1 files changed, 75 insertions, 106 deletions

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index c0205990a9f5..907870e81a72 100644
--- 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[];
 };
 
@@ -40,6 +39,7 @@ struct ovl_readdir_data {
         struct rb_root root;
         struct list_head *list;
         struct list_head middle;
+        struct dentry *dir;
         int count;
         int err;
 };
@@ -48,7 +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;
 };
@@ -79,23 +79,49 @@ static struct ovl_cache_entry *ovl_cache_entry_find(struct rb_root *root,
         return NULL;
 }
 
-static struct ovl_cache_entry *ovl_cache_entry_new(const char *name, int len,
+static struct ovl_cache_entry *ovl_cache_entry_new(struct dentry *dir,
+                                                   const char *name, int len,
                                                    u64 ino, unsigned int d_type)
 {
         struct ovl_cache_entry *p;
         size_t size = offsetof(struct ovl_cache_entry, name[len + 1]);
 
         p = kmalloc(size, GFP_KERNEL);
-        if (p) {
-                memcpy(p->name, name, len);
-                p->name[len] = '\0';
-                p->len = len;
-                p->type = d_type;
-                p->ino = ino;
-                p->is_whiteout = false;
-                p->is_cursor = false;
-        }
+        if (!p)
+                return NULL;
+
+        memcpy(p->name, name, len);
+        p->name[len] = '\0';
+        p->len = len;
+        p->type = d_type;
+        p->ino = ino;
+        p->is_whiteout = false;
+
+        if (d_type == DT_CHR) {
+                struct dentry *dentry;
+                const struct cred *old_cred;
+                struct cred *override_cred;
+
+                override_cred = prepare_creds();
+                if (!override_cred) {
+                        kfree(p);
+                        return NULL;
+                }
+
+                /*
+                 * CAP_DAC_OVERRIDE for lookup
+                 */
+                cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
+                old_cred = override_creds(override_cred);
 
+                dentry = lookup_one_len(name, dir, len);
+                if (!IS_ERR(dentry)) {
+                        p->is_whiteout = ovl_is_whiteout(dentry);
+                        dput(dentry);
+                }
+                revert_creds(old_cred);
+                put_cred(override_cred);
+        }
         return p;
 }
 
@@ -122,7 +148,7 @@ static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
                         return 0;
         }
 
-        p = ovl_cache_entry_new(name, len, ino, d_type);
+        p = ovl_cache_entry_new(rdd->dir, name, len, ino, d_type);
         if (p == NULL)
                 return -ENOMEM;
 
@@ -143,7 +169,7 @@ static int ovl_fill_lower(struct ovl_readdir_data *rdd,
         if (p) {
                 list_move_tail(&p->l_node, &rdd->middle);
         } else {
-                p = ovl_cache_entry_new(name, namelen, ino, d_type);
+                p = ovl_cache_entry_new(rdd->dir, name, namelen, ino, d_type);
                 if (p == NULL)
                         rdd->err = -ENOMEM;
                 else
@@ -168,7 +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) {
@@ -204,6 +229,7 @@ static inline int ovl_dir_read(struct path *realpath,
         if (IS_ERR(realfile))
                 return PTR_ERR(realfile);
 
+        rdd->dir = realpath->dentry;
         rdd->ctx.pos = 0;
         do {
                 rdd->count = 0;
@@ -227,108 +253,58 @@ 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 && type != OVL_PATH_MERGE);
-        if (od->is_real && type == OVL_PATH_MERGE)
+        WARN_ON(!od->is_real && !OVL_TYPE_MERGE(type));
+        if (od->is_real && OVL_TYPE_MERGE(type))
                 od->is_real = false;
 }
 
-static int ovl_dir_mark_whiteouts(struct dentry *dir,
-                                  struct ovl_readdir_data *rdd)
-{
-        struct ovl_cache_entry *p;
-        struct dentry *dentry;
-        const struct cred *old_cred;
-        struct cred *override_cred;
-
-        override_cred = prepare_creds();
-        if (!override_cred) {
-                ovl_cache_free(rdd->list);
-                return -ENOMEM;
-        }
-
-        /*
-         * CAP_DAC_OVERRIDE for lookup
-         */
-        cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
-        old_cred = override_creds(override_cred);
-
-        mutex_lock(&dir->d_inode->i_mutex);
-        list_for_each_entry(p, rdd->list, l_node) {
-                if (p->is_cursor)
-                        continue;
-
-                if (p->type != DT_CHR)
-                        continue;
-
-                dentry = lookup_one_len(p->name, dir, p->len);
-                if (IS_ERR(dentry))
-                        continue;
-
-                p->is_whiteout = ovl_is_whiteout(dentry);
-                dput(dentry);
-        }
-        mutex_unlock(&dir->d_inode->i_mutex);
-
-        revert_creds(old_cred);
-        put_cred(override_cred);
-
-        return 0;
-}
-
 static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
 {
         int err;
-        struct path lowerpath;
-        struct path upperpath;
+        struct path realpath;
         struct ovl_readdir_data rdd = {
                 .ctx.actor = ovl_fill_merge,
                 .list = list,
                 .root = RB_ROOT,
                 .is_merge = false,
         };
+        int idx, next;
 
-        ovl_path_lower(dentry, &lowerpath);
-        ovl_path_upper(dentry, &upperpath);
+        for (idx = 0; idx != -1; idx = next) {
+                next = ovl_path_next(idx, dentry, &realpath);
 
-        if (upperpath.dentry) {
-                err = ovl_dir_read(&upperpath, &rdd);
-                if (err)
-                        goto out;
-
-                if (lowerpath.dentry) {
-                        err = ovl_dir_mark_whiteouts(upperpath.dentry, &rdd);
+                if (next != -1) {
+                        err = ovl_dir_read(&realpath, &rdd);
                         if (err)
-                                goto out;
+                                break;
+                } else {
+                        /*
+                         * Insert lowest layer entries before upper ones, this
+                         * allows offsets to be reasonably constant
+                         */
+                        list_add(&rdd.middle, rdd.list);
+                        rdd.is_merge = true;
+                        err = ovl_dir_read(&realpath, &rdd);
+                        list_del(&rdd.middle);
                 }
         }
-        if (lowerpath.dentry) {
-                /*
-                 * Insert lowerpath entries before upperpath ones, this allows
-                 * offsets to be reasonably constant
-                 */
-                list_add(&rdd.middle, rdd.list);
-                rdd.is_merge = true;
-                err = ovl_dir_read(&lowerpath, &rdd);
-                list_del(&rdd.middle);
-        }
-out:
         return err;
 }
 
 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)
@@ -367,6 +343,7 @@ 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);
@@ -385,19 +362,13 @@ 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;
 }
@@ -452,7 +423,7 @@ static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
         /*
          * Need to check if we started out being a lower dir, but got copied up
          */
-        if (!od->is_upper && ovl_path_type(dentry) != OVL_PATH_LOWER) {
+        if (!od->is_upper && OVL_TYPE_UPPER(ovl_path_type(dentry))) {
                 struct inode *inode = file_inode(file);
 
                 realfile = lockless_dereference(od->upperfile);
@@ -516,11 +487,9 @@ 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 = (type != OVL_PATH_MERGE);
-        od->is_upper = (type != OVL_PATH_LOWER);
-        od->cursor.is_cursor = true;
+        od->is_real = !OVL_TYPE_MERGE(type);
+        od->is_upper = OVL_TYPE_UPPER(type);
         file->private_data = od;
 
         return 0;