[PATCH 5.15.y 2/3] svcrdma: Adjust the number of entries in svc_rdma_recv_ctxt::rc_pages

[Sasha Levin <sashal@kernel.org>]

From: Chuck Lever <chuck.lever@oracle.com>

[ Upstream commit 81381d1a90dea186ce4585d9bd3cdc40b50e9c48 ]

Allow allocation of more entries in the rc_pages[] array when the
maximum size of an RPC message is increased.

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

For the 5.15 backport, keep the existing kmalloc allocation policy and
size the flexible rc_pages array with RPCSVC_MAXPAGES. This tree retains
fixed-size RPC request page arrays and does not have svc_serv_maxpages(),
so using the existing limit preserves both allocation capacity and the
accepted segment-count upper bound without adding a helper function.
Omit __counted_by, which is not available in this tree.

Retain rc_maxpages and use it in xdr_check_write_chunk() so that target
9808eb765666 ("svcrdma: Reject Write/Reply chunks with segcount 0") applies
without changes. Initialize rc_maxpages before the context is published.

Include linux/pagemap.h explicitly for release_pages(). The preceding
rc_pages backport added this call without its declaration, causing an
implicit-function-declaration build error on this stable tree.

Stable-dep-of: 9808eb765666 ("svcrdma: Reject Write/Reply chunks with segcount 0")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/sunrpc/svc_rdma.h         | 3 ++-
 net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 8 ++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 2bfc32337bc2e..bab8d45fcb58c 100644
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -148,7 +148,8 @@ struct svc_rdma_recv_ctxt {
 	struct svc_rdma_pcl	rc_reply_pcl;
 
 	unsigned int		rc_page_count;
-	struct page		*rc_pages[RPCSVC_MAXPAGES];
+	unsigned long		rc_maxpages;
+	struct page		*rc_pages[];
 };
 
 struct svc_rdma_send_ctxt {
diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index cf673cf9584d5..7d3b8fea9c682 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -92,6 +92,7 @@
  * are transferred from the svc_rdma_recv_ctxt to the second svc_rqst.
  */
 
+#include <linux/pagemap.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <asm/unaligned.h>
@@ -126,12 +127,15 @@ static struct svc_rdma_recv_ctxt *
 svc_rdma_recv_ctxt_alloc(struct svcxprt_rdma *rdma)
 {
 	struct svc_rdma_recv_ctxt *ctxt;
+	unsigned long pages;
 	dma_addr_t addr;
 	void *buffer;
 
-	ctxt = kmalloc(sizeof(*ctxt), GFP_KERNEL);
+	pages = RPCSVC_MAXPAGES;
+	ctxt = kmalloc(struct_size(ctxt, rc_pages, pages), GFP_KERNEL);
 	if (!ctxt)
 		goto fail0;
+	ctxt->rc_maxpages = pages;
 	buffer = kmalloc(rdma->sc_max_req_size, GFP_KERNEL);
 	if (!buffer)
 		goto fail1;
@@ -486,7 +490,7 @@ static bool xdr_check_write_chunk(struct svc_rdma_recv_ctxt *rctxt)
 	 * a computation, perform a simple range check. This is an
 	 * arbitrary but sensible limit (ie, not architectural).
 	 */
-	if (unlikely(segcount > RPCSVC_MAXPAGES))
+	if (unlikely(segcount > rctxt->rc_maxpages))
 		return false;
 
 	p = xdr_inline_decode(&rctxt->rc_stream,
-- 
2.53.0