *iomap_split_ioend(struct iomap_ioend *ioend,
+		unsigned int max_len, bool is_append);
 void iomap_finish_ioends(struct iomap_ioend *ioend, int error);
 void iomap_ioend_try_merge(struct iomap_ioend *ioend,
 		struct list_head *more_ioends);
@@ -479,4 +486,6 @@  int iomap_swapfile_activate(struct swap_info_struct *sis,
 # define iomap_swapfile_activate(sis, swapfile, pagespan, ops)	(-EIO)
 #endif /* CONFIG_SWAP */
 
+extern struct bio_set iomap_ioend_bioset;
+
 #endif /* LINUX_IOMAP_H */