[PATCH 6/6] NFSv4: allow getacl rpc to allocate pages on demand

["J. Bruce Fields" <bfields@redhat.com>]

From: Weston Andros Adamson <dros@netapp.com>

Instead of preallocating pags, allow xdr_partial_copy_from_skb() to
allocate whatever pages we need on demand.  This is what the NFSv3 ACL
code does.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
---
 fs/nfs/nfs4proc.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 3e3dbba4aa74..7842c73fddfc 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5068,6 +5068,7 @@ static ssize_t nfs4_do_get_acl(struct inode *inode, void *buf, size_t buflen)
 	struct page *pages[NFS4ACL_MAXPAGES + 1] = {NULL, };
 	struct nfs_getaclargs args = {
 		.fh = NFS_FH(inode),
+		/* The xdr layer may allocate pages here. */
 		.acl_pages = pages,
 	};
 	struct nfs_getaclres res = {
@@ -5079,32 +5080,22 @@ static ssize_t nfs4_do_get_acl(struct inode *inode, void *buf, size_t buflen)
 		.rpc_argp = &args,
 		.rpc_resp = &res,
 	};
-	unsigned int npages = DIV_ROUND_UP(buflen, PAGE_SIZE) + 1;
-	int ret = -ENOMEM, i;
-
-	if (npages > ARRAY_SIZE(pages))
-		return -ERANGE;
-
-	for (i = 0; i < npages; i++) {
-		pages[i] = alloc_page(GFP_KERNEL);
-		if (!pages[i])
-			goto out_free;
-	}
+	int ret, i;
 
 	/* for decoding across pages */
 	res.acl_scratch = alloc_page(GFP_KERNEL);
 	if (!res.acl_scratch)
-		goto out_free;
+		return -ENOMEM;
 
-	args.acl_len = npages * PAGE_SIZE;
+	args.acl_len = ARRAY_SIZE(pages) << PAGE_SHIFT;
 
-	dprintk("%s  buf %p buflen %zu npages %d args.acl_len %zu\n",
-		__func__, buf, buflen, npages, args.acl_len);
+	dprintk("%s  buf %p buflen %zu args.acl_len %zu\n",
+		__func__, buf, buflen, args.acl_len);
 	ret = nfs4_call_sync(NFS_SERVER(inode)->client, NFS_SERVER(inode),
 			     &msg, &args.seq_args, &res.seq_res, 0);
 	if (ret == 0)
 		ret = res.acl_len;
-out_free:
+
 	for (i = 0; i < ARRAY_SIZE(pages) && pages[i]; i++)
 		__free_page(pages[i]);
 	__free_page(res.acl_scratch);
-- 
2.9.3