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xprtrdma: Revert 586a0787ce 

Commit 9ed5af268e ("SUNRPC: Clean up the handling of page padding
in rpc_prepare_reply_pages()") [Dec 2020] affects RPC Replies that
have a data payload (i.e., Write chunks).

rpcrdma_prepare_readch(), as its name suggests, sets up Read chunks
which are data payloads within RPC Calls. Those payloads are
constructed by xdr_write_pages(), which continues to stuff the call
buffer's tail kvec with the payload's XDR roundup. Thus removing
the tail buffer logic in rpcrdma_prepare_readch() was the wrong
thing to do.

Fixes: 586a0787ce ("xprtrdma: Clean up rpcrdma_prepare_readch()")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Chuck Lever 2021-05-26 15:35:20 -04:00 committed by Trond Myklebust
parent e67afa7ee4
commit ae605ee983
1 changed files with 18 additions and 9 deletions
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27
net/sunrpc/xprtrdma/rpc_rdma.c
View File

@ -628,8 +628,9 @@ out_mapping_err:
return false;
}
/* The tail iovec might not reside in the same page as the
* head iovec.
/* The tail iovec may include an XDR pad for the page list,
* as well as additional content, and may not reside in the
* same page as the head iovec.
*/
static bool rpcrdma_prepare_tail_iov(struct rpcrdma_req *req,
struct xdr_buf *xdr,
@ -747,19 +748,27 @@ static bool rpcrdma_prepare_readch(struct rpcrdma_xprt *r_xprt,
struct rpcrdma_req *req,
struct xdr_buf *xdr)
{
struct kvec *tail = &xdr->tail[0];
if (!rpcrdma_prepare_head_iov(r_xprt, req, xdr->head[0].iov_len))
return false;
/* If there is a Read chunk, the page list is handled
/* If there is a Read chunk, the page list is being handled
* via explicit RDMA, and thus is skipped here.
*/
if (tail->iov_len) {
if (!rpcrdma_prepare_tail_iov(req, xdr,
offset_in_page(tail->iov_base),
tail->iov_len))
/* Do not include the tail if it is only an XDR pad */
if (xdr->tail[0].iov_len > 3) {
unsigned int page_base, len;
/* If the content in the page list is an odd length,
* xdr_write_pages() adds a pad at the beginning of
* the tail iovec. Force the tail's non-pad content to
* land at the next XDR position in the Send message.
*/
page_base = offset_in_page(xdr->tail[0].iov_base);
len = xdr->tail[0].iov_len;
page_base += len & 3;
len -= len & 3;
if (!rpcrdma_prepare_tail_iov(req, xdr, page_base, len))
return false;
kref_get(&req->rl_kref);
}