svcrdma: Remove max_sge check at connect time
commit e248aa7be86e8179f20ac0931774ecd746f3f5bf upstream. Two and a half years ago, the client was changed to use gathered Send for larger inline messages, in commit 655fec69 ("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 25fd86ec ("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: NDon Dutile <ddutile@redhat.com> Fixes: 25fd86ec ("svcrdma: Don't overrun the SGE array in ...") Cc: stable@vger.kernel.org Signed-off-by: NChuck Lever <chuck.lever@oracle.com> Signed-off-by: NJ. Bruce Fields <bfields@redhat.com> Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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