Overlay directory inodes report overlay st_dev to stat(2).
Overlay non-dir inodes report real st_dev and real st_ino to stat(2).
Due to the different st_dev 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 disk usage.
The reason that the overlay st_dev is not used for non-dir is because
the tuple overlay st_dev and real st_ino is not unique when overlay
layers are not on the same fs.
When all overlay layers are on the same fs, that tuple is unique, so
use overlay st_dev for non-dirs to get the correct result from du -x.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/inode.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 9c0c4e1..ec5230f 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -73,8 +73,10 @@ static int ovl_getattr(const struct path *path, struct kstat *stat,
return err;
/*
- * When all layers are on the same fs, we use st_ino of the copy up
- * origin, if we know it.
+ * When all layers are on the same fs, all real inode number are
+ * unique, so we use the overlay st_dev, which is friendly to du -x.
+ *
+ * We also use st_ino of the copy up origin, if we know it.
* This guaranties constant st_dev/st_ino across copy up.
*
* When redirect_fh is enabled, this also guaranties persistent
@@ -83,15 +85,14 @@ static int ovl_getattr(const struct path *path, struct kstat *stat,
if (ovl_same_sb(dentry->d_sb)) {
struct dentry *lower = ovl_dentry_lower(dentry);
+ stat->dev = dentry->d_sb->s_dev;
/*
* Lower hardlinks are broken on copy up to differnt upper
* files, so we cannot use the lower origin st_ino for those
* different files, even for the same fs case.
*/
- if (lower && lower->d_inode->i_nlink == 1) {
- stat->dev = lower->d_sb->s_dev;
+ if (lower && lower->d_inode->i_nlink == 1)
stat->ino = lower->d_inode->i_ino;
- }
}
return 0;
--
2.7.4
