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SubjectRe: [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@microsoft.com>
>
> RDMA recv function needs to place data to the correct place starting at
> page offset.
>
> Signed-off-by: Long Li <longli@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--;
>

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