[PATCH 7/7] ovl: replace lowerdata inode reference with lowerdata redirect

[Amir Goldstein <amir73il@gmail.com>]

Now that we have the entire lower stack in ovl_inode, we do not
need to hold another reference to the lowerdata inode.

Instead, use the vacant ovl_inode space as a place holder for lowerdata
redirect path from the metacopy to lowerdata, which is going to be used
later on for lazy lowerdata lookup.

Use accessors to get the lowerdata path and dentry.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/overlayfs/inode.c     |  4 ++--
 fs/overlayfs/namei.c     |  7 +++++--
 fs/overlayfs/overlayfs.h |  3 ++-
 fs/overlayfs/ovl_entry.h | 16 +++++++++++++++-
 fs/overlayfs/super.c     |  4 ++--
 fs/overlayfs/util.c      | 26 ++++++++++++++++----------
 6 files changed, 42 insertions(+), 18 deletions(-)

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 9f29fc3e9fa5..35d51a6dced7 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -1006,8 +1006,7 @@ void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
 	oi->__upperdentry = oip->upperdentry;
 	oi->oe = *oip->oe;
 	oi->redirect = oip->redirect;
-	if (oip->lowerdata)
-		oi->lowerdata = igrab(d_inode(oip->lowerdata));
+	oi->lowerdata_redirect = oip->lowerdata_redirect;
 
 	realinode = ovl_inode_real(inode);
 	ovl_copyattr(inode);
@@ -1368,6 +1367,7 @@ struct inode *ovl_get_inode(struct super_block *sb,
 			dput(upperdentry);
 			ovl_destroy_entry(oip->oe);
 			kfree(oip->redirect);
+			kfree(oip->lowerdata_redirect);
 			goto out;
 		}
 
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index cdcb2ac5d95c..b629261324f1 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -1105,10 +1105,13 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			.oe = &oe,
 			.index = index,
 			.redirect = upperredirect,
-			.lowerdata = (ctr > 1 && !d.is_dir) ?
-				      stack[ctr - 1].dentry : NULL,
 		};
 
+		/* Store lowerdata redirect for lazy lookup */
+		if (ctr > 1 && !d.is_dir && !stack[ctr - 1].dentry) {
+			oip.lowerdata_redirect = d.redirect;
+			d.redirect = NULL;
+		}
 		inode = ovl_get_inode(dentry->d_sb, &oip);
 		err = PTR_ERR(inode);
 		if (IS_ERR(inode))
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 32532342e56a..011b7b466f70 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -409,6 +409,7 @@ struct inode *ovl_inode_lower(struct inode *inode);
 struct inode *ovl_inode_lowerdata(struct inode *inode);
 struct inode *ovl_inode_real(struct inode *inode);
 struct inode *ovl_inode_realdata(struct inode *inode);
+const char *ovl_lowerdata_redirect(struct inode *inode);
 struct ovl_dir_cache *ovl_dir_cache(struct inode *inode);
 void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache);
 void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry);
@@ -660,7 +661,7 @@ struct ovl_inode_params {
 	struct ovl_entry *oe;
 	bool index;
 	char *redirect;
-	struct dentry *lowerdata;
+	char *lowerdata_redirect;
 };
 void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
 		    unsigned long ino, int fsid);
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 5d95e937f555..221f0cbe748e 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -125,6 +125,20 @@ static inline struct ovl_path *ovl_lowerstack(struct ovl_entry *oe)
 	return oe && oe->__numlower > 1 ? oe->__lowerstack : &oe->__lowerpath;
 }
 
