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 return f; 93 94 over: 95 /* Ran out of filps - report that */ 96 if (files_stat.nr_files > old_max) { 97 printk(KERN_INFO "VFS: file-max limit %d reached\n", 98 files_stat.max_files); 99 old_max = files_stat.nr_files; 100 } 101 goto fail; 102 103 fail_sec: 104 file_free(f); 105 fail: 106 return NULL; 107 } 108 109 EXPORT_SYMBOL(get_empty_filp); 110 111 void fastcall fput(struct file *file) 112 { 113 if (atomic_dec_and_test(&file->f_count)) 114 __fput(file); 115 } 116 117 EXPORT_SYMBOL(fput); 118 119 /* __fput is called from task context when aio completion releases the last 120 * last use of a struct file *. Do not use otherwise. 121 */ 122 void fastcall __fput(struct file *file) 123 { 124 struct dentry *dentry = file->f_dentry; 125 struct vfsmount *mnt = file->f_vfsmnt; 126 struct inode *inode = dentry->d_inode; 127 128 might_sleep(); 129 130 fsnotify_close(file); 131 /* 132 * The function eventpoll_release() should be the first called 133 * in the file cleanup chain. 134 */ 135 eventpoll_release(file); 136 locks_remove_flock(file); 137 138 if (file->f_op && file->f_op->release) 139 file->f_op->release(inode, file); 140 security_file_free(file); 141 if (unlikely(inode->i_cdev != NULL)) 142 cdev_put(inode->i_cdev); 143 fops_put(file->f_op); 144 if (file->f_mode & FMODE_WRITE) 145 put_write_access(inode); 146 file_kill(file); 147 file->f_dentry = NULL; 148 file->f_vfsmnt = NULL; 149 file_free(file); 150 dput(dentry); 151 mntput(mnt); 152 } 153 154 struct file fastcall *fget(unsigned int fd) 155 { 156 struct file *file; 157 struct files_struct *files = current->files; 158 159 spin_lock(&files->file_lock); 160 file = fcheck_files(files, fd); 161 if (file) 162 get_file(file); 163 spin_unlock(&files->file_lock); 164 return file; 165 } 166 167 EXPORT_SYMBOL(fget); 168 169 /* 170 * Lightweight file lookup - no refcnt increment if fd table isn't shared. 171 * You can use this only if it is guranteed that the current task already 172 * holds a refcnt to that file. That check has to be done at fget() only 173 * and a flag is returned to be passed to the corresponding fput_light(). 174 * There must not be a cloning between an fget_light/fput_light pair. 175 */ 176 struct file fastcall *fget_light(unsigned int fd, int *fput_needed) 177 { 178 struct file *file; 179 struct files_struct *files = current->files; 180 181 *fput_needed = 0; 182 if (likely((atomic_read(&files->count) == 1))) { 183 file = fcheck_files(files, fd); 184 } else { 185 spin_lock(&files->file_lock); 186 file = fcheck_files(files, fd); 187 if (file) { 188 get_file(file); 189 *fput_needed = 1; 190 } 191 spin_unlock(&files->file_lock); 192 } 193 return file; 194 } 195 196 197 void put_filp(struct file *file) 198 { 199 if (atomic_dec_and_test(&file->f_count)) { 200 security_file_free(file); 201 file_kill(file); 202 file_free(file); 203 } 204 } 205 206 void file_move(struct file *file, struct list_head *list) 207 { 208 if (!list) 209 return; 210 file_list_lock(); 211 list_move(&file->f_list, list); 212 file_list_unlock(); 213 } 214 215 void file_kill(struct file *file) 216 { 217 if (!list_empty(&file->f_list)) { 218 file_list_lock(); 219 list_del_init(&file->f_list); 220 file_list_unlock(); 221 } 222 } 223 224 int fs_may_remount_ro(struct super_block *sb) 225 { 226 struct list_head *p; 227 228 /* Check that no files are currently opened for writing. */ 229 file_list_lock(); 230 list_for_each(p, &sb->s_files) { 231 struct file *file = list_entry(p, struct file, f_list); 232 struct inode *inode = file->f_dentry->d_inode; 233 234 /* File with pending delete? */ 235 if (inode->i_nlink == 0) 236 goto too_bad; 237 238 /* Writeable file? */ 239 if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE)) 240 goto too_bad; 241 } 242 file_list_unlock(); 243 return 1; /* Tis' cool bro. */ 244 too_bad: 245 file_list_unlock(); 246 return 0; 247 } 248 249 void __init files_init(unsigned long mempages) 250 { 251 int n; 252 /* One file with associated inode and dcache is very roughly 1K. 253 * Per default don't use more than 10% of our memory for files. 254 */ 255 256 n = (mempages * (PAGE_SIZE / 1024)) / 10; 257 files_stat.max_files = n; 258 if (files_stat.max_files < NR_FILE) 259 files_stat.max_files = NR_FILE; 260 } 261