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

[Mezgani Ali <ali.mezgani@xxxxxxxxxx>]

Hello Kernel,

Whom made this bad quality of code :

- 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;

I pretend that keeping the file clear, clean and explicit far from new comers is much more needed.

Please a cache flush is wonderful here.

Kind regards,
--

Mezgani Ali

SVP of Engineering

https://www.nativelabs.ma/

ali.mezgani@xxxxxxxxxxxxx

+212 6 44 17 94 51

 

On 14/02/2023, at 18:13, David Howells <dhowells@xxxxxxxxxx> 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@xxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: Christoph Hellwig <hch@xxxxxx>
cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
cc: David Hildenbrand <david@xxxxxxxxxx>
cc: John Hubbard <jhubbard@xxxxxxxxxx>
cc: linux-mm@xxxxxxxxx
cc: linux-block@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
---

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);
+ return filemap_splice_read(in, ppos, pipe, len, flags);
}
EXPORT_SYMBOL(generic_file_splice_read);