fdtable.h

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/*
 * descriptor table internals; you almost certainly want file.h instead.
 */

#ifndef __LINUX_FDTABLE_H
#define __LINUX_FDTABLE_H

#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 <linux/fs.h>

#include <linux/atomic.h>

/*
 * The default fd array needs to be at least BITS_PER_LONG,
 * as this is the granularity returned by copy_fdset().
 */
#define NR_OPEN_DEFAULT BITS_PER_LONG

struct fdtable {
    unsigned int max_fds;
    struct file __rcu **fd;      /* current fd array */
    unsigned long *close_on_exec;
    unsigned long *open_fds;
    struct rcu_head rcu;
    struct fdtable *next;
};

static inline bool close_on_exec(int fd, const struct fdtable *fdt)
{
    return test_bit(fd, fdt->close_on_exec);
}

static inline bool fd_is_open(int fd, const struct fdtable *fdt)
{
    return test_bit(fd, fdt->open_fds);
}

/*
 * Open file table structure
 */
struct files_struct {
  /*
   * read mostly part
   */
    atomic_t count;
    struct fdtable __rcu *fdt;
    struct fdtable fdtab;
  /*
   * written part on a separate cache line in SMP
   */
    spinlock_t file_lock ____cacheline_aligned_in_smp;
    int next_fd;
    unsigned long close_on_exec_init[1];
    unsigned long open_fds_init[1];
    struct file __rcu * fd_array[NR_OPEN_DEFAULT];
};

#define rcu_dereference_check_fdtable(files, fdtfd) \
    (rcu_dereference_check((fdtfd), \
                   lockdep_is_held(&(files)->file_lock) || \
                   atomic_read(&(files)->count) == 1 || \
                   rcu_my_thread_group_empty()))

#define files_fdtable(files) \
        (rcu_dereference_check_fdtable((files), (files)->fdt))

struct file_operations;
struct vfsmount;
struct dentry;

extern void __init files_defer_init(void);

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 *);
void daemonize_descriptors(void);
int unshare_files(struct files_struct **);
struct files_struct *dup_fd(struct files_struct *, int *);
void do_close_on_exec(struct files_struct *);
int iterate_fd(struct files_struct *, unsigned,
        int (*)(const void *, struct file *, unsigned),
        const void *);

extern int __alloc_fd(struct files_struct *files,
              unsigned start, unsigned end, unsigned flags);
extern void __fd_install(struct files_struct *files,
              unsigned int fd, struct file *file);
extern int __close_fd(struct files_struct *files,
              unsigned int fd);

extern struct kmem_cache *files_cachep;

#endif /* __LINUX_FDTABLE_H */