diff mbox series

[v14,08/17] splice: Do splice read from a file without using ITER_PIPE

Message ID 20230214171330.2722188-9-dhowells@redhat.com
State New
Headers
Series iov_iter: Improve page extraction (pin or just list) |

Commit Message

David Howells Feb. 14, 2023, 5:13 p.m. UTC 
  Make generic_file_splice_read() use filemap_splice_read() and
direct_splice_read() rather than using an ITER_PIPE and call_read_iter().

With this, ITER_PIPE is no longer used.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: David Hildenbrand <david@redhat.com>
cc: John Hubbard <jhubbard@nvidia.com>
cc: linux-mm@kvack.org
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
---

Notes:
    ver #14)
    - Split out filemap_splice_read() into a separate patch.

 fs/splice.c | 30 +++++++-----------------------
 1 file changed, 7 insertions(+), 23 deletions(-)

Comments

Ming Lei Feb. 17, 2023, 8:22 a.m. UTC | #1 
On Tue, Feb 14, 2023 at 05:13:21PM +0000, David Howells wrote:
> Make generic_file_splice_read() use filemap_splice_read() and
> direct_splice_read() rather than using an ITER_PIPE and call_read_iter().
> 
> With this, ITER_PIPE is no longer used.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Christoph Hellwig <hch@lst.de>
> cc: Al Viro <viro@zeniv.linux.org.uk>
> cc: David Hildenbrand <david@redhat.com>
> cc: John Hubbard <jhubbard@nvidia.com>
> cc: linux-mm@kvack.org
> cc: linux-block@vger.kernel.org
> cc: linux-fsdevel@vger.kernel.org
> ---
> 
> Notes:
>     ver #14)
>     - Split out filemap_splice_read() into a separate patch.
> 
>  fs/splice.c | 30 +++++++-----------------------
>  1 file changed, 7 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/splice.c b/fs/splice.c
> index 4c6332854b63..a93478338cec 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -391,29 +391,13 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
>  				 struct pipe_inode_info *pipe, size_t len,
>  				 unsigned int flags)
>  {
> -	struct iov_iter to;
> -	struct kiocb kiocb;
> -	int ret;
> -
> -	iov_iter_pipe(&to, ITER_DEST, pipe, len);
> -	init_sync_kiocb(&kiocb, in);
> -	kiocb.ki_pos = *ppos;
> -	ret = call_read_iter(in, &kiocb, &to);
> -	if (ret > 0) {
> -		*ppos = kiocb.ki_pos;
> -		file_accessed(in);
> -	} else if (ret < 0) {
> -		/* free what was emitted */
> -		pipe_discard_from(pipe, to.start_head);
> -		/*
> -		 * callers of ->splice_read() expect -EAGAIN on
> -		 * "can't put anything in there", rather than -EFAULT.
> -		 */
> -		if (ret == -EFAULT)
> -			ret = -EAGAIN;
> -	}
> -
> -	return ret;
> +	if (unlikely(*ppos >= file_inode(in)->i_sb->s_maxbytes))
> +		return 0;
> +	if (unlikely(!len))
> +		return 0;
> +	if (in->f_flags & O_DIRECT)
> +		return direct_splice_read(in, ppos, pipe, len, flags);

Hello David,

I have one question, for dio, pages need to map to userspace
memory, but direct_splice_read() just allocates pages and not
see when the user mapping is setup, can you give one hint?


