file.c 8.86 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
/*
 *  linux/fs/file.c
 *
 *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
 *
 *  Manage the dynamic fd arrays in the process files_struct.
 */

#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/file.h>
#include <linux/bitops.h>
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>

struct fdtable_defer {
	spinlock_t lock;
	struct work_struct wq;
	struct timer_list timer;
	struct fdtable *next;
};

/*
 * We use this list to defer free fdtables that have vmalloced
 * sets/arrays. By keeping a per-cpu list, we avoid having to embed
 * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
 * this per-task structure.
 */
static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
Linus Torvalds's avatar
Linus Torvalds committed
35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69


/*
 * Allocate an fd array, using kmalloc or vmalloc.
 * Note: the array isn't cleared at allocation time.
 */
struct file ** alloc_fd_array(int num)
{
	struct file **new_fds;
	int size = num * sizeof(struct file *);

	if (size <= PAGE_SIZE)
		new_fds = (struct file **) kmalloc(size, GFP_KERNEL);
	else 
		new_fds = (struct file **) vmalloc(size);
	return new_fds;
}

void free_fd_array(struct file **array, int num)
{
	int size = num * sizeof(struct file *);

	if (!array) {
		printk (KERN_ERR "free_fd_array: array = 0 (num = %d)\n", num);
		return;
	}

	if (num <= NR_OPEN_DEFAULT) /* Don't free the embedded fd array! */
		return;
	else if (size <= PAGE_SIZE)
		kfree(array);
	else
		vfree(array);
}

70
static void __free_fdtable(struct fdtable *fdt)
Linus Torvalds's avatar
Linus Torvalds committed
71
{
72
	int fdset_size, fdarray_size;
Linus Torvalds's avatar
Linus Torvalds committed
73

74 75 76 77 78 79 80
	fdset_size = fdt->max_fdset / 8;
	fdarray_size = fdt->max_fds * sizeof(struct file *);
	free_fdset(fdt->open_fds, fdset_size);
	free_fdset(fdt->close_on_exec, fdset_size);
	free_fd_array(fdt->fd, fdarray_size);
	kfree(fdt);
}
Linus Torvalds's avatar
Linus Torvalds committed
81

82 83 84
static void fdtable_timer(unsigned long data)
{
	struct fdtable_defer *fddef = (struct fdtable_defer *)data;
Linus Torvalds's avatar
Linus Torvalds committed
85

86 87 88
	spin_lock(&fddef->lock);
	/*
	 * If someone already emptied the queue return.
Linus Torvalds's avatar
Linus Torvalds committed
89
	 */
90 91 92 93 94 95 96
	if (!fddef->next)
		goto out;
	if (!schedule_work(&fddef->wq))
		mod_timer(&fddef->timer, 5);
out:
	spin_unlock(&fddef->lock);
}
Linus Torvalds's avatar
Linus Torvalds committed
97

98 99 100
static void free_fdtable_work(struct fdtable_defer *f)
{
	struct fdtable *fdt;
Linus Torvalds's avatar
Linus Torvalds committed
101

102 103 104 105 106 107 108 109 110 111
	spin_lock_bh(&f->lock);
	fdt = f->next;
	f->next = NULL;
	spin_unlock_bh(&f->lock);
	while(fdt) {
		struct fdtable *next = fdt->next;
		__free_fdtable(fdt);
		fdt = next;
	}
}
Linus Torvalds's avatar
Linus Torvalds committed
112

113 114 115 116 117
static void free_fdtable_rcu(struct rcu_head *rcu)
{
	struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
	int fdset_size, fdarray_size;
	struct fdtable_defer *fddef;
Linus Torvalds's avatar
Linus Torvalds committed
118

119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142
	BUG_ON(!fdt);
	fdset_size = fdt->max_fdset / 8;
	fdarray_size = fdt->max_fds * sizeof(struct file *);

	if (fdt->free_files) {
		/*
		 * The this fdtable was embedded in the files structure
		 * and the files structure itself was getting destroyed.
		 * It is now safe to free the files structure.
		 */
		kmem_cache_free(files_cachep, fdt->free_files);
		return;
	}
	if (fdt->max_fdset <= __FD_SETSIZE && fdt->max_fds <= NR_OPEN_DEFAULT) {
		/*
		 * The fdtable was embedded
		 */
		return;
	}
	if (fdset_size <= PAGE_SIZE && fdarray_size <= PAGE_SIZE) {
		kfree(fdt->open_fds);
		kfree(fdt->close_on_exec);
		kfree(fdt->fd);
		kfree(fdt);
Linus Torvalds's avatar
Linus Torvalds committed
143
	} else {
144 145 146 147 148 149 150 151 152 153 154 155 156
		fddef = &get_cpu_var(fdtable_defer_list);
		spin_lock(&fddef->lock);
		fdt->next = fddef->next;
		fddef->next = fdt;
		/*
		 * vmallocs are handled from the workqueue context.
		 * If the per-cpu workqueue is running, then we
		 * defer work scheduling through a timer.
		 */
		if (!schedule_work(&fddef->wq))
			mod_timer(&fddef->timer, 5);
		spin_unlock(&fddef->lock);
		put_cpu_var(fdtable_defer_list);
Linus Torvalds's avatar
Linus Torvalds committed
157
	}
158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206
}

