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