file.c 10.5 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14
/*
 *  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>
A
Al Viro 已提交
15
#include <linux/fdtable.h>
L
Linus Torvalds 已提交
16
#include <linux/bitops.h>
17 18 19 20 21 22 23 24 25 26 27
#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 fdtable *next;
};

28 29
int sysctl_nr_open __read_mostly = 1024*1024;

30 31 32 33 34 35 36
/*
 * 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);
L
Linus Torvalds 已提交
37

38
static inline void * alloc_fdmem(unsigned int size)
L
Linus Torvalds 已提交
39 40
{
	if (size <= PAGE_SIZE)
41 42 43
		return kmalloc(size, GFP_KERNEL);
	else
		return vmalloc(size);
L
Linus Torvalds 已提交
44 45
}

46
static inline void free_fdarr(struct fdtable *fdt)
L
Linus Torvalds 已提交
47
{
48 49
	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *)))
		kfree(fdt->fd);
L
Linus Torvalds 已提交
50
	else
51
		vfree(fdt->fd);
L
Linus Torvalds 已提交
52 53
}

54
static inline void free_fdset(struct fdtable *fdt)
L
Linus Torvalds 已提交
55
{
56 57 58 59
	if (fdt->max_fds <= (PAGE_SIZE * BITS_PER_BYTE / 2))
		kfree(fdt->open_fds);
	else
		vfree(fdt->open_fds);
60
}
L
Linus Torvalds 已提交
61

62
static void free_fdtable_work(struct work_struct *work)
63
{
64 65
	struct fdtable_defer *f =
		container_of(work, struct fdtable_defer, wq);
66
	struct fdtable *fdt;
L
Linus Torvalds 已提交
67

68 69 70 71 72 73
	spin_lock_bh(&f->lock);
	fdt = f->next;
	f->next = NULL;
	spin_unlock_bh(&f->lock);
	while(fdt) {
		struct fdtable *next = fdt->next;
74 75 76
		vfree(fdt->fd);
		free_fdset(fdt);
		kfree(fdt);
77 78 79
		fdt = next;
	}
}
L
Linus Torvalds 已提交
80

81
void free_fdtable_rcu(struct rcu_head *rcu)
82 83 84
{
	struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
	struct fdtable_defer *fddef;
L
Linus Torvalds 已提交
85

86 87
	BUG_ON(!fdt);

88
	if (fdt->max_fds <= NR_OPEN_DEFAULT) {
89
		/*
90 91
		 * This fdtable is embedded in the files structure and that
		 * structure itself is getting destroyed.
92
		 */
93 94
		kmem_cache_free(files_cachep,
				container_of(fdt, struct files_struct, fdtab));
95 96
		return;
	}
97
	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *))) {
98
		kfree(fdt->fd);
99
		kfree(fdt->open_fds);
100
		kfree(fdt);
L
Linus Torvalds 已提交
101
	} else {
102 103 104 105
		fddef = &get_cpu_var(fdtable_defer_list);
		spin_lock(&fddef->lock);
		fdt->next = fddef->next;
		fddef->next = fdt;
106 107
		/* vmallocs are handled from the workqueue context */
		schedule_work(&fddef->wq);
108 109
		spin_unlock(&fddef->lock);
		put_cpu_var(fdtable_defer_list);
L
Linus Torvalds 已提交
110
	}
111 112 113 114 115 116
}

/*
 * Expand the fdset in the files_struct.  Called with the files spinlock
 * held for write.
 */
117
static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
118
{
119
	unsigned int cpy, set;
120

121 122 123 124 125 126 127 128 129 130 131 132 133
	BUG_ON(nfdt->max_fds < ofdt->max_fds);

	cpy = ofdt->max_fds * sizeof(struct file *);
	set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
	memcpy(nfdt->fd, ofdt->fd, cpy);
	memset((char *)(nfdt->fd) + cpy, 0, set);

	cpy = ofdt->max_fds / BITS_PER_BYTE;
	set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
	memset((char *)(nfdt->open_fds) + cpy, 0, set);
	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
	memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
L
Linus Torvalds 已提交
134 135
}

136
static struct fdtable * alloc_fdtable(unsigned int nr)
L
Linus Torvalds 已提交
137
{
138 139
	struct fdtable *fdt;
	char *data;
L
Linus Torvalds 已提交
140

