[PATCH v4] cifs: Do not modify mid entry after submitting I/O in cifs_call_async

[Steve French]

merged into cifs-2.6.git for-next

On Wed, Jun 28, 2017 at 5:55 PM, Long Li <longli at exchange.microsoft.com> wrote:
> From: Long Li <longli at microsoft.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 at microsoft.com>
> Reviewed-by: Pavel Shilovsky <pshilov at microsoft.com>
> ---
>  fs/cifs/transport.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index 47a125e..7efbab0 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -536,11 +536,14 @@ 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 may 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,

Steve