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sunrpc: Replace the rq_bvec array with dynamically-allocated memory

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As a step towards making NFSD's maximum rsize and wsize variable at
run-time, replace the fixed-size rq_bvec[] array in struct svc_rqst
with a chunk of dynamically-allocated memory.

The rq_bvec[] array contains enough bio_vecs to handle each page in
a maximum size RPC message.

On a system with 8-byte pointers and 4KB pages, pahole reports that
the rq_bvec[] array is 4144 bytes. This patch replaces that array
with a single 8-byte pointer field.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
Chuck Lever
2025-04-28 15:36:54 -04:00
parent ed603bcf4f
commit 59cf734654
3 changed files with 11 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/sunrpc/svc.h
View File

@@ -213,7 +213,7 @@ struct svc_rqst {
struct folio_batch rq_fbatch;
struct kvec rq_vec[RPCSVC_MAXPAGES]; /* generally useful.. */
struct bio_vec rq_bvec[RPCSVC_MAXPAGES];
struct bio_vec *rq_bvec;
__be32 rq_xid; /* transmission id */
u32 rq_prog; /* program number */

7
net/sunrpc/svc.c
View File

@@ -672,6 +672,7 @@ static void
svc_rqst_free(struct svc_rqst *rqstp)
{
folio_batch_release(&rqstp->rq_fbatch);
kfree(rqstp->rq_bvec);
svc_release_buffer(rqstp);
if (rqstp->rq_scratch_page)
put_page(rqstp->rq_scratch_page);
@@ -710,6 +711,12 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)
if (!svc_init_buffer(rqstp, serv, node))
goto out_enomem;
rqstp->rq_bvec = kcalloc_node(rqstp->rq_maxpages,
sizeof(struct bio_vec),
GFP_KERNEL, node);
if (!rqstp->rq_bvec)
goto out_enomem;
rqstp->rq_err = -EAGAIN; /* No error yet */
serv->sv_nrthreads += 1;

7
net/sunrpc/svcsock.c
View File

@@ -713,8 +713,7 @@ static int svc_udp_sendto(struct svc_rqst *rqstp)
if (svc_xprt_is_dead(xprt))
goto out_notconn;
count = xdr_buf_to_bvec(rqstp->rq_bvec,
ARRAY_SIZE(rqstp->rq_bvec), xdr);
count = xdr_buf_to_bvec(rqstp->rq_bvec, rqstp->rq_maxpages, xdr);
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
count, rqstp->rq_res.len);
@@ -1219,8 +1218,8 @@ static int svc_tcp_sendmsg(struct svc_sock *svsk, struct svc_rqst *rqstp,
memcpy(buf, &marker, sizeof(marker));
bvec_set_virt(rqstp->rq_bvec, buf, sizeof(marker));
count = xdr_buf_to_bvec(rqstp->rq_bvec + 1,
ARRAY_SIZE(rqstp->rq_bvec) - 1, &rqstp->rq_res);
count = xdr_buf_to_bvec(rqstp->rq_bvec + 1, rqstp->rq_maxpages,
&rqstp->rq_res);
iov_iter_bvec(&msg.msg_iter, ITER_SOURCE, rqstp->rq_bvec,
1 + count, sizeof(marker) + rqstp->rq_res.len);