ovl: decode lower file handles of unlinked but open files

Lookup overlay inode in cache by origin inode, so we can decode a file
handle of an open file even if the index has a whiteout index entry to
mark this overlay inode was unlinked.

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

3 files changed, 38 insertions, 2 deletions

diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index f475a10eec07..0bca38c79244 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -443,14 +443,22 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
         struct ovl_path *stack = &origin;
         struct dentry *dentry = NULL;
         struct dentry *index = NULL;
+        struct inode *inode = NULL;
+        bool is_deleted = false;
         int err;
 
         /* First lookup indexed upper by fh */
         if (ofs->indexdir) {
                 index = ovl_get_index_fh(ofs, fh);
                 err = PTR_ERR(index);
-                if (IS_ERR(index))
-                        return ERR_PTR(err);
+                if (IS_ERR(index)) {
+                        if (err != -ESTALE)
+                                return ERR_PTR(err);
+
+                        /* Found a whiteout index - treat as deleted inode */
+                        is_deleted = true;
+                        index = NULL;
+                }
         }
 
         /* Then lookup origin by fh */
@@ -461,6 +469,16 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
                 err = ovl_verify_origin(index, origin.dentry, false);
                 if (err)
                         goto out_err;
+        } else if (is_deleted) {
+                /* Lookup deleted non-dir by origin inode */
+                if (!d_is_dir(origin.dentry))
+                        inode = ovl_lookup_inode(sb, origin.dentry);
+                err = -ESTALE;
+                if (!inode || atomic_read(&inode->i_count) == 1)
+                        goto out_err;
+
+                /* Deleted but still open? */
+                index = dget(ovl_i_dentry_upper(inode));
         }
 
         dentry = ovl_get_dentry(sb, NULL, &origin, index);
@@ -468,6 +486,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
 out:
         dput(origin.dentry);
         dput(index);
+        iput(inode);
         return dentry;
 
 out_err:
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index bfd7c766b5cd..56ba015b9f5e 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -645,6 +645,22 @@ static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
         return true;
 }
 
+struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *origin)
+{
+        struct inode *inode, *key = d_inode(origin);
+
+        inode = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
+        if (!inode)
+                return NULL;
+
+        if (!ovl_verify_inode(inode, origin, NULL)) {
+                iput(inode);
+                return ERR_PTR(-ESTALE);
+        }
+
+        return inode;
+}
+
 struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
                             struct dentry *lowerdentry, struct dentry *index,
                             unsigned int numlower)
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 40ba11e412b1..a47f9142b6be 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -322,6 +322,7 @@ int ovl_update_time(struct inode *inode, struct timespec *ts, int flags);
 bool ovl_is_private_xattr(const char *name);
 
 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 *origin);
 struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
                             struct dentry *lowerdentry, struct dentry *index,
                             unsigned int numlower);