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svcrdma: Introduce local rdma_rw API helpers

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The plan is to replace the local bespoke code that constructs and
posts RDMA Read and Write Work Requests with calls to the rdma_rw
API. This shares code with other RDMA-enabled ULPs that manages the
gory details of buffer registration and posting Work Requests.

Some design notes:

 o The structure of RPC-over-RDMA transport headers is flexible,
   allowing multiple segments per Reply with arbitrary alignment,
   each with a unique R_key. Write and Send WRs continue to be
   built and posted in separate code paths. However, one whole
   chunk (with one or more RDMA segments apiece) gets exactly
   one ib_post_send and one work completion.

 o svc_xprt reference counting is modified, since a chain of
   rdma_rw_ctx structs generates one completion, no matter how
   many Write WRs are posted.

 o The current code builds the transport header as it is construct-
   ing Write WRs. I've replaced that with marshaling of transport
   header data items in a separate step. This is because the exact
   structure of client-provided segments may not align with the
   components of the server's reply xdr_buf, or the pages in the
   page list. Thus parts of each client-provided segment may be
   written at different points in the send path.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Chuck Lever 2017-04-09 13:06:16 -04:00 committed by J. Bruce Fields
parent c238c4c034
commit f13193f50b
5 changed files with 529 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
include/linux/sunrpc/svc_rdma.h
View File

@ -145,12 +145,15 @@ struct svcxprt_rdma {
u32 sc_max_requests; /* Max requests */
u32 sc_max_bc_requests;/* Backward credits */
int sc_max_req_size; /* Size of each RQ WR buf */
u8 sc_port_num;
struct ib_pd *sc_pd;
spinlock_t sc_ctxt_lock;
struct list_head sc_ctxts;
int sc_ctxt_used;
spinlock_t sc_rw_ctxt_lock;
struct list_head sc_rw_ctxts;
spinlock_t sc_map_lock;
struct list_head sc_maps;
@ -224,6 +227,14 @@ extern int rdma_read_chunk_frmr(struct svcxprt_rdma *, struct svc_rqst *,
struct svc_rdma_op_ctxt *, int *, u32 *,
u32, u32, u64, bool);
/* svc_rdma_rw.c */
extern void svc_rdma_destroy_rw_ctxts(struct svcxprt_rdma *rdma);
extern int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma,
__be32 *wr_ch, struct xdr_buf *xdr);
extern int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma,
__be32 *rp_ch, bool writelist,
struct xdr_buf *xdr);
/* svc_rdma_sendto.c */
extern int svc_rdma_map_xdr(struct svcxprt_rdma *, struct xdr_buf *,
struct svc_rdma_req_map *, bool);

1
net/sunrpc/Kconfig
View File

@ -52,6 +52,7 @@ config SUNRPC_XPRT_RDMA
tristate "RPC-over-RDMA transport"
depends on SUNRPC && INFINIBAND && INFINIBAND_ADDR_TRANS
default SUNRPC && INFINIBAND
select SG_POOL
help
This option allows the NFS client and server to use RDMA
transports (InfiniBand, iWARP, or RoCE).

2
net/sunrpc/xprtrdma/Makefile
View File

@ -4,5 +4,5 @@ rpcrdma-y := transport.o rpc_rdma.o verbs.o \
fmr_ops.o frwr_ops.o \
svc_rdma.o svc_rdma_backchannel.o svc_rdma_transport.o \
svc_rdma_marshal.o svc_rdma_sendto.o svc_rdma_recvfrom.o \
module.o
svc_rdma_rw.o module.o
rpcrdma-$(CONFIG_SUNRPC_BACKCHANNEL) += backchannel.o

