[PATCH] loop: add fs_start_write() and fs_end_write()

[PATCH] loop: add fs_start_write() and fs_end_write()

[Ming Lei]

fs_start_write() and fs_end_write() should be added around ->write_iter().

Recently we switch to ->write_iter() from vfs_iter_write(), and the
implied fs_start_write() and fs_end_write() are lost.

Also we never add them for dio code path, so add them back for covering
both.

Cc: Jeff Moyer <jmoyer@redhat.com>
Fixes: f2fed441c69b ("loop: stop using vfs_iter_{read,write} for buffered I/O")
Fixes: bc07c10a3603 ("block: loop: support DIO & AIO")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 drivers/block/loop.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 46cba261075f..5107cc9a1872 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -308,11 +308,14 @@ static void lo_complete_rq(struct request *rq)
 static void lo_rw_aio_do_completion(struct loop_cmd *cmd)
 {
 	struct request *rq = blk_mq_rq_from_pdu(cmd);
+	struct loop_device *lo = rq->q->queuedata;
 
 	if (!atomic_dec_and_test(&cmd->ref))
 		return;
 	kfree(cmd->bvec);
 	cmd->bvec = NULL;
+	if (req_op(rq) == REQ_OP_WRITE)
+		file_end_write(lo->lo_backing_file);
 	if (likely(!blk_should_fake_timeout(rq->q)))
 		blk_mq_complete_request(rq);
 }
@@ -387,9 +390,10 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 		cmd->iocb.ki_flags = 0;
 	}
 
-	if (rw == ITER_SOURCE)
+	if (rw == ITER_SOURCE) {
+		file_start_write(lo->lo_backing_file);
 		ret = file->f_op->write_iter(&cmd->iocb, &iter);
-	else
+	} else
 		ret = file->f_op->read_iter(&cmd->iocb, &iter);
 
 	lo_rw_aio_do_completion(cmd);
-- 
2.47.1

Re: [PATCH] loop: add fs_start_write() and fs_end_write()

[Caleb Sander Mateos]

On Thu, May 22, 2025 at 7:37 AM Ming Lei <ming.lei@redhat.com> wrote:
>
> fs_start_write() and fs_end_write() should be added around ->write_iter().

Do you mean file_start_write() and file_end_write()?

Best,
Caleb

>
> Recently we switch to ->write_iter() from vfs_iter_write(), and the
> implied fs_start_write() and fs_end_write() are lost.
>
> Also we never add them for dio code path, so add them back for covering
> both.
>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Fixes: f2fed441c69b ("loop: stop using vfs_iter_{read,write} for buffered I/O")
> Fixes: bc07c10a3603 ("block: loop: support DIO & AIO")
> Signed-off-by: Ming Lei <ming.lei@redhat.com>
> ---
>  drivers/block/loop.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/block/loop.c b/drivers/block/loop.c
> index 46cba261075f..5107cc9a1872 100644
> --- a/drivers/block/loop.c
> +++ b/drivers/block/loop.c
> @@ -308,11 +308,14 @@ static void lo_complete_rq(struct request *rq)
>  static void lo_rw_aio_do_completion(struct loop_cmd *cmd)
>  {
>         struct request *rq = blk_mq_rq_from_pdu(cmd);
> +       struct loop_device *lo = rq->q->queuedata;
>
>         if (!atomic_dec_and_test(&cmd->ref))
>                 return;
>         kfree(cmd->bvec);
>         cmd->bvec = NULL;
> +       if (req_op(rq) == REQ_OP_WRITE)
> +               file_end_write(lo->lo_backing_file);
>         if (likely(!blk_should_fake_timeout(rq->q)))
>                 blk_mq_complete_request(rq);
>  }
> @@ -387,9 +390,10 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
>                 cmd->iocb.ki_flags = 0;
>         }
>
> -       if (rw == ITER_SOURCE)
> +       if (rw == ITER_SOURCE) {
> +               file_start_write(lo->lo_backing_file);
>                 ret = file->f_op->write_iter(&cmd->iocb, &iter);
> -       else
> +       } else
>                 ret = file->f_op->read_iter(&cmd->iocb, &iter);
>
>         lo_rw_aio_do_completion(cmd);
> --
> 2.47.1
>
>

Re: [PATCH] loop: add fs_start_write() and fs_end_write()

[Ming Lei]

On Thu, May 22, 2025 at 08:31:41AM -0700, Caleb Sander Mateos wrote:
> On Thu, May 22, 2025 at 7:37 AM Ming Lei <ming.lei@redhat.com> wrote:
> >
> > fs_start_write() and fs_end_write() should be added around ->write_iter().
> 
> Do you mean file_start_write() and file_end_write()?

Yeah, will change it if V2 is needed.

Thanks,
Ming