[neon/backports-focal/xdg-desktop-portal/Neon/unstable] document-portal: document-portal: Ensure root docdir inode alive while there are other inodes

[Alexander Larsson]

Git commit 74f70ad153f256e70bb3cae4a3c81f5f559e794a by Alexander Larsson.
Committed on 02/04/2020 at 15:01.
Pushed by ash into branch 'Neon/unstable'.

document-portal: Ensure root docdir inode alive while there are other inodes

The root inode of the document directory is cheap to keep alive (no fd)
and it keeps the document domain alive. If the kernel forgets it and
it has no other reference then the next time the kernel asks for it
we will create a new document domain. This is bad because other existing
inodes might still be using the old document domain.

So, we keep a ref from the non-root inodes of a domain to the root inode.

M  +21   -11   document-portal/document-portal-fuse.c

https://invent.kde.org/neon/backports-focal/xdg-desktop-portal/commit/74f70ad153f256e70bb3cae4a3c81f5f559e794a

diff --git a/document-portal/document-portal-fuse.c b/document-portal/document-portal-fuse.c
index 8b7e66f..19b9c5a 100644
--- a/document-portal/document-portal-fuse.c
+++ b/document-portal/document-portal-fuse.c
@@ -181,7 +181,11 @@ struct _XdpInode {
 
   /* The below are only used for XDP_DOMAIN_DOCUMENT inodes */
   XdpPhysicalInode *physical;
-
+  /* The root of the domain, or NULL for the domain.  We use this to
+   * keep the root document inode alive so that when the kernel
+   * forgets it and then looks it up we will not get a new inode and
+   * thus a new domain. */
+  XdpInode *domain_root_inode;
 };
 
 typedef struct {
@@ -755,6 +759,7 @@ retry_atomic_decrement1:
       g_hash_table_remove (all_inodes, inode);
       G_UNLOCK (all_inodes);
 
+      g_clear_pointer (&inode->domain_root_inode, xdp_inode_unref);
       g_clear_pointer (&inode->physical, xdp_physical_inode_unref);
       xdp_domain_unref (inode->domain);
       g_free (inode);
@@ -1474,10 +1479,11 @@ abort_reply_entry (struct fuse_entry_param *e)
 }
 
 static int
-ensure_docdir_inode (XdpDomain *domain,
+ensure_docdir_inode (XdpInode *parent,
                      int o_path_fd_in, /* Takes ownership */
                      struct fuse_entry_param *e)
 {
+  XdpDomain *domain = parent->domain;
   g_autoptr(XdpPhysicalInode) physical = NULL;
   g_autoptr(XdpInode) inode = NULL;
   xdp_autofd int o_path_fd = o_path_fd_in;
@@ -1501,7 +1507,11 @@ ensure_docdir_inode (XdpDomain *domain,
   else
     {
       inode = xdp_inode_new (domain, physical);
-      g_hash_table_insert (domain->inodes, physical, inode);
+      if (parent->domain_root_inode)
+        inode->domain_root_inode = xdp_inode_ref (parent->domain_root_inode);
+      else
+        inode->domain_root_inode = xdp_inode_ref (parent);
+     g_hash_table_insert (domain->inodes, physical, inode);
     }
   G_UNLOCK(domain_inodes);
 
@@ -1513,7 +1523,7 @@ ensure_docdir_inode (XdpDomain *domain,
 }
 
 static int
-ensure_docdir_inode_by_name (XdpDomain *domain,
+ensure_docdir_inode_by_name (XdpInode *parent,
                              int dirfd,
                              const char *name,
                              struct fuse_entry_param *e)
@@ -1524,7 +1534,7 @@ ensure_docdir_inode_by_name (XdpDomain *domain,
   if (o_path_fd == -1)
       return -errno;
 
-  return ensure_docdir_inode (domain, o_path_fd, e); /* Takes ownershif of o_path_fd */
+  return ensure_docdir_inode (parent, o_path_fd, e); /* Takes ownershif of o_path_fd */
 }
 
 
@@ -1647,7 +1657,7 @@ xdp_fuse_lookup (fuse_req_t req,
           if (strcmp (name, BY_APP_NAME) == 0)
             inode = xdp_inode_ref (by_app_inode);
           else
-            inode = ensure_doc_inode (parent,name);
+            inode = ensure_doc_inode (parent, name);
           break;
         case XDP_DOMAIN_BY_APP:
           inode = ensure_by_app_inode (parent, name);
@@ -1672,7 +1682,7 @@ xdp_fuse_lookup (fuse_req_t req,
       if (fd < 0)
         return xdp_reply_err (op, req, -fd);
 
-      res = ensure_docdir_inode (parent->domain, fd, &e); /* Takes ownershif of fd */
+      res = ensure_docdir_inode (parent, fd, &e); /* Takes ownershif of fd */
       if (res != 0)
         return xdp_reply_err (op, req, -res);
 
@@ -1773,7 +1783,7 @@ xdp_fuse_create (fuse_req_t             req,
   if (o_path_fd < 0)
     return xdp_reply_err (op, req, errno);
 
-  res = ensure_docdir_inode (parent->domain, xdp_steal_fd (&o_path_fd), &e); /* Takes ownershif of o_path_fd */
+  res = ensure_docdir_inode (parent, xdp_steal_fd (&o_path_fd), &e); /* Takes ownershif of o_path_fd */
   if (res != 0)
     return xdp_reply_err (op, req, -res);
 
@@ -2322,7 +2332,7 @@ xdp_fuse_mkdir (fuse_req_t  req,
   if (res != 0)
     return xdp_reply_err (op, req, errno);
 
-  res = ensure_docdir_inode_by_name (parent->domain, dirfd, name, &e); /* Takes ownershif of o_path_fd */
+  res = ensure_docdir_inode_by_name (parent, dirfd, name, &e); /* Takes ownershif of o_path_fd */
   if (res != 0)
     return xdp_reply_err (op, req, -res);
 
@@ -2681,7 +2691,7 @@ xdp_fuse_symlink (fuse_req_t req,
   if (res != 0)
     return xdp_reply_err (op, req, errno);
 
-  res = ensure_docdir_inode_by_name (parent->domain, dirfd, name, &e); /* Takes ownershif of o_path_fd */
+  res = ensure_docdir_inode_by_name (parent, dirfd, name, &e); /* Takes ownershif of o_path_fd */
   if (res != 0)
     return xdp_reply_err (op, req, -res);
 
@@ -2726,7 +2736,7 @@ xdp_fuse_link (fuse_req_t req,
   if (res != 0)
     return xdp_reply_err (op, req, errno);
 
-  res = ensure_docdir_inode_by_name (inode->domain, newparent_dirfd, newname, &e); /* Takes ownership of o_path_fd */
+  res = ensure_docdir_inode_by_name (inode, newparent_dirfd, newname, &e); /* Takes ownership of o_path_fd */
   if (res != 0)
     return xdp_reply_err (op, req, -res);