ovl: constant d_ino for non-merge dirs

Impure directories are ones which contain objects with origins (i.e. those
that have been copied up).  These are relevant to readdir operation only
because of the d_ino field, no other transformation is necessary.  Also a
directory can become impure between two getdents(2) calls.

This patch creates a cache for impure directories.  Unlike the cache for
merged directories, this one only contains entries with origin and is not
refcounted but has a its lifetime tied to that of the dentry.

Similarly to the merged cache, the impure cache is invalidated based on a
version number.  This version number is incremented when an entry with
origin is added or removed from the directory.

If the cache is empty, then the impure xattr is removed from the directory.

This patch also fixes up handling of d_ino for the ".." entry if the parent
directory is merged.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 236 insertions, 31 deletions

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 2aab37054027..3e27e455a502 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -34,13 +34,14 @@ struct ovl_dir_cache {
 	long refcount;
 	u64 version;
 	struct list_head entries;
+	struct rb_root root;
 };
 
 struct ovl_readdir_data {
 	struct dir_context ctx;
 	struct dentry *dentry;
 	bool is_lowest;
-	struct rb_root root;
+	struct rb_root *root;
 	struct list_head *list;
 	struct list_head middle;
 	struct ovl_cache_entry *first_maybe_whiteout;
@@ -61,7 +62,33 @@ struct ovl_dir_file {
 
 static struct ovl_cache_entry *ovl_cache_entry_from_node(struct rb_node *n)
 {
-	return container_of(n, struct ovl_cache_entry, node);
+	return rb_entry(n, struct ovl_cache_entry, node);
+}
+
+static bool ovl_cache_entry_find_link(const char *name, int len,
+				      struct rb_node ***link,
+				      struct rb_node **parent)
+{
+	bool found = false;
+	struct rb_node **newp = *link;
+
+	while (!found && *newp) {
+		int cmp;
+		struct ovl_cache_entry *tmp;
+
+		*parent = *newp;
+		tmp = ovl_cache_entry_from_node(*newp);
+		cmp = strncmp(name, tmp->name, len);
+		if (cmp > 0)
+			newp = &tmp->node.rb_right;
+		else if (cmp < 0 || len < tmp->len)
+			newp = &tmp->node.rb_left;
+		else
+			found = true;
+	}
+	*link = newp;
+
+	return found;
 }
 
 static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
@@ -144,24 +171,12 @@ static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
 				  const char *name, int len, u64 ino,
 				  unsigned int d_type)
 {
-	struct rb_node **newp = &rdd->root.rb_node;
+	struct rb_node **newp = &rdd->root->rb_node;
 	struct rb_node *parent = NULL;
 	struct ovl_cache_entry *p;
 
-	while (*newp) {
-		int cmp;
-		struct ovl_cache_entry *tmp;
-
-		parent = *newp;
-		tmp = ovl_cache_entry_from_node(*newp);
-		cmp = strncmp(name, tmp->name, len);
-		if (cmp > 0)
-			newp = &tmp->node.rb_right;
-		else if (cmp < 0 || len < tmp->len)
-			newp = &tmp->node.rb_left;
-		else
-			return 0;
-	}
+	if (ovl_cache_entry_find_link(name, len, &newp, &parent))
+		return 0;
 
 	p = ovl_cache_entry_new(rdd, name, len, ino, d_type);
 	if (p == NULL) {
@@ -171,7 +186,7 @@ static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
 
 	list_add_tail(&p->l_node, rdd->list);
 	rb_link_node(&p->node, parent, newp);
-	rb_insert_color(&p->node, &rdd->root);
+	rb_insert_color(&p->node, rdd->root);
 
 	return 0;
 }
@@ -182,7 +197,7 @@ static int ovl_fill_lowest(struct ovl_readdir_data *rdd,
 {
 	struct ovl_cache_entry *p;
 
-	p = ovl_cache_entry_find(&rdd->root, name, namelen);
+	p = ovl_cache_entry_find(rdd->root, name, namelen);
 	if (p) {
 		list_move_tail(&p->l_node, &rdd->middle);
 	} else {
@@ -207,6 +222,16 @@ void ovl_cache_free(struct list_head *list)
 	INIT_LIST_HEAD(list);
 }
 
+void ovl_dir_cache_free(struct inode *inode)
+{
+	struct ovl_dir_cache *cache = ovl_dir_cache(inode);
+
+	if (cache) {
+		ovl_cache_free(&cache->entries);
+		kfree(cache);
+	}
+}
+
 static void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry)
 {
 	struct ovl_dir_cache *cache = od->cache;
@@ -214,8 +239,8 @@ static void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry)
 	WARN_ON(cache->refcount <= 0);
 	cache->refcount--;
 	if (!cache->refcount) {
-		if (ovl_dir_cache(dentry) == cache)
-			ovl_set_dir_cache(dentry, NULL);
+		if (ovl_dir_cache(d_inode(dentry)) == cache)
+			ovl_set_dir_cache(d_inode(dentry), NULL);
 
 		ovl_cache_free(&cache->entries);
 		kfree(cache);
@@ -308,7 +333,8 @@ static void ovl_dir_reset(struct file *file)
 		od->is_real = false;
 }
 
