NFS: various changes relating to reporting IO errors.

1/ remove 'start' and 'end' args from nfs_file_fsync_commit().
They aren't used.

2/ Make nfs_context_set_write_error() a "static inline" in internal.h
so we can...

3/ Use nfs_context_set_write_error() instead of mapping_set_error()
if nfs_pageio_add_request() fails before sending any request.
NFS generally keeps errors in the open_context, not the mapping,
so this is more consistent.

4/ If filemap_write_and_write_range() reports any error, still
check ctx->error. The value in ctx->error is likely to be
more useful. As part of this, NFS_CONTEXT_ERROR_WRITE is
cleared slightly earlier, before nfs_file_fsync_commit() is called,
rather than at the start of that function.

Signed-off-by: NeilBrown <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

fs/nfs/file.c

···
  * fall back to doing a synchronous write.
  */
 static int
-nfs_file_fsync_commit(struct file *file, loff_t start, loff_t end, int datasync)
+nfs_file_fsync_commit(struct file *file, int datasync)
 {
 	struct nfs_open_context *ctx = nfs_file_open_context(file);
 	struct inode *inode = file_inode(file);
-	int have_error, do_resend, status;
+	int do_resend, status;
 	int ret = 0;
 
 	dprintk("NFS: fsync file(%pD2) datasync %d\n", file, datasync);
 
 	nfs_inc_stats(inode, NFSIOS_VFSFSYNC);
 	do_resend = test_and_clear_bit(NFS_CONTEXT_RESEND_WRITES, &ctx->flags);
-	have_error = test_and_clear_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
 	status = nfs_commit_inode(inode, FLUSH_SYNC);
-	have_error |= test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
-	if (have_error) {
+	if (test_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags)) {
 		ret = xchg(&ctx->error, 0);
 		if (ret)
 			goto out;
···
 	trace_nfs_fsync_enter(inode);
 
 	do {
+		struct nfs_open_context *ctx = nfs_file_open_context(file);
 		ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
+		if (test_and_clear_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags)) {
+			int ret2 = xchg(&ctx->error, 0);
+			if (ret2)
+				ret = ret2;
+		}
 		if (ret != 0)
 			break;
-		ret = nfs_file_fsync_commit(file, start, end, datasync);
+		ret = nfs_file_fsync_commit(file, datasync);
 		if (!ret)
 			ret = pnfs_sync_inode(inode, !!datasync);
 		/*

fs/nfs/internal.h

···
 		return false;
 	}
 }
+
+static inline void nfs_context_set_write_error(struct nfs_open_context *ctx, int error)
+{
+	ctx->error = error;
+	smp_wmb();
+	set_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
+}

fs/nfs/pagelist.c

···
 
 		/* remember fatal errors */
 		if (nfs_error_is_fatal(desc->pg_error))
-			mapping_set_error(desc->pg_inode->i_mapping,
-					  desc->pg_error);
+			nfs_context_set_write_error(req->wb_context,
+						    desc->pg_error);
 
 		func = desc->pg_completion_ops->error_cleanup;
 		for (midx = 0; midx < desc->pg_mirror_count; midx++) {

fs/nfs/write.c

···
 		kref_put(&ioc->refcount, nfs_io_completion_release);
 }
 
-static void nfs_context_set_write_error(struct nfs_open_context *ctx, int error)
-{
-	ctx->error = error;
-	smp_wmb();
-	set_bit(NFS_CONTEXT_ERROR_WRITE, &ctx->flags);
-}
-
 static struct nfs_page *
 nfs_page_private_request(struct page *page)
 {