512
net/sunrpc/xprtrdma/svc_rdma_rw.c Normal file
View File

@ -0,0 +1,512 @@
/*
* Copyright (c) 2016 Oracle. All rights reserved.
*
* Use the core R/W API to move RPC-over-RDMA Read and Write chunks.
*/
#include <linux/sunrpc/rpc_rdma.h>
#include <linux/sunrpc/svc_rdma.h>
#include <linux/sunrpc/debug.h>
#include <rdma/rw.h>
#define RPCDBG_FACILITY RPCDBG_SVCXPRT
/* Each R/W context contains state for one chain of RDMA Read or
* Write Work Requests.
*
* Each WR chain handles a single contiguous server-side buffer,
* because scatterlist entries after the first have to start on
* page alignment. xdr_buf iovecs cannot guarantee alignment.
*
* Each WR chain handles only one R_key. Each RPC-over-RDMA segment
* from a client may contain a unique R_key, so each WR chain moves
* up to one segment at a time.
*
* The scatterlist makes this data structure over 4KB in size. To
* make it less likely to fail, and to handle the allocation for
* smaller I/O requests without disabling bottom-halves, these
* contexts are created on demand, but cached and reused until the
* controlling svcxprt_rdma is destroyed.
*/
struct svc_rdma_rw_ctxt {
struct list_head rw_list;
struct rdma_rw_ctx rw_ctx;
int rw_nents;
struct sg_table rw_sg_table;
struct scatterlist rw_first_sgl[0];
};
static inline struct svc_rdma_rw_ctxt *
svc_rdma_next_ctxt(struct list_head *list)
{
return list_first_entry_or_null(list, struct svc_rdma_rw_ctxt,
rw_list);
}
static struct svc_rdma_rw_ctxt *
svc_rdma_get_rw_ctxt(struct svcxprt_rdma *rdma, unsigned int sges)
{
struct svc_rdma_rw_ctxt *ctxt;
spin_lock(&rdma->sc_rw_ctxt_lock);
ctxt = svc_rdma_next_ctxt(&rdma->sc_rw_ctxts);
if (ctxt) {
list_del(&ctxt->rw_list);
spin_unlock(&rdma->sc_rw_ctxt_lock);
} else {
spin_unlock(&rdma->sc_rw_ctxt_lock);
ctxt = kmalloc(sizeof(*ctxt) +
SG_CHUNK_SIZE * sizeof(struct scatterlist),
GFP_KERNEL);
if (!ctxt)
goto out;
INIT_LIST_HEAD(&ctxt->rw_list);
}
ctxt->rw_sg_table.sgl = ctxt->rw_first_sgl;
if (sg_alloc_table_chained(&ctxt->rw_sg_table, sges,
ctxt->rw_sg_table.sgl)) {
kfree(ctxt);
ctxt = NULL;
}
out:
return ctxt;
}
static void svc_rdma_put_rw_ctxt(struct svcxprt_rdma *rdma,
struct svc_rdma_rw_ctxt *ctxt)
{
sg_free_table_chained(&ctxt->rw_sg_table, true);
spin_lock(&rdma->sc_rw_ctxt_lock);
list_add(&ctxt->rw_list, &rdma->sc_rw_ctxts);
spin_unlock(&rdma->sc_rw_ctxt_lock);
}
/**
* svc_rdma_destroy_rw_ctxts - Free accumulated R/W contexts
* @rdma: transport about to be destroyed
*
*/
void svc_rdma_destroy_rw_ctxts(struct svcxprt_rdma *rdma)
{
struct svc_rdma_rw_ctxt *ctxt;
while ((ctxt = svc_rdma_next_ctxt(&rdma->sc_rw_ctxts)) != NULL) {
list_del(&ctxt->rw_list);
kfree(ctxt);
}
}
/* A chunk context tracks all I/O for moving one Read or Write
* chunk. This is a a set of rdma_rw's that handle data movement
* for all segments of one chunk.
*
* These are small, acquired with a single allocator call, and
* no more than one is needed per chunk. They are allocated on
* demand, and not cached.
*/
struct svc_rdma_chunk_ctxt {
struct ib_cqe cc_cqe;
struct svcxprt_rdma *cc_rdma;
struct list_head cc_rwctxts;
int cc_sqecount;
enum dma_data_direction cc_dir;
};
static void svc_rdma_cc_init(struct svcxprt_rdma *rdma,
struct svc_rdma_chunk_ctxt *cc,
enum dma_data_direction dir)
