RE: [Patch v2 3/6] cifs: smbd: Avoid allocating iov on the stack

[Long Li]

> Subject: Re: [Patch v2 3/6] cifs: smbd: Avoid allocating iov on the stack
> 
> Didn't see any obvious problems, but can you fix the checkpatch warnings
> and resend to the list (I am more concerned about the last two warnings
> rather than the first one).

Yes, I will fix it and resend.

> 
> $ scripts/checkpatch.pl 0001-cifs-smbd-Avoid-allocating-iov-on-the-
> stack.patch
> WARNING: line over 80 characters
> #60: FILE: fs/cifs/smbdirect.c:2106:
> +        log_write(ERR, "expected the pdu length in 1st iov, but got
> 0x%lu\n", rqst->rq_iov[0].iov_len);
> 
> ERROR: Prefixing 0x with decimal output is defective
> #60: FILE: fs/cifs/smbdirect.c:2106:
> +        log_write(ERR, "expected the pdu length in 1st iov, but got
> 0x%lu\n", rqst->rq_iov[0].iov_len);
> 
> WARNING: braces {} are not necessary for single statement blocks
> #69: FILE: fs/cifs/smbdirect.c:2112:
> +    for (i = 0; i < rqst->rq_nvec-1; i++) {
>          buflen += iov[i].iov_len;
>      }
> 
> total: 1 errors, 2 warnings, 65 lines checked
> 
> NOTE: For some of the reported defects, checkpatch may be able to
>       mechanically convert to the typical style using --fix or --fix-inplace.
> 
> 0001-cifs-smbd-Avoid-allocating-iov-on-the-stack.patch has style problems,
> please review.
> 
> On Tue, Apr 17, 2018 at 2:17 PM, Long Li <longli@xxxxxxxxxxxxxxxxx> wrote:
> > From: Long Li <longli@xxxxxxxxxxxxx>
> >
> > It's not necessary to allocate another iov when going through the
> > buffers in smbd_send() through RDMA send.
> >
> > Remove it to reduce stack size.
> >
> > Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> >  fs/cifs/smbdirect.c | 36 ++++++++++++------------------------
> >  1 file changed, 12 insertions(+), 24 deletions(-)
> >
> > diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c index
> > b5c6c0d..f575e9a 100644
> > --- a/fs/cifs/smbdirect.c
> > +++ b/fs/cifs/smbdirect.c
> > @@ -2088,7 +2088,7 @@ int smbd_send(struct smbd_connection *info,
> struct smb_rqst *rqst)
> >         int start, i, j;
> >         int max_iov_size =
> >                 info->max_send_size - sizeof(struct smbd_data_transfer);
> > -       struct kvec iov[SMBDIRECT_MAX_SGE];
> > +       struct kvec *iov;
> >         int rc;
> >
> >         info->smbd_send_pending++;
> > @@ -2099,32 +2099,20 @@ int smbd_send(struct smbd_connection *info,
> struct smb_rqst *rqst)
> >         }
> >
> >         /*
> > -        * This usually means a configuration error
> > -        * We use RDMA read/write for packet size >
> rdma_readwrite_threshold
> > -        * as long as it's properly configured we should never get into this
> > -        * situation
> > -        */
> > -       if (rqst->rq_nvec + rqst->rq_npages > SMBDIRECT_MAX_SGE) {
> > -               log_write(ERR, "maximum send segment %x exceeding %x\n",
> > -                        rqst->rq_nvec + rqst->rq_npages, SMBDIRECT_MAX_SGE);
> > -               rc = -EINVAL;
> > -               goto done;
> > -       }
> > -
> > -       /*
> > -        * Remove the RFC1002 length defined in MS-SMB2 section 2.1
> > -        * It is used only for TCP transport
> > +        * Skip the RFC1002 length defined in MS-SMB2 section 2.1
> > +        * It is used only for TCP transport in the iov[0]
> >          * In future we may want to add a transport layer under protocol
> >          * layer so this will only be issued to TCP transport
> >          */
> > -       iov[0].iov_base = (char *)rqst->rq_iov[0].iov_base + 4;
> > -       iov[0].iov_len = rqst->rq_iov[0].iov_len - 4;
> > -       buflen += iov[0].iov_len;
> > +
> > +       if (rqst->rq_iov[0].iov_len != 4) {
> > +               log_write(ERR, "expected the pdu length in 1st iov, but got
> 0x%lu\n", rqst->rq_iov[0].iov_len);
> > +               return -EINVAL;
> > +       }
> > +       iov = &rqst->rq_iov[1];
> >
> >         /* total up iov array first */
> > -       for (i = 1; i < rqst->rq_nvec; i++) {
> > -               iov[i].iov_base = rqst->rq_iov[i].iov_base;
> > -               iov[i].iov_len = rqst->rq_iov[i].iov_len;
> > +       for (i = 0; i < rqst->rq_nvec-1; i++) {
> >                 buflen += iov[i].iov_len;
> >         }
> >
> > @@ -2197,14 +2185,14 @@ int smbd_send(struct smbd_connection *info,
> struct smb_rqst *rqst)
> >                                                 goto done;
> >                                 }
> >                                 i++;
> > -                               if (i == rqst->rq_nvec)
> > +                               if (i == rqst->rq_nvec-1)
> >                                         break;
> >                         }
> >                         start = i;
> >                         buflen = 0;
> >                 } else {
> >                         i++;
> > -                       if (i == rqst->rq_nvec) {
> > +                       if (i == rqst->rq_nvec-1) {
> >                                 /* send out all remaining vecs */
> >                                 remaining_data_length -= buflen;
> >                                 log_write(INFO,
> > --
> > 2.7.4
> >
> > --
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> 
> 
> --
> Thanks,
> 
> Steve
> --
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