Quoting Eric W. Biederman (ebiederm@xxxxxxxxxxxx):
> From: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
>
> 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.
>
> Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Acked-by: Serge E. Hallyn <serge.hallyn@xxxxxxxxxx>
> ---
> fs/proc/generic.c | 26 +++++++++++++-------------
> include/linux/proc_fs.h | 10 ++++++++++
> 2 files changed, 23 insertions(+), 13 deletions(-)
>
> diff --git a/fs/proc/generic.c b/fs/proc/generic.c
> index 0d80cef..7b3ae3c 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 3144781..bf1d000 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)
> --
> 1.7.5.4
>
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