[UNIKRAFT PATCH 7/7] lib/9pfs: Simplify the logic for removes

[Cristian Banu <cristb@xxxxxxxxx>]

The logic for unlinking is simplified, either:
- there are no open files, remove now;
- there are open files, defer until all open files are closed

This is now possible since successive open and closes update
the dentry reference count correctly, so VOP_INACTIVE is called
in time to free the fid before the qid starts being reused
on the server-side (and we get an inode collision).

This also means that on unmounting, releasing all non-root
dentries and calling vfscore_release_mp_dentries() for m_covered
and m_root is enough to ensure all fids are clunked before
disconnecting.

Signed-off-by: Cristian Banu <cristb@xxxxxxxxx>
---
 lib/9pfs/9pfs_vfsops.c |  7 +++----
 lib/9pfs/9pfs_vnops.c  | 37 +++++++++++--------------------------
 2 files changed, 14 insertions(+), 30 deletions(-)

diff --git a/lib/9pfs/9pfs_vfsops.c b/lib/9pfs/9pfs_vfsops.c
index accb3a5..5293b22 100644
--- a/lib/9pfs/9pfs_vfsops.c
+++ b/lib/9pfs/9pfs_vfsops.c
@@ -169,11 +169,10 @@ static void uk_9pfs_release_tree_fids(struct dentry *d)
 {
        struct dentry *p;
 
-       uk_list_for_each_entry(p, &d->d_child_list, d_child_link)
+       uk_list_for_each_entry(p, &d->d_child_list, d_child_link) {
                uk_9pfs_release_tree_fids(p);
-
-       if (d->d_vnode->v_data)
-               uk_9pfs_free_vnode_data(d->d_vnode);
+               drele(p);
+       }
 }
 
 static int uk_9pfs_unmount(struct mount *mp, int flags __unused)
diff --git a/lib/9pfs/9pfs_vnops.c b/lib/9pfs/9pfs_vnops.c
index 6d3ece3..c81c82a 100644
--- a/lib/9pfs/9pfs_vnops.c
+++ b/lib/9pfs/9pfs_vnops.c
@@ -147,7 +147,7 @@ void uk_9pfs_free_vnode_data(struct vnode *vp)
        struct uk_9pdev *dev = UK_9PFS_MD(vp->v_mount)->dev;
        struct uk_9pfs_node_data *nd = UK_9PFS_ND(vp);
 
-       if (nd->nb_open_files > 0)
+       if (!vp->v_data)
                return;
 
        if (nd->removed)
@@ -158,20 +158,6 @@ void uk_9pfs_free_vnode_data(struct vnode *vp)
        vp->v_data = NULL;
 }
 
-/*
- * The closing variant of the function will enforce freeing the associated
- * resources only if the vnode was removed via an unlink/rmdir operation.
- */
-static void uk_9pfs_free_vnode_data_closing(struct vnode *vp)
-{
-       struct uk_9pfs_node_data *nd = UK_9PFS_ND(vp);
-
-       if (!nd->removed)
-               return;
-
-       uk_9pfs_free_vnode_data(vp);
-}
-
 static int uk_9pfs_open(struct vfscore_file *file)
 {
        struct uk_9pdev *dev = UK_9PFS_MD(file->f_dentry->d_mount)->dev;
@@ -222,7 +208,6 @@ static int uk_9pfs_close(struct vnode *vn __unused, struct 
vfscore_file *file)
        uk_9pfid_put(fd->fid);
        free(fd);
        UK_9PFS_ND(file->f_dentry->d_vnode)->nb_open_files--;
-       uk_9pfs_free_vnode_data_closing(file->f_dentry->d_vnode);
 
        return 0;
 }
@@ -327,22 +312,22 @@ static int uk_9pfs_remove_generic(struct vnode *dvp, 
struct vnode *vp)
 {
        struct uk_9pdev *dev = UK_9PFS_MD(dvp->v_mount)->dev;
        struct uk_9pfs_node_data *nd = UK_9PFS_ND(vp);
-       int rc = 0;
-
-       if (!nd->removed && !nd->nb_open_files)
-               rc = uk_9p_remove(dev, nd->fid);
-       else
-               nd->removed = true;
-
-       uk_9pfs_free_vnode_data(vp);
 
-       return -rc;
+       return -uk_9p_remove(dev, nd->fid);
 }
 
 static int uk_9pfs_remove(struct vnode *dvp, struct vnode *vp,
                char *name __unused)
 {
-       return uk_9pfs_remove_generic(dvp, vp);
+       struct uk_9pfs_node_data *nd = UK_9PFS_ND(vp);
+       int rc = 0;
+
+       if (!nd->nb_open_files)
+               rc = uk_9pfs_remove_generic(dvp, vp);
+       else
+               nd->removed = true;
+
+       return rc;
 }
 
 static int uk_9pfs_mkdir(struct vnode *dvp, char *name, mode_t mode)
-- 
2.26.2