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sunrpc: Replace the rq_pages 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_vec[] array in struct svc_rqst
with a chunk of dynamically-allocated memory.

On a system with 8-byte pointers and 4KB pages, pahole reports that
the rq_pages[] array is 2080 bytes. This patch replaces that 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 15:36:52 -04:00
parent 1a58791292
commit ed603bcf4f
4 changed files with 21 additions and 25 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

3
include/linux/sunrpc/svc.h
View file

@ -205,7 +205,8 @@ struct svc_rqst {
struct xdr_stream rq_res_stream; struct xdr_stream rq_res_stream;
struct page *rq_scratch_page; struct page *rq_scratch_page;
struct xdr_buf rq_res; struct xdr_buf rq_res;
struct page *rq_pages[RPCSVC_MAXPAGES + 1]; unsigned long rq_maxpages; /* num of entries in rq_pages */
struct page * *rq_pages;
struct page * *rq_respages; /* points into rq_pages */ struct page * *rq_respages; /* points into rq_pages */
struct page * *rq_next_page; /* next reply page to use */ struct page * *rq_next_page; /* next reply page to use */
struct page * *rq_page_end; /* one past the last page */ struct page * *rq_page_end; /* one past the last page */

31
net/sunrpc/svc.c
View file

@ -636,20 +636,22 @@ svc_destroy(struct svc_serv **servp)
EXPORT_SYMBOL_GPL(svc_destroy); EXPORT_SYMBOL_GPL(svc_destroy);
static bool static bool
svc_init_buffer(struct svc_rqst *rqstp, unsigned int size, int node) svc_init_buffer(struct svc_rqst *rqstp, const struct svc_serv *serv, int node)
{ {
unsigned long pages, ret; unsigned long ret;
pages = size / PAGE_SIZE + 1; /* extra page as we hold both request and reply. rqstp->rq_maxpages = svc_serv_maxpages(serv);
* We assume one is at most one page
*/
WARN_ON_ONCE(pages > RPCSVC_MAXPAGES);
if (pages > RPCSVC_MAXPAGES)
pages = RPCSVC_MAXPAGES;
ret = alloc_pages_bulk_node(GFP_KERNEL, node, pages, /* rq_pages' last entry is NULL for historical reasons. */
rqstp->rq_pages = kcalloc_node(rqstp->rq_maxpages + 1,
sizeof(struct page *),
GFP_KERNEL, node);
if (!rqstp->rq_pages)
return false;
ret = alloc_pages_bulk_node(GFP_KERNEL, node, rqstp->rq_maxpages,
rqstp->rq_pages); rqstp->rq_pages);
return ret == pages; return ret == rqstp->rq_maxpages;
} }
/* /*
@ -658,11 +660,12 @@ svc_init_buffer(struct svc_rqst *rqstp, unsigned int size, int node)
static void static void
svc_release_buffer(struct svc_rqst *rqstp) svc_release_buffer(struct svc_rqst *rqstp)
{ {
unsigned int i; unsigned long i;
for (i = 0; i < ARRAY_SIZE(rqstp->rq_pages); i++) for (i = 0; i < rqstp->rq_maxpages; i++)
if (rqstp->rq_pages[i]) if (rqstp->rq_pages[i])
put_page(rqstp->rq_pages[i]); put_page(rqstp->rq_pages[i]);
kfree(rqstp->rq_pages);
} }
static void static void
@ -704,7 +707,7 @@ svc_prepare_thread(struct svc_serv *serv, struct svc_pool *pool, int node)
if (!rqstp->rq_resp) if (!rqstp->rq_resp)
goto out_enomem; goto out_enomem;
if (!svc_init_buffer(rqstp, serv->sv_max_mesg, node)) if (!svc_init_buffer(rqstp, serv, node))
goto out_enomem; goto out_enomem;
rqstp->rq_err = -EAGAIN; /* No error yet */ rqstp->rq_err = -EAGAIN; /* No error yet */
@ -896,7 +899,7 @@ EXPORT_SYMBOL_GPL(svc_set_num_threads);
bool svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page) bool svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page)
{ {
struct page **begin = rqstp->rq_pages; struct page **begin = rqstp->rq_pages;
struct page **end = &rqstp->rq_pages[RPCSVC_MAXPAGES]; struct page **end = &rqstp->rq_pages[rqstp->rq_maxpages];
if (unlikely(rqstp->rq_next_page < begin || rqstp->rq_next_page > end)) { if (unlikely(rqstp->rq_next_page < begin || rqstp->rq_next_page > end)) {
trace_svc_replace_page_err(rqstp); trace_svc_replace_page_err(rqstp);

10
net/sunrpc/svc_xprt.c
View file

@ -652,18 +652,10 @@ static void svc_check_conn_limits(struct svc_serv *serv)
static bool svc_alloc_arg(struct svc_rqst *rqstp) static bool svc_alloc_arg(struct svc_rqst *rqstp)
{ {
struct svc_serv *serv = rqstp->rq_server;
struct xdr_buf *arg = &rqstp->rq_arg; struct xdr_buf *arg = &rqstp->rq_arg;
unsigned long pages, filled, ret; unsigned long pages, filled, ret;
pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT; pages = rqstp->rq_maxpages;
if (pages > RPCSVC_MAXPAGES) {
pr_warn_once("svc: warning: pages=%lu > RPCSVC_MAXPAGES=%lu\n",
pages, RPCSVC_MAXPAGES);
/* use as many pages as possible */
pages = RPCSVC_MAXPAGES;
}
for (filled = 0; filled < pages; filled = ret) { for (filled = 0; filled < pages; filled = ret) {
ret = alloc_pages_bulk(GFP_KERNEL, pages, rqstp->rq_pages); ret = alloc_pages_bulk(GFP_KERNEL, pages, rqstp->rq_pages);
if (ret > filled) if (ret > filled)

2
net/sunrpc/xprtrdma/svc_rdma_rw.c
View file

@ -765,7 +765,7 @@ static int svc_rdma_build_read_segment(struct svc_rqst *rqstp,
} }
len -= seg_len; len -= seg_len;
if (len && ((head->rc_curpage + 1) > ARRAY_SIZE(rqstp->rq_pages))) if (len && ((head->rc_curpage + 1) > rqstp->rq_maxpages))
goto out_overrun; goto out_overrun;
} }