NFS: clean up NFS client's a_ops->direct_IO method

The NFS client's a_ops->direct_IO method, nfs_direct_IO, is required to
be present to allow NFS files to be opened with O_DIRECT, but is never
called because the NFS client shunts reads and writes to files opened
with O_DIRECT directly to its own routines.

Gut the nfs_direct_IO function.  This eliminates the only part of the
NFS client's direct I/O path that requires support for multi-segment
iovs, allowing further simplification in subsequent patches.

Test plan:
Compile the kernel with CONFIG_NFS and CONFIG_NFS_DIRECTIO enabled.  Millions
of fsx-odirect ops.  OraSim.

Signed-off-by: Chuck Lever <cel@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 23 insertions, 47 deletions

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 3f87a72bd137..8096d326bd79 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -79,6 +79,29 @@ struct nfs_direct_req {
 
 
 /**
+ * nfs_direct_IO - NFS address space operation for direct I/O
+ * @rw: direction (read or write)
+ * @iocb: target I/O control block
+ * @iov: array of vectors that define I/O buffer
+ * @pos: offset in file to begin the operation
+ * @nr_segs: size of iovec array
+ *
+ * The presence of this routine in the address space ops vector means
+ * the NFS client supports direct I/O.  However, we shunt off direct
+ * read and write requests before the VFS gets them, so this method
+ * should never be called.
+ */
+ssize_t nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs)
+{
+        struct dentry *dentry = iocb->ki_filp->f_dentry;
+
+        dprintk("NFS: nfs_direct_IO (%s) off/no(%Ld/%lu) EINVAL\n",
+                        dentry->d_name.name, (long long) pos, nr_segs);
+
+        return -EINVAL;
+}
+
+/**
  * nfs_get_user_pages - find and set up pages underlying user's buffer
  * rw: direction (read or write)
  * user_addr: starting address of this segment of user's buffer
@@ -606,53 +629,6 @@ static ssize_t nfs_direct_write(struct inode *inode,
 }
 
 /**
- * nfs_direct_IO - NFS address space operation for direct I/O
- * rw: direction (read or write)
- * @iocb: target I/O control block
- * @iov: array of vectors that define I/O buffer
- * file_offset: offset in file to begin the operation
- * nr_segs: size of iovec array
- *
- */
-ssize_t
-nfs_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
-                loff_t file_offset, unsigned long nr_segs)
-{
-        ssize_t result = -EINVAL;
-        struct file *file = iocb->ki_filp;
-        struct nfs_open_context *ctx;
-        struct dentry *dentry = file->f_dentry;
-        struct inode *inode = dentry->d_inode;
-
-        /*
-         * No support for async yet
-         */
-        if (!is_sync_kiocb(iocb))
-                return result;
-
-        ctx = (struct nfs_open_context *)file->private_data;
-        switch (rw) {
-        case READ:
-                dprintk("NFS: direct_IO(read) (%s) off/no(%Lu/%lu)\n",
-                                dentry->d_name.name, file_offset, nr_segs);
-
-                result = nfs_direct_read(inode, ctx, iov,
-                                                file_offset, nr_segs);
-                break;
-        case WRITE:
-                dprintk("NFS: direct_IO(write) (%s) off/no(%Lu/%lu)\n",
-                                dentry->d_name.name, file_offset, nr_segs);
-
-                result = nfs_direct_write(inode, ctx, iov,
-                                                file_offset, nr_segs);
-                break;
-        default:
-                break;
-        }
-        return result;
-}
-
-/**
  * nfs_file_direct_read - file direct read operation for NFS files
  * @iocb: target I/O control block
  * @buf: user's buffer into which to read data