[1/2] cifs: add a warning if we try to to dequeue a deleted mid

cifs_delete_mid() is called once we are finished handling a mid and we
expect no more work done on this mid.

Add a warning if someone tries to dequeue a mid that has already been
flagged to be deleted.
Also change list_del() to list_del_init() so that if we have similar bugs
resurface in the future we will not oops.

Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
---
 fs/cifs/cifsglob.h  |  1 +
 fs/cifs/connect.c   | 10 +++++++++-
 fs/cifs/transport.c |  3 ++-
 3 files changed, 12 insertions(+), 2 deletions(-)

ср, 29 авг. 2018 г. в 17:13, Ronnie Sahlberg <lsahlber@redhat.com>:
>
> cifs_delete_mid() is called once we are finished handling a mid and we
> expect no more work done on this mid.
>
> Add a warning if someone tries to dequeue a mid that has already been
> flagged to be deleted.
> Also change list_del() to list_del_init() so that if we have similar bugs
> resurface in the future we will not oops.
>
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/cifsglob.h  |  1 +
>  fs/cifs/connect.c   | 10 +++++++++-
>  fs/cifs/transport.c |  3 ++-
>  3 files changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 0c9ab62c3df4..9dcaed031843 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1553,6 +1553,7 @@ static inline void free_dfs_info_array(struct dfs_info3_param *param,
>
>  /* Flags */
>  #define   MID_WAIT_CANCELLED    1 /* Cancelled while waiting for response */
> +#define   MID_DELETED            2 /* Mid has been dequeued/deleted */
>
>  /* Types of response buffer returned from SendReceive2 */
>  #define   CIFS_NO_BUFFER        0    /* Response buffer not returned */
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 4b82cf77da78..216b28e27ad0 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -659,7 +659,15 @@ dequeue_mid(struct mid_q_entry *mid, bool malformed)
>                 mid->mid_state = MID_RESPONSE_RECEIVED;
>         else
>                 mid->mid_state = MID_RESPONSE_MALFORMED;
> -       list_del_init(&mid->qhead);
> +       /*
> +        * Trying to handle/dequeue a mid after the send_recv()
> +        * function has finished processing it is a bug.
> +        */
> +       if (mid->mid_flags & MID_DELETED)
> +               printk_once(KERN_WARNING
> +                           "trying to dequeue a deleted mid\n");
> +       else
> +               list_del_init(&mid->qhead);
>         spin_unlock(&GlobalMid_Lock);
>  }
>
> diff --git a/fs/cifs/transport.c b/fs/cifs/transport.c
> index 78f96fa3d7d9..9cc9a127749e 100644
> --- a/fs/cifs/transport.c
> +++ b/fs/cifs/transport.c
> @@ -142,7 +142,8 @@ void
>  cifs_delete_mid(struct mid_q_entry *mid)
>  {
>         spin_lock(&GlobalMid_Lock);
> -       list_del(&mid->qhead);
> +       list_del_init(&mid->qhead);
> +       mid->mid_flags |= MID_DELETED;
>         spin_unlock(&GlobalMid_Lock);
>
>         DeleteMidQEntry(mid);
> --
> 2.13.3
>

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

--
Best regards,
Pavel Shilovsky