Subject: RE: [Patch v2 1/6] cifs: smbd: Check for iov length on sending the last iov
-----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().
It is safe. The transport sending path is locked by TCP_Server_Info->srv_mutex.
The transport receiving path is single threaded.
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