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