Overlay directory inodes report overlay bdev to stat(2). Overlay non-dir inodes report real bdev and real ino to stat(2). Due to the different bdev values for dir and non-dir inodes, when executing the command du -x on an overlay mount, the result is wrong because non-dirs are not accounted for in the overlay bdev usage. The reasons for this bdev inconsistecy is: 1. The overlay ino is not persistent, so real ino is used for non-dirs 2. The tupple overlay bdev and real ino is not unique, so real bdev is used for non-dirs In case all overlay layers are on the same underlying fs, the tupple from reason 2 above is unique, so use this tupple for non-dirs to get the correct result from du -x. Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- fs/overlayfs/inode.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 3615a52..39c3bb0 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -78,6 +78,13 @@ static int ovl_getattr(const struct path *path, struct kstat *stat, stat->dev = lower->d_sb->s_dev; stat->ino = lower->d_inode->i_ino; } + /* + * When all layers are on same fs, the tupple overlay bdev + * and real inode ino is unique, so it is preferred to expose + * overlay bdev for overlay inodes for things like du -x. + */ + if (ovl_same_sb(dentry->d_sb)) + stat->dev = dentry->d_sb->s_dev; return err; } -- 2.7.4
