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xprtrdma: Decouple frwr_wp_create from frwr_map

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frwr_wp_create is the only caller of frwr_map outside the encode
path. It registers a single 4-byte write-pad region from a stack-
local rpcrdma_mr_seg. Inlining the registration logic directly
(sg_init_table + sg_set_page + ib_dma_map_sg + ib_map_mr_sg +
IOVA mangle + reg_wr setup) eliminates the coupling that would
otherwise complicate the removal of rpcrdma_mr_seg from frwr_map's
interface.

The inlined version adds a proper error-unwind ladder: on failure,
the DMA mapping (if established) is released, ep->re_write_pad_mr is
cleared, and the MR is returned to the transport free list. The old
frwr_map-based code relied on rpcrdma_mrs_destroy at teardown to
reclaim partially-initialized MRs.

This is a one-time setup path; duplicating ~20 lines is a reasonable
tradeoff for decoupling the write-pad registration from the data-
path MR registration.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Chuck Lever 2026-03-06 16:56:25 -05:00 committed by Trond Myklebust
parent 765bde47fe
commit 6f2e565fb3
1 changed files with 50 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
net/sunrpc/xprtrdma/frwr_ops.c
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@ -669,9 +669,13 @@ void frwr_unmap_async(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
*/
int frwr_wp_create(struct rpcrdma_xprt *r_xprt)
{
struct rpcrdma_buffer *buf = &r_xprt->rx_buf;
struct rpcrdma_ep *ep = r_xprt->rx_ep;
struct rpcrdma_mr_seg seg;
struct ib_reg_wr *reg_wr;
struct rpcrdma_mr *mr;
struct ib_mr *ibmr;
int dma_nents;
int ret;
mr = rpcrdma_mr_get(r_xprt);
if (!mr)
@ -679,11 +683,39 @@ int frwr_wp_create(struct rpcrdma_xprt *r_xprt)
mr->mr_req = NULL;
ep->re_write_pad_mr = mr;
seg.mr_len = XDR_UNIT;
seg.mr_page = virt_to_page(ep->re_write_pad);
seg.mr_offset = offset_in_page(ep->re_write_pad);
if (IS_ERR(frwr_map(r_xprt, &seg, 1, true, xdr_zero, mr)))
return -EIO;
sg_init_table(mr->mr_sg, 1);
sg_set_page(mr->mr_sg, virt_to_page(ep->re_write_pad),
XDR_UNIT, offset_in_page(ep->re_write_pad));
mr->mr_dir = DMA_FROM_DEVICE;
mr->mr_nents = 1;
dma_nents = ib_dma_map_sg(ep->re_id->device, mr->mr_sg,
mr->mr_nents, mr->mr_dir);
if (!dma_nents) {
ret = -EIO;
goto out_mr;
}
mr->mr_device = ep->re_id->device;
ibmr = mr->mr_ibmr;
if (ib_map_mr_sg(ibmr, mr->mr_sg, dma_nents, NULL,
PAGE_SIZE) != dma_nents) {
ret = -EIO;
goto out_unmap;
}
/* IOVA is not tagged with an XID; the write-pad is not RPC-specific. */
ib_update_fast_reg_key(ibmr, ib_inc_rkey(ibmr->rkey));
reg_wr = &mr->mr_regwr;
reg_wr->mr = ibmr;
reg_wr->key = ibmr->rkey;
reg_wr->access = IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE;
mr->mr_handle = ibmr->rkey;
mr->mr_length = ibmr->length;
mr->mr_offset = ibmr->iova;
trace_xprtrdma_mr_fastreg(mr);
mr->mr_cqe.done = frwr_wc_fastreg;
@ -693,5 +725,16 @@ int frwr_wp_create(struct rpcrdma_xprt *r_xprt)
mr->mr_regwr.wr.opcode = IB_WR_REG_MR;
mr->mr_regwr.wr.send_flags = 0;
return ib_post_send(ep->re_id->qp, &mr->mr_regwr.wr, NULL);
ret = ib_post_send(ep->re_id->qp, &mr->mr_regwr.wr, NULL);
if (!ret)
return 0;
out_unmap:
frwr_mr_unmap(mr);
out_mr:
ep->re_write_pad_mr = NULL;
spin_lock(&buf->rb_lock);
rpcrdma_mr_push(mr, &buf->rb_mrs);
spin_unlock(&buf->rb_lock);
return ret;
}