NFS: add support for splice writes

Adds support for splice writes. It effectively calls
generic_file_splice_write() to do the writes.

We need not worry about O_APPEND case as the combination of splice()
writes and O_APPEND is disallowed. This patch propagates NFS write
errors back to the caller. The number of bytes written via splice are
being added to NFSIO_NORMALWRITTENBYTES as these are effectively
cached writes.

Signed-off-by: Suresh Jayaraman <sjayaraman@suse.de>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 52ed56762583..0055b813ec2c 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -48,6 +48,9 @@ static ssize_t nfs_file_splice_read(struct file *filp, loff_t *ppos,
                                         size_t count, unsigned int flags);
 static ssize_t nfs_file_read(struct kiocb *, const struct iovec *iov,
                                 unsigned long nr_segs, loff_t pos);
+static ssize_t nfs_file_splice_write(struct pipe_inode_info *pipe,
+                                        struct file *filp, loff_t *ppos,
+                                        size_t count, unsigned int flags);
 static ssize_t nfs_file_write(struct kiocb *, const struct iovec *iov,
                                 unsigned long nr_segs, loff_t pos);
 static int  nfs_file_flush(struct file *, fl_owner_t id);
@@ -73,6 +76,7 @@ const struct file_operations nfs_file_operations = {
         .lock           = nfs_lock,
         .flock          = nfs_flock,
         .splice_read    = nfs_file_splice_read,
+        .splice_write   = nfs_file_splice_write,
         .check_flags    = nfs_check_flags,
         .setlease       = nfs_setlease,
 };
@@ -587,6 +591,33 @@ out_swapfile:
         goto out;
 }
 
+static ssize_t nfs_file_splice_write(struct pipe_inode_info *pipe,
+                                     struct file *filp, loff_t *ppos,
+                                     size_t count, unsigned int flags)
+{
+        struct dentry *dentry = filp->f_path.dentry;
+        struct inode *inode = dentry->d_inode;
+        ssize_t ret;
+
+        dprintk("NFS splice_write(%s/%s, %lu@%llu)\n",
+                dentry->d_parent->d_name.name, dentry->d_name.name,
+                (unsigned long) count, (unsigned long long) *ppos);
+
+        /*
+         * The combination of splice and an O_APPEND destination is disallowed.
+         */
+
+        nfs_add_stats(inode, NFSIOS_NORMALWRITTENBYTES, count);
+
+        ret = generic_file_splice_write(pipe, filp, ppos, count, flags);
+        if (ret >= 0 && nfs_need_sync_write(filp, inode)) {
+                int err = nfs_do_fsync(nfs_file_open_context(filp), inode);
+                if (err < 0)
+                        ret = err;
+        }
+        return ret;
+}
+
 static int do_getlk(struct file *filp, int cmd, struct file_lock *fl)
 {
         struct inode *inode = filp->f_mapping->host;