On Fri, Aug 08, 2014 at 12:11:39AM +0100, Anton Altaparmakov wrote:
> Hi Al,
>
> Was just looking at __generic_file_write_iter() and found a bug in the code
> that you added in 3b93f911d5.
>
> Consider the case where generic_file_direct_write() returns a partial write,
> i.e. written > 0 && written < count.
>
> Also consider that the following generic_perform_write() fails with an error,
> i.e. status < 0.
*nod*
What we ought to do, AFAICS, is this:
diff --git a/mm/filemap.c b/mm/filemap.c
index 900edfa..8163e04 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2584,7 +2584,7 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb,
struct iov_iter *from)
* that this differs from normal direct-io semantics, which
* will return -EFOO even if some bytes were written.
*/
- if (unlikely(status < 0) && !written) {
+ if (unlikely(status < 0)) {
err = status;
goto out;
}
Note that we return written ? written : err, so assignment to err will be
the right thing both when status < 0 && written == 0 and when status < 0 &&
written > 0. In the latter case err will be simply ignored.
Objections?
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