original development tree for Linux kernel GTP module; now long in mainline.
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* descriptor table internals; you almost certainly want file.h instead.
#include <linux/posix_types.h>
#include <linux/compiler.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <linux/types.h>
#include <linux/init.h>
#include <asm/atomic.h>
* The default fd array needs to be at least BITS_PER_LONG,
* as this is the granularity returned by copy_fdset().
* The embedded_fd_set is a small fd_set,
* suitable for most tasks (which open <= BITS_PER_LONG files)
struct embedded_fd_set {
unsigned long fds_bits[1];
struct fdtable {
unsigned int max_fds;
struct file ** fd; /* current fd array */
fd_set *close_on_exec;
fd_set *open_fds;
struct rcu_head rcu;
struct fdtable *next;
* Open file table structure
struct files_struct {
* read mostly part
atomic_t count;
struct fdtable *fdt;
struct fdtable fdtab;
* written part on a separate cache line in SMP
spinlock_t file_lock ____cacheline_aligned_in_smp;
int next_fd;
struct embedded_fd_set close_on_exec_init;
struct embedded_fd_set open_fds_init;
struct file * fd_array[NR_OPEN_DEFAULT];
#define rcu_dereference_check_fdtable(files, fdtfd) \
(rcu_dereference_check((fdtfd), \
rcu_read_lock_held() || \
lockdep_is_held(&(files)->file_lock) || \
atomic_read(&(files)->count) == 1))
#define files_fdtable(files) \
(rcu_dereference_check_fdtable((files), (files)->fdt))
struct file_operations;
struct vfsmount;
struct dentry;
extern int expand_files(struct files_struct *, int nr);
extern void free_fdtable_rcu(struct rcu_head *rcu);
extern void __init files_defer_init(void);
static inline void free_fdtable(struct fdtable *fdt)
call_rcu(&fdt->rcu, free_fdtable_rcu);
static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd)
struct file * file = NULL;
struct fdtable *fdt = files_fdtable(files);
if (fd < fdt->max_fds)
file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
return file;
* Check whether the specified fd has an open file.
#define fcheck(fd) fcheck_files(current->files, fd)
struct task_struct;
struct files_struct *get_files_struct(struct task_struct *);
void put_files_struct(struct files_struct *fs);
void reset_files_struct(struct files_struct *);
int unshare_files(struct files_struct **);
struct files_struct *dup_fd(struct files_struct *, int *);
extern struct kmem_cache *files_cachep;
#endif /* __LINUX_FDTABLE_H */