-static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
+static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list,
+	struct rb_root *root)
 {
 	int err;
 	struct path realpath;
@@ -316,7 +342,7 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
 		.ctx.actor = ovl_fill_merge,
 		.dentry = dentry,
 		.list = list,
-		.root = RB_ROOT,
+		.root = root,
 		.is_lowest = false,
 	};
 	int idx, next;
@@ -362,12 +388,13 @@ static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
 	int res;
 	struct ovl_dir_cache *cache;
 
-	cache = ovl_dir_cache(dentry);
+	cache = ovl_dir_cache(d_inode(dentry));
 	if (cache && ovl_dentry_version_get(dentry) == cache->version) {
+		WARN_ON(!cache->refcount);
 		cache->refcount++;
 		return cache;
 	}
-	ovl_set_dir_cache(dentry, NULL);
+	ovl_set_dir_cache(d_inode(dentry), NULL);
 
 	cache = kzalloc(sizeof(struct ovl_dir_cache), GFP_KERNEL);
 	if (!cache)
@@ -375,8 +402,9 @@ static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
 
 	cache->refcount = 1;
 	INIT_LIST_HEAD(&cache->entries);
+	cache->root = RB_ROOT;
 
-	res = ovl_dir_read_merged(dentry, &cache->entries);
+	res = ovl_dir_read_merged(dentry, &cache->entries, &cache->root);
 	if (res) {
 		ovl_cache_free(&cache->entries);
 		kfree(cache);
@@ -384,7 +412,7 @@ static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
 	}
 
 	cache->version = ovl_dentry_version_get(dentry);
-	ovl_set_dir_cache(dentry, cache);
+	ovl_set_dir_cache(d_inode(dentry), cache);
 
 	return cache;
 }
@@ -458,6 +486,169 @@ fail:
 	goto out;
 }
 
+static int ovl_fill_plain(struct dir_context *ctx, const char *name,
+			  int namelen, loff_t offset, u64 ino,
+			  unsigned int d_type)
+{
+	struct ovl_cache_entry *p;
+	struct ovl_readdir_data *rdd =
+		container_of(ctx, struct ovl_readdir_data, ctx);
+
+	rdd->count++;
+	p = ovl_cache_entry_new(rdd, name, namelen, ino, d_type);
+	if (p == NULL) {
+		rdd->err = -ENOMEM;
+		return -ENOMEM;
+	}
+	list_add_tail(&p->l_node, rdd->list);
+
+	return 0;
+}
+
+static int ovl_dir_read_impure(struct path *path,  struct list_head *list,
+			       struct rb_root *root)
+{
+	int err;
+	struct path realpath;
+	struct ovl_cache_entry *p, *n;
+	struct ovl_readdir_data rdd = {
+		.ctx.actor = ovl_fill_plain,
+		.list = list,
+		.root = root,
+	};
+
+	INIT_LIST_HEAD(list);
+	*root = RB_ROOT;
+	ovl_path_upper(path->dentry, &realpath);
+
+	err = ovl_dir_read(&realpath, &rdd);
+	if (err)
+		return err;
+
+	list_for_each_entry_safe(p, n, list, l_node) {
+		if (strcmp(p->name, ".") != 0 &&
+		    strcmp(p->name, "..") != 0) {
+			err = ovl_cache_update_ino(path, p);
+			if (err)
+				return err;
+		}
+		if (p->ino == p->real_ino) {
+			list_del(&p->l_node);
+			kfree(p);
+		} else {
+			struct rb_node **newp = &root->rb_node;
+			struct rb_node *parent = NULL;
+
+			if (WARN_ON(ovl_cache_entry_find_link(p->name, p->len,
+							      &newp, &parent)))
+				return -EIO;
+
+			rb_link_node(&p->node, parent, newp);
+			rb_insert_color(&p->node, root);
+		}
+	}
+	return 0;
+}
+
+static struct ovl_dir_cache *ovl_cache_get_impure(struct path *path)
+{
+	int res;
+	struct dentry *dentry = path->dentry;
+	struct ovl_dir_cache *cache;
+
+	cache = ovl_dir_cache(d_inode(dentry));
+	if (cache && ovl_dentry_version_get(dentry) == cache->version)
+		return cache;
+
+	/* Impure cache is not refcounted, free it here */
+	ovl_dir_cache_free(d_inode(dentry));
+	ovl_set_dir_cache(d_inode(dentry), NULL);
+
+	cache = kzalloc(sizeof(struct ovl_dir_cache), GFP_KERNEL);
+	if (!cache)
+		return ERR_PTR(-ENOMEM);
+
+	res = ovl_dir_read_impure(path, &cache->entries, &cache->root);
+	if (res) {
+		ovl_cache_free(&cache->entries);
+		kfree(cache);
+		return ERR_PTR(res);
+	}
+	if (list_empty(&cache->entries)) {
+		/* Good oportunity to get rid of an unnecessary "impure" flag */
+		ovl_do_removexattr(ovl_dentry_upper(dentry), OVL_XATTR_IMPURE);
+		ovl_clear_flag(OVL_IMPURE, d_inode(dentry));
+		kfree(cache);
+		return NULL;
+	}
+
+	cache->version = ovl_dentry_version_get(dentry);
+	ovl_set_dir_cache(d_inode(dentry), cache);
+
+	return cache;
+}
+
+struct ovl_readdir_translate {
+	struct dir_context *orig_ctx;
+	struct ovl_dir_cache *cache;
+	struct dir_context ctx;
+	u64 parent_ino;
+};
+
+static int ovl_fill_real(struct dir_context *ctx, const char *name,
+			   int namelen, loff_t offset, u64 ino,
+			   unsigned int d_type)
+{
+	struct ovl_readdir_translate *rdt =
+		container_of(ctx, struct ovl_readdir_translate, ctx);
+	struct dir_context *orig_ctx = rdt->orig_ctx;
+
+	if (rdt->parent_ino && strcmp(name, "..") == 0)
+		ino = rdt->parent_ino;
+	else if (rdt->cache) {
+		struct ovl_cache_entry *p;
+
+		p = ovl_cache_entry_find(&rdt->cache->root, name, namelen);
+		if (p)
+			ino = p->ino;
+	}
+
+	return orig_ctx->actor(orig_ctx, name, namelen, offset, ino, d_type);
+}
+
+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_readdir_translate rdt = {
+		.ctx.actor = ovl_fill_real,
+		.orig_ctx = ctx,
+	};
+
+	if (OVL_TYPE_MERGE(ovl_path_type(dir->d_parent))) {
+		struct kstat stat;
+		struct path statpath = file->f_path;
+
+		statpath.dentry = dir->d_parent;
+		err = vfs_getattr(&statpath, &stat, STATX_INO, 0);
+		if (err)
+			return err;
+
+		WARN_ON_ONCE(dir->d_sb->s_dev != stat.dev);
+		rdt.parent_ino = stat.ino;
+	}
+
+	if (ovl_test_flag(OVL_IMPURE, d_inode(dir))) {
+		rdt.cache = ovl_cache_get_impure(&file->f_path);
+		if (IS_ERR(rdt.cache))
+			return PTR_ERR(rdt.cache);
+	}
+
+	return iterate_dir(od->realfile, &rdt.ctx);
+}
+
+
 static int ovl_iterate(struct file *file, struct dir_context *ctx)
 {
 	struct ovl_dir_file *od = file->private_data;
@@ -468,8 +659,19 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
 	if (!ctx->pos)
 		ovl_dir_reset(file);
 
