afs: Set mtime from the client for yfs create operations

For operations that create vnodes on the server such as CreateFile,
MakeDir or Symlink, the server will store its own current time as
the mtime if the client doesn't pass in a time in the accompanying
StoreStatus structure.

If the server and client clocks are not well synchronized, the client
may see timestamps in the future or inconsistent dependency checks
with "make" for files that are not modified after creation:

make[2]: Warning: File 'arch/x86/kernel/apic/modules.order' has
modification time 0.14 s in the future
make[2]: warning:  Clock skew detected.  Your build may be incomplete.

This is already handled correctly for non yfs operations; also
set the mtime for the corresponding yfs operations.

Changes:
v3: Replace S_IRWXUGO with 0777, per checkpatch
v2: [dhowells] Merge the two xdr_encode_YFSStoreStatus*() functions together
Signed-off-by: Marc Dionne <marc.dionne@auristor.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Link: http://lists.infradead.org/pipermail/linux-afs/2021-October/004395.html

fs/afs/yfsclient.c

@@ -83,25 +83,18 @@ static s64 linux_to_yfs_time(const struct timespec64 *t)
 	return (u64)t->tv_sec * 10000000 + t->tv_nsec/100;
 }
 
-static __be32 *xdr_encode_YFSStoreStatus_mode(__be32 *bp, mode_t mode)
-{
-	struct yfs_xdr_YFSStoreStatus *x = (void *)bp;
-
-	x->mask		= htonl(AFS_SET_MODE);
-	x->mode		= htonl(mode & S_IALLUGO);
-	x->mtime_client	= u64_to_xdr(0);
-	x->owner	= u64_to_xdr(0);
-	x->group	= u64_to_xdr(0);
-	return bp + xdr_size(x);
-}
-
-static __be32 *xdr_encode_YFSStoreStatus_mtime(__be32 *bp, const struct timespec64 *t)
+static __be32 *xdr_encode_YFSStoreStatus(__be32 *bp, mode_t *mode,
+					 const struct timespec64 *t)
 {
 	struct yfs_xdr_YFSStoreStatus *x = (void *)bp;
+	mode_t masked_mode = mode ? *mode & S_IALLUGO : 0;
 	s64 mtime = linux_to_yfs_time(t);
+	u32 mask = AFS_SET_MTIME;
 
-	x->mask		= htonl(AFS_SET_MTIME);
-	x->mode		= htonl(0);
+	mask |= mode ? AFS_SET_MODE : 0;
+
+	x->mask		= htonl(mask);
+	x->mode		= htonl(masked_mode);
 	x->mtime_client	= u64_to_xdr(mtime);
 	x->owner	= u64_to_xdr(0);
 	x->group	= u64_to_xdr(0);
@@ -576,7 +569,7 @@ void yfs_fs_create_file(struct afs_operation *op)
 	bp = xdr_encode_u32(bp, 0); /* RPC flags */
 	bp = xdr_encode_YFSFid(bp, &dvp->fid);
 	bp = xdr_encode_name(bp, name);
-	bp = xdr_encode_YFSStoreStatus_mode(bp, op->create.mode);
+	bp = xdr_encode_YFSStoreStatus(bp, &op->create.mode, &op->mtime);
 	bp = xdr_encode_u32(bp, yfs_LockNone); /* ViceLockType */
 	yfs_check_req(call, bp);
 
@@ -625,7 +618,7 @@ void yfs_fs_make_dir(struct afs_operation *op)
 	bp = xdr_encode_u32(bp, 0); /* RPC flags */
 	bp = xdr_encode_YFSFid(bp, &dvp->fid);
 	bp = xdr_encode_name(bp, name);
-	bp = xdr_encode_YFSStoreStatus_mode(bp, op->create.mode);
+	bp = xdr_encode_YFSStoreStatus(bp, &op->create.mode, &op->mtime);
 	yfs_check_req(call, bp);
 
 	trace_afs_make_fs_call1(call, &dvp->fid, name);
@@ -946,6 +939,7 @@ void yfs_fs_symlink(struct afs_operation *op)
 	struct afs_vnode_param *dvp = &op->file[0];
 	struct afs_call *call;
 	size_t contents_sz;
+	mode_t mode = 0777;
 	__be32 *bp;
 
 	_enter("");
@@ -972,7 +966,7 @@ void yfs_fs_symlink(struct afs_operation *op)
 	bp = xdr_encode_YFSFid(bp, &dvp->fid);
 	bp = xdr_encode_name(bp, name);
 	bp = xdr_encode_string(bp, op->create.symlink, contents_sz);
-	bp = xdr_encode_YFSStoreStatus_mode(bp, S_IRWXUGO);
+	bp = xdr_encode_YFSStoreStatus(bp, &mode, &op->mtime);
 	yfs_check_req(call, bp);
 
 	trace_afs_make_fs_call1(call, &dvp->fid, name);
@@ -1103,7 +1097,7 @@ void yfs_fs_store_data(struct afs_operation *op)
 	bp = xdr_encode_u32(bp, YFSSTOREDATA64);
 	bp = xdr_encode_u32(bp, 0); /* RPC flags */
 	bp = xdr_encode_YFSFid(bp, &vp->fid);
-	bp = xdr_encode_YFSStoreStatus_mtime(bp, &op->mtime);
+	bp = xdr_encode_YFSStoreStatus(bp, NULL, &op->mtime);
 	bp = xdr_encode_u64(bp, op->store.pos);
 	bp = xdr_encode_u64(bp, op->store.size);
 	bp = xdr_encode_u64(bp, op->store.i_size);