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SubjectRE: [Patch v2 08/15] CIFS: SMBD: Support page offset in RDMA send
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> Subject: Re: [Patch v2 08/15] CIFS: SMBD: Support page offset in RDMA send
>
> On 5/30/2018 3:48 PM, Long Li wrote:
> > From: Long Li <longli@microsoft.com>
> >
> > The RDMA send function needs to look at offset in the request pages,
> > and send data starting from there.
> >
> > Signed-off-by: Long Li <longli@microsoft.com>
> > ---
> > fs/cifs/smbdirect.c | 27 +++++++++++++++++++--------
> > 1 file changed, 19 insertions(+), 8 deletions(-)
> >
> > diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c index
> > c62f7c9..6141e3c 100644
> > --- a/fs/cifs/smbdirect.c
> > +++ b/fs/cifs/smbdirect.c
> > @@ -17,6 +17,7 @@
> > #include <linux/highmem.h>
> > #include "smbdirect.h"
> > #include "cifs_debug.h"
> > +#include "cifsproto.h"
> >
> > static struct smbd_response *get_empty_queue_buffer(
> > struct smbd_connection *info);
> > @@ -2082,7 +2083,7 @@ int smbd_send(struct smbd_connection *info,
> struct smb_rqst *rqst)
> > struct kvec vec;
> > int nvecs;
> > int size;
> > - int buflen = 0, remaining_data_length;
> > + unsigned int buflen = 0, remaining_data_length;
> > int start, i, j;
> > int max_iov_size =
> > info->max_send_size - sizeof(struct smbd_data_transfer);
> @@
> > -2113,10 +2114,17 @@ int smbd_send(struct smbd_connection *info,
> struct smb_rqst *rqst)
> > buflen += iov[i].iov_len;
> > }
> >
> > - /* add in the page array if there is one */
> > + /*
> > + * Add in the page array if there is one. The caller needs to set
> > + * rq_tailsz to PAGE_SIZE when the buffer has multiple pages and
> > + * ends at page boundary
> > + */
> > 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;
> > }
>
> This code is really confusing and redundant. It tests npages > 0, then tests
> npages == 1, then does an else. Why not call the helper like the following
> smbd_send()?

This code needs to get the combined length of all the pages in the request (but excluding iov, this is different to the function rqst_len in patch 05), but the following is for getting a single page from the request.

I can simplify the code a little bit by following your suggestion in patch 05.

>
> Tom.
>
> >
> > if (buflen + sizeof(struct smbd_data_transfer) > @@ -2213,8 +2221,9
> > @@ 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;
> > +
> > + rqst_page_get_length(rqst, i, &buflen, &offset);
> > nvecs = (buflen + max_iov_size - 1) / max_iov_size;
> > log_write(INFO, "sending pages buflen=%d nvecs=%d\n",
> > buflen, nvecs);
> > @@ -2225,9 +2234,11 @@ 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;
> >
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