new_sync_write(): discard ->ki_pos unless the return value is positive
That allows ->write_iter() instances much more convenient life wrt
iocb->ki_pos (and fixes several filesystems with borderline POSIX
violations when zero-length write succeeds and changes the current
position).
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/read_write.c b/fs/read_write.c
index 45d583c..819ef3f 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -477,7 +477,8 @@
ret = filp->f_op->write_iter(&kiocb, &iter);
BUG_ON(ret == -EIOCBQUEUED);
- *ppos = kiocb.ki_pos;
+ if (ret > 0)
+ *ppos = kiocb.ki_pos;
return ret;
}