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Chuck LeverandGreg Kroah-Hartman
5573193597
[ Upstream commit60e7870052] rpcrdma_prepare_send_sges() gets a sendctx before it maps the SGEs for the Send WR. If one of the mapping helpers fails, no Send WR is posted, so no Send completion is guaranteed to advance rb_sc_tail. Current cleanup clears sc_req so a later completion can sweep over that slot, but a consecutive run of preparation failures can still advance rb_sc_head until the ring appears full. At that point rpcrdma_sendctx_get_locked() returns NULL and no Send can be posted to produce the completion needed to recover the ring. The trigger requires CONFIG_SUNRPC_XPRT_RDMA and an NFS/RDMA mount. Mount setup and reliable DMA-map fault injection require local admin authority. Unprivileged I/O on an existing mount can exercise the send path, but a remote peer alone cannot force this local DMA-map failure. Add rpcrdma_sendctx_unget_locked() for the single-consumer send path to rewind rb_sc_head when the just-acquired sendctx is canceled before ib_post_send(). Wake waiters after making the slot available again. After the rewind, every slot the completion sweep visits belongs to a posted Send, so rpcrdma_sendctx_put_locked() no longer needs to test sc_req before unmapping. Fixes:ae72950abf("xprtrdma: Add data structure to manage RDMA Send arguments") Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com> Signed-off-by: Sasha Levin <sashal@kernel.org>