NFS: Remove private spinlock in struct nfs_pgio_header

Now that each struct nfs_pgio_header corresponds to one RPC call, we
only have one writer to the struct nfs_pgio_header.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

fs/nfs/pagelist.c

@@ -63,14 +63,14 @@ EXPORT_SYMBOL_GPL(nfs_pgheader_init);
 
 void nfs_set_pgio_error(struct nfs_pgio_header *hdr, int error, loff_t pos)
 {
-	spin_lock(&hdr->lock);
-	if (!test_and_set_bit(NFS_IOHDR_ERROR, &hdr->flags)
-	    || pos < hdr->io_start + hdr->good_bytes) {
+	unsigned int new = pos - hdr->io_start;
+
+	if (hdr->good_bytes > new) {
+		hdr->good_bytes = new;
 		clear_bit(NFS_IOHDR_EOF, &hdr->flags);
-		hdr->good_bytes = pos - hdr->io_start;
+		if (!test_and_set_bit(NFS_IOHDR_ERROR, &hdr->flags))
 			hdr->error = error;
 	}
-	spin_unlock(&hdr->lock);
 }
 
 static inline struct nfs_page *
@@ -494,7 +494,6 @@ struct nfs_pgio_header *nfs_pgio_header_alloc(const struct nfs_rw_ops *ops)
 
 	if (hdr) {
 		INIT_LIST_HEAD(&hdr->pages);
-		spin_lock_init(&hdr->lock);
 		hdr->rw_ops = ops;
 	}
 	return hdr;

fs/nfs/read.c

@@ -276,16 +276,14 @@ static void nfs_readpage_result(struct rpc_task *task,
 				struct nfs_pgio_header *hdr)
 {
 	if (hdr->res.eof) {
-		loff_t bound;
+		loff_t pos = hdr->args.offset + hdr->res.count;
+		unsigned int new = pos - hdr->io_start;
 
-		bound = hdr->args.offset + hdr->res.count;
-		spin_lock(&hdr->lock);
-		if (bound < hdr->io_start + hdr->good_bytes) {
+		if (hdr->good_bytes > new) {
+			hdr->good_bytes = new;
 			set_bit(NFS_IOHDR_EOF, &hdr->flags);
 			clear_bit(NFS_IOHDR_ERROR, &hdr->flags);
-			hdr->good_bytes = bound - hdr->io_start;
 		}
-		spin_unlock(&hdr->lock);
 	} else if (hdr->res.count < hdr->args.count)
 		nfs_readpage_retry(task, hdr);
 }

include/linux/nfs_xdr.h

@@ -1482,11 +1482,10 @@ struct nfs_pgio_header {
 	const struct nfs_rw_ops	*rw_ops;
 	struct nfs_io_completion *io_completion;
 	struct nfs_direct_req	*dreq;
-	spinlock_t		lock;
-	/* fields protected by lock */
+
 	int			pnfs_error;
 	int			error;		/* merge with pnfs_error */
-	unsigned long		good_bytes;	/* boundary of good data */
+	unsigned int		good_bytes;	/* boundary of good data */
 	unsigned long		flags;
 
 	/*