linux-ext4 - [PATCH v20 05/32] splice: Make splice from a DAX file use direct_splice

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Date:   Fri, 19 May 2023 08:40:20 +0100
From:   David Howells <dhowells@...hat.com>
To:     Jens Axboe <axboe@...nel.dk>, Al Viro <viro@...iv.linux.org.uk>,
        Christoph Hellwig <hch@...radead.org>
Cc:     David Howells <dhowells@...hat.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Jeff Layton <jlayton@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Hillf Danton <hdanton@...a.com>,
        Christian Brauner <brauner@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Christoph Hellwig <hch@....de>, linux-erofs@...ts.ozlabs.org,
        linux-ext4@...r.kernel.org, linux-xfs@...r.kernel.org
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 <dhowells@...hat.com>
cc: Christoph Hellwig <hch@....de>
cc: Al Viro <viro@...iv.linux.org.uk>
cc: Jens Axboe <axboe@...nel.dk>
cc: linux-erofs@...ts.ozlabs.org
cc: linux-ext4@...r.kernel.org
cc: linux-fsdevel@...r.kernel.org
cc: linux-xfs@...r.kernel.org
cc: linux-fsdevel@...r.kernel.org
cc: linux-block@...r.kernel.org
cc: linux-mm@...ck.org
---
 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;