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

From: Tom Talpey
Date: Sat Jun 23 2018 - 22:16:27 EST


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--;