Thanks, 
Ming
Ming Lei Feb. 17, 2023, 9:18 a.m. UTC | #2 
On Fri, Feb 17, 2023 at 4:22 PM Ming Lei <ming.lei@redhat.com> wrote:
>
> On Tue, Feb 14, 2023 at 05:13:21PM +0000, David Howells wrote:
> > Make generic_file_splice_read() use filemap_splice_read() and
> > direct_splice_read() rather than using an ITER_PIPE and call_read_iter().
> >
> > With this, ITER_PIPE is no longer used.
> >
> > Signed-off-by: David Howells <dhowells@redhat.com>
> > cc: Jens Axboe <axboe@kernel.dk>
> > cc: Christoph Hellwig <hch@lst.de>
> > cc: Al Viro <viro@zeniv.linux.org.uk>
> > cc: David Hildenbrand <david@redhat.com>
> > cc: John Hubbard <jhubbard@nvidia.com>
> > cc: linux-mm@kvack.org
> > cc: linux-block@vger.kernel.org
> > cc: linux-fsdevel@vger.kernel.org
> > ---
> >
> > Notes:
> >     ver #14)
> >     - Split out filemap_splice_read() into a separate patch.
> >
> >  fs/splice.c | 30 +++++++-----------------------
> >  1 file changed, 7 insertions(+), 23 deletions(-)
> >
> > diff --git a/fs/splice.c b/fs/splice.c
> > index 4c6332854b63..a93478338cec 100644
> > --- a/fs/splice.c
> > +++ b/fs/splice.c
> > @@ -391,29 +391,13 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
> >                                struct pipe_inode_info *pipe, size_t len,
> >                                unsigned int flags)
> >  {
> > -     struct iov_iter to;
> > -     struct kiocb kiocb;
> > -     int ret;
> > -
> > -     iov_iter_pipe(&to, ITER_DEST, pipe, len);
> > -     init_sync_kiocb(&kiocb, in);
> > -     kiocb.ki_pos = *ppos;
> > -     ret = call_read_iter(in, &kiocb, &to);
> > -     if (ret > 0) {
> > -             *ppos = kiocb.ki_pos;
> > -             file_accessed(in);
> > -     } else if (ret < 0) {
> > -             /* free what was emitted */
> > -             pipe_discard_from(pipe, to.start_head);
> > -             /*
> > -              * callers of ->splice_read() expect -EAGAIN on
> > -              * "can't put anything in there", rather than -EFAULT.
> > -              */
> > -             if (ret == -EFAULT)
> > -                     ret = -EAGAIN;
> > -     }
> > -
> > -     return ret;
> > +     if (unlikely(*ppos >= file_inode(in)->i_sb->s_maxbytes))
> > +             return 0;
> > +     if (unlikely(!len))
> > +             return 0;
> > +     if (in->f_flags & O_DIRECT)
> > +             return direct_splice_read(in, ppos, pipe, len, flags);
>
> Hello David,
>
> I have one question, for dio, pages need to map to userspace
> memory, but direct_splice_read() just allocates pages and not
> see when the user mapping is setup, can you give one hint?

oops, it is ->splice_read,  not ->read_iter, and pipe buffer isn't
user-backed, sorry for the noise.

Thanks,
Ming
diff mbox series

Patch

diff --git a/fs/splice.c b/fs/splice.c
index 4c6332854b63..a93478338cec 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -391,29 +391,13 @@  ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 				 struct pipe_inode_info *pipe, size_t len,
 				 unsigned int flags)
 {
-	struct iov_iter to;
-	struct kiocb kiocb;
-	int ret;
-
-	iov_iter_pipe(&to, ITER_DEST, pipe, len);
-	init_sync_kiocb(&kiocb, in);
-	kiocb.ki_pos = *ppos;
-	ret = call_read_iter(in, &kiocb, &to);
-	if (ret > 0) {
-		*ppos = kiocb.ki_pos;
-		file_accessed(in);
-	} else if (ret < 0) {
-		/* free what was emitted */
-		pipe_discard_from(pipe, to.start_head);
-		/*
-		 * callers of ->splice_read() expect -EAGAIN on
-		 * "can't put anything in there", rather than -EFAULT.
-		 */
-		if (ret == -EFAULT)
-			ret = -EAGAIN;
-	}
-
-	return ret;
+	if (unlikely(*ppos >= file_inode(in)->i_sb->s_maxbytes))
+		return 0;
+	if (unlikely(!len))
+		return 0;
+	if (in->f_flags & O_DIRECT)
+		return direct_splice_read(in, ppos, pipe, len, flags);
+	return filemap_splice_read(in, ppos, pipe, len, flags);
 }
 EXPORT_SYMBOL(generic_file_splice_read);