141
	/*
142 143 144 145 146
	 * Figure out how many fds we actually want to support in this fdtable.
	 * Allocation steps are keyed to the size of the fdarray, since it
	 * grows far faster than any of the other dynamic data. We try to fit
	 * the fdarray into comfortable page-tuned chunks: starting at 1024B
	 * and growing in powers of two from there on.
147
	 */
148 149 150
	nr /= (1024 / sizeof(struct file *));
	nr = roundup_pow_of_two(nr + 1);
	nr *= (1024 / sizeof(struct file *));
A
Al Viro 已提交
151 152 153 154 155 156 157 158 159 160
	/*
	 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
	 * had been set lower between the check in expand_files() and here.  Deal
	 * with that in caller, it's cheaper that way.
	 *
	 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
	 * bitmaps handling below becomes unpleasant, to put it mildly...
	 */
	if (unlikely(nr > sysctl_nr_open))
		nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
161

162 163
	fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
	if (!fdt)
164
		goto out;
165 166 167 168 169 170 171 172 173 174 175 176 177 178 179
	fdt->max_fds = nr;
	data = alloc_fdmem(nr * sizeof(struct file *));
	if (!data)
		goto out_fdt;
	fdt->fd = (struct file **)data;
	data = alloc_fdmem(max_t(unsigned int,
				 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
	if (!data)
		goto out_arr;
	fdt->open_fds = (fd_set *)data;
	data += nr / BITS_PER_BYTE;
	fdt->close_on_exec = (fd_set *)data;
	INIT_RCU_HEAD(&fdt->rcu);
	fdt->next = NULL;

180
	return fdt;
181 182 183 184

out_arr:
	free_fdarr(fdt);
out_fdt:
185
	kfree(fdt);
186
out:
187 188
	return NULL;
}
L
Linus Torvalds 已提交
189

190
/*
191 192 193 194 195
 * Expand the file descriptor table.
 * This function will allocate a new fdtable and both fd array and fdset, of
 * the given size.
 * Return <0 error code on error; 1 on successful completion.
 * The files->file_lock should be held on entry, and will be held on exit.
196 197 198 199 200
 */
static int expand_fdtable(struct files_struct *files, int nr)
	__releases(files->file_lock)
	__acquires(files->file_lock)
{
201
	struct fdtable *new_fdt, *cur_fdt;
202 203

	spin_unlock(&files->file_lock);
204
	new_fdt = alloc_fdtable(nr);
205
	spin_lock(&files->file_lock);
206 207
	if (!new_fdt)
		return -ENOMEM;
A
Al Viro 已提交
208 209 210 211 212 213 214 215 216 217
	/*
	 * extremely unlikely race - sysctl_nr_open decreased between the check in
	 * caller and alloc_fdtable().  Cheaper to catch it here...
	 */
	if (unlikely(new_fdt->max_fds <= nr)) {
		free_fdarr(new_fdt);
		free_fdset(new_fdt);
		kfree(new_fdt);
		return -EMFILE;
	}
218
	/*
219 220
	 * Check again since another task may have expanded the fd table while
	 * we dropped the lock
221
	 */
222
	cur_fdt = files_fdtable(files);
223
	if (nr >= cur_fdt->max_fds) {
224 225 226
		/* Continue as planned */
		copy_fdtable(new_fdt, cur_fdt);
		rcu_assign_pointer(files->fdt, new_fdt);
227
		if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
228
			free_fdtable(cur_fdt);
229
	} else {
230
		/* Somebody else expanded, so undo our attempt */
231 232 233
		free_fdarr(new_fdt);
		free_fdset(new_fdt);
		kfree(new_fdt);
234
	}
235
	return 1;
L
Linus Torvalds 已提交
236 237 238 239
}

/*
 * Expand files.
240 241 242 243 244
 * This function will expand the file structures, if the requested size exceeds
 * the current capacity and there is room for expansion.
 * Return <0 error code on error; 0 when nothing done; 1 when files were
 * expanded and execution may have blocked.
 * The files->file_lock should be held on entry, and will be held on exit.
L
Linus Torvalds 已提交
245 246 247
 */
int expand_files(struct files_struct *files, int nr)
{
248
	struct fdtable *fdt;
L
Linus Torvalds 已提交
249

250
	fdt = files_fdtable(files);
251
	/* Do we need to expand? */
252
	if (nr < fdt->max_fds)
253 254
		return 0;
	/* Can we expand? */
255
	if (nr >= sysctl_nr_open)
256 257 258 259
		return -EMFILE;

	/* All good, so we try */
	return expand_fdtable(files, nr);
L
Linus Torvalds 已提交
260
}
261

A
Al Viro 已提交
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
static int count_open_files(struct fdtable *fdt)
{
	int size = fdt->max_fds;
	int i;

	/* Find the last open fd */
	for (i = size/(8*sizeof(long)); i > 0; ) {
		if (fdt->open_fds->fds_bits[--i])
			break;
	}
	i = (i+1) * 8 * sizeof(long);
	return i;
}

/*
 * Allocate a new files structure and copy contents from the
 * passed in files structure.
 * errorp will be valid only when the returned files_struct is NULL.
 */
struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
{
	struct files_struct *newf;
	struct file **old_fds, **new_fds;
	int open_files, size, i;
	struct fdtable *old_fdt, *new_fdt;