+static inline struct ovl_path *ovl_lowerdata(struct ovl_entry *oe)
+{
+	struct ovl_path *lowerstack = ovl_lowerstack(oe);
+
+	return lowerstack ? &lowerstack[oe->__numlower - 1] : NULL;
+}
+
+static inline struct dentry *ovl_lowerdata_dentry(struct ovl_entry *oe)
+{
+	struct ovl_path *lowerdata = ovl_lowerdata(oe);
+
+	return lowerdata ? lowerdata->dentry : NULL;
+}
+
 /* private information held for every overlayfs dentry */
 static inline unsigned long *OVL_E_FLAGS(struct dentry *dentry)
 {
@@ -134,7 +148,7 @@ static inline unsigned long *OVL_E_FLAGS(struct dentry *dentry)
 struct ovl_inode {
 	union {
 		struct ovl_dir_cache *cache;	/* directory */
-		struct inode *lowerdata;	/* regular file */
+		const char *lowerdata_redirect;	/* regular file */
 	};
 	const char *redirect;
 	u64 version;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index e01a76de787c..6e4231799b86 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -172,7 +172,7 @@ static struct inode *ovl_alloc_inode(struct super_block *sb)
 	oi->flags = 0;
 	oi->__upperdentry = NULL;
 	ovl_init_entry(&oi->oe, NULL, 0);
-	oi->lowerdata = NULL;
+	oi->lowerdata_redirect = NULL;
 	mutex_init(&oi->lock);
 
 	return &oi->vfs_inode;
@@ -196,7 +196,7 @@ static void ovl_destroy_inode(struct inode *inode)
 	if (S_ISDIR(inode->i_mode))
 		ovl_dir_cache_free(inode);
 	else
-		iput(oi->lowerdata);
+		kfree(oi->lowerdata_redirect);
 }
 
 static void ovl_free_fs(struct ovl_fs *ofs)
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 540819ac9b9c..fe2e5a8b216b 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -245,11 +245,12 @@ void ovl_path_lower(struct dentry *dentry, struct path *path)
 void ovl_path_lowerdata(struct dentry *dentry, struct path *path)
 {
 	struct ovl_entry *oe = OVL_E(dentry);
-	struct ovl_path *lowerstack = ovl_lowerstack(oe);
+	struct ovl_path *lowerdata = ovl_lowerdata(oe);
+	struct dentry *lowerdata_dentry = ovl_lowerdata_dentry(oe);
 
-	if (ovl_numlower(oe)) {
-		path->mnt = lowerstack[ovl_numlower(oe) - 1].layer->mnt;
-		path->dentry = lowerstack[ovl_numlower(oe) - 1].dentry;
+	if (lowerdata_dentry) {
+		path->dentry = lowerdata_dentry;
+		path->mnt = lowerdata->layer->mnt;
 	} else {
 		*path = (struct path) { };
 	}
@@ -308,10 +309,7 @@ const struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
  */
 struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
 {
-	struct ovl_entry *oe = OVL_E(dentry);
-
-	return ovl_numlower(oe) ?
-		ovl_lowerstack(oe)[ovl_numlower(oe) - 1].dentry : NULL;
+	return ovl_lowerdata_dentry(OVL_E(dentry));
 }
 
 struct dentry *ovl_dentry_real(struct dentry *dentry)
@@ -359,10 +357,12 @@ struct inode *ovl_inode_real(struct inode *inode)
 /* Return inode which contains lower data. Do not return metacopy */
 struct inode *ovl_inode_lowerdata(struct inode *inode)
 {
+	struct dentry *lowerdata = ovl_lowerdata_dentry(OVL_I_E(inode));
+
 	if (WARN_ON(!S_ISREG(inode->i_mode)))
 		return NULL;
 
-	return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode);
+	return lowerdata ? d_inode(lowerdata) : NULL;
 }
 
 /* Return real inode which contains data. Does not return metacopy inode */
@@ -377,9 +377,15 @@ struct inode *ovl_inode_realdata(struct inode *inode)
 	return ovl_inode_lowerdata(inode);
 }
 
+const char *ovl_lowerdata_redirect(struct inode *inode)
+{
+	return inode && S_ISREG(inode->i_mode) ?
+		OVL_I(inode)->lowerdata_redirect : NULL;
+}
+
 struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
 {
-	return OVL_I(inode)->cache;
+	return inode && S_ISDIR(inode->i_mode) ? OVL_I(inode)->cache : NULL;
 }
 
 void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
-- 
2.34.1