[PATCH v3 10/16] ovl: set the COPYUP type flag for non-dirs

Amir Goldstein
2017-04-26T21:35:37Z

For directory entries, non zero oe->numlower implies OVL_TYPE_MERGE.
Define a new type flag OVL_TYPE_COPYUP to indicate that an entry is
a target of a copy up.

For directory entries COPYUP = MERGE && UPPER. For non-dir entries
non zero oe->numlower implies COPYUP, but COPYUP does not imply
non zero oe->numlower. COPYUP can also be set on lookup when detecting
an overlay.fh xattr on a non-dir, even if that fh cannot be followed.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
fs/overlayfs/namei.c | 3 +++
fs/overlayfs/overlayfs.h | 2 ++
fs/overlayfs/util.c | 12 ++++++++----
3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index ad2c784..3ebde1b 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -457,6 +457,9 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
}
if (d.opaque)
type |= __OVL_PATH_OPAQUE;
+ /* overlay.fh xattr implies this is a copy up */
+ if (d.fh)
+ type |= __OVL_PATH_COPYUP;
}

/*
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index ea23bef..d9633b3 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -13,11 +13,13 @@ enum ovl_path_type {
__OVL_PATH_UPPER = (1 << 0),
__OVL_PATH_MERGE = (1 << 1),
__OVL_PATH_OPAQUE = (1 << 2),
+ __OVL_PATH_COPYUP = (1 << 3),
};

#define OVL_TYPE_UPPER(type) ((type) & __OVL_PATH_UPPER)
#define OVL_TYPE_MERGE(type) ((type) & __OVL_PATH_MERGE)
#define OVL_TYPE_OPAQUE(type) ((type) & __OVL_PATH_OPAQUE)
+#define OVL_TYPE_COPYUP(type) ((type) & __OVL_PATH_COPYUP)

#define OVL_XATTR_PREFIX XATTR_TRUSTED_PREFIX "overlay."
#define OVL_XATTR_OPAQUE OVL_XATTR_PREFIX "opaque"
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index a36ca7b..931d199 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -101,11 +101,15 @@ enum ovl_path_type ovl_update_type(struct dentry *dentry, bool is_dir)
if (oe->__upperdentry) {
type |= __OVL_PATH_UPPER;
/*
- * Non-dir dentry can hold lower dentry from before
- * copy-up.
+ * oe->numlower implies a copy up, but copy up does not imply
+ * oe->numlower. It can also be set on lookup when detecting
+ * an overlay.fh xattr on a non-dir that cannot be followed.
*/
- if (oe->numlower && is_dir)
- type |= __OVL_PATH_MERGE;
+ if (oe->numlower) {
+ type |= __OVL_PATH_COPYUP;
+ if (is_dir)
+ type |= __OVL_PATH_MERGE;
+ }
} else {
if (oe->numlower > 1)
type |= __OVL_PATH_MERGE;
--
2.7.4