The patch titled
svcrdma: check num_sge when setting LAST_CTXT bit
has been added to the -mm tree. Its filename is
svcrdma-check-num_sge-when-setting-last_ctxt-bit.patch
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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: svcrdma: check num_sge when setting LAST_CTXT bit
From: Tom Tucker <tom@xxxxxxxxxxxxxxxxxxxxx>
The RDMACTXT_F_LAST_CTXT bit was getting set incorrectly when the last chunk
in the read-list spanned multiple pages. This resulted in a kernel panic when
the wrong context was used to build the RPC iovec page list.
RDMA_READ is used to fetch RPC data from the client for NFS_WRITE requests. A
scatter-gather is used to map the advertised client side buffer to the
server-side iovec and associated page list.
WR contexts are used to convey which scatter-gather entries are handled by
each WR. When the write data is large, a single RPC may require multiple
RDMA_READ requests so the contexts for a single RPC are chained together in a
linked list. The last context in this list is marked with a bit
RDMACTXT_F_LAST_CTXT so that when this WR completes, the CQ handler code can
enqueue the RPC for processing.
The code in rdma_read_xdr was setting this bit on the last two contexts on
this list when the last read-list chunk spanned multiple pages. This caused
the svc_rdma_recvfrom logic to incorrectly build the RPC and caused the kernel
to crash because the second-to-last context doesn't contain the iovec page
list.
Modified the condition that sets this bit so that it correctly detects the
last context for the RPC.
Signed-off-by: Tom Tucker <tom@xxxxxxxxxxxxxxxxxxxxx>
Tested-by: Roland Dreier <rolandd@xxxxxxxxx>
Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)
diff -puN net/sunrpc/xprtrdma/svc_rdma_recvfrom.c~svcrdma-check-num_sge-when-setting-last_ctxt-bit net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c~svcrdma-check-num_sge-when-setting-last_ctxt-bit
+++ a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -322,15 +322,6 @@ next_sge:
ctxt->direction = DMA_FROM_DEVICE;
clear_bit(RDMACTXT_F_READ_DONE, &ctxt->flags);
clear_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
- if ((ch+1)->rc_discrim == 0) {
- /*
- * Checked in sq_cq_reap to see if we need to
- * be enqueued
- */
- set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
- ctxt->next = hdr_ctxt;
- hdr_ctxt->next = head;
- }
/* Prepare READ WR */
memset(&read_wr, 0, sizeof read_wr);
@@ -348,7 +339,17 @@ next_sge:
rdma_set_ctxt_sge(ctxt, &sge[ch_sge_ary[ch_no].start],
&sgl_offset,
read_wr.num_sge);
-
+ if (((ch+1)->rc_discrim == 0) &&
+ (read_wr.num_sge == ch_sge_ary[ch_no].count)) {
+ /*
+ * Mark the last RDMA_READ with a bit to
+ * indicate all RPC data has been fetched from
+ * the client and the RPC needs to be enqueued.
+ */
+ set_bit(RDMACTXT_F_LAST_CTXT, &ctxt->flags);
+ ctxt->next = hdr_ctxt;
+ hdr_ctxt->next = head;
+ }
/* Post the read */
err = svc_rdma_send(xprt, &read_wr);
if (err) {
_
Patches currently in -mm which might be from tom@xxxxxxxxxxxxxxxxxxxxx are
origin.patch
svcrdma-check-num_sge-when-setting-last_ctxt-bit.patch
git-nfsd.patch
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