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authorTom Tucker <tom@opengridcomputing.com>2008-03-25 22:27:19 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-03-26 11:24:19 -0700
commitc8237a5fcea9d49a73275b4c8f541dd42f8da1a4 (patch)
treeb93287513360a027baf3a8936c457ab2e21aa532 /net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
parent12c22d6ef299ccf0955e5756eb57d90d7577ac68 (diff)
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SVCRDMA: Check num_sge when setting LAST_CTXT bit
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@opengridcomputing.com> Tested-by: Roland Dreier <rolandd@cisco.com> Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'net/sunrpc/xprtrdma/svc_rdma_recvfrom.c')
-rw-r--r--net/sunrpc/xprtrdma/svc_rdma_recvfrom.c21
1 files changed, 11 insertions, 10 deletions
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index 971271602dd0..c22d6b6f2db4 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/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) {