linux-kernel - Re: [PATCH] add check do_direct

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Date:	Fri, 27 Jul 2007 07:31:27 +0000
From:	"Dave Young" <hidave.darkstar@...il.com>
To:	"Joe Jin" <joe.jin@...cle.com>
Cc:	"Andrew Morton" <akpm@...ux-foundation.org>,
	torvalds@...ux-foundation.org, jens.axboe@...cle.com,
	linux-kernel@...r.kernel.org, gurudas.pai@...cle.com,
	wen.gang.wang@...cle.com, "Badari Pulavarty" <pbadari@...ibm.com>,
	"Zach Brown" <zach.brown@...cle.com>
Subject: Re: [PATCH] add check do_direct_IO() return val

>On 7/27/07, Joe Jin <joe.jin@...cle.com> wrote:
> > 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?
> >
>
> Yes, I think we'll out from here if get EFAULT/ENOMEM error, also maybe -EIO
> return, return diretly should ok.
>
> > 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;
> >
>
> Yes, we need call dio_cleanup() to release page cache, I lost it.
>
> However, we need do more while return -ENOTBLK, right?
> so I think the patch maybe like following:
>
>
> --- linux-2.6.22/fs/direct-io.c.orig    2007-07-27 14:39:15.000000000 +0800
> +++ linux-2.6.22/fs/direct-io.c 2007-07-27 15:08:58.000000000 +0800
> @@ -1032,18 +1032,19 @@ direct_io_worker(int rw, struct kiocb *i
>                                         blkbits);
>
>                 if (ret) {
> +                       if (ret == -ENOTBLK && (rw & WRITE)) {
> +                               /*
> +                                * The remaining part of the request will be
> +                                * be handled by buffered I/O when we return
> +                                */
> +                               ret = 0;
> +                               break;
> +                       }
>                         dio_cleanup(dio);
> -                       break;
> +                       goto out;
>                 }
>         } /* end iovec loop */
>
> -       if (ret == -ENOTBLK && (rw & WRITE)) {
> -               /*
> -                * The remaining part of the request will be
> -                * be handled by buffered I/O when we return
> -                */
> -               ret = 0;
> -       }
>         /*
>          * There may be some unwritten disk at the end of a part-written
>          * fs-block-sized block.  Go zero that now.
>
>
>
>
> > _
> >
> > However I'd like to ask you guys to carefully review and test that please.
> >
> Gurudas, would you please give more test of this patch?
>
Hi,
If you are sure the problem is caused by EFAULT or ENOMEM , why not:
               if (ret) {
                       dio_cleanup(dio);
                       if (ret == -EFAULT || ret == -ENOMEM)
                               goto out;
                       break;
               }

regards
dave
-
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