1 /* 2 * linux/fs/file_table.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu) 6 */ 7 8 #include <linux/string.h> 9 #include <linux/slab.h> 10 #include <linux/file.h> 11 #include <linux/init.h> 12 #include <linux/module.h> 13 #include <linux/smp_lock.h> 14 #include <linux/fs.h> 15 #include <linux/security.h> 16 #include <linux/eventpoll.h> 17 #include <linux/rcupdate.h> 18 #include <linux/mount.h> 19 #include <linux/cdev.h> 20 #include <linux/fsnotify.h> 21 22 /* sysctl tunables... */ 23 struct files_stat_struct files_stat = { 24 .max_files = NR_FILE 25 }; 26 27 EXPORT_SYMBOL(files_stat); /* Needed by unix.o */ 28 29 /* public. Not pretty! */ 30 __cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock); 31 32 static DEFINE_SPINLOCK(filp_count_lock); 33 34 /* slab constructors and destructors are called from arbitrary 35 * context and must be fully threaded - use a local spinlock 36 * to protect files_stat.nr_files 37 */ 38 void filp_ctor(void *objp, struct kmem_cache *cachep, unsigned long cflags) 39 { 40 if ((cflags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) == 41 SLAB_CTOR_CONSTRUCTOR) { 42 unsigned long flags; 43 spin_lock_irqsave(&filp_count_lock, flags); 44 files_stat.nr_files++; 45 spin_unlock_irqrestore(&filp_count_lock, flags); 46 } 47 } 48 49 void filp_dtor(void *objp, struct kmem_cache *cachep, unsigned long dflags) 50 { 51 unsigned long flags; 52 spin_lock_irqsave(&filp_count_lock, flags); 53 files_stat.nr_files--; 54 spin_unlock_irqrestore(&filp_count_lock, flags); 55 } 56 57 static inline void file_free_rcu(struct rcu_head *head) 58 { 59 struct file *f = container_of(head, struct file, f_u.fu_rcuhead); 60 kmem_cache_free(filp_cachep, f); 61 } 62 63 static inline void file_free(struct file *f) 64 { 65 call_rcu(&f->f_u.fu_rcuhead, file_free_rcu); 66 } 67 68 /* Find an unused file structure and return a pointer to it. 69 * Returns NULL, if there are no more free file structures or 70 * we run out of memory. 71 */ 72 struct file *get_empty_filp(void) 73 { 74 static int old_max; 75 struct file * f; 76 77 /* 78 * Privileged users can go above max_files 79 */ 80 if (files_stat.nr_files >= files_stat.max_files && 81 !capable(CAP_SYS_ADMIN)) 82 goto over; 83 84 f = kmem_cache_alloc(filp_cachep, GFP_KERNEL); 85 if (f == NULL) 86 goto fail; 87 88 memset(f, 0, sizeof(*f)); 89 if (security_file_alloc(f)) 90 goto fail_sec; 91 92 eventpoll_init_file(f); 93 atomic_set(&f->f_count, 1); 94 f->f_uid = current->fsuid; 95 f->f_gid = current->fsgid; 96 rwlock_init(&f->f_owner.lock); 97 /* f->f_version: 0 */ 98 INIT_LIST_HEAD(&f->f_u.fu_list); 99 return f; 100 101 over: 102 /* Ran out of filps - report that */ 103 if (files_stat.nr_files > old_max) { 104 printk(KERN_INFO "VFS: file-max limit %d reached\n", 105 files_stat.max_files); 106 old_max = files_stat.nr_files; 107 } 108 goto fail; 109 110 fail_sec: 111 file_free(f); 112 fail: 113 return NULL; 114 } 115 116 EXPORT_SYMBOL(get_empty_filp); 117 118 void fastcall fput(struct file *file) 119 { 120 if (rcuref_dec_and_test(&file->f_count)) 121 __fput(file); 122 } 123 124 EXPORT_SYMBOL(fput); 125 126 /* __fput is called from task context when aio completion releases the last 127 * last use of a struct file *. Do not use otherwise. 128 */ 129 void fastcall __fput(struct file *file) 130 { 131 struct dentry *dentry = file->f_dentry; 132 struct vfsmount *mnt = file->f_vfsmnt; 133 struct inode *inode = dentry->d_inode; 134 135 might_sleep(); 136 137 fsnotify_close(file); 138 /* 139 * The function eventpoll_release() should be the first called 140 * in the file cleanup chain. 