svcrdma: handle rdma read with a non-zero initial page offset

The server rdma_read_chunk_lcl() and rdma_read_chunk_frmr() functions
were not taking into account the initial page_offset when determining
the rdma read length.  This resulted in a read who's starting address
and length exceeded the base/bounds of the frmr.

The server gets an async error from the rdma device and kills the
connection, and the client then reconnects and resends.  This repeats
indefinitely, and the application hangs.

Most work loads don't tickle this bug apparently, but one test hit it
every time: building the linux kernel on a 16 core node with 'make -j
16 O=/mnt/0' where /mnt/0 is a ramdisk mounted via NFSRDMA.

This bug seems to only be tripped with devices having small fastreg page
list depths.  I didn't see it with mlx4, for instance.

Fixes: 0bf4828983df ('svcrdma: refactor marshalling logic')
Signed-off-by: Steve Wise <[email protected]>
Tested-by: Chuck Lever <[email protected]>
Cc: [email protected]
Signed-off-by: J. Bruce Fields <[email protected]>

diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index cb51742840740f790d24797e585e7fb520646a09..5f6ca47092b039a1c927420a51b851a83047b5fc 100644 (file)
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -136,7 +136,8 @@ int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt,
        ctxt->direction = DMA_FROM_DEVICE;
        ctxt->read_hdr = head;
        pages_needed = min_t(int, pages_needed, xprt->sc_max_sge_rd);
-       read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
+       read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset,
+                    rs_length);
 
        for (pno = 0; pno < pages_needed; pno++) {
                int len = min_t(int, rs_length, PAGE_SIZE - pg_off);
@@ -235,7 +236,8 @@ int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt,
        ctxt->direction = DMA_FROM_DEVICE;
        ctxt->frmr = frmr;
        pages_needed = min_t(int, pages_needed, xprt->sc_frmr_pg_list_len);
-       read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
+       read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset,
+                    rs_length);
 
        frmr->kva = page_address(rqstp->rq_arg.pages[pg_no]);
        frmr->direction = DMA_FROM_DEVICE;