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

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On 5/30/2018 3:48 PM, Long Li wrote:
From: Long Li <longli@xxxxxxxxxxxxx>

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

Signed-off-by: Long Li <longli@xxxxxxxxxxxxx>
---
  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--;

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