Re: [Patch v2 09/15] CIFS: SMBD: Support page offset in RDMA recv

[Tom Talpey]

On 5/30/2018 3:48 PM, Long Li wrote:

From: Long Li <lon...@microsoft.com>

RDMA recv function needs to place data to the correct place starting at
page offset.

Signed-off-by: Long Li <lon...@microsoft.com>
---
  fs/cifs/smbdirect.c | 18 +++++++++++-------
  1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index 6141e3c..ba53c52 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -2004,10 +2004,12 @@ static int smbd_recv_buf(struct smbd_connection *info, 
char *buf,
   * return value: actual data read
   */
  static int smbd_recv_page(struct smbd_connection *info,
-               struct page *page, unsigned int to_read)
+               struct page *page, unsigned int page_offset,
+               unsigned int to_read)
  {
        int ret;
        char *to_address;
+       void *page_address;

/* make sure we have the page ready for read */

        ret = wait_event_interruptible(
@@ -2015,16 +2017,17 @@ static int smbd_recv_page(struct smbd_connection *info,
                info->reassembly_data_length >= to_read ||
                        info->transport_status != SMBD_CONNECTED);
        if (ret)
-               return 0;
+               return ret;

/* now we can read from reassembly queue and not sleep */

-       to_address = kmap_atomic(page);
+       page_address = kmap_atomic(page);
+       to_address = (char *) page_address + page_offset;

log_read(INFO, "reading from page=%p address=%p to_read=%d\n",

                page, to_address, to_read);

ret = smbd_recv_buf(info, to_address, to_read);

-       kunmap_atomic(to_address);
+       kunmap_atomic(page_address);

Is "page" truly not mapped? This kmap/kunmap for each received 4KB is
very expensive. Is there not a way to keep a kva for the reassembly
queue segments?

return ret;

  }
@@ -2038,7 +2041,7 @@ int smbd_recv(struct smbd_connection *info, struct msghdr 
*msg)
  {
        char *buf;
        struct page *page;
-       unsigned int to_read;
+       unsigned int to_read, page_offset;
        int rc;

info->smbd_recv_pending++;

@@ -2052,15 +2055,16 @@ int smbd_recv(struct smbd_connection *info, struct 
msghdr *msg)

case READ | ITER_BVEC:

                page = msg->msg_iter.bvec->bv_page;
+               page_offset = msg->msg_iter.bvec->bv_offset;
                to_read = msg->msg_iter.bvec->bv_len;
-               rc = smbd_recv_page(info, page, to_read);
+               rc = smbd_recv_page(info, page, page_offset, to_read);
                break;

default:

                /* It's a bug in upper layer to get there */
                cifs_dbg(VFS, "CIFS: invalid msg type %d\n",
                        msg->msg_iter.type);
-               rc = -EIO;
+               rc = -EINVAL;
        }

info->smbd_recv_pending--;