{
cc->cc_rdma = rdma;
svc_xprt_get(&rdma->sc_xprt);
INIT_LIST_HEAD(&cc->cc_rwctxts);
cc->cc_sqecount = 0;
cc->cc_dir = dir;
}
static void svc_rdma_cc_release(struct svc_rdma_chunk_ctxt *cc)
{
struct svcxprt_rdma *rdma = cc->cc_rdma;
struct svc_rdma_rw_ctxt *ctxt;
while ((ctxt = svc_rdma_next_ctxt(&cc->cc_rwctxts)) != NULL) {
list_del(&ctxt->rw_list);
rdma_rw_ctx_destroy(&ctxt->rw_ctx, rdma->sc_qp,
rdma->sc_port_num, ctxt->rw_sg_table.sgl,
ctxt->rw_nents, cc->cc_dir);
svc_rdma_put_rw_ctxt(rdma, ctxt);
}
svc_xprt_put(&rdma->sc_xprt);
}
/* State for sending a Write or Reply chunk.
* - Tracks progress of writing one chunk over all its segments
* - Stores arguments for the SGL constructor functions
*/
struct svc_rdma_write_info {
/* write state of this chunk */
unsigned int wi_seg_off;
unsigned int wi_seg_no;
unsigned int wi_nsegs;
__be32 *wi_segs;
/* SGL constructor arguments */
struct xdr_buf *wi_xdr;
unsigned char *wi_base;
unsigned int wi_next_off;
struct svc_rdma_chunk_ctxt wi_cc;
};
static struct svc_rdma_write_info *
svc_rdma_write_info_alloc(struct svcxprt_rdma *rdma, __be32 *chunk)
{
struct svc_rdma_write_info *info;
info = kmalloc(sizeof(*info), GFP_KERNEL);
if (!info)
return info;
info->wi_seg_off = 0;
info->wi_seg_no = 0;
info->wi_nsegs = be32_to_cpup(++chunk);
info->wi_segs = ++chunk;
svc_rdma_cc_init(rdma, &info->wi_cc, DMA_TO_DEVICE);
return info;
}
static void svc_rdma_write_info_free(struct svc_rdma_write_info *info)
{
svc_rdma_cc_release(&info->wi_cc);
kfree(info);
}
/**
* svc_rdma_write_done - Write chunk completion
* @cq: controlling Completion Queue
* @wc: Work Completion
*
* Pages under I/O are freed by a subsequent Send completion.
*/
static void svc_rdma_write_done(struct ib_cq *cq, struct ib_wc *wc)
{
struct ib_cqe *cqe = wc->wr_cqe;
struct svc_rdma_chunk_ctxt *cc =
container_of(cqe, struct svc_rdma_chunk_ctxt, cc_cqe);
struct svcxprt_rdma *rdma = cc->cc_rdma;
struct svc_rdma_write_info *info =
container_of(cc, struct svc_rdma_write_info, wi_cc);
atomic_add(cc->cc_sqecount, &rdma->sc_sq_avail);
wake_up(&rdma->sc_send_wait);
if (unlikely(wc->status != IB_WC_SUCCESS)) {
set_bit(XPT_CLOSE, &rdma->sc_xprt.xpt_flags);
if (wc->status != IB_WC_WR_FLUSH_ERR)
pr_err("svcrdma: write ctx: %s (%u/0x%x)\n",
ib_wc_status_msg(wc->status),
wc->status, wc->vendor_err);
}
svc_rdma_write_info_free(info);
}
/* This function sleeps when the transport's Send Queue is congested.
*
* Assumptions:
* - If ib_post_send() succeeds, only one completion is expected,
* even if one or more WRs are flushed. This is true when posting
* an rdma_rw_ctx or when posting a single signaled WR.
*/
static int svc_rdma_post_chunk_ctxt(struct svc_rdma_chunk_ctxt *cc)
{
struct svcxprt_rdma *rdma = cc->cc_rdma;
struct svc_xprt *xprt = &rdma->sc_xprt;
struct ib_send_wr *first_wr, *bad_wr;
struct list_head *tmp;
struct ib_cqe *cqe;
int ret;
first_wr = NULL;
cqe = &cc->cc_cqe;
list_for_each(tmp, &cc->cc_rwctxts) {
struct svc_rdma_rw_ctxt *ctxt;
ctxt = list_entry(tmp, struct svc_rdma_rw_ctxt, rw_list);
first_wr = rdma_rw_ctx_wrs(&ctxt->rw_ctx, rdma->sc_qp,
rdma->sc_port_num, cqe, first_wr);
cqe = NULL;
}
do {
if (atomic_sub_return(cc->cc_sqecount,
&rdma->sc_sq_avail) > 0) {
ret = ib_post_send(rdma->sc_qp, first_wr, &bad_wr);
