fs: Allow a NULL pos pointer to __kernel_write

Linus prefers that callers be allowed to pass in a NULL pointer for ppos
like new_sync_write().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/read_write.c b/fs/read_write.c
index 8c61f67453e3d3a518b47bc4933b82c01309d490..516eb51af70e256a9759fc90f574d4bea1a91145 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -544,11 +544,12 @@ ssize_t __kernel_write(struct file *file, const void *buf, size_t count, loff_t
                return warn_unsupported(file, "write");
 
        init_sync_kiocb(&kiocb, file);
-       kiocb.ki_pos = *pos;
+       kiocb.ki_pos = pos ? *pos : 0;
        iov_iter_kvec(&iter, WRITE, &iov, 1, iov.iov_len);
        ret = file->f_op->write_iter(&kiocb, &iter);
        if (ret > 0) {
-               *pos = kiocb.ki_pos;
+               if (pos)
+                       *pos = kiocb.ki_pos;
                fsnotify_modify(file);
                add_wchar(current, ret);
        }