use bio_complete_in_task for iomap error reporting

use bio_complete_in_task for iomap error reporting

[Christoph Hellwig]

Hi all,

this series replaces three pieces of code to queue up I/O completions
in user context for error reporting with the relatively new block layer
bio_complete_in_task() mechanism.

Diffstat:
 bio.c       |   46 ++--------------------------------------------
 direct-io.c |   19 +------------------
 ioend.c     |   48 ++----------------------------------------------
 3 files changed, 5 insertions(+), 108 deletions(-)

[PATCH 1/3] iomap: use bio_complete_in_task for buffered read failures

[Christoph Hellwig]

Use bio_complete_in_task to defer the bio completion handler to task
context instead of the homegrown deferral.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/bio.c | 46 ++--------------------------------------------
 1 file changed, 2 insertions(+), 44 deletions(-)

diff --git a/fs/iomap/bio.c b/fs/iomap/bio.c
index 48100c614431..e83524c46838 100644
--- a/fs/iomap/bio.c
+++ b/fs/iomap/bio.c
@@ -9,9 +9,6 @@
 #include "internal.h"
 #include "trace.h"
 
-static DEFINE_SPINLOCK(failed_read_lock);
-static struct bio_list failed_read_list = BIO_EMPTY_LIST;
-
 static u32 __iomap_read_end_io(struct bio *bio, int error)
 {
 	struct folio_iter fi;
@@ -27,50 +24,11 @@ static u32 __iomap_read_end_io(struct bio *bio, int error)
 	return folio_count;
 }
 
-static void
-iomap_fail_reads(
-	struct work_struct	*work)
-{
-	struct bio		*bio;
-	struct bio_list		tmp = BIO_EMPTY_LIST;
-	unsigned long		flags;
-
-	spin_lock_irqsave(&failed_read_lock, flags);
-	bio_list_merge_init(&tmp, &failed_read_list);
-	spin_unlock_irqrestore(&failed_read_lock, flags);
-
-	while ((bio = bio_list_pop(&tmp)) != NULL) {
-		__iomap_read_end_io(bio, blk_status_to_errno(bio->bi_status));
-		cond_resched();
-	}
-}
-
-static DECLARE_WORK(failed_read_work, iomap_fail_reads);
-
-static void iomap_fail_buffered_read(struct bio *bio)
-{
-	unsigned long flags;
-
-	/*
-	 * Bounce I/O errors to a workqueue to avoid nested i_lock acquisitions
-	 * in the fserror code.  The caller no longer owns the bio reference
-	 * after the spinlock drops.
-	 */
-	spin_lock_irqsave(&failed_read_lock, flags);
-	if (bio_list_empty(&failed_read_list))
-		WARN_ON_ONCE(!schedule_work(&failed_read_work));
-	bio_list_add(&failed_read_list, bio);
-	spin_unlock_irqrestore(&failed_read_lock, flags);
-}
-
 static void iomap_read_end_io(struct bio *bio)
 {
-	if (bio->bi_status) {
-		iomap_fail_buffered_read(bio);
+	if (bio->bi_status && bio_complete_in_task(bio))
 		return;
-	}
-
-	__iomap_read_end_io(bio, 0);
+	__iomap_read_end_io(bio, blk_status_to_errno(bio->bi_status));
 }
 
 u32 iomap_finish_ioend_buffered_read(struct iomap_ioend *ioend)
-- 
2.53.0

[PATCH 2/3] iomap: use bio_complete_in_task for buffered write failures

[Christoph Hellwig]

Use bio_complete_in_task to defer the bio completion handler to task
context instead of the homegrown deferral.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/ioend.c | 48 ++----------------------------------------------
 1 file changed, 2 insertions(+), 46 deletions(-)

diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
index 7bbbb417f915..1c8840bde1ff 100644
--- a/fs/iomap/ioend.c
+++ b/fs/iomap/ioend.c
@@ -74,57 +74,13 @@ static u32 iomap_finish_ioend_buffered_write(struct iomap_ioend *ioend)
 	return folio_count;
 }
 
