NFSv4.1 Fix gdia_maxcount calculation to fit in ca_maxresponsesize

The GETDEVICEINFO gdia_maxcount represents all of the data being returned
within the GETDEVICEINFO4resok structure and includes the XDR overhead.

The CREATE_SESSION ca_maxresponsesize is the maximum reply and includes the RPC
headers (including security flavor credentials and verifiers).

Split out the struct pnfs_device field maxcount which is the gdia_maxcount
from the pglen field which is the reply (the total) buffer length.
Signed-off-by: Andy Adamson <andros@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/internal.h

@@ -255,6 +255,7 @@ extern int nfs4_decode_dirent(struct xdr_stream *,
 #ifdef CONFIG_NFS_V4_1
 extern const u32 nfs41_maxread_overhead;
 extern const u32 nfs41_maxwrite_overhead;
+extern const u32 nfs41_maxgetdevinfo_overhead;
 #endif
 
 /* nfs4proc.c */

fs/nfs/nfs4filelayoutdev.c

@@ -711,6 +711,7 @@ filelayout_get_device_info(struct inode *inode,
 	pdev->pgbase = 0;
 	pdev->pglen = max_resp_sz;
 	pdev->mincount = 0;
+	pdev->maxcount = max_resp_sz - nfs41_maxgetdevinfo_overhead;
 
 	rc = nfs4_proc_getdeviceinfo(server, pdev, cred);
 	dprintk("%s getdevice info returns %d\n", __func__, rc);

fs/nfs/nfs4xdr.c

@@ -853,6 +853,12 @@ const u32 nfs41_maxread_overhead = ((RPC_MAX_HEADER_WITH_AUTH +
 				     decode_sequence_maxsz +
 				     decode_putfh_maxsz) *
 				    XDR_UNIT);
+
+const u32 nfs41_maxgetdevinfo_overhead = ((RPC_MAX_REPHEADER_WITH_AUTH +
+					   compound_decode_hdr_maxsz +
+					   decode_sequence_maxsz) *
+					  XDR_UNIT);
+EXPORT_SYMBOL_GPL(nfs41_maxgetdevinfo_overhead);
 #endif /* CONFIG_NFS_V4_1 */
 
 static const umode_t nfs_type2fmt[] = {
@@ -1889,7 +1895,7 @@ encode_getdeviceinfo(struct xdr_stream *xdr,
 	p = xdr_encode_opaque_fixed(p, args->pdev->dev_id.data,
 				    NFS4_DEVICEID4_SIZE);
 	*p++ = cpu_to_be32(args->pdev->layout_type);
-	*p++ = cpu_to_be32(args->pdev->pglen);		/* gdia_maxcount */
+	*p++ = cpu_to_be32(args->pdev->maxcount);	/* gdia_maxcount */
 	*p++ = cpu_to_be32(0);				/* bitmap length 0 */
 }
 

fs/nfs/pnfs.h

@@ -149,9 +149,10 @@ struct pnfs_device {
 	struct nfs4_deviceid dev_id;
 	unsigned int  layout_type;
 	unsigned int  mincount;
+	unsigned int  maxcount;	/* gdia_maxcount */
 	struct page **pages;
 	unsigned int  pgbase;
-	unsigned int  pglen;
+	unsigned int  pglen;	/* reply buffer length */
 };
 
 #define NFS4_PNFS_GETDEVLIST_MAXNUM 16