proc: Generalize proc inode allocation

Generalize the proc inode allocation so that it can be
used without having to having to create a proc_dir_entry.

This will allow namespace file descriptors to remain light
weight entitities but still have the same inode number
when the backing namespace is the same.

Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

2 files changed, 23 insertions, 13 deletions

diff --git a/fs/proc/generic.c b/fs/proc/generic.c
index 0d80cef4cfb9..7b3ae3cc0ef9 100644
--- a/fs/proc/generic.c
+++ b/fs/proc/generic.c
@@ -350,14 +350,14 @@ static DEFINE_SPINLOCK(proc_inum_lock); /* protects the above */
  * Return an inode number between PROC_DYNAMIC_FIRST and
  * 0xffffffff, or zero on failure.
  */
-static unsigned int get_inode_number(void)
+int proc_alloc_inum(unsigned int *inum)
 {
         unsigned int i;
         int error;
 
 retry:
-        if (ida_pre_get(&proc_inum_ida, GFP_KERNEL) == 0)
-                return 0;
+        if (!ida_pre_get(&proc_inum_ida, GFP_KERNEL))
+                return -ENOMEM;
 
         spin_lock(&proc_inum_lock);
         error = ida_get_new(&proc_inum_ida, &i);
@@ -365,18 +365,19 @@ retry:
         if (error == -EAGAIN)
                 goto retry;
         else if (error)
-                return 0;
+                return error;
 
         if (i > UINT_MAX - PROC_DYNAMIC_FIRST) {
                 spin_lock(&proc_inum_lock);
                 ida_remove(&proc_inum_ida, i);
                 spin_unlock(&proc_inum_lock);
-                return 0;
+                return -ENOSPC;
         }
-        return PROC_DYNAMIC_FIRST + i;
+        *inum = PROC_DYNAMIC_FIRST + i;
+        return 0;
 }
 
-static void release_inode_number(unsigned int inum)
+void proc_free_inum(unsigned int inum)
 {
         spin_lock(&proc_inum_lock);
         ida_remove(&proc_inum_ida, inum - PROC_DYNAMIC_FIRST);
@@ -554,13 +555,12 @@ static const struct inode_operations proc_dir_inode_operations = {
 
 static int proc_register(struct proc_dir_entry * dir, struct proc_dir_entry * dp)
 {
-        unsigned int i;
         struct proc_dir_entry *tmp;
+        int ret;
         
-        i = get_inode_number();
-        if (i == 0)
-                return -EAGAIN;
-        dp->low_ino = i;
+        ret = proc_alloc_inum(&dp->low_ino);
+        if (ret)
+                return ret;
 
         if (S_ISDIR(dp->mode)) {
                 if (dp->proc_iops == NULL) {
@@ -764,7 +764,7 @@ EXPORT_SYMBOL(proc_create_data);
 
 static void free_proc_entry(struct proc_dir_entry *de)
 {
-        release_inode_number(de->low_ino);
+        proc_free_inum(de->low_ino);
 
         if (S_ISLNK(de->mode))
                 kfree(de->data);
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index 31447819bc55..bf1d000fbba6 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h
@@ -176,6 +176,8 @@ extern struct proc_dir_entry *proc_net_mkdir(struct net *net, const char *name,
 extern struct file *proc_ns_fget(int fd);
 extern bool proc_ns_inode(struct inode *inode);
 
+extern int proc_alloc_inum(unsigned int *pino);
+extern void proc_free_inum(unsigned int inum);
 #else
 
 #define proc_net_fops_create(net, name, mode, fops)  ({ (void)(mode), NULL; })
@@ -235,6 +237,14 @@ static inline bool proc_ns_inode(struct inode *inode)
         return false;
 }
 
+static inline int proc_alloc_inum(unsigned int *inum)
+{
+        *inum = 1;
+        return 0;
+}
+static inline void proc_free_inum(unsigned int inum)
+{
+}
 #endif /* CONFIG_PROC_FS */
 
 #if !defined(CONFIG_PROC_KCORE)