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References: <20190315075500.27747-1-longli@linuxonhyperv.com>
In-Reply-To: <20190315075500.27747-1-longli@linuxonhyperv.com>
From:   Pavel Shilovsky <piastryyy@gmail.com>
Date:   Sat, 16 Mar 2019 11:01:03 -0700
Message-ID: <CAKywueREsB2gfrOoAiExUQg98MDcUtdjQD2-jd5ET3NqsdmE2A@mail.gmail.com>
Subject: Re: [Patch v2 1/2] CIFS: Fix an issue with re-sending wdata when
 transport returning -EAGAIN
To:     Long Li <longli@microsoft.com>
Cc:     Steve French <sfrench@samba.org>,
        linux-cifs <linux-cifs@vger.kernel.org>,
        samba-technical <samba-technical@lists.samba.org>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>
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=D0=BF=D1=82, 15 =D0=BC=D0=B0=D1=80. 2019 =D0=B3. =D0=B2 00:56, Long Li <lo=
ngli@linuxonhyperv.com>:
>
> From: Long Li <longli@microsoft.com>
>
> When sending a wdata, transport may return -EAGAIN. In this case
> we should re-obtain credits because the session may have been
> reconnected.
>
> Change in v2: adjust_credits before re-sending
>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
>  fs/cifs/file.c | 77 ++++++++++++++++++++++++++++++++++------------------=
------
>  1 file changed, 45 insertions(+), 32 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 9b53f33137b3..321df1d27422 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2620,43 +2620,56 @@ cifs_resend_wdata(struct cifs_writedata *wdata, s=
truct list_head *wdata_list,
>         struct TCP_Server_Info *server =3D
>                 tlink_tcon(wdata->cfile->tlink)->ses->server;
>
> -       /*
> -        * Wait for credits to resend this wdata.
> -        * Note: we are attempting to resend the whole wdata not in segme=
nts
> -        */
>         do {
> -               rc =3D server->ops->wait_mtu_credits(server, wdata->bytes=
, &wsize,
> -                                                  &credits);
> +               if (wdata->cfile->invalidHandle) {
> +                       rc =3D cifs_reopen_file(wdata->cfile, false);
> +                       if (rc =3D=3D -EAGAIN)
> +                               continue;
> +                       else if (rc)
> +                               break;
> +               }
>
> -               if (rc)
> -                       goto out;
>
> -               if (wsize < wdata->bytes) {
> -                       add_credits_and_wake_if(server, &credits, 0);
> -                       msleep(1000);
> -               }
> -       } while (wsize < wdata->bytes);
> +               /*
> +                * Wait for credits to resend this wdata.
> +                * Note: we are attempting to resend the whole wdata not =
in
> +                * segments
> +                */
> +               do {
> +                       rc =3D server->ops->wait_mtu_credits(server, wdat=
a->bytes,
> +                                               &wsize, &credits);
> +                       if (rc)
> +                               goto fail;
> +
> +                       if (wsize < wdata->bytes) {
> +                               add_credits_and_wake_if(server, &credits,=
 0);
> +                               msleep(1000);
> +                       }
> +               } while (wsize < wdata->bytes);
> +               wdata->credits =3D credits;
>
> -       wdata->credits =3D credits;
> -       rc =3D -EAGAIN;
> -       while (rc =3D=3D -EAGAIN) {
> -               rc =3D 0;
> -               if (wdata->cfile->invalidHandle)
> -                       rc =3D cifs_reopen_file(wdata->cfile, false);
> -               if (!rc)
> -                       rc =3D server->ops->async_writev(wdata,
> +               rc =3D adjust_credits(server, &wdata->credits, wdata->byt=
es);
> +
> +               if (!rc) {
> +                       if (wdata->cfile->invalidHandle)
> +                               rc =3D -EAGAIN;
> +                       else
> +                               rc =3D server->ops->async_writev(wdata,
>                                         cifs_uncached_writedata_release);
> -       }
> +               }
>
> -       if (!rc) {
> -               list_add_tail(&wdata->list, wdata_list);
> -               return 0;
> -       }
> +               /* If the write was successfully sent, we are done */
> +               if (!rc) {
> +                       list_add_tail(&wdata->list, wdata_list);
> +                       return 0;
> +               }
>
> -       add_credits_and_wake_if(server, &wdata->credits, 0);
> -out:
> -       kref_put(&wdata->refcount, cifs_uncached_writedata_release);
> +               /* Roll back credits and retry if needed */
> +               add_credits_and_wake_if(server, &wdata->credits, 0);
> +       } while (rc =3D=3D -EAGAIN);
>
> +fail:
> +       kref_put(&wdata->refcount, cifs_uncached_writedata_release);
>         return rc;
>  }
>
> @@ -2884,12 +2897,12 @@ static void collect_uncached_write_data(struct ci=
fs_aio_ctx *ctx)
>                                                 wdata->bytes, &tmp_from,
>                                                 ctx->cfile, cifs_sb, &tmp=
_list,
>                                                 ctx);
> +
> +                                       kref_put(&wdata->refcount,
> +                                               cifs_uncached_writedata_r=
elease);
>                                 }
>
>                                 list_splice(&tmp_list, &ctx->list);
> -
> -                               kref_put(&wdata->refcount,
> -                                        cifs_uncached_writedata_release)=
;
>                                 goto restart_loop;
>                         }
>                 }
> --
> 2.14.1
>

Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>

--
Best regards,
Pavel Shilovsky