void free_fdtable(struct fdtable *fdt)
{
	if (fdt->free_files || fdt->max_fdset > __FD_SETSIZE ||
					fdt->max_fds > NR_OPEN_DEFAULT)
		call_rcu(&fdt->rcu, free_fdtable_rcu);
}

/*
 * Expand the fdset in the files_struct.  Called with the files spinlock
 * held for write.
 */
static void copy_fdtable(struct fdtable *nfdt, struct fdtable *fdt)
{
	int i;
	int count;

	BUG_ON(nfdt->max_fdset < fdt->max_fdset);
	BUG_ON(nfdt->max_fds < fdt->max_fds);
	/* Copy the existing tables and install the new pointers */

	i = fdt->max_fdset / (sizeof(unsigned long) * 8);
	count = (nfdt->max_fdset - fdt->max_fdset) / 8;

	/*
	 * Don't copy the entire array if the current fdset is
	 * not yet initialised.
	 */
	if (i) {
		memcpy (nfdt->open_fds, fdt->open_fds,
						fdt->max_fdset/8);
		memcpy (nfdt->close_on_exec, fdt->close_on_exec,
						fdt->max_fdset/8);
		memset (&nfdt->open_fds->fds_bits[i], 0, count);
		memset (&nfdt->close_on_exec->fds_bits[i], 0, count);
	}

	/* Don't copy/clear the array if we are creating a new
	   fd array for fork() */
	if (fdt->max_fds) {
		memcpy(nfdt->fd, fdt->fd,
			fdt->max_fds * sizeof(struct file *));
		/* clear the remainder of the array */
		memset(&nfdt->fd[fdt->max_fds], 0,
		       (nfdt->max_fds - fdt->max_fds) *
					sizeof(struct file *));
	}
	nfdt->next_fd = fdt->next_fd;
Linus Torvalds's avatar
Linus Torvalds committed
207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236
}

/*
 * Allocate an fdset array, using kmalloc or vmalloc.
 * Note: the array isn't cleared at allocation time.
 */
fd_set * alloc_fdset(int num)
{
	fd_set *new_fdset;
	int size = num / 8;

	if (size <= PAGE_SIZE)
		new_fdset = (fd_set *) kmalloc(size, GFP_KERNEL);
	else
		new_fdset = (fd_set *) vmalloc(size);
	return new_fdset;
}

void free_fdset(fd_set *array, int num)
{
	int size = num / 8;

	if (num <= __FD_SETSIZE) /* Don't free an embedded fdset */
		return;
	else if (size <= PAGE_SIZE)
		kfree(array);
	else
		vfree(array);
}

237
static struct fdtable *alloc_fdtable(int nr)
Linus Torvalds's avatar
Linus Torvalds committed
238
{
239 240 241 242
	struct fdtable *fdt = NULL;
	int nfds = 0;
  	fd_set *new_openset = NULL, *new_execset = NULL;
	struct file **new_fds;
Linus Torvalds's avatar
Linus Torvalds committed
243

244 245 246 247
	fdt = kmalloc(sizeof(*fdt), GFP_KERNEL);
	if (!fdt)
  		goto out;
	memset(fdt, 0, sizeof(*fdt));
Linus Torvalds's avatar
Linus Torvalds committed
248

249 250 251
	nfds = __FD_SETSIZE;
  	/* Expand to the max in easy steps */
  	do {
Linus Torvalds's avatar
Linus Torvalds committed
252 253 254 255 256 257 258 259 260
		if (nfds < (PAGE_SIZE * 8))
			nfds = PAGE_SIZE * 8;
		else {
			nfds = nfds * 2;
			if (nfds > NR_OPEN)
				nfds = NR_OPEN;
		}
	} while (nfds <= nr);

