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SUNRPC: Fix large reads on NFS/RDMA 

After commit a11a2bf4, "SUNRPC: Optimise away unnecessary data moves
in xdr_align_pages", Thu Aug 2 13:21:43 2012, READs larger than a
few hundred bytes via NFS/RDMA no longer work.  This commit exposed
a long-standing bug in rpcrdma_inline_fixup().

I reproduce this with an rsize=4096 mount using the cthon04 basic
tests.  Test 5 fails with an EIO error.

For my reproducer, kernel log shows:

  NFS: server cheating in read reply: count 4096 > recvd 0

rpcrdma_inline_fixup() is zeroing the xdr_stream::page_len field,
and xdr_align_pages() is now returning that value to the READ XDR
decoder function.

That field is set up by xdr_inline_pages() by the READ XDR encoder
function.  As far as I can tell, it is supposed to be left alone
after that, as it describes the dimensions of the reply xdr_stream,
not the contents of that stream.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=68391
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Chuck Lever 2014-03-12 12:51:30 -04:00 committed by Trond Myklebust
parent a7697f6ff8
commit 2b7bbc963d
1 changed files with 1 additions and 3 deletions
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4
net/sunrpc/xprtrdma/rpc_rdma.c
View File

@ -649,9 +649,7 @@ rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
break;
page_base = 0;
}
rqst->rq_rcv_buf.page_len = olen - copy_len;
} else
rqst->rq_rcv_buf.page_len = 0;
}
if (copy_len && rqst->rq_rcv_buf.tail[0].iov_len) {
curlen = copy_len;