1 files changed, 45 insertions, 8 deletions

diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index fdaf28f75e12..6ec1e43a9a54 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -36,13 +36,14 @@ struct ovl_dir_cache {
 
 struct ovl_readdir_data {
         struct dir_context ctx;
-        bool is_merge;
+        bool is_lowest;
         struct rb_root root;
         struct list_head *list;
         struct list_head middle;
         struct ovl_cache_entry *first_maybe_whiteout;
         int count;
         int err;
+        bool d_type_supported;
 };
 
 struct ovl_dir_file {
@@ -139,9 +140,9 @@ static int ovl_cache_entry_add_rb(struct ovl_readdir_data *rdd,
         return 0;
 }
 
-static int ovl_fill_lower(struct ovl_readdir_data *rdd,
-                          const char *name, int namelen,
-                          loff_t offset, u64 ino, unsigned int d_type)
+static int ovl_fill_lowest(struct ovl_readdir_data *rdd,
+                           const char *name, int namelen,
+                           loff_t offset, u64 ino, unsigned int d_type)
 {
         struct ovl_cache_entry *p;
 
@@ -193,10 +194,10 @@ static int ovl_fill_merge(struct dir_context *ctx, const char *name,
                 container_of(ctx, struct ovl_readdir_data, ctx);
 
         rdd->count++;
-        if (!rdd->is_merge)
+        if (!rdd->is_lowest)
                 return ovl_cache_entry_add_rb(rdd, name, namelen, ino, d_type);
         else
-                return ovl_fill_lower(rdd, name, namelen, offset, ino, d_type);
+                return ovl_fill_lowest(rdd, name, namelen, offset, ino, d_type);
 }
 
 static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
@@ -289,7 +290,7 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
                 .ctx.actor = ovl_fill_merge,
                 .list = list,
                 .root = RB_ROOT,
-                .is_merge = false,
+                .is_lowest = false,
         };
         int idx, next;
 
@@ -306,7 +307,7 @@ static int ovl_dir_read_merged(struct dentry *dentry, struct list_head *list)
                          * allows offsets to be reasonably constant
                          */
                         list_add(&rdd.middle, rdd.list);
-                        rdd.is_merge = true;
+                        rdd.is_lowest = true;
                         err = ovl_dir_read(&realpath, &rdd);
                         list_del(&rdd.middle);
                 }
@@ -577,3 +578,39 @@ void ovl_cleanup_whiteouts(struct dentry *upper, struct list_head *list)
         }
         inode_unlock(upper->d_inode);
 }
+
+static int ovl_check_d_type(struct dir_context *ctx, const char *name,
+                          int namelen, loff_t offset, u64 ino,
+                          unsigned int d_type)
+{
+        struct ovl_readdir_data *rdd =
+                container_of(ctx, struct ovl_readdir_data, ctx);
+
+        /* Even if d_type is not supported, DT_DIR is returned for . and .. */
+        if (!strncmp(name, ".", namelen) || !strncmp(name, "..", namelen))
+                return 0;
+
+        if (d_type != DT_UNKNOWN)
+                rdd->d_type_supported = true;
+
+        return 0;
+}
+
+/*
+ * Returns 1 if d_type is supported, 0 not supported/unknown. Negative values
+ * if error is encountered.
+ */
+int ovl_check_d_type_supported(struct path *realpath)
+{
+        int err;
+        struct ovl_readdir_data rdd = {
+                .ctx.actor = ovl_check_d_type,
+                .d_type_supported = false,
+        };
+
+        err = ovl_dir_read(realpath, &rdd);
+        if (err)
+                return err;
+
+        return rdd.d_type_supported;
+}