141 */ 142 eventpoll_release(file); 143 locks_remove_flock(file); 144 145 if (file->f_op && file->f_op->release) 146 file->f_op->release(inode, file); 147 security_file_free(file); 148 if (unlikely(inode->i_cdev != NULL)) 149 cdev_put(inode->i_cdev); 150 fops_put(file->f_op); 151 if (file->f_mode & FMODE_WRITE) 152 put_write_access(inode); 153 file_kill(file); 154 file->f_dentry = NULL; 155 file->f_vfsmnt = NULL; 156 file_free(file); 157 dput(dentry); 158 mntput(mnt); 159 } 160 161 struct file fastcall *fget(unsigned int fd) 162 { 163 struct file *file; 164 struct files_struct *files = current->files; 165 166 rcu_read_lock(); 167 file = fcheck_files(files, fd); 168 if (file) { 169 if (!rcuref_inc_lf(&file->f_count)) { 170 /* File object ref couldn't be taken */ 171 rcu_read_unlock(); 172 return NULL; 173 } 174 } 175 rcu_read_unlock(); 176 177 return file; 178 } 179 180 EXPORT_SYMBOL(fget); 181 182 /* 183 * Lightweight file lookup - no refcnt increment if fd table isn't shared. 184 * You can use this only if it is guranteed that the current task already 185 * holds a refcnt to that file. That check has to be done at fget() only 186 * and a flag is returned to be passed to the corresponding fput_light(). 187 * There must not be a cloning between an fget_light/fput_light pair. 188 */ 189 struct file fastcall *fget_light(unsigned int fd, int *fput_needed) 190 { 191 struct file *file; 192 struct files_struct *files = current->files; 193 194 *fput_needed = 0; 195 if (likely((atomic_read(&files->count) == 1))) { 196 file = fcheck_files(files, fd); 197 } else { 198 rcu_read_lock(); 199 file = fcheck_files(files, fd); 200 if (file) { 201 if (rcuref_inc_lf(&file->f_count)) 202 *fput_needed = 1; 203 else 204 /* Didn't get the reference, someone's freed */ 205 file = NULL; 206 } 207 rcu_read_unlock(); 208 } 209 210 return file; 211 } 212 213 214 void put_filp(struct file *file) 215 { 216 if (rcuref_dec_and_test(&file->f_count)) { 217 security_file_free(file); 218 file_kill(file); 219 file_free(file); 220 } 221 } 222 223 void file_move(struct file *file, struct list_head *list) 224 { 225 if (!list) 226 return; 227 file_list_lock(); 228 list_move(&file->f_u.fu_list, list); 229 file_list_unlock(); 230 } 231 232 void file_kill(struct file *file) 233 { 234 if (!list_empty(&file->f_u.fu_list)) { 235 file_list_lock(); 236 list_del_init(&file->f_u.fu_list); 237 file_list_unlock(); 238 } 239 } 240 241 int fs_may_remount_ro(struct super_block *sb) 242 { 243 struct list_head *p; 244 245 /* Check that no files are currently opened for writing. */ 246 file_list_lock(); 247 list_for_each(p, &sb->s_files) { 248 struct file *file = list_entry(p, struct file, f_u.fu_list); 249 struct inode *inode = file->f_dentry->d_inode; 250 251 /* File with pending delete? */ 252 if (inode->i_nlink == 0) 253 goto too_bad; 254 255 /* Writeable file? */ 256 if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE)) 257 goto too_bad; 258 } 259 file_list_unlock(); 260 return 1; /* Tis' cool bro. */ 261 too_bad: 262 file_list_unlock(); 263 return 0; 264 } 265 266 void __init files_init(unsigned long mempages) 267 { 268 int n; 269 /* One file with associated inode and dcache is very roughly 1K. 270 * Per default don't use more than 10% of our memory for files. 271 */ 272 273 n = (mempages * (PAGE_SIZE / 1024)) / 10; 274 files_stat.max_files = n; 275 if (files_stat.max_files < NR_FILE) 276 files_stat.max_files = NR_FILE; 277 files_defer_init(); 278 } 279