-static DEFINE_SPINLOCK(failed_ioend_lock);
-static LIST_HEAD(failed_ioend_list);
-
-static void
-iomap_fail_ioends(
-	struct work_struct	*work)
-{
-	struct iomap_ioend	*ioend;
-	struct list_head	tmp;
-	unsigned long		flags;
-
-	spin_lock_irqsave(&failed_ioend_lock, flags);
-	list_replace_init(&failed_ioend_list, &tmp);
-	spin_unlock_irqrestore(&failed_ioend_lock, flags);
-
-	while ((ioend = list_first_entry_or_null(&tmp, struct iomap_ioend,
-			io_list))) {
-		list_del_init(&ioend->io_list);
-		iomap_finish_ioend_buffered_write(ioend);
-		cond_resched();
-	}
-}
-
-static DECLARE_WORK(failed_ioend_work, iomap_fail_ioends);
-
-static void iomap_fail_ioend_buffered(struct iomap_ioend *ioend)
-{
-	unsigned long flags;
-
-	/*
-	 * Bounce I/O errors to a workqueue to avoid nested i_lock acquisitions
-	 * in the fserror code.  The caller no longer owns the ioend reference
-	 * after the spinlock drops.
-	 */
-	spin_lock_irqsave(&failed_ioend_lock, flags);
-	if (list_empty(&failed_ioend_list))
-		WARN_ON_ONCE(!schedule_work(&failed_ioend_work));
-	list_add_tail(&ioend->io_list, &failed_ioend_list);
-	spin_unlock_irqrestore(&failed_ioend_lock, flags);
-}
-
 static void ioend_writeback_end_bio(struct bio *bio)
 {
 	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
 
-	ioend->io_error = blk_status_to_errno(bio->bi_status);
-	if (ioend->io_error) {
-		iomap_fail_ioend_buffered(ioend);
+	if (bio->bi_status && bio_complete_in_task(bio))
 		return;
-	}
-
+	ioend->io_error = blk_status_to_errno(bio->bi_status);
 	iomap_finish_ioend_buffered_write(ioend);
 }
 
-- 
2.53.0

[PATCH 3/3] iomap: use bio_complete_in_task for buffered simple dio read failures

[Christoph Hellwig]

Use bio_complete_in_task to defer the bio completion handler to task
context instead of the homegrown deferral.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/iomap/direct-io.c | 19 +------------------
 1 file changed, 1 insertion(+), 18 deletions(-)

diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
index 8b4039d16ce8..8ee8db6bb794 100644
--- a/fs/iomap/direct-io.c
+++ b/fs/iomap/direct-io.c
@@ -919,7 +919,6 @@ struct iomap_dio_simple {
 	struct kiocb		*iocb;
 	size_t			size;
 	unsigned int		dio_flags;
-	struct work_struct	work;
 	/*
 	 * Align @bio to a cacheline boundary so that, combined with the
 	 * front_pad passed to bioset_init(), the bio sits at the start of
@@ -961,30 +960,14 @@ static ssize_t iomap_dio_simple_complete(struct iomap_dio_simple *sr)
 	return ret;
 }
 
-static void iomap_dio_simple_complete_work(struct work_struct *work)
-{
-	struct iomap_dio_simple *sr =
-		container_of(work, struct iomap_dio_simple, work);
-	struct kiocb *iocb = sr->iocb;
-
-	WRITE_ONCE(iocb->private, NULL);
-	iocb->ki_complete(iocb, iomap_dio_simple_complete(sr));
-}
-
 static void iomap_dio_simple_end_io(struct bio *bio)
 {
 	struct iomap_dio_simple *sr =
 		container_of(bio, struct iomap_dio_simple, bio);
 	struct kiocb *iocb = sr->iocb;
 
-	if (unlikely(sr->bio.bi_status)) {
-		struct inode *inode = file_inode(iocb->ki_filp);
-
-		INIT_WORK(&sr->work, iomap_dio_simple_complete_work);
-		queue_work(inode->i_sb->s_dio_done_wq, &sr->work);
+	if (unlikely(bio->bi_status) && bio_complete_in_task(bio))
 		return;
-	}
-
 	WRITE_ONCE(iocb->private, NULL);
 	iocb->ki_complete(iocb, iomap_dio_simple_complete(sr));
 }
-- 
2.53.0

