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v3.1
 
  1/*
  2 *  linux/fs/file.c
  3 *
  4 *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
  5 *
  6 *  Manage the dynamic fd arrays in the process files_struct.
  7 */
  8
  9#include <linux/module.h>
 
 10#include <linux/fs.h>
 11#include <linux/mm.h>
 12#include <linux/mmzone