-	if (od->is_real)
+	if (od->is_real) {
+		/*
+		 * If parent is merge, then need to adjust d_ino for '..', if
+		 * dir is impure then need to adjust d_ino for copied up
+		 * entries.
+		 */
+		if (ovl_same_sb(dentry->d_sb) &&
+		    (ovl_test_flag(OVL_IMPURE, d_inode(dentry)) ||
+		     OVL_TYPE_MERGE(ovl_path_type(dentry->d_parent)))) {
+			return ovl_iterate_real(file, ctx);
+		}
 		return iterate_dir(od->realfile, ctx);
+	}
 
 	if (!od->cache) {
 		struct ovl_dir_cache *cache;
@@ -634,8 +836,9 @@ int ovl_check_empty_dir(struct dentry *dentry, struct list_head *list)
 {
 	int err;
 	struct ovl_cache_entry *p;
+	struct rb_root root = RB_ROOT;
 
-	err = ovl_dir_read_merged(dentry, list);
+	err = ovl_dir_read_merged(dentry, list, &root);
 	if (err)
 		return err;
 
@@ -724,12 +927,13 @@ static void ovl_workdir_cleanup_recurse(struct path *path, int level)
 	int err;
 	struct inode *dir = path->dentry->d_inode;
 	LIST_HEAD(list);
+	struct rb_root root = RB_ROOT;
 	struct ovl_cache_entry *p;
 	struct ovl_readdir_data rdd = {
 		.ctx.actor = ovl_fill_merge,
 		.dentry = NULL,
 		.list = &list,
-		.root = RB_ROOT,
+		.root = &root,
 		.is_lowest = false,
 	};
 
@@ -787,12 +991,13 @@ int ovl_indexdir_cleanup(struct dentry *dentry, struct vfsmount *mnt,
 	struct inode *dir = dentry->d_inode;
 	struct path path = { .mnt = mnt, .dentry = dentry };
 	LIST_HEAD(list);
+	struct rb_root root = RB_ROOT;
 	struct ovl_cache_entry *p;
 	struct ovl_readdir_data rdd = {
 		.ctx.actor = ovl_fill_merge,
 		.dentry = NULL,
 		.list = &list,
-		.root = RB_ROOT,
+		.root = &root,
 		.is_lowest = false,
 	};