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From:   "Michael Kelley (EOSG)" <Michael.H.Kelley@microsoft.com>
To:     Long Li <longli@microsoft.com>, Steve French <sfrench@samba.org>,
        "linux-cifs@vger.kernel.org" <linux-cifs@vger.kernel.org>,
        "samba-technical@lists.samba.org" <samba-technical@lists.samba.org>,
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        "linux-rdma@vger.kernel.org" <linux-rdma@vger.kernel.org>
CC:     "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [Patch v2 1/6] cifs: smbd: Check for iov length on sending the
 last iov
Thread-Topic: [Patch v2 1/6] cifs: smbd: Check for iov length on sending the
 last iov
Thread-Index: AQHT1oDjzGcq39RzU0qbElHNScrUY6QNco3g
Date:   Sun, 22 Apr 2018 23:27:08 +0000
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References: <20180417191710.14855-1-longli@linuxonhyperv.com>
In-Reply-To: <20180417191710.14855-1-longli@linuxonhyperv.com>
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> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org <linux-kernel-owner@vger.kernel.=
org> On Behalf
> Of Long Li
> Sent: Tuesday, April 17, 2018 12:17 PM
> To: Steve French <sfrench@samba.org>; linux-cifs@vger.kernel.org; samba-
> technical@lists.samba.org; linux-kernel@vger.kernel.org; linux-rdma@vger.=
kernel.org
> Cc: Long Li <longli@microsoft.com>; stable@vger.kernel.org
> Subject: [Patch v2 1/6] cifs: smbd: Check for iov length on sending the l=
ast iov
>=20
> From: Long Li <longli@microsoft.com>
>=20
> When sending the last iov that breaks into smaller buffers to fit the
> transfer size, it's necessary to check if this is the last iov.
>=20
> If this is the latest iov, stop and proceed to send pages.
>=20
> Signed-off-by: Long Li <longli@microsoft.com>
> Cc: stable@vger.kernel.org

Reviewed-by: Michael Kelley <mikelley@microsoft.com>

But a question unrelated to this change arose during my review:  At the
beginning and end of smbd_send(), the field smbd_send_pending is
incremented and decremented, respectively.   The increment/decrement
are not done as atomic operations.  Is this code guaranteed to be single
threaded?  If not, the count could become corrupted, and
smbd_destroy_rdma_work(), which waits for the count to become zero,
could hang.  A similar question applies to smbd_recv_pending in smbd_recv()=
.

> ---
>  fs/cifs/smbdirect.c | 2 ++
>  1 file changed, 2 insertions(+)
>=20
> diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
> index 90e673c..b5c6c0d 100644
> --- a/fs/cifs/smbdirect.c
> +++ b/fs/cifs/smbdirect.c
> @@ -2197,6 +2197,8 @@ int smbd_send(struct smbd_connection *info, struct =
smb_rqst *rqst)
>  						goto done;
>  				}
>  				i++;
> +				if (i =3D=3D rqst->rq_nvec)
> +					break;
>  			}
>  			start =3D i;
>  			buflen =3D 0;
> --
> 2.7.4