261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289
  	new_openset = alloc_fdset(nfds);
  	new_execset = alloc_fdset(nfds);
  	if (!new_openset || !new_execset)
  		goto out;
	fdt->open_fds = new_openset;
	fdt->close_on_exec = new_execset;
	fdt->max_fdset = nfds;

	nfds = NR_OPEN_DEFAULT;
	/*
	 * Expand to the max in easy steps, and keep expanding it until
	 * we have enough for the requested fd array size.
	 */
	do {
#if NR_OPEN_DEFAULT < 256
		if (nfds < 256)
			nfds = 256;
		else
#endif
		if (nfds < (PAGE_SIZE / sizeof(struct file *)))
			nfds = PAGE_SIZE / sizeof(struct file *);
		else {
			nfds = nfds * 2;
			if (nfds > NR_OPEN)
				nfds = NR_OPEN;
  		}
	} while (nfds <= nr);
	new_fds = alloc_fd_array(nfds);
	if (!new_fds)
Linus Torvalds's avatar
Linus Torvalds committed
290
		goto out;
291 292 293 294 295 296 297 298 299 300 301 302
	fdt->fd = new_fds;
	fdt->max_fds = nfds;
	fdt->free_files = NULL;
	return fdt;
out:
  	if (new_openset)
  		free_fdset(new_openset, nfds);
  	if (new_execset)
  		free_fdset(new_execset, nfds);
	kfree(fdt);
	return NULL;
}
Linus Torvalds's avatar
Linus Torvalds committed
303

304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325
/*
 * Expands the file descriptor table - it will allocate a new fdtable and
 * both fd array and fdset. It is expected to be called with the
 * files_lock held.
 */
static int expand_fdtable(struct files_struct *files, int nr)
	__releases(files->file_lock)
	__acquires(files->file_lock)
{
	int error = 0;
	struct fdtable *fdt;
	struct fdtable *nfdt = NULL;

	spin_unlock(&files->file_lock);
	nfdt = alloc_fdtable(nr);
	if (!nfdt) {
		error = -ENOMEM;
		spin_lock(&files->file_lock);
		goto out;
	}

	spin_lock(&files->file_lock);
326
	fdt = files_fdtable(files);
327 328 329 330 331 332 333 334
	/*
	 * Check again since another task may have expanded the
	 * fd table while we dropped the lock
	 */
	if (nr >= fdt->max_fds || nr >= fdt->max_fdset) {
		copy_fdtable(nfdt, fdt);
	} else {
		/* Somebody expanded while we dropped file_lock */
Linus Torvalds's avatar
Linus Torvalds committed
335
		spin_unlock(&files->file_lock);
336
		__free_fdtable(nfdt);
Linus Torvalds's avatar
Linus Torvalds committed
337
		spin_lock(&files->file_lock);
338 339 340 341
		goto out;
	}
	rcu_assign_pointer(files->fdt, nfdt);
	free_fdtable(fdt);
Linus Torvalds's avatar
Linus Torvalds committed
342 343 344 345 346 347 348 349 350 351 352 353
out:
	return error;
}

/*
 * Expand files.
 * Return <0 on error; 0 nothing done; 1 files expanded, we may have blocked.
 * Should be called with the files->file_lock spinlock held for write.
 */
int expand_files(struct files_struct *files, int nr)
{
	int err, expand = 0;
354
	struct fdtable *fdt;
Linus Torvalds's avatar
Linus Torvalds committed
355

356
	fdt = files_fdtable(files);
357 358 359 360
	if (nr >= fdt->max_fdset || nr >= fdt->max_fds) {
		if (fdt->max_fdset >= NR_OPEN ||
			fdt->max_fds >= NR_OPEN || nr >= NR_OPEN) {
			err = -EMFILE;
Linus Torvalds's avatar
Linus Torvalds committed
361
			goto out;
362
		}
Linus Torvalds's avatar
Linus Torvalds committed
363
		expand = 1;
364
		if ((err = expand_fdtable(files, nr)))
Linus Torvalds's avatar
Linus Torvalds committed
365 366 367 368 369 370
			goto out;
	}
	err = expand;
out:
	return err;
}
371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389

static void __devinit fdtable_defer_list_init(int cpu)
{
	struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
	spin_lock_init(&fddef->lock);
	INIT_WORK(&fddef->wq, (void (*)(void *))free_fdtable_work, fddef);
	init_timer(&fddef->timer);
	fddef->timer.data = (unsigned long)fddef;
	fddef->timer.function = fdtable_timer;
	fddef->next = NULL;
}

void __init files_defer_init(void)
{
	int i;
	/* Really early - can't use for_each_cpu */
	for (i = 0; i < NR_CPUS; i++)
		fdtable_defer_list_init(i);
}