Re: [PATCH 1/3] iomap: use bio_complete_in_task for buffered read failures

[Darrick J. Wong]

On Mon, Sep 28, 2026 at 11:11:07AM +0200, Christoph Hellwig wrote:
> Use bio_complete_in_task to defer the bio completion handler to task
> context instead of the homegrown deferral.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  fs/iomap/bio.c | 46 ++--------------------------------------------
>  1 file changed, 2 insertions(+), 44 deletions(-)
> 
> diff --git a/fs/iomap/bio.c b/fs/iomap/bio.c
> index 48100c614431..e83524c46838 100644
> --- a/fs/iomap/bio.c
> +++ b/fs/iomap/bio.c
> @@ -9,9 +9,6 @@
>  #include "internal.h"
>  #include "trace.h"
>  
> -static DEFINE_SPINLOCK(failed_read_lock);
> -static struct bio_list failed_read_list = BIO_EMPTY_LIST;
> -
>  static u32 __iomap_read_end_io(struct bio *bio, int error)
>  {
>  	struct folio_iter fi;
> @@ -27,50 +24,11 @@ static u32 __iomap_read_end_io(struct bio *bio, int error)
>  	return folio_count;
>  }
>  
> -static void
> -iomap_fail_reads(
> -	struct work_struct	*work)
> -{
> -	struct bio		*bio;
> -	struct bio_list		tmp = BIO_EMPTY_LIST;
> -	unsigned long		flags;
> -
> -	spin_lock_irqsave(&failed_read_lock, flags);
> -	bio_list_merge_init(&tmp, &failed_read_list);
> -	spin_unlock_irqrestore(&failed_read_lock, flags);
> -
> -	while ((bio = bio_list_pop(&tmp)) != NULL) {
> -		__iomap_read_end_io(bio, blk_status_to_errno(bio->bi_status));
> -		cond_resched();
> -	}
> -}
> -
> -static DECLARE_WORK(failed_read_work, iomap_fail_reads);
> -
> -static void iomap_fail_buffered_read(struct bio *bio)
> -{
> -	unsigned long flags;
> -
> -	/*
> -	 * Bounce I/O errors to a workqueue to avoid nested i_lock acquisitions
> -	 * in the fserror code.  The caller no longer owns the bio reference
> -	 * after the spinlock drops.
> -	 */
> -	spin_lock_irqsave(&failed_read_lock, flags);
> -	if (bio_list_empty(&failed_read_list))
> -		WARN_ON_ONCE(!schedule_work(&failed_read_work));
> -	bio_list_add(&failed_read_list, bio);
> -	spin_unlock_irqrestore(&failed_read_lock, flags);
> -}
> -
>  static void iomap_read_end_io(struct bio *bio)
>  {
> -	if (bio->bi_status) {
> -		iomap_fail_buffered_read(bio);
> +	if (bio->bi_status && bio_complete_in_task(bio))

Hmm.

If bio failed, we call bio_complete_in_task to do something with the
bio.  If the bio wasn't flagged COMPLETE_IN_TASK and we're in atomic
context, then __bio_complete_in_task will queue the bio to a per-cpu
completion batch, (maybe) schedule a worker to deal with the batch,
and we're done.

If the bio was already a COMPLETE_IN_TASK bio or we're not in atomic
context, the function returns false and we fall through to the
__iomap_read_end_io call below.

That looks like a correct conversion of the iomap_fail_buffered_read
code, with only the slight change that we're using a per-cpu batch
instead of a single static list.  Right?

