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From:   David Howells <dhowells@redhat.com>
To:     Jens Axboe <axboe@kernel.dk>, Al Viro <viro@zeniv.linux.org.uk>,
        Christoph Hellwig <hch@infradead.org>
Cc:     David Howells <dhowells@redhat.com>,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        Jeff Layton <jlayton@kernel.org>,
        David Hildenbrand <david@redhat.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Logan Gunthorpe <logang@deltatee.com>,
        Hillf Danton <hdanton@sina.com>,
        Christian Brauner <brauner@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Christoph Hellwig <hch@lst.de>,
        Trond Myklebust <trond.myklebust@hammerspace.com>,
        Anna Schumaker <anna@kernel.org>, linux-nfs@vger.kernel.org
Subject: [PATCH v20 17/32] nfs: Provide a splice-read stub
Date:   Fri, 19 May 2023 08:40:32 +0100
Message-Id: <20230519074047.1739879-18-dhowells@redhat.com>
In-Reply-To: <20230519074047.1739879-1-dhowells@redhat.com>
References: <20230519074047.1739879-1-dhowells@redhat.com>
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Provide a splice_read stub for NFS.  This locks the inode around
filemap_splice_read() and revalidates the mapping.  It cannot do this
around direct_splice_read() as that calls ->read_iter().

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Trond Myklebust <trond.myklebust@hammerspace.com>
cc: Anna Schumaker <anna@kernel.org>
cc: linux-nfs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-mm@kvack.org
---
 fs/nfs/file.c     | 26 +++++++++++++++++++++++++-
 fs/nfs/internal.h |  2 ++
 fs/nfs/nfs4file.c |  2 +-
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index f0edf5a36237..91fe48b47f3c 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -178,6 +178,30 @@ nfs_file_read(struct kiocb *iocb, struct iov_iter *to)
 }
 EXPORT_SYMBOL_GPL(nfs_file_read);
 
+ssize_t
+nfs_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 result;
+
+	if (in->f_flags & O_DIRECT)
+		return direct_splice_read(in, ppos, pipe, len, flags);
+
+	dprintk("NFS: splice_read(%pD2, %zu@%lu)\n", in, len, *pos);
+
+	nfs_start_io_read(inode);
+	result = nfs_revalidate_mapping(inode, in->f_mapping);
+	if (!result) {
+		result = filemap_splice_read(in, ppos, pipe, len, flags);
+		if (result > 0)
+			nfs_add_stats(inode, NFSIOS_NORMALREADBYTES, result);
+	}
+	nfs_end_io_read(inode);
+	return result;
+}
+EXPORT_SYMBOL_GPL(nfs_file_splice_read);
+
 int
 nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
 {
@@ -879,7 +903,7 @@ const struct file_operations nfs_file_operations = {
 	.fsync		= nfs_file_fsync,
 	.lock		= nfs_lock,
 	.flock		= nfs_flock,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= nfs_file_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.check_flags	= nfs_check_flags,
 	.setlease	= simple_nosetlease,
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 3cc027d3bd58..b5f21d35d30e 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -416,6 +416,8 @@ static inline __u32 nfs_access_xattr_mask(const struct nfs_server *server)
 int nfs_file_fsync(struct file *file, loff_t start, loff_t end, int datasync);
 loff_t nfs_file_llseek(struct file *, loff_t, int);
 ssize_t nfs_file_read(struct kiocb *, struct iov_iter *);
+ssize_t nfs_file_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe,
+			     size_t len, unsigned int flags);
 int nfs_file_mmap(struct file *, struct vm_area_struct *);
 ssize_t nfs_file_write(struct kiocb *, struct iov_iter *);
 int nfs_file_release(struct inode *, struct file *);
diff --git a/fs/nfs/nfs4file.c b/fs/nfs/nfs4file.c
index 2563ed8580f3..4aeadd6e1a6d 100644
--- a/fs/nfs/nfs4file.c
+++ b/fs/nfs/nfs4file.c
@@ -454,7 +454,7 @@ const struct file_operations nfs4_file_operations = {
 	.fsync		= nfs_file_fsync,
 	.lock		= nfs_lock,
 	.flock		= nfs_flock,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= nfs_file_splice_read,
 	.splice_write	= iter_file_splice_write,
 	.check_flags	= nfs_check_flags,
 	.setlease	= nfs4_setlease,