Re: [PATCH] add check do_direct_IO() return val

gurudas pai
2007-07-27T08:09:37Z

Andrew Morton wrote:
> On Thu, 26 Jul 2007 17:04:00 +0800 Joe Jin <joe.jin@oracle.com> wrote:
>
>> This is the patch for check do_direct_IO() return val.
>>
>> At do_direct_IO(), sometimes dio_get_page() will return -EFAULT/-ENOMEM,
>> according to orig source, it will go on left work. buf for dio_get_page()
>> return a error will made many useful member of dio not initialized like
>> dio->map_bh and others, at this point, kernel will panic.
>>
>> Signed-off-by: Joe Jin <joe.jin@oracle.com>
>>
>>
>> ---
>> --- linux-2.6.22/fs/direct-io.c.orig 2007-07-26 11:32:27.000000000 +0800
>> +++ linux-2.6.22/fs/direct-io.c 2007-07-26 11:33:58.000000000 +0800
>> @@ -1031,7 +1031,9 @@ direct_io_worker(int rw, struct kiocb *i
>> ((dio->final_block_in_request - dio->block_in_file) <<
>> blkbits);
>>
>> - if (ret) {
>> + if (ret == -EFAULT || ret == -ENOMEM)
>> + goto out;
>> + else if (ret) {
>> dio_cleanup(dio);
>> break;
>> }
>> @@ -1113,6 +1115,7 @@ direct_io_worker(int rw, struct kiocb *i
>> } else
>> BUG_ON(ret != -EIOCBQUEUED);
>>
>> +out:
>> return ret;
>> }
>>
>
> I think we still want to run dio_cleanup() if do_direct_IO() failed?
> Otherwise we can leak pages.
>
> And there's nothing special about EFAULT or ENOMEM here: if do_direct_IO()
> returns any error then that's it: we bale out, yes?
>
> In fact I'm suspecting that this is what the code in there used to do.
> Something like:
>
> for (...) {
> ...
> ret = do_direct_IO(...);
> ...
> if (ret) {
> dio_dleanup(dio);
> break
> }
> }
> return ret;
>
> but then someone later came along and added more code between the end of
> the for loop and the `return' statement.
>
> <I do miss the BK diffviewer sometimes>
>
> <does a binary search>
>
> yep, that's exactly what happened. We broke it in the 2.5.45 release back
> in October 2002. (Where "we" == "Badari")
>
> So I think what we need to do is something close to this:
>
> --- a/fs/direct-io.c~add-check-do_direct_io-return-val
> +++ a/fs/direct-io.c
> @@ -1033,7 +1033,7 @@ direct_io_worker(int rw, struct kiocb *i
>
> if (ret) {
> dio_cleanup(dio);
> - break;
> + goto out;
> }
> } /* end iovec loop */
>
> @@ -1112,7 +1112,7 @@ direct_io_worker(int rw, struct kiocb *i
> kfree(dio);
> } else
> BUG_ON(ret != -EIOCBQUEUED);
> -
> +out:
> return ret;
> }
>
> _
>
> However I'd like to ask you guys to carefully review and test that please.
Tested Andrew's patch , works! . My test case passed without any panic.
But got couple of ENOTBLK.

Thanks,
-Guru