fdtable.h 3.12 KB
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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>
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#include <linux/init.h>
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#include <linux/fs.h>
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#include <linux/atomic.h>
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/*
 * 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;
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	struct file __rcu **fd;      /* current fd array */
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	unsigned long *close_on_exec;
	unsigned long *open_fds;
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	unsigned long *full_fds_bits;
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	struct rcu_head rcu;
};

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

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

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/*
 * Open file table structure
 */
struct files_struct {
  /*
   * read mostly part
   */
	atomic_t count;
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	bool resize_in_progress;
	wait_queue_head_t resize_wait;

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	struct fdtable __rcu *fdt;
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	struct fdtable fdtab;
  /*
   * written part on a separate cache line in SMP
   */
	spinlock_t file_lock ____cacheline_aligned_in_smp;
	int next_fd;
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	unsigned long close_on_exec_init[1];
	unsigned long open_fds_init[1];
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	unsigned long full_fds_bits_init[1];
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	struct file __rcu * fd_array[NR_OPEN_DEFAULT];
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};

struct file_operations;
struct vfsmount;
struct dentry;

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#define rcu_dereference_check_fdtable(files, fdtfd) \
	rcu_dereference_check((fdtfd), lockdep_is_held(&(files)->file_lock))

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

/*
 * The caller must ensure that fd table isn't shared or hold rcu or file lock
 */
static inline struct file *__fcheck_files(struct files_struct *files, unsigned int fd)
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{
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	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
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	if (fd < fdt->max_fds)
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		return rcu_dereference_raw(fdt->fd[fd]);
	return NULL;
}

static inline struct file *fcheck_files(struct files_struct *files, unsigned int fd)
{
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	RCU_LOCKDEP_WARN(!rcu_read_lock_held() &&
			   !lockdep_is_held(&files->file_lock),
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			   "suspicious rcu_dereference_check() usage");
	return __fcheck_files(files, fd);
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}

/*
 * 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 **);
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struct files_struct *dup_fd(struct files_struct *, int *);
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void do_close_on_exec(struct files_struct *);
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int iterate_fd(struct files_struct *, unsigned,
		int (*)(const void *, struct file *, unsigned),
		const void *);
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extern int __alloc_fd(struct files_struct *files,
		      unsigned start, unsigned end, unsigned flags);
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extern void __fd_install(struct files_struct *files,
		      unsigned int fd, struct file *file);
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extern int __close_fd(struct files_struct *files,
		      unsigned int fd);
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extern struct kmem_cache *files_cachep;

#endif /* __LINUX_FDTABLE_H */