linux-kernel - [PATCH v20 20/32] orangefs: Provide a splice-read stub

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Message-Id: <20230519074047.1739879-21-dhowells@redhat.com>
Date:   Fri, 19 May 2023 08:40:35 +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>,
        Mike Marshall <hubcap@...ibond.com>,
        Martin Brandenburg <martin@...ibond.com>,
        devel@...ts.orangefs.org
Subject: [PATCH v20 20/32] orangefs: Provide a splice-read stub

Provide a splice_read stub for ocfs2.  This increments the read stats and
then locks the inode across the call to filemap_splice_read() and a
revalidation of the mapping.

The lock must not be held across the call to direct_splice_read() as this
calls ->read_iter(); this might also mean that the stat increment doesn't
need to be done in DIO mode.

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: Mike Marshall <hubcap@...ibond.com>
cc: Martin Brandenburg <martin@...ibond.com>
cc: devel@...ts.orangefs.org
cc: linux-fsdevel@...r.kernel.org
cc: linux-block@...r.kernel.org
cc: linux-mm@...ck.org
---
 fs/orangefs/file.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/fs/orangefs/file.c b/fs/orangefs/file.c
index 1a4301a38aa7..c1eae145e4a8 100644
--- a/fs/orangefs/file.c
+++ b/fs/orangefs/file.c
@@ -337,6 +337,29 @@ static ssize_t orangefs_file_read_iter(struct kiocb *iocb,
 	return ret;
 }
 
+static ssize_t orangefs_file_splice_read(struct file *in, loff_t *ppos,
+					 struct pipe_inode_info *pipe,
+					 size_t len, unsigned int flags)
+{
+	struct inode *inode = file_inode(in);
+	ssize_t ret;
+
+	orangefs_stats.reads++;
+
+	if (in->f_flags & O_DIRECT)
+		return direct_splice_read(in, ppos, pipe, len, flags);
+
+	down_read(&inode->i_rwsem);
+	ret = orangefs_revalidate_mapping(inode);
+	if (ret)
+		goto out;
+
+	ret = filemap_splice_read(in, ppos, pipe, len, flags);
+out:
+	up_read(&inode->i_rwsem);
+	return ret;
+}
+
 static ssize_t orangefs_file_write_iter(struct kiocb *iocb,
     struct iov_iter *iter)
 {
@@ -556,7 +579,7 @@ const struct file_operations orangefs_file_operations = {
 	.lock		= orangefs_lock,
 	.mmap		= orangefs_file_mmap,
 	.open		= generic_file_open,
-	.splice_read    = generic_file_splice_read,
+	.splice_read    = orangefs_file_splice_read,
 	.splice_write   = iter_file_splice_write,
 	.flush		= orangefs_flush,
 	.release	= orangefs_file_release,