Merge branch 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs

Pull overlayfs updates from Miklos Szeredi:
 "This fixes d_ino correctness in readdir, which brings overlayfs on par
  with normal filesystems regarding inode number semantics, as long as
  all layers are on the same filesystem.

  There are also some bug fixes, one in particular (random ioctl's
  shouldn't be able to modify lower layers) that touches some vfs code,
  but of course no-op for non-overlay fs"

* 'overlayfs-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs:
  ovl: fix false positive ESTALE on lookup
  ovl: don't allow writing ioctl on lower layer
  ovl: fix relatime for directories
  vfs: add flags to d_real()
  ovl: cleanup d_real for negative
  ovl: constant d_ino for non-merge dirs
  ovl: constant d_ino across copy up
  ovl: fix readdir error value
  ovl: check snprintf return

1 files changed, 17 insertions, 4 deletions

diff --git a/fs/inode.c b/fs/inode.c
index 210054157a49..d1e35b53bb23 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1570,11 +1570,24 @@ EXPORT_SYMBOL(bmap);
 static void update_ovl_inode_times(struct dentry *dentry, struct inode *inode,
 			       bool rcu)
 {
-	if (!rcu) {
-		struct inode *realinode = d_real_inode(dentry);
+	struct dentry *upperdentry;
 
-		if (unlikely(inode != realinode) &&
-		    (!timespec_equal(&inode->i_mtime, &realinode->i_mtime) ||
+	/*
+	 * Nothing to do if in rcu or if non-overlayfs
+	 */
+	if (rcu || likely(!(dentry->d_flags & DCACHE_OP_REAL)))
+		return;
+
+	upperdentry = d_real(dentry, NULL, 0, D_REAL_UPPER);
+
+	/*
+	 * If file is on lower then we can't update atime, so no worries about
+	 * stale mtime/ctime.
+	 */
+	if (upperdentry) {
+		struct inode *realinode = d_inode(upperdentry);
+
+		if ((!timespec_equal(&inode->i_mtime, &realinode->i_mtime) ||
 		     !timespec_equal(&inode->i_ctime, &realinode->i_ctime))) {
 			inode->i_mtime = realinode->i_mtime;
 			inode->i_ctime = realinode->i_ctime;