Hi Al,
On 8 Aug 2014, at 16:54, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
> 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?
No objections from me. As you say, that will do the right thing in all cases.
Best regards,
Anton
--
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
University of Cambridge Information Services, Roger Needham Building
7 JJ Thomson Avenue, Cambridge, CB3 0RB, UK
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