RE: [RFC PATCH 05/09] Change RDMA send to regonize page offset in the 1st page

[Long Li <longli@microsoft.com>]

> Subject: Re: [RFC PATCH 05/09] Change RDMA send to regonize page offset
> in the 1st page
> 
> On 5/17/2018 5:22 PM, Long Li wrote:
> > From: Long Li <longli@microsoft.com>
> 
> There's a typo "recognize" in the patch title
> 
> 
> > When doing RDMA send, the offset needs to be checked as data may start
> > in an offset in the 1st page.
> 
> Doesn't this patch alter the generic smb2pdu.c code too? I think this should
> note "any" send, not just RDMA?

Yes, but for TCP the direct_pages and page_offset are always NULL and 0 when cache=rdma is in mounting options, so it doesn't really affect he TCP code path in this patch set.

This behavior can be changed, and it will work with TCP too.

> 
> Tom.
> 
> >
> > Signed-off-by: Long Li <longli@microsoft.com>
> > ---
> >   fs/cifs/smb2pdu.c   |  3 ++-
> >   fs/cifs/smbdirect.c | 25 +++++++++++++++++++------
> >   2 files changed, 21 insertions(+), 7 deletions(-)
> >
> > diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c index
> > 5097f28..fdcf97e 100644
> > --- a/fs/cifs/smb2pdu.c
> > +++ b/fs/cifs/smb2pdu.c
> > @@ -3015,7 +3015,8 @@ smb2_async_writev(struct cifs_writedata *wdata,
> >
> >   	rqst.rq_iov = iov;
> >   	rqst.rq_nvec = 2;
> > -	rqst.rq_pages = wdata->pages;
> > +	rqst.rq_pages = wdata->direct_pages ? wdata->direct_pages :
> wdata->pages;
> > +	rqst.rq_offset = wdata->page_offset;
> >   	rqst.rq_npages = wdata->nr_pages;
> >   	rqst.rq_pagesz = wdata->pagesz;
> >   	rqst.rq_tailsz = wdata->tailsz;
> > diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c index
> > b0a1955..b46586d 100644
> > --- a/fs/cifs/smbdirect.c
> > +++ b/fs/cifs/smbdirect.c
> > @@ -2084,8 +2084,10 @@ int smbd_send(struct smbd_connection *info,
> > struct smb_rqst *rqst)
> >
> >   	/* add in the page array if there is one */
> >   	if (rqst->rq_npages) {
> > -		buflen += rqst->rq_pagesz * (rqst->rq_npages - 1);
> > -		buflen += rqst->rq_tailsz;
> > +		if (rqst->rq_npages == 1)
> > +			buflen += rqst->rq_tailsz;
> > +		else
> > +			buflen += rqst->rq_pagesz * (rqst->rq_npages - 1) -
> > +rqst->rq_offset + rqst->rq_tailsz;
> >   	}
> >
> >   	if (buflen + sizeof(struct smbd_data_transfer) > @@ -2182,8
> > +2184,19 @@ int smbd_send(struct smbd_connection *info, struct
> > smb_rqst *rqst)
> >
> >   	/* now sending pages if there are any */
> >   	for (i = 0; i < rqst->rq_npages; i++) {
> > -		buflen = (i == rqst->rq_npages-1) ?
> > -			rqst->rq_tailsz : rqst->rq_pagesz;
> > +		unsigned int offset = 0;
> > +		if (i == 0)
> > +			offset = rqst->rq_offset;
> > +		if (rqst->rq_npages == 1 || i == rqst->rq_npages-1)
> > +			buflen = rqst->rq_tailsz;
> > +		else {
> > +			/* We have at least two pages, and this is not the last
> page */
> > +			if (i == 0)
> > +				buflen = rqst->rq_pagesz - rqst->rq_offset;
> > +			else
> > +				buflen = rqst->rq_pagesz;
> > +		}
> > +
> >   		nvecs = (buflen + max_iov_size - 1) / max_iov_size;
> >   		log_write(INFO, "sending pages buflen=%d nvecs=%d\n",
> >   			buflen, nvecs);
> > @@ -2194,9 +2207,9 @@ int smbd_send(struct smbd_connection *info,
> struct smb_rqst *rqst)
> >   			remaining_data_length -= size;
> >   			log_write(INFO, "sending pages i=%d offset=%d
> size=%d"
> >   				" remaining_data_length=%d\n",
> > -				i, j*max_iov_size, size,
> remaining_data_length);
> > +				i, j*max_iov_size+offset, size,
> remaining_data_length);
> >   			rc = smbd_post_send_page(
> > -				info, rqst->rq_pages[i], j*max_iov_size,
> > +				info, rqst->rq_pages[i], j*max_iov_size +
> offset,
> >   				size, remaining_data_length);
> >   			if (rc)
> >   				goto done;
> >