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SubjectRE: [Patch v2 1/6] cifs: smbd: Check for iov length on sending the last iov
Date
> -----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 last iov
>
> From: Long Li <longli@microsoft.com>
>
> 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.
>
> If this is the latest iov, stop and proceed to send pages.
>
> 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(+)
>
> 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 == rqst->rq_nvec)
> + break;
> }
> start = i;
> buflen = 0;
> --
> 2.7.4

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