This is a note to let you know that I've just added the patch titled
SUNRPC: Add svc_rqst_replace_page() API
to the 5.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sunrpc-add-svc_rqst_replace_page-api.patch
and it can be found in the queue-5.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6b682b75ddffbeb5c11a1aa670d53d368b970d1f
Author: Chuck Lever <chuck.lever@xxxxxxxxxx>
Date: Thu Jul 1 10:03:10 2021 -0400
SUNRPC: Add svc_rqst_replace_page() API
[ Upstream commit 2f0f88f42f2eab0421ed37d7494de9124fdf0d34 ]
Replacing a page in rq_pages[] requires a get_page(), which is a
bus-locked operation, and a put_page(), which can be even more
costly.
To reduce the cost of replacing a page in rq_pages[], batch the
put_page() operations by collecting "freed" pages in a pagevec,
and then release those pages when the pagevec is full. This
pagevec is also emptied when each RPC completes.
[ cel: adjusted to apply without f6e70aab9dfe ]
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index e91d51ea028bb..ab9afbf0a0d8b 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -19,6 +19,7 @@
#include <linux/sunrpc/svcauth.h>
#include <linux/wait.h>
#include <linux/mm.h>
+#include <linux/pagevec.h>
/* statistics for svc_pool structures */
struct svc_pool_stats {
@@ -256,6 +257,7 @@ struct svc_rqst {
struct page * *rq_next_page; /* next reply page to use */
struct page * *rq_page_end; /* one past the last page */
+ struct pagevec rq_pvec;
struct kvec rq_vec[RPCSVC_MAXPAGES]; /* generally useful.. */
struct bio_vec rq_bvec[RPCSVC_MAXPAGES];
@@ -502,6 +504,8 @@ struct svc_rqst *svc_rqst_alloc(struct svc_serv *serv,
struct svc_pool *pool, int node);
struct svc_rqst *svc_prepare_thread(struct svc_serv *serv,
struct svc_pool *pool, int node);
+void svc_rqst_replace_page(struct svc_rqst *rqstp,
+ struct page *page);
void svc_rqst_free(struct svc_rqst *);
void svc_exit_thread(struct svc_rqst *);
unsigned int svc_pool_map_get(void);
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 73e02ba4ed53a..27f98756d1751 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -842,6 +842,27 @@ svc_set_num_threads_sync(struct svc_serv *serv, struct svc_pool *pool, int nrser
}
EXPORT_SYMBOL_GPL(svc_set_num_threads_sync);
+/**
+ * svc_rqst_replace_page - Replace one page in rq_pages[]
+ * @rqstp: svc_rqst with pages to replace
+ * @page: replacement page
+ *
+ * When replacing a page in rq_pages, batch the release of the
+ * replaced pages to avoid hammering the page allocator.
+ */
+void svc_rqst_replace_page(struct svc_rqst *rqstp, struct page *page)
+{
+ if (*rqstp->rq_next_page) {
+ if (!pagevec_space(&rqstp->rq_pvec))
+ __pagevec_release(&rqstp->rq_pvec);
+ pagevec_add(&rqstp->rq_pvec, *rqstp->rq_next_page);
+ }
+
+ get_page(page);
+ *(rqstp->rq_next_page++) = page;
+}
+EXPORT_SYMBOL_GPL(svc_rqst_replace_page);
+
/*
* Called from a server thread as it's exiting. Caller must hold the "service
* mutex" for the service.
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index d150e25b4d45e..570b092165d73 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -525,6 +525,7 @@ static void svc_xprt_release(struct svc_rqst *rqstp)
kfree(rqstp->rq_deferred);
rqstp->rq_deferred = NULL;
+ pagevec_release(&rqstp->rq_pvec);
svc_free_res_pages(rqstp);
rqstp->rq_res.page_len = 0;
rqstp->rq_res.page_base = 0;
@@ -651,6 +652,8 @@ static int svc_alloc_arg(struct svc_rqst *rqstp)
int pages;
int i;
+ pagevec_init(&rqstp->rq_pvec);
+
/* now allocate needed pages. If we get a failure, sleep briefly */
pages = (serv->sv_max_mesg + 2 * PAGE_SIZE) >> PAGE_SHIFT;
if (pages > RPCSVC_MAXPAGES) {
