ovl: discard independent cursor in readdir()

Since the ovl_dir_cache is stable during a directory reading, the cursor
of struct ovl_dir_file don't need to be an independent entry in the list
of a merged directory.

This patch changes *cursor* to a pointer which points to the entry in the
ovl_dir_cache. After this, we don't need to check *is_cursor* either.

Signed-off-by: hujianyang <hujianyang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 9df848f..dcf1d41 100644 (file)
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -24,7 +24,6 @@ struct ovl_cache_entry {
        struct list_head l_node;
        struct rb_node node;
        bool is_whiteout;
-       bool is_cursor;
        char name[];
 };
 
@@ -49,7 +48,7 @@ struct ovl_dir_file {
        bool is_real;
        bool is_upper;
        struct ovl_dir_cache *cache;
-       struct ovl_cache_entry cursor;
+       struct list_head *cursor;
        struct file *realfile;
        struct file *upperfile;
 };
@@ -97,7 +96,6 @@ static struct ovl_cache_entry *ovl_cache_entry_new(struct dentry *dir,
        p->type = d_type;
        p->ino = ino;
        p->is_whiteout = false;
-       p->is_cursor = false;
 
        if (d_type == DT_CHR) {
                struct dentry *dentry;
@@ -196,7 +194,6 @@ static void ovl_cache_put(struct ovl_dir_file *od, struct dentry *dentry)
 {
        struct ovl_dir_cache *cache = od->cache;
 
-       list_del_init(&od->cursor.l_node);
        WARN_ON(cache->refcount <= 0);
        cache->refcount--;
        if (!cache->refcount) {
@@ -254,6 +251,7 @@ static void ovl_dir_reset(struct file *file)
        if (cache && ovl_dentry_version_get(dentry) != cache->version) {
                ovl_cache_put(od, dentry);
                od->cache = NULL;
+               od->cursor = NULL;
        }
        WARN_ON(!od->is_real && !OVL_TYPE_MERGE(type));
        if (od->is_real && OVL_TYPE_MERGE(type))
@@ -295,17 +293,16 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
 
 static void ovl_seek_cursor(struct ovl_dir_file *od, loff_t pos)
 {
-       struct ovl_cache_entry *p;
+       struct list_head *p;
        loff_t off = 0;
 
-       list_for_each_entry(p, &od->cache->entries, l_node) {
-               if (p->is_cursor)
-                       continue;
+       list_for_each(p, &od->cache->entries) {
                if (off >= pos)
                        break;
                off++;
        }
-       list_move_tail(&od->cursor.l_node, &p->l_node);
+       /* Cursor is safe since the cache is stable */
+       od->cursor = p;
 }
 
 static struct ovl_dir_cache *ovl_cache_get(struct dentry *dentry)
@@ -344,6 +341,7 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
 {
        struct ovl_dir_file *od = file->private_data;
        struct dentry *dentry = file->f_path.dentry;
+       struct ovl_cache_entry *p;
 
        if (!ctx->pos)
                ovl_dir_reset(file);
@@ -362,19 +360,13 @@ static int ovl_iterate(struct file *file, struct dir_context *ctx)
                ovl_seek_cursor(od, ctx->pos);
        }
 
-       while (od->cursor.l_node.next != &od->cache->entries) {
-               struct ovl_cache_entry *p;
-
-               p = list_entry(od->cursor.l_node.next, struct ovl_cache_entry, l_node);
-               /* Skip cursors */
-               if (!p->is_cursor) {
-                       if (!p->is_whiteout) {
-                               if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
-                                       break;
-                       }
-                       ctx->pos++;
-               }
-               list_move(&od->cursor.l_node, &p->l_node);
+       while (od->cursor != &od->cache->entries) {
+               p = list_entry(od->cursor, struct ovl_cache_entry, l_node);
+               if (!p->is_whiteout)
+                       if (!dir_emit(ctx, p->name, p->len, p->ino, p->type))
+                               break;
+               od->cursor = p->l_node.next;
+               ctx->pos++;
        }
        return 0;
 }
@@ -493,11 +485,9 @@ static int ovl_dir_open(struct inode *inode, struct file *file)
                kfree(od);
                return PTR_ERR(realfile);
        }
-       INIT_LIST_HEAD(&od->cursor.l_node);
        od->realfile = realfile;
        od->is_real = !OVL_TYPE_MERGE(type);
        od->is_upper = OVL_TYPE_UPPER(type);
-       od->cursor.is_cursor = true;
        file->private_data = od;
 
        return 0;