linux-kernel - Re: [PATCH v3] cifs: Do not modify mid entry after submitting I/O in cifs_call

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Message-ID: <CAKywueSce0nkKa986RC6CmDo0U7zcC7ou3qzEjcraKm+=t_GWA@mail.gmail.com>
Date:   Wed, 28 Jun 2017 15:23:01 -0700
From:   Pavel Shilovsky <piastryyy@...il.com>
To:     Long Li <longli@...hange.microsoft.com>
Cc:     Steve French <sfrench@...ba.org>,
        linux-cifs <linux-cifs@...r.kernel.org>,
        samba-technical <samba-technical@...ts.samba.org>,
        Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Long Li <longli@...rosoft.com>
Subject: Re: [PATCH v3] cifs: Do not modify mid entry after submitting I/O in cifs_call_async

2017-06-28 15:02 GMT-07:00 Long Li <longli@...hange.microsoft.com>:
> From: Long Li <longli@...rosoft.com>
>
> In cifs_call_async, server may respond as soon as I/O is submitted. Because
> mid entry is freed on the return path, it should not be modified after I/O
> is submitted.
>
> cifs_save_when_sent modifies the sent timestamp in mid entry, and should not
> be called after I/O. Call it before I/O.
>
> Signed-off-by: Long Li <longli@...rosoft.com>
> ---
>  fs/cifs/transport.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index 47a125e..f49b73f 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -536,11 +536,13 @@ cifs_call_async(struct TCP_Server_Info *server, struct smb_rqst *rqst,
>         list_add_tail(&mid->qhead, &server->pending_mid_q);
>         spin_unlock(&GlobalMid_Lock);
>
> -
> +       /* Need to store the time in mid before calling I/O. For call_async,
> +        * I/O response can come back and free the mid entry on another thread.
> +        */
> +       cifs_save_when_sent(mid);
>         cifs_in_send_inc(server);
>         rc = smb_send_rqst(server, rqst, flags);
>         cifs_in_send_dec(server);
> -       cifs_save_when_sent(mid);
>
>         if (rc < 0) {
>                 server->sequence_number -= 2;
> --
> 2.7.4
>
> --
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Thanks! Please fix the comment style to

/*
 * ....
 */

Other than that -

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

--
Best regards,
Pavel Shilovsky