overlayfs: barriers for opening upper-layer directory

[firefly-linux-kernel-4.4.55.git] / fs / overlayfs / readdir.c

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index a9ee2c1176fe221b6eb3b2f9c5f74ae3d38cd835..8c8ce9d87ba35cbe02a1607f3f2565e0f2bafc56 100644 (file)
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -38,7 +38,7 @@ struct ovl_readdir_data {
        bool is_merge;
        struct rb_root root;
        struct list_head *list;
-       struct list_head *middle;
+       struct list_head middle;
        int count;
        int err;
 };
@@ -139,13 +139,13 @@ static int ovl_fill_lower(struct ovl_readdir_data *rdd,
 
        p = ovl_cache_entry_find(&rdd->root, name, namelen);
        if (p) {
-               list_move_tail(&p->l_node, rdd->middle);
+               list_move_tail(&p->l_node, &rdd->middle);
        } else {
                p = ovl_cache_entry_new(name, namelen, ino, d_type);
                if (p == NULL)
                        rdd->err = -ENOMEM;
                else
-                       list_add_tail(&p->l_node, rdd->middle);
+                       list_add_tail(&p->l_node, &rdd->middle);
        }
 
        return rdd->err;
@@ -277,7 +277,6 @@ static inline int ovl_dir_read_merged(struct path *upperpath,
                                      struct list_head *list)
 {
        int err;
-       struct list_head middle;
        struct ovl_readdir_data rdd = {
                .ctx.actor = ovl_fill_merge,
                .list = list,
@@ -301,11 +300,10 @@ static inline int ovl_dir_read_merged(struct path *upperpath,
                 * Insert lowerpath entries before upperpath ones, this allows
                 * offsets to be reasonably constant
                 */
-               list_add(&middle, rdd.list);
-               rdd.middle = &middle;
+               list_add(&rdd.middle, rdd.list);
                rdd.is_merge = true;
                err = ovl_dir_read(lowerpath, &rdd);
-               list_del(&middle);
+               list_del(&rdd.middle);
        }
 out:
        return err;
@@ -456,12 +454,13 @@ static int ovl_dir_fsync(struct file *file, loff_t start, loff_t end,
        if (!od->is_upper && ovl_path_type(dentry) == OVL_PATH_MERGE) {
                struct inode *inode = file_inode(file);
 
-               realfile = od->upperfile;
+               realfile =lockless_dereference(od->upperfile);
                if (!realfile) {
                        struct path upperpath;
 
                        ovl_path_upper(dentry, &upperpath);
                        realfile = ovl_path_open(&upperpath, O_RDONLY);
+                       smp_mb__before_spinlock();
                        mutex_lock(&inode->i_mutex);
                        if (!od->upperfile) {
                                if (IS_ERR(realfile)) {