	*errorp = -ENOMEM;
A
Al Viro 已提交
289
	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
A
Al Viro 已提交
290 291 292
	if (!newf)
		goto out;

A
Al Viro 已提交
293 294 295 296 297 298 299 300 301 302 303 304
	atomic_set(&newf->count, 1);

	spin_lock_init(&newf->file_lock);
	newf->next_fd = 0;
	new_fdt = &newf->fdtab;
	new_fdt->max_fds = NR_OPEN_DEFAULT;
	new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
	new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
	new_fdt->fd = &newf->fd_array[0];
	INIT_RCU_HEAD(&new_fdt->rcu);
	new_fdt->next = NULL;

A
Al Viro 已提交
305 306 307 308 309 310 311 312 313 314
	spin_lock(&oldf->file_lock);
	old_fdt = files_fdtable(oldf);
	open_files = count_open_files(old_fdt);

	/*
	 * Check whether we need to allocate a larger fd array and fd set.
	 * Note: we're not a clone task, so the open count won't change.
	 */
	if (open_files > new_fdt->max_fds) {
		spin_unlock(&oldf->file_lock);
A
Al Viro 已提交
315 316 317 318 319 320 321 322 323 324 325 326 327

		new_fdt = alloc_fdtable(open_files - 1);
		if (!new_fdt) {
			*errorp = -ENOMEM;
			goto out_release;
		}

		/* beyond sysctl_nr_open; nothing to do */
		if (unlikely(new_fdt->max_fds < open_files)) {
			free_fdarr(new_fdt);
			free_fdset(new_fdt);
			kfree(new_fdt);
			*errorp = -EMFILE;
A
Al Viro 已提交
328
			goto out_release;
A
Al Viro 已提交
329 330
		}

A
Al Viro 已提交
331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378
		/*
		 * Reacquire the oldf lock and a pointer to its fd table
		 * who knows it may have a new bigger fd table. We need
		 * the latest pointer.
		 */
		spin_lock(&oldf->file_lock);
		old_fdt = files_fdtable(oldf);
	}

	old_fds = old_fdt->fd;
	new_fds = new_fdt->fd;

	memcpy(new_fdt->open_fds->fds_bits,
		old_fdt->open_fds->fds_bits, open_files/8);
	memcpy(new_fdt->close_on_exec->fds_bits,
		old_fdt->close_on_exec->fds_bits, open_files/8);

	for (i = open_files; i != 0; i--) {
		struct file *f = *old_fds++;
		if (f) {
			get_file(f);
		} else {
			/*
			 * The fd may be claimed in the fd bitmap but not yet
			 * instantiated in the files array if a sibling thread
			 * is partway through open().  So make sure that this
			 * fd is available to the new process.
			 */
			FD_CLR(open_files - i, new_fdt->open_fds);
		}
		rcu_assign_pointer(*new_fds++, f);
	}
	spin_unlock(&oldf->file_lock);

	/* compute the remainder to be cleared */
	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);

	/* This is long word aligned thus could use a optimized version */
	memset(new_fds, 0, size);

	if (new_fdt->max_fds > open_files) {
		int left = (new_fdt->max_fds-open_files)/8;
		int start = open_files / (8 * sizeof(unsigned long));

		memset(&new_fdt->open_fds->fds_bits[start], 0, left);
		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
	}

A
Al Viro 已提交
379 380
	rcu_assign_pointer(newf->fdt, new_fdt);

A
Al Viro 已提交
381 382 383 384 385 386 387 388
	return newf;

out_release:
	kmem_cache_free(files_cachep, newf);
out:
	return NULL;
}

389 390 391 392
static void __devinit fdtable_defer_list_init(int cpu)
{
	struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
	spin_lock_init(&fddef->lock);
393
	INIT_WORK(&fddef->wq, free_fdtable_work);
394 395 396 397 398 399
	fddef->next = NULL;
}

void __init files_defer_init(void)
{
	int i;
400
	for_each_possible_cpu(i)
401 402
		fdtable_defer_list_init(i);
}
A
Al Viro 已提交
403 404 405 406 407 408 409 410 411 412 413 414 415

struct files_struct init_files = {
	.count		= ATOMIC_INIT(1),
	.fdt		= &init_files.fdtab,
	.fdtab		= {
		.max_fds	= NR_OPEN_DEFAULT,
		.fd		= &init_files.fd_array[0],
		.close_on_exec	= (fd_set *)&init_files.close_on_exec_init,
		.open_fds	= (fd_set *)&init_files.open_fds_init,
		.rcu		= RCU_HEAD_INIT,
	},
	.file_lock	= __SPIN_LOCK_UNLOCKED(init_task.file_lock),
};