2023-05-19 07:43:33

by David Howells

Subject: [PATCH v20 05/32] splice: Make splice from a DAX file use direct_splice_read()

Make a read splice from a DAX file go directly to direct_splice_read() to
do the reading as filemap_splice_read() is unlikely to find any pagecache
to splice.

I think this affects only erofs, Ext2, Ext4, fuse and XFS.

Signed-off-by: David Howells <[email protected]>
cc: Christoph Hellwig <[email protected]>
cc: Al Viro <[email protected]>
cc: Jens Axboe <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
cc: [email protected]
---
fs/splice.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/fs/splice.c b/fs/splice.c
index 1e0b7c7038b5..7b818b5b18d4 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -421,6 +421,11 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
struct kiocb kiocb;
int ret;

+#ifdef CONFIG_FS_DAX
+ if (IS_DAX(in->f_mapping->host))
+ return direct_splice_read(in, ppos, pipe, len, flags);
+#endif
+
iov_iter_pipe(&to, ITER_DEST, pipe, len);
init_sync_kiocb(&kiocb, in);
kiocb.ki_pos = *ppos;

2023-05-19 08:10:45

by Christoph Hellwig

Subject: Re: [PATCH v20 05/32] splice: Make splice from a DAX file use direct_splice_read()

On Fri, May 19, 2023 at 08:40:20AM +0100, David Howells wrote:
> +#ifdef CONFIG_FS_DAX
> + if (IS_DAX(in->f_mapping->host))

No need for the ifdef. IS_DAX is compile-time false if CONFIG_FS_DAX
is not set.

A comment on why we're doing this in the code would probably be useful
as well.