if (ret)
break;
return 0;
}
atomic_inc(&rdma_stat_sq_starve);
atomic_add(cc->cc_sqecount, &rdma->sc_sq_avail);
wait_event(rdma->sc_send_wait,
atomic_read(&rdma->sc_sq_avail) > cc->cc_sqecount);
} while (1);
pr_err("svcrdma: ib_post_send failed (%d)\n", ret);
set_bit(XPT_CLOSE, &xprt->xpt_flags);
/* If even one was posted, there will be a completion. */
if (bad_wr != first_wr)
return 0;
atomic_add(cc->cc_sqecount, &rdma->sc_sq_avail);
wake_up(&rdma->sc_send_wait);
return -ENOTCONN;
}
/* Build and DMA-map an SGL that covers one kvec in an xdr_buf
*/
static void svc_rdma_vec_to_sg(struct svc_rdma_write_info *info,
unsigned int len,
struct svc_rdma_rw_ctxt *ctxt)
{
struct scatterlist *sg = ctxt->rw_sg_table.sgl;
sg_set_buf(&sg[0], info->wi_base, len);
info->wi_base += len;
ctxt->rw_nents = 1;
}
/* Build and DMA-map an SGL that covers part of an xdr_buf's pagelist.
*/
static void svc_rdma_pagelist_to_sg(struct svc_rdma_write_info *info,
unsigned int remaining,
struct svc_rdma_rw_ctxt *ctxt)
{
unsigned int sge_no, sge_bytes, page_off, page_no;
struct xdr_buf *xdr = info->wi_xdr;
struct scatterlist *sg;
struct page **page;
page_off = (info->wi_next_off + xdr->page_base) & ~PAGE_MASK;
page_no = (info->wi_next_off + xdr->page_base) >> PAGE_SHIFT;
page = xdr->pages + page_no;
info->wi_next_off += remaining;
sg = ctxt->rw_sg_table.sgl;
sge_no = 0;
do {
sge_bytes = min_t(unsigned int, remaining,
PAGE_SIZE - page_off);
sg_set_page(sg, *page, sge_bytes, page_off);
remaining -= sge_bytes;
sg = sg_next(sg);
page_off = 0;
sge_no++;
page++;
} while (remaining);
ctxt->rw_nents = sge_no;
}
/* Construct RDMA Write WRs to send a portion of an xdr_buf containing
* an RPC Reply.
*/
static int
svc_rdma_build_writes(struct svc_rdma_write_info *info,
void (*constructor)(struct svc_rdma_write_info *info,
unsigned int len,
struct svc_rdma_rw_ctxt *ctxt),
unsigned int remaining)
{
struct svc_rdma_chunk_ctxt *cc = &info->wi_cc;
struct svcxprt_rdma *rdma = cc->cc_rdma;
struct svc_rdma_rw_ctxt *ctxt;
__be32 *seg;
int ret;
cc->cc_cqe.done = svc_rdma_write_done;
seg = info->wi_segs + info->wi_seg_no * rpcrdma_segment_maxsz;
do {
unsigned int write_len;
u32 seg_length, seg_handle;
u64 seg_offset;
if (info->wi_seg_no >= info->wi_nsegs)
goto out_overflow;
seg_handle = be32_to_cpup(seg);
seg_length = be32_to_cpup(seg + 1);
xdr_decode_hyper(seg + 2, &seg_offset);
seg_offset += info->wi_seg_off;
write_len = min(remaining, seg_length - info->wi_seg_off);
ctxt = svc_rdma_get_rw_ctxt(rdma,
(write_len >> PAGE_SHIFT) + 2);
if (!ctxt)
goto out_noctx;
constructor(info, write_len, ctxt);
ret = rdma_rw_ctx_init(&ctxt->rw_ctx, rdma->sc_qp,
rdma->sc_port_num, ctxt->rw_sg_table.sgl,
ctxt->rw_nents, 0, seg_offset,
seg_handle, DMA_TO_DEVICE);
if (ret < 0)
goto out_initerr;
list_add(&ctxt->rw_list, &cc->cc_rwctxts);
cc->cc_sqecount += ret;
if (write_len == seg_length - info->wi_seg_off) {
seg += 4;
info->wi_seg_no++;
info->wi_seg_off = 0;
} else {
info->wi_seg_off += write_len;
}
remaining -= write_len;
} while (remaining);
return 0;
out_overflow:
dprintk("svcrdma: inadequate space in Write chunk (%u)\n",
info->wi_nsegs);
return -E2BIG;
out_noctx:
dprintk("svcrdma: no R/W ctxs available\n");
return -ENOMEM;
out_initerr:
