ovl: layer is const

The ovl_layer struct is never modified except at initialization.
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/export.c

@@ -358,7 +358,7 @@ static struct dentry *ovl_dentry_real_at(struct dentry *dentry, int idx)
  */
 static struct dentry *ovl_lookup_real_one(struct dentry *connected,
 					  struct dentry *real,
-					  struct ovl_layer *layer)
+					  const struct ovl_layer *layer)
 {
 	struct inode *dir = d_inode(connected);
 	struct dentry *this, *parent = NULL;
@@ -414,14 +414,14 @@ static struct dentry *ovl_lookup_real_one(struct dentry *connected,
 
 static struct dentry *ovl_lookup_real(struct super_block *sb,
 				      struct dentry *real,
-				      struct ovl_layer *layer);
+				      const struct ovl_layer *layer);
 
 /*
  * Lookup an indexed or hashed overlay dentry by real inode.
  */
 static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
 					    struct dentry *real,
-					    struct ovl_layer *layer)
+					    const struct ovl_layer *layer)
 {
 	struct ovl_fs *ofs = sb->s_fs_info;
 	struct dentry *index = NULL;
@@ -486,7 +486,7 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
  */
 static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb,
 					       struct dentry *real,
-					       struct ovl_layer *layer)
+					       const struct ovl_layer *layer)
 {
 	struct dentry *next, *parent = NULL;
 	struct dentry *ancestor = ERR_PTR(-EIO);
@@ -539,7 +539,7 @@ static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb,
  */
 static struct dentry *ovl_lookup_real(struct super_block *sb,
 				      struct dentry *real,
-				      struct ovl_layer *layer)
+				      const struct ovl_layer *layer)
 {
 	struct dentry *connected;
 	int err = 0;
@@ -645,7 +645,7 @@ static struct dentry *ovl_get_dentry(struct super_block *sb,
 				     struct dentry *index)
 {
 	struct ovl_fs *ofs = sb->s_fs_info;
-	struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
+	const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
 	struct dentry *real = upper ?: (index ?: lowerpath->dentry);
 
 	/*

fs/overlayfs/overlayfs.h

@@ -239,7 +239,7 @@ enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path);
 struct dentry *ovl_dentry_upper(struct dentry *dentry);
 struct dentry *ovl_dentry_lower(struct dentry *dentry);
 struct dentry *ovl_dentry_lowerdata(struct dentry *dentry);
-struct ovl_layer *ovl_layer_lower(struct dentry *dentry);
+const struct ovl_layer *ovl_layer_lower(struct dentry *dentry);
 struct dentry *ovl_dentry_real(struct dentry *dentry);
 struct dentry *ovl_i_dentry_upper(struct inode *inode);
 struct inode *ovl_inode_upper(struct inode *inode);

fs/overlayfs/ovl_entry.h

@@ -40,7 +40,7 @@ struct ovl_layer {
 };
 
 struct ovl_path {
-	struct ovl_layer *layer;
+	const struct ovl_layer *layer;
 	struct dentry *dentry;
 };
 
@@ -50,7 +50,7 @@ struct ovl_fs {
 	unsigned int numlayer;
 	/* Number of unique fs among layers including upper fs */
 	unsigned int numfs;
-	struct ovl_layer *layers;
+	const struct ovl_layer *layers;
 	struct ovl_sb *fs;
 	/* workbasedir is the path at workdir= mount option */
 	struct dentry *workbasedir;

fs/overlayfs/readdir.c

@@ -691,7 +691,7 @@ static int ovl_iterate_real(struct file *file, struct dir_context *ctx)
 	int err;
 	struct ovl_dir_file *od = file->private_data;
 	struct dentry *dir = file->f_path.dentry;
-	struct ovl_layer *lower_layer = ovl_layer_lower(dir);
+	const struct ovl_layer *lower_layer = ovl_layer_lower(dir);
 	struct ovl_readdir_translate rdt = {
 		.ctx.actor = ovl_fill_real,
 		.orig_ctx = ctx,

fs/overlayfs/super.c

@@ -1320,12 +1320,13 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 {
 	int err;
 	unsigned int i;
+	struct ovl_layer *layers;
 
 	err = -ENOMEM;
-	ofs->layers = kcalloc(numlower + 1, sizeof(struct ovl_layer),
-			      GFP_KERNEL);
-	if (ofs->layers == NULL)
+	layers = kcalloc(numlower + 1, sizeof(struct ovl_layer), GFP_KERNEL);
+	if (!layers)
 		goto out;
+	ofs->layers = layers;
 
 	ofs->fs = kcalloc(numlower + 1, sizeof(struct ovl_sb), GFP_KERNEL);
 	if (ofs->fs == NULL)
@@ -1334,9 +1335,9 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 	/* idx/fsid 0 are reserved for upper fs even with lower only overlay */
 	ofs->numfs++;
 
-	ofs->layers[0].mnt = ofs->upper_mnt;
-	ofs->layers[0].idx = 0;
-	ofs->layers[0].fsid = 0;
+	layers[0].mnt = ofs->upper_mnt;
+	layers[0].idx = 0;
+	layers[0].fsid = 0;
 	ofs->numlayer = 1;
 
 	/*
@@ -1389,11 +1390,11 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
 		 */
 		mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
 
-		ofs->layers[ofs->numlayer].trap = trap;
-		ofs->layers[ofs->numlayer].mnt = mnt;
-		ofs->layers[ofs->numlayer].idx = ofs->numlayer;
-		ofs->layers[ofs->numlayer].fsid = fsid;
-		ofs->layers[ofs->numlayer].fs = &ofs->fs[fsid];
+		layers[ofs->numlayer].trap = trap;
+		layers[ofs->numlayer].mnt = mnt;
+		layers[ofs->numlayer].idx = ofs->numlayer;
+		layers[ofs->numlayer].fsid = fsid;
+		layers[ofs->numlayer].fs = &ofs->fs[fsid];
 		ofs->numlayer++;
 		ofs->fs[fsid].is_lower = true;
 	}

fs/overlayfs/util.c

@@ -186,7 +186,7 @@ struct dentry *ovl_dentry_lower(struct dentry *dentry)
 	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
 }
 
-struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
+const struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
 {
 	struct ovl_entry *oe = dentry->d_fsdata;