[PATCH 2/3] NFS: Allocate a scratch page for READ_PLUS

[schumaker.anna@gmail.com]

From: Anna Schumaker <Anna.Schumaker@Netapp.com>

We might need this to better handle shifting around data in the reply
buffer.

Suggested-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
---
 fs/nfs/nfs42xdr.c       |  2 ++
 fs/nfs/read.c           | 13 +++++++++++--
 include/linux/nfs_xdr.h |  1 +
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/nfs/nfs42xdr.c b/fs/nfs/nfs42xdr.c
index 8432bd6b95f0..ef095a5f86f7 100644
--- a/fs/nfs/nfs42xdr.c
+++ b/fs/nfs/nfs42xdr.c
@@ -1297,6 +1297,8 @@ static int nfs4_xdr_dec_read_plus(struct rpc_rqst *rqstp,
 	struct compound_hdr hdr;
 	int status;
 
+	xdr_set_scratch_buffer(xdr, page_address(res->scratch), PAGE_SIZE);
+
 	status = decode_compound_hdr(xdr, &hdr);
 	if (status)
 		goto out;
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index eb854f1f86e2..012deb5a136f 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -37,15 +37,24 @@ static struct kmem_cache *nfs_rdata_cachep;
 
 static struct nfs_pgio_header *nfs_readhdr_alloc(void)
 {
-	struct nfs_pgio_header *p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
+	struct nfs_pgio_header *p;
+	struct page *page;
 
-	if (p)
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return ERR_PTR(-ENOMEM);
+
+	p = kmem_cache_zalloc(nfs_rdata_cachep, GFP_KERNEL);
+	if (p) {
 		p->rw_mode = FMODE_READ;
+		p->res.scratch = page;
+	}
 	return p;
 }
 
 static void nfs_readhdr_free(struct nfs_pgio_header *rhdr)
 {
+	__free_page(rhdr->res.scratch);
 	kmem_cache_free(nfs_rdata_cachep, rhdr);
 }
 
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index d63cb862d58e..e0a1c97f11a9 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -659,6 +659,7 @@ struct nfs_pgio_res {
 	struct nfs_fattr *	fattr;
 	__u64			count;
 	__u32			op_status;
+	struct page *		scratch;
 	union {
 		struct {
 			unsigned int		replen;		/* used by read */
-- 
2.29.2