switch generic_write_checks() to iocb and iter

... returning -E... upon error and amount of data left in iter after
(possible) truncation upon success.  Note, that normal case gives
a non-zero (positive) return value, so any tests for != 0 _must_ be
updated.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Conflicts:
	fs/ext4/file.c

1 files changed, 10 insertions, 15 deletions

diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c
index 5ddd77acb3f7..9634189b8545 100644
--- a/fs/nfs/direct.c
+++ b/fs/nfs/direct.c
@@ -969,24 +969,19 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
         struct nfs_direct_req *dreq;
         struct nfs_lock_context *l_ctx;
         loff_t end;
-        size_t count = iov_iter_count(iter);
-        end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
-
-        nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES, count);
 
         dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n",
-                file, count, (long long) pos);
+                file, iov_iter_count(iter), (long long) iocb->ki_pos);
 
-        result = generic_write_checks(file, &pos, &count);
-        if (result)
+        result = generic_write_checks(iocb, iter);
+        if (result <= 0)
                 goto out;
 
-        result = -EINVAL;
-        if ((ssize_t) count < 0)
-                goto out;
-        result = 0;
-        if (!count)
-                goto out;
+        nfs_add_stats(mapping->host, NFSIOS_DIRECTWRITTENBYTES,
+                      iov_iter_count(iter));
+
+        pos = iocb->ki_pos;
+        end = (pos + iov_iter_count(iter) - 1) >> PAGE_CACHE_SHIFT;
 
         mutex_lock(&inode->i_mutex);
 
@@ -1001,7 +996,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
                         goto out_unlock;
         }
 
-        task_io_account_write(count);
+        task_io_account_write(iov_iter_count(iter));
 
         result = -ENOMEM;
         dreq = nfs_direct_req_alloc();
@@ -1009,7 +1004,7 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter,
                 goto out_unlock;
 
         dreq->inode = inode;
-        dreq->bytes_left = count;
+        dreq->bytes_left = iov_iter_count(iter);
         dreq->io_start = pos;
         dreq->ctx = get_nfs_open_context(nfs_file_open_context(iocb->ki_filp));
         l_ctx = nfs_get_lock_context(dreq->ctx);