1 /* 2 * descriptor table internals; you almost certainly want file.h instead. 3 */ 4 5 #ifndef __LINUX_FDTABLE_H 6 #define __LINUX_FDTABLE_H 7 8 #include <linux/posix_types.h> 9 #include <linux/compiler.h> 10 #include <linux/spinlock.h> 11 #include <linux/rcupdate.h> 12 #include <linux/types.h> 13 #include <linux/init.h> 14 15 #include <asm/atomic.h> 16 17 /* 18 * The default fd array needs to be at least BITS_PER_LONG, 19 * as this is the granularity returned by copy_fdset(). 20 */ 21 #define NR_OPEN_DEFAULT BITS_PER_LONG 22 23 /* 24 * The embedded_fd_set is a small fd_set, 25 * suitable for most tasks (which open <= BITS_PER_LONG files) 26 */ 27 struct embedded_fd_set { 28 unsigned long fds_bits[1]; 29 }; 30 31 struct fdtable { 32 unsigned int max_fds; 33 struct file ** fd; /* current fd array */ 34 fd_set *close_on_exec; 35 fd_set *open_fds; 36 struct rcu_head rcu; 37 struct fdtable *next; 38 }; 39 40 /* 41 * Open file table structure 42 */ 43 struct files_struct { 44 /* 45 * read mostly part 46 */ 47 atomic_t count; 48 struct fdtable *fdt; 49 struct fdtable fdtab; 50 /* 51 * written part on a separate cache line in SMP 52 */ 53 spinlock_t file_lock ____cacheline_aligned_in_smp; 54 int next_fd; 55 struct embedded_fd_set close_on_exec_init; 56 struct embedded_fd_set open_fds_init; 57 struct file * fd_array[NR_OPEN_DEFAULT]; 58 }; 59 60 #define rcu_dereference_check_fdtable(files, fdtfd) \ 61 (rcu_dereference_check((fdtfd), \ 62 rcu_read_lock_held() || \ 63 lockdep_is_held(&(files)->file_lock) || \ 64 atomic_read(&(files)->count) == 1 || \ 65 rcu_my_thread_group_empty())) 66 67 #define files_fdtable(files) \ 68 (rcu_dereference_check_fdtable((files), (files)->fdt)) 69 70 struct file_operations; 71 struct vfsmount; 72 struct dentry; 73 74 extern int expand_files(struct files_struct *, int nr); 75 extern void free_fdtable_rcu(struct rcu_head *rcu); 76 extern void __init files_defer_init(void); 77 78 static inline void free_fdtable(struct fdtable *fdt) 79 { 80 call_rcu(&fdt->rcu, free_fdtable_rcu); 81 } 82 83 static inline struct file * fcheck_files(struct files_struct *files, unsigned int fd) 84 { 85 struct file * file = NULL; 86 struct fdtable *fdt = files_fdtable(files); 87 88 if (fd < fdt->max_fds) 89 file = rcu_dereference_check_fdtable(files, fdt->fd[fd]); 90 return file; 91 } 92 93 /* 94 * Check whether the specified fd has an open file. 95 */ 96 #define fcheck(fd) fcheck_files(current->files, fd) 97 98 struct task_struct; 99 100 struct files_struct *get_files_struct(struct task_struct *); 101 void put_files_struct(struct files_struct *fs); 102 void reset_files_struct(struct files_struct *); 103 int unshare_files(struct files_struct **); 104 struct files_struct *dup_fd(struct files_struct *, int *); 105 106 extern struct kmem_cache *files_cachep; 107 108 #endif /* __LINUX_FDTABLE_H */ 109