ovl: Store lower data inode in ovl_inode

Right now ovl_inode stores inode pointer for lower inode.  This helps with
quickly getting lower inode given overlay inode (ovl_inode_lower()).

Now with metadata only copy-up, we can have metacopy inode in middle layer
as well and inode containing data can be different from ->lower.  I need to
be able to open the real file in ovl_open_realfile() and for that I need to
quickly find the lower data inode.

Hence store lower data inode also in ovl_inode.  Also provide an helper
ovl_inode_lowerdata() to access this field.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

6 files changed, 27 insertions, 6 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 2a5a38c81961..12553274eae7 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -864,7 +864,7 @@ struct inode *ovl_get_inode(struct super_block *sb,
                 }
         }
         ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev, ino, fsid);
-        ovl_inode_init(inode, upperdentry, lowerdentry);
+        ovl_inode_init(inode, upperdentry, lowerdentry, oip->lowerdata);
 
         if (upperdentry && ovl_is_impuredir(upperdentry))
                 ovl_set_flag(OVL_IMPURE, inode);
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index f562bbb59ddb..85ab856dd134 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -1080,6 +1080,8 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
                         .index = index,
                         .numlower = ctr,
                         .redirect = upperredirect,
+                        .lowerdata = (ctr > 1 && !d.is_dir) ?
+                                      stack[ctr - 1].dentry : NULL,
                 };
 
                 inode = ovl_get_inode(dentry->d_sb, &oip);
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index de80250b379f..0ad593a85121 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -227,6 +227,7 @@ struct dentry *ovl_dentry_real(struct dentry *dentry);
 struct dentry *ovl_i_dentry_upper(struct inode *inode);
 struct inode *ovl_inode_upper(struct inode *inode);
 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 ovl_dir_cache *ovl_dir_cache(struct inode *inode);
 void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache);
@@ -246,7 +247,7 @@ bool ovl_redirect_dir(struct super_block *sb);
 const char *ovl_dentry_get_redirect(struct dentry *dentry);
 void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect);
 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
-                    struct dentry *lowerdentry);
+                    struct dentry *lowerdentry, struct dentry *lowerdata);
 void ovl_inode_update(struct inode *inode, struct dentry *upperdentry);
 void ovl_dir_modified(struct dentry *dentry, bool impurity);
 u64 ovl_dentry_version_get(struct dentry *dentry);
@@ -354,6 +355,7 @@ struct ovl_inode_params {
         struct dentry *index;
         unsigned int numlower;
         char *redirect;
+        struct dentry *lowerdata;
 };
 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev);
 struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index ea4134e97d0d..ec237035333a 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -89,7 +89,10 @@ static inline struct ovl_entry *OVL_E(struct dentry *dentry)
 }
 
 struct ovl_inode {
-        struct ovl_dir_cache *cache;
+        union {
+                struct ovl_dir_cache *cache;    /* directory */
+                struct inode *lowerdata;        /* regular file */
+        };
         const char *redirect;
         u64 version;
         unsigned long flags;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index ab0039161f85..6d22bbd5f27f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -181,6 +181,7 @@ static struct inode *ovl_alloc_inode(struct super_block *sb)
         oi->flags = 0;
         oi->__upperdentry = NULL;
         oi->lower = NULL;
+        oi->lowerdata = NULL;
         mutex_init(&oi->lock);
 
         return &oi->vfs_inode;
@@ -199,8 +200,11 @@ static void ovl_destroy_inode(struct inode *inode)
 
         dput(oi->__upperdentry);
         iput(oi->lower);
+        if (S_ISDIR(inode->i_mode))
+                ovl_dir_cache_free(inode);
+        else
+                iput(oi->lowerdata);
         kfree(oi->redirect);
-        ovl_dir_cache_free(inode);
         mutex_destroy(&oi->lock);
 
         call_rcu(&inode->i_rcu, ovl_i_callback);
@@ -1487,7 +1491,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
         ovl_dentry_set_flag(OVL_E_CONNECTED, root_dentry);
         ovl_set_upperdata(d_inode(root_dentry));
         ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
-                       ovl_dentry_lower(root_dentry));
+                       ovl_dentry_lower(root_dentry), NULL);
 
         sb->s_root = root_dentry;
 
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 4f9c2ecee74c..63311c536216 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -247,6 +247,14 @@ struct inode *ovl_inode_real(struct inode *inode)
         return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
 }
 
+/* Return inode which contains lower data. Do not return metacopy */
+struct inode *ovl_inode_lowerdata(struct inode *inode)
+{
+        if (WARN_ON(!S_ISREG(inode->i_mode)))
+                return NULL;
+
+        return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode);
+}
 
 struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
 {
@@ -381,7 +389,7 @@ void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
 }
 
 void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
-                    struct dentry *lowerdentry)
+                    struct dentry *lowerdentry, struct dentry *lowerdata)
 {
         struct inode *realinode = d_inode(upperdentry ?: lowerdentry);
 
@@ -389,6 +397,8 @@ void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
                 OVL_I(inode)->__upperdentry = upperdentry;
         if (lowerdentry)
                 OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
+        if (lowerdata)
+                OVL_I(inode)->lowerdata = igrab(d_inode(lowerdata));
 
         ovl_copyattr(realinode, inode);
         ovl_copyflags(realinode, inode);