If yes, then
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D


>  		return;
> -	}
> -
> -	__iomap_read_end_io(bio, 0);
> +	__iomap_read_end_io(bio, blk_status_to_errno(bio->bi_status));
>  }
>  
>  u32 iomap_finish_ioend_buffered_read(struct iomap_ioend *ioend)
> -- 
> 2.53.0
> 

Re: [PATCH 2/3] iomap: use bio_complete_in_task for buffered write failures

[Darrick J. Wong]

On Mon, Sep 28, 2026 at 11:11:08AM +0200, Christoph Hellwig wrote:
> Use bio_complete_in_task to defer the bio completion handler to task
> context instead of the homegrown deferral.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks about the same as the previous conversion, so
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/ioend.c | 48 ++----------------------------------------------
>  1 file changed, 2 insertions(+), 46 deletions(-)
> 
> diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c
> index 7bbbb417f915..1c8840bde1ff 100644
> --- a/fs/iomap/ioend.c
> +++ b/fs/iomap/ioend.c
> @@ -74,57 +74,13 @@ static u32 iomap_finish_ioend_buffered_write(struct iomap_ioend *ioend)
>  	return folio_count;
>  }
>  
> -static DEFINE_SPINLOCK(failed_ioend_lock);
> -static LIST_HEAD(failed_ioend_list);
> -
> -static void
> -iomap_fail_ioends(
> -	struct work_struct	*work)
> -{
> -	struct iomap_ioend	*ioend;
> -	struct list_head	tmp;
> -	unsigned long		flags;
> -
> -	spin_lock_irqsave(&failed_ioend_lock, flags);
> -	list_replace_init(&failed_ioend_list, &tmp);
> -	spin_unlock_irqrestore(&failed_ioend_lock, flags);
> -
> -	while ((ioend = list_first_entry_or_null(&tmp, struct iomap_ioend,
> -			io_list))) {
> -		list_del_init(&ioend->io_list);
> -		iomap_finish_ioend_buffered_write(ioend);
> -		cond_resched();
> -	}
> -}
> -
> -static DECLARE_WORK(failed_ioend_work, iomap_fail_ioends);
> -
> -static void iomap_fail_ioend_buffered(struct iomap_ioend *ioend)
> -{
> -	unsigned long flags;
> -
> -	/*
> -	 * Bounce I/O errors to a workqueue to avoid nested i_lock acquisitions
> -	 * in the fserror code.  The caller no longer owns the ioend reference
> -	 * after the spinlock drops.
> -	 */
> -	spin_lock_irqsave(&failed_ioend_lock, flags);
> -	if (list_empty(&failed_ioend_list))
> -		WARN_ON_ONCE(!schedule_work(&failed_ioend_work));
> -	list_add_tail(&ioend->io_list, &failed_ioend_list);
> -	spin_unlock_irqrestore(&failed_ioend_lock, flags);
> -}
> -
>  static void ioend_writeback_end_bio(struct bio *bio)
>  {
>  	struct iomap_ioend *ioend = iomap_ioend_from_bio(bio);
>  
> -	ioend->io_error = blk_status_to_errno(bio->bi_status);
> -	if (ioend->io_error) {
> -		iomap_fail_ioend_buffered(ioend);
> +	if (bio->bi_status && bio_complete_in_task(bio))
>  		return;
> -	}
> -
> +	ioend->io_error = blk_status_to_errno(bio->bi_status);
>  	iomap_finish_ioend_buffered_write(ioend);
>  }
>  
> -- 
> 2.53.0
> 

Re: [PATCH 3/3] iomap: use bio_complete_in_task for buffered simple dio read failures

[Darrick J. Wong]

On Mon, Sep 28, 2026 at 11:11:09AM +0200, Christoph Hellwig wrote:
> Use bio_complete_in_task to defer the bio completion handler to task
> context instead of the homegrown deferral.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Nice conversion here too.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

