4.20-stable review patch. If anyone has any objections, please let me know.
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From: Chuck Lever chuck.lever@oracle.com
commit e248aa7be86e8179f20ac0931774ecd746f3f5bf upstream.
Two and a half years ago, the client was changed to use gathered Send for larger inline messages, in commit 655fec6987b ("xprtrdma: Use gathered Send for large inline messages"). Several fixes were required because there are a few in-kernel device drivers whose max_sge is 3, and these were broken by the change.
Apparently my memory is going, because some time later, I submitted commit 25fd86eca11c ("svcrdma: Don't overrun the SGE array in svc_rdma_send_ctxt"), and after that, commit f3c1fd0ee294 ("svcrdma: Reduce max_send_sges"). These too incorrectly assumed in-kernel device drivers would have more than a few Send SGEs available.
The fix for the server side is not the same. This is because the fundamental problem on the server is that, whether or not the client has provisioned a chunk for the RPC reply, the server must squeeze even the most complex RPC replies into a single RDMA Send. Failing in the send path because of Send SGE exhaustion should never be an option.
Therefore, instead of failing when the send path runs out of SGEs, switch to using a bounce buffer mechanism to handle RPC replies that are too complex for the device to send directly. That allows us to remove the max_sge check to enable drivers with small max_sge to work again.
Reported-by: Don Dutile ddutile@redhat.com Fixes: 25fd86eca11c ("svcrdma: Don't overrun the SGE array in ...") Cc: stable@vger.kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: J. Bruce Fields bfields@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/sunrpc/xprtrdma/svc_rdma_sendto.c | 105 +++++++++++++++++++++++++++++-- net/sunrpc/xprtrdma/svc_rdma_transport.c | 9 -- 2 files changed, 102 insertions(+), 12 deletions(-)
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c +++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c @@ -563,6 +563,99 @@ void svc_rdma_sync_reply_hdr(struct svcx DMA_TO_DEVICE); }
+/* If the xdr_buf has more elements than the device can + * transmit in a single RDMA Send, then the reply will + * have to be copied into a bounce buffer. + */ +static bool svc_rdma_pull_up_needed(struct svcxprt_rdma *rdma, + struct xdr_buf *xdr, + __be32 *wr_lst) +{ + int elements; + + /* xdr->head */ + elements = 1; + + /* xdr->pages */ + if (!wr_lst) { + unsigned int remaining; + unsigned long pageoff; + + pageoff = xdr->page_base & ~PAGE_MASK; + remaining = xdr->page_len; + while (remaining) { + ++elements; + remaining -= min_t(u32, PAGE_SIZE - pageoff, + remaining); + pageoff = 0; + } + } + + /* xdr->tail */ + if (xdr->tail[0].iov_len) + ++elements; + + /* assume 1 SGE is needed for the transport header */ + return elements >= rdma->sc_max_send_sges; +} + +/* The device is not capable of sending the reply directly. + * Assemble the elements of @xdr into the transport header + * buffer. + */ +static int svc_rdma_pull_up_reply_msg(struct svcxprt_rdma *rdma, + struct svc_rdma_send_ctxt *ctxt, + struct xdr_buf *xdr, __be32 *wr_lst) +{ + unsigned char *dst, *tailbase; + unsigned int taillen; + + dst = ctxt->sc_xprt_buf; + dst += ctxt->sc_sges[0].length; + + memcpy(dst, xdr->head[0].iov_base, xdr->head[0].iov_len); + dst += xdr->head[0].iov_len; + + tailbase = xdr->tail[0].iov_base; + taillen = xdr->tail[0].iov_len; + if (wr_lst) { + u32 xdrpad; + + xdrpad = xdr_padsize(xdr->page_len); + if (taillen && xdrpad) { + tailbase += xdrpad; + taillen -= xdrpad; + } + } else { + unsigned int len, remaining; + unsigned long pageoff; + struct page **ppages; + + ppages = xdr->pages + (xdr->page_base >> PAGE_SHIFT); + pageoff = xdr->page_base & ~PAGE_MASK; + remaining = xdr->page_len; + while (remaining) { + len = min_t(u32, PAGE_SIZE - pageoff, remaining); + + memcpy(dst, page_address(*ppages), len); + remaining -= len; + dst += len; + pageoff = 0; + } + } + + if (taillen) + memcpy(dst, tailbase, taillen); + + ctxt->sc_sges[0].length += xdr->len; + ib_dma_sync_single_for_device(rdma->sc_pd->device, + ctxt->sc_sges[0].addr, + ctxt->sc_sges[0].length, + DMA_TO_DEVICE); + + return 0; +} + /* svc_rdma_map_reply_msg - Map the buffer holding RPC message * @rdma: controlling transport * @ctxt: send_ctxt for the Send WR @@ -585,8 +678,10 @@ int svc_rdma_map_reply_msg(struct svcxpr u32 xdr_pad; int ret;
- if (++ctxt->sc_cur_sge_no >= rdma->sc_max_send_sges) - return -EIO; + if (svc_rdma_pull_up_needed(rdma, xdr, wr_lst)) + return svc_rdma_pull_up_reply_msg(rdma, ctxt, xdr, wr_lst); + + ++ctxt->sc_cur_sge_no; ret = svc_rdma_dma_map_buf(rdma, ctxt, xdr->head[0].iov_base, xdr->head[0].iov_len); @@ -617,8 +712,7 @@ int svc_rdma_map_reply_msg(struct svcxpr while (remaining) { len = min_t(u32, PAGE_SIZE - page_off, remaining);
- if (++ctxt->sc_cur_sge_no >= rdma->sc_max_send_sges) - return -EIO; + ++ctxt->sc_cur_sge_no; ret = svc_rdma_dma_map_page(rdma, ctxt, *ppages++, page_off, len); if (ret < 0) @@ -632,8 +726,7 @@ int svc_rdma_map_reply_msg(struct svcxpr len = xdr->tail[0].iov_len; tail: if (len) { - if (++ctxt->sc_cur_sge_no >= rdma->sc_max_send_sges) - return -EIO; + ++ctxt->sc_cur_sge_no; ret = svc_rdma_dma_map_buf(rdma, ctxt, base, len); if (ret < 0) return ret; --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c @@ -478,12 +478,9 @@ static struct svc_xprt *svc_rdma_accept( /* Transport header, head iovec, tail iovec */ newxprt->sc_max_send_sges = 3; /* Add one SGE per page list entry */ - newxprt->sc_max_send_sges += svcrdma_max_req_size / PAGE_SIZE; - if (newxprt->sc_max_send_sges > dev->attrs.max_send_sge) { - pr_err("svcrdma: too few Send SGEs available (%d needed)\n", - newxprt->sc_max_send_sges); - goto errout; - } + newxprt->sc_max_send_sges += (svcrdma_max_req_size / PAGE_SIZE) + 1; + if (newxprt->sc_max_send_sges > dev->attrs.max_send_sge) + newxprt->sc_max_send_sges = dev->attrs.max_send_sge; newxprt->sc_max_req_size = svcrdma_max_req_size; newxprt->sc_max_requests = svcrdma_max_requests; newxprt->sc_max_bc_requests = svcrdma_max_bc_requests;