From: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
For non-samefs setup, to make sure that st_dev/st_ino pair
is unique across the system, we return a unique anonymous
st_dev for stat(2) of lower layer inode.
We need to make this change before fixing constant st_dev/st_ino across
copy up for non-samefs. Otherwise, we can end up with two objects
in the system, the real lower inode and the overlay inode which
have same st_dev/st_ino value, but different content.
[amir: simplify ovl_get_pseudo_dev()
split from allocate anonymous bdev patch]
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/inode.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index b772e5a2a730..607a50c50042 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -15,6 +15,14 @@
#include <linux/ratelimit.h>
#include "overlayfs.h"
+
+static dev_t ovl_get_pseudo_dev(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return oe->lowerstack[0].layer->pseudo_dev;
+}
+
int ovl_setattr(struct dentry *dentry, struct iattr *attr)
{
int err;
@@ -121,6 +129,13 @@ int ovl_getattr(const struct path *path, struct kstat *stat,
*/
stat->dev = dentry->d_sb->s_dev;
stat->ino = dentry->d_inode->i_ino;
+ } else if (!OVL_TYPE_UPPER(type)) {
+ /*
+ * For non-samefs setup, to make sure that st_dev/st_ino pair
+ * is unique across the system, we use a unique anonymous
+ * st_dev for lower layer inode.
+ */
+ stat->dev = ovl_get_pseudo_dev(dentry);
}
/*
--
2.7.4
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