--D

> ---
>  fs/iomap/direct-io.c | 19 +------------------
>  1 file changed, 1 insertion(+), 18 deletions(-)
> 
> diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c
> index 8b4039d16ce8..8ee8db6bb794 100644
> --- a/fs/iomap/direct-io.c
> +++ b/fs/iomap/direct-io.c
> @@ -919,7 +919,6 @@ struct iomap_dio_simple {
>  	struct kiocb		*iocb;
>  	size_t			size;
>  	unsigned int		dio_flags;
> -	struct work_struct	work;
>  	/*
>  	 * Align @bio to a cacheline boundary so that, combined with the
>  	 * front_pad passed to bioset_init(), the bio sits at the start of
> @@ -961,30 +960,14 @@ static ssize_t iomap_dio_simple_complete(struct iomap_dio_simple *sr)
>  	return ret;
>  }
>  
> -static void iomap_dio_simple_complete_work(struct work_struct *work)
> -{
> -	struct iomap_dio_simple *sr =
> -		container_of(work, struct iomap_dio_simple, work);
> -	struct kiocb *iocb = sr->iocb;
> -
> -	WRITE_ONCE(iocb->private, NULL);
> -	iocb->ki_complete(iocb, iomap_dio_simple_complete(sr));
> -}
> -
>  static void iomap_dio_simple_end_io(struct bio *bio)
>  {
>  	struct iomap_dio_simple *sr =
>  		container_of(bio, struct iomap_dio_simple, bio);
>  	struct kiocb *iocb = sr->iocb;
>  
> -	if (unlikely(sr->bio.bi_status)) {
> -		struct inode *inode = file_inode(iocb->ki_filp);
> -
> -		INIT_WORK(&sr->work, iomap_dio_simple_complete_work);
> -		queue_work(inode->i_sb->s_dio_done_wq, &sr->work);
> +	if (unlikely(bio->bi_status) && bio_complete_in_task(bio))
>  		return;
> -	}
> -
>  	WRITE_ONCE(iocb->private, NULL);
>  	iocb->ki_complete(iocb, iomap_dio_simple_complete(sr));
>  }
> -- 
> 2.53.0
> 

Re: [PATCH 1/3] iomap: use bio_complete_in_task for buffered read failures

[Andrey Albershteyn]

On 2026-09-28 11:11:07, Christoph Hellwig wrote:
> Use bio_complete_in_task to defer the bio completion handler to task
> context instead of the homegrown deferral.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me
Reviewed-by: Andrey Albershteyn <aalbersh@kernel.org>

-- 
- Andrey

Re: [PATCH 2/3] iomap: use bio_complete_in_task for buffered write failures

[Andrey Albershteyn]

On 2026-09-28 11:11:08, Christoph Hellwig wrote:
> Use bio_complete_in_task to defer the bio completion handler to task
> context instead of the homegrown deferral.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me
Reviewed-by: Andrey Albershteyn <aalbersh@kernel.org>

-- 
- Andrey

Re: [PATCH 3/3] iomap: use bio_complete_in_task for buffered simple dio read failures

[Andrey Albershteyn]

On 2026-09-28 11:11:09, Christoph Hellwig wrote:
> Use bio_complete_in_task to defer the bio completion handler to task
> context instead of the homegrown deferral.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks good to me
Reviewed-by: Andrey Albershteyn <aalbersh@kernel.org>

-- 
- Andrey

Re: use bio_complete_in_task for iomap error reporting

[Christian Brauner]

On Mon, 28 Sep 2026 11:11:06 +0200, Christoph Hellwig wrote:
> this series replaces three pieces of code to queue up I/O completions
> in user context for error reporting with the relatively new block layer
> bio_complete_in_task() mechanism.
> 
> Diffstat:
>  bio.c       |   46 ++--------------------------------------------
>  direct-io.c |   19 +------------------
>  ioend.c     |   48 ++----------------------------------------------
>  3 files changed, 5 insertions(+), 108 deletions(-)
> 
> [...]

Applied to the vfs-7.3.iomap.final branch of the vfs/vfs.git tree.
Patches in the vfs-7.3.iomap.final branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-7.3.iomap.final

[1/3] iomap: use bio_complete_in_task for buffered read failures
      https://git.kernel.org/vfs/vfs/c/062de5a4ef9d
[2/3] iomap: use bio_complete_in_task for buffered write failures
      https://git.kernel.org/vfs/vfs/c/9d098dfc5522
[3/3] iomap: use bio_complete_in_task for buffered simple dio read failures
      https://git.kernel.org/vfs/vfs/c/26db1836053f