[PATCH v2 13/17] xen/hypfs: support dynamic hypfs nodes

[Juergen Gross <jgross@suse.com>]

Add a HYPFS_VARDIR_INIT() macro for initializing such a directory
statically, taking a struct hypfs_funcs pointer as parameter additional
to those of HYPFS_DIR_INIT().

Modify HYPFS_VARSIZE_INIT() to take the function vector pointer as an
additional parameter as this will be needed for dynamical entries.

For being able to let the generic hypfs coding continue to work on
normal struct hypfs_entry entities even for dynamical nodes add some
infrastructure for allocating a working area for the current hypfs
request in order to store needed information for traversing the tree.
This area is anchored in a percpu pointer and can be retrieved by any
level of the dynamic entries. The normal way to handle allocation and
freeing is to allocate the data in the enter() callback of a node and
to free it in the related exit() callback.

Add a hypfs_add_dyndir() function for adding a dynamic directory
template to the tree, which is needed for having the correct reference
to its position in hypfs.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- switch to xzalloc_bytes() in hypfs_alloc_dyndata() (Jan Beulich)
- carved out from previous patch
- use enter() and exit() callbacks for allocating and freeing
  dyndata memory
- add hypfs_add_dyndir()
---
 xen/common/hypfs.c      | 31 +++++++++++++++++++++++++++++++
 xen/include/xen/hypfs.h | 28 ++++++++++++++++++----------
 2 files changed, 49 insertions(+), 10 deletions(-)

diff --git a/xen/common/hypfs.c b/xen/common/hypfs.c
index e5adc9defe..39448c5409 100644
--- a/xen/common/hypfs.c
+++ b/xen/common/hypfs.c
@@ -72,6 +72,7 @@ enum hypfs_lock_state {
     hypfs_write_locked
 };
 static DEFINE_PER_CPU(enum hypfs_lock_state, hypfs_locked);
+static DEFINE_PER_CPU(struct hypfs_dyndata *, hypfs_dyndata);
 
 static DEFINE_PER_CPU(const struct hypfs_entry *, hypfs_last_node_entered);
 
@@ -157,6 +158,30 @@ static void node_exit_all(void)
         node_exit(*last);
 }
 
+void *hypfs_alloc_dyndata(unsigned long size)
+{
+    unsigned int cpu = smp_processor_id();
+
+    ASSERT(per_cpu(hypfs_locked, cpu) != hypfs_unlocked);
+    ASSERT(per_cpu(hypfs_dyndata, cpu) == NULL);
+
+    per_cpu(hypfs_dyndata, cpu) = xzalloc_bytes(size);
+
+    return per_cpu(hypfs_dyndata, cpu);
+}
+
+void *hypfs_get_dyndata(void)
+{
+    ASSERT(this_cpu(hypfs_dyndata));
+
+    return this_cpu(hypfs_dyndata);
+}
+
+void hypfs_free_dyndata(void)
+{
+    XFREE(this_cpu(hypfs_dyndata));
+}
+
 static int add_entry(struct hypfs_entry_dir *parent, struct hypfs_entry *new)
 {
     int ret = -ENOENT;
@@ -218,6 +243,12 @@ int hypfs_add_dir(struct hypfs_entry_dir *parent,
     return ret;
 }
 
+void hypfs_add_dyndir(struct hypfs_entry_dir *parent,
+                      struct hypfs_entry_dir *template)
+{
+    template->e.parent = &parent->e;
+}
+
 int hypfs_add_leaf(struct hypfs_entry_dir *parent,
                    struct hypfs_entry_leaf *leaf, bool nofault)
 {
diff --git a/xen/include/xen/hypfs.h b/xen/include/xen/hypfs.h
index 8d96abd805..be8d6c508a 100644
--- a/xen/include/xen/hypfs.h
+++ b/xen/include/xen/hypfs.h
@@ -76,7 +76,7 @@ struct hypfs_entry_dir {
     struct list_head dirlist;
 };
 
-#define HYPFS_DIR_INIT(var, nam)                  \
+#define HYPFS_VARDIR_INIT(var, nam, fn)           \
     struct hypfs_entry_dir __read_mostly var = {  \
         .e.type = XEN_HYPFS_TYPE_DIR,             \
         .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
@@ -84,22 +84,25 @@ struct hypfs_entry_dir {
         .e.size = 0,                              \
         .e.max_size = 0,                          \
         .e.list = LIST_HEAD_INIT(var.e.list),     \
-        .e.funcs = &hypfs_dir_funcs,              \
+        .e.funcs = (fn),                          \
         .dirlist = LIST_HEAD_INIT(var.dirlist),   \
     }
 
-#define HYPFS_VARSIZE_INIT(var, typ, nam, msz)    \
-    struct hypfs_entry_leaf __read_mostly var = { \
-        .e.type = (typ),                          \
-        .e.encoding = XEN_HYPFS_ENC_PLAIN,        \
-        .e.name = (nam),                          \
-        .e.max_size = (msz),                      \
-        .e.funcs = &hypfs_leaf_ro_funcs,          \
+#define HYPFS_DIR_INIT(var, nam)                  \
+    HYPFS_VARDIR_INIT(var, nam, &hypfs_dir_funcs)
+
+#define HYPFS_VARSIZE_INIT(var, typ, nam, msz, fn) \
+    struct hypfs_entry_leaf __read_mostly var = {  \
+        .e.type = (typ),                           \
+        .e.encoding = XEN_HYPFS_ENC_PLAIN,         \
+        .e.name = (nam),                           \
+        .e.max_size = (msz),                       \
+        .e.funcs = (fn),                           \
     }
 
 /* Content and size need to be set via hypfs_string_set_reference(). */
 #define HYPFS_STRING_INIT(var, nam)               \
-    HYPFS_VARSIZE_INIT(var, XEN_HYPFS_TYPE_STRING, nam, 0)
+    HYPFS_VARSIZE_INIT(var, XEN_HYPFS_TYPE_STRING, nam, 0, &hypfs_leaf_ro_funcs)
 
 /*
  * Set content and size of a XEN_HYPFS_TYPE_STRING node. The node will point
@@ -150,6 +153,8 @@ extern struct hypfs_entry_dir hypfs_root;
 
 int hypfs_add_dir(struct hypfs_entry_dir *parent,
                   struct hypfs_entry_dir *dir, bool nofault);
+void hypfs_add_dyndir(struct hypfs_entry_dir *parent,
+                      struct hypfs_entry_dir *template);
 int hypfs_add_leaf(struct hypfs_entry_dir *parent,
                    struct hypfs_entry_leaf *leaf, bool nofault);
 const struct hypfs_entry *hypfs_node_enter(const struct hypfs_entry *entry);
@@ -173,6 +178,9 @@ struct hypfs_entry *hypfs_leaf_findentry(const struct hypfs_entry_dir *dir,
 struct hypfs_entry *hypfs_dir_findentry(const struct hypfs_entry_dir *dir,
                                         const char *name,
                                         unsigned int name_len);
+void *hypfs_alloc_dyndata(unsigned long size);
+void *hypfs_get_dyndata(void);
+void hypfs_free_dyndata(void);
 #endif
 
 #endif /* __XEN_HYPFS_H__ */
-- 
2.26.2