[PATCH] NFSD: Rework encoding and decoding of nfsd4_deviceid

[Sergey Bashirov <sergeybashirov@gmail.com>]

Compilers may optimize the layout of C structures, so we should not rely
on sizeof and memcpy to encode and decode XDR structures. The byte order
of the fields should also be taken into account. This patch adds the
correct functions to handle the nfsd4_deviceid structure and removes the
pad field, which is currently unused.

Signed-off-by: Sergey Bashirov <sergeybashirov@gmail.com>
---
 Tested on the block layout setup, checked with smatch.

 fs/nfsd/blocklayoutxdr.c    |  7 ++-----
 fs/nfsd/flexfilelayoutxdr.c |  3 +--
 fs/nfsd/nfs4layouts.c       |  1 -
 fs/nfsd/nfs4xdr.c           | 14 +-------------
 fs/nfsd/xdr4.h              | 31 ++++++++++++++++++++++++++++++-
 5 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/fs/nfsd/blocklayoutxdr.c b/fs/nfsd/blocklayoutxdr.c
index bcf21fde91207..9ff2a23470e61 100644
--- a/fs/nfsd/blocklayoutxdr.c
+++ b/fs/nfsd/blocklayoutxdr.c
@@ -29,8 +29,7 @@ nfsd4_block_encode_layoutget(struct xdr_stream *xdr,
 	*p++ = cpu_to_be32(len);
 	*p++ = cpu_to_be32(1);		/* we always return a single extent */
 
-	p = xdr_encode_opaque_fixed(p, &b->vol_id,
-			sizeof(struct nfsd4_deviceid));
+	p = nfsd4_encode_deviceid(p, &b->vol_id);
 	p = xdr_encode_hyper(p, b->foff);
 	p = xdr_encode_hyper(p, b->len);
 	p = xdr_encode_hyper(p, b->soff);
@@ -156,9 +155,7 @@ nfsd4_block_decode_layoutupdate(__be32 *p, u32 len, struct iomap **iomapp,
 	for (i = 0; i < nr_iomaps; i++) {
 		struct pnfs_block_extent bex;
 
-		memcpy(&bex.vol_id, p, sizeof(struct nfsd4_deviceid));
-		p += XDR_QUADLEN(sizeof(struct nfsd4_deviceid));
-
+		p = nfsd4_decode_deviceid(p, &bex.vol_id);
 		p = xdr_decode_hyper(p, &bex.foff);
 		if (bex.foff & (block_size - 1)) {
 			goto fail;
diff --git a/fs/nfsd/flexfilelayoutxdr.c b/fs/nfsd/flexfilelayoutxdr.c
index aeb71c10ff1b9..28eb5bedb7e13 100644
--- a/fs/nfsd/flexfilelayoutxdr.c
+++ b/fs/nfsd/flexfilelayoutxdr.c
@@ -54,8 +54,7 @@ nfsd4_ff_encode_layoutget(struct xdr_stream *xdr,
 	*p++ = cpu_to_be32(1);			/* single mirror */
 	*p++ = cpu_to_be32(1);			/* single data server */
 
-	p = xdr_encode_opaque_fixed(p, &fl->deviceid,
-			sizeof(struct nfsd4_deviceid));
+	p = nfsd4_encode_deviceid(p, &fl->deviceid);
 
 	*p++ = cpu_to_be32(1);			/* efficiency */
 
diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
index aea905fcaf87a..683bd1130afe2 100644
--- a/fs/nfsd/nfs4layouts.c
+++ b/fs/nfsd/nfs4layouts.c
@@ -120,7 +120,6 @@ nfsd4_set_deviceid(struct nfsd4_deviceid *id, const struct svc_fh *fhp,
 
 	id->fsid_idx = fhp->fh_export->ex_devid_map->idx;
 	id->generation = device_generation;
-	id->pad = 0;
 	return 0;
 }
 
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index ea91bad4eee2c..f3a089df164c6 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -587,18 +587,6 @@ nfsd4_decode_state_owner4(struct nfsd4_compoundargs *argp,
 }
 
 #ifdef CONFIG_NFSD_PNFS
-static __be32
-nfsd4_decode_deviceid4(struct nfsd4_compoundargs *argp,
-		       struct nfsd4_deviceid *devid)
-{
-	__be32 *p;
-
-	p = xdr_inline_decode(argp->xdr, NFS4_DEVICEID4_SIZE);
-	if (!p)
-		return nfserr_bad_xdr;
-	memcpy(devid, p, sizeof(*devid));
-	return nfs_ok;
-}
 
 static __be32
 nfsd4_decode_layoutupdate4(struct nfsd4_compoundargs *argp,
@@ -1783,7 +1771,7 @@ nfsd4_decode_getdeviceinfo(struct nfsd4_compoundargs *argp,
 	__be32 status;
 
 	memset(gdev, 0, sizeof(*gdev));
-	status = nfsd4_decode_deviceid4(argp, &gdev->gd_devid);
+	status = nfsd4_stream_decode_deviceid(argp->xdr, &gdev->gd_devid);
 	if (status)
 		return status;
 	if (xdr_stream_decode_u32(argp->xdr, &gdev->gd_layout_type) < 0)
diff --git a/fs/nfsd/xdr4.h b/fs/nfsd/xdr4.h
index a23bc56051caf..ec70cb9c17788 100644
--- a/fs/nfsd/xdr4.h
+++ b/fs/nfsd/xdr4.h
@@ -595,9 +595,38 @@ struct nfsd4_reclaim_complete {
 struct nfsd4_deviceid {
 	u64			fsid_idx;
 	u32			generation;
-	u32			pad;
 };
 
+static inline __be32 *
+nfsd4_encode_deviceid(__be32 *p, const struct nfsd4_deviceid *devid)
+{
+	p = xdr_encode_hyper(p, devid->fsid_idx);
+	*p++ = cpu_to_be32(devid->generation);
+	*p++ = cpu_to_be32(0); /* pad field is currently unused */
+	return p;
+}
+
+static inline __be32 *
+nfsd4_decode_deviceid(__be32 *p, struct nfsd4_deviceid *devid)
+{
+	p = xdr_decode_hyper(p, &devid->fsid_idx);
+	devid->generation = be32_to_cpup(p++);
+	p++; /* pad field is currently unused */
+	return p;
+}
+
+static inline __be32
+nfsd4_stream_decode_deviceid(struct xdr_stream *xdr,
+			     struct nfsd4_deviceid *devid)
+{
+	__be32 *p = xdr_inline_decode(xdr, NFS4_DEVICEID4_SIZE);
+
+	if (unlikely(!p))
+		return nfserr_bad_xdr;
+	nfsd4_decode_deviceid(p, devid);
+	return nfs_ok;
+}
+
 struct nfsd4_layout_seg {
 	u32			iomode;
 	u64			offset;
-- 
2.43.0