svc_rdma_put_rw_ctxt(rdma, ctxt);
pr_err("svcrdma: failed to map pagelist (%d)\n", ret);
return -EIO;
}
/* Send one of an xdr_buf's kvecs by itself. To send a Reply
* chunk, the whole RPC Reply is written back to the client.
* This function writes either the head or tail of the xdr_buf
* containing the Reply.
*/
static int svc_rdma_send_xdr_kvec(struct svc_rdma_write_info *info,
struct kvec *vec)
{
info->wi_base = vec->iov_base;
return svc_rdma_build_writes(info, svc_rdma_vec_to_sg,
vec->iov_len);
}
/* Send an xdr_buf's page list by itself. A Write chunk is
* just the page list. a Reply chunk is the head, page list,
* and tail. This function is shared between the two types
* of chunk.
*/
static int svc_rdma_send_xdr_pagelist(struct svc_rdma_write_info *info,
struct xdr_buf *xdr)
{
info->wi_xdr = xdr;
info->wi_next_off = 0;
return svc_rdma_build_writes(info, svc_rdma_pagelist_to_sg,
xdr->page_len);
}
/**
* svc_rdma_send_write_chunk - Write all segments in a Write chunk
* @rdma: controlling RDMA transport
* @wr_ch: Write chunk provided by client
* @xdr: xdr_buf containing the data payload
*
* Returns a non-negative number of bytes the chunk consumed, or
* %-E2BIG if the payload was larger than the Write chunk,
* %-ENOMEM if rdma_rw context pool was exhausted,
* %-ENOTCONN if posting failed (connection is lost),
* %-EIO if rdma_rw initialization failed (DMA mapping, etc).
*/
int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma, __be32 *wr_ch,
struct xdr_buf *xdr)
{
struct svc_rdma_write_info *info;
int ret;
if (!xdr->page_len)
return 0;
info = svc_rdma_write_info_alloc(rdma, wr_ch);
if (!info)
return -ENOMEM;
ret = svc_rdma_send_xdr_pagelist(info, xdr);
if (ret < 0)
goto out_err;
ret = svc_rdma_post_chunk_ctxt(&info->wi_cc);
if (ret < 0)
goto out_err;
return xdr->page_len;
out_err:
svc_rdma_write_info_free(info);
return ret;
}
/**
* svc_rdma_send_reply_chunk - Write all segments in the Reply chunk
* @rdma: controlling RDMA transport
* @rp_ch: Reply chunk provided by client
* @writelist: true if client provided a Write list
* @xdr: xdr_buf containing an RPC Reply
*
* Returns a non-negative number of bytes the chunk consumed, or
* %-E2BIG if the payload was larger than the Reply chunk,
* %-ENOMEM if rdma_rw context pool was exhausted,
* %-ENOTCONN if posting failed (connection is lost),
* %-EIO if rdma_rw initialization failed (DMA mapping, etc).
*/
int svc_rdma_send_reply_chunk(struct svcxprt_rdma *rdma, __be32 *rp_ch,
bool writelist, struct xdr_buf *xdr)
{
struct svc_rdma_write_info *info;
int consumed, ret;
info = svc_rdma_write_info_alloc(rdma, rp_ch);
if (!info)
return -ENOMEM;
ret = svc_rdma_send_xdr_kvec(info, &xdr->head[0]);
if (ret < 0)
goto out_err;
consumed = xdr->head[0].iov_len;
/* Send the page list in the Reply chunk only if the
* client did not provide Write chunks.
*/
if (!writelist && xdr->page_len) {
ret = svc_rdma_send_xdr_pagelist(info, xdr);
if (ret < 0)
goto out_err;
consumed += xdr->page_len;
}
if (xdr->tail[0].iov_len) {
ret = svc_rdma_send_xdr_kvec(info, &xdr->tail[0]);
if (ret < 0)
goto out_err;
consumed += xdr->tail[0].iov_len;
}
ret = svc_rdma_post_chunk_ctxt(&info->wi_cc);
if (ret < 0)
goto out_err;
return consumed;
out_err:
svc_rdma_write_info_free(info);
return ret;
}

4
net/sunrpc/xprtrdma/svc_rdma_transport.c
View File

@ -561,6 +561,7 @@ static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv,
INIT_LIST_HEAD(&cma_xprt->sc_read_complete_q);
INIT_LIST_HEAD(&cma_xprt->sc_frmr_q);
INIT_LIST_HEAD(&cma_xprt->sc_ctxts);
INIT_LIST_HEAD(&cma_xprt->sc_rw_ctxts);
INIT_LIST_HEAD(&cma_xprt->sc_maps);
init_waitqueue_head(&cma_xprt->sc_send_wait);
@ -568,6 +569,7 @@ static struct svcxprt_rdma *rdma_create_xprt(struct svc_serv *serv,
spin_lock_init(&cma_xprt->sc_rq_dto_lock);
spin_lock_init(&cma_xprt->sc_frmr_q_lock);
spin_lock_init(&cma_xprt->sc_ctxt_lock);
spin_lock_init(&cma_xprt->sc_rw_ctxt_lock);
spin_lock_init(&cma_xprt->sc_map_lock);
/*
@ -999,6 +1001,7 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
newxprt, newxprt->sc_cm_id);
dev = newxprt->sc_cm_id->device;
newxprt->sc_port_num = newxprt->sc_cm_id->port_num;
/* Qualify the transport resource defaults with the
* capabilities of this particular device */
@ -1248,6 +1251,7 @@ static void __svc_rdma_free(struct work_struct *work)
}
rdma_dealloc_frmr_q(rdma);
svc_rdma_destroy_rw_ctxts(rdma);
svc_rdma_destroy_ctxts(rdma);
svc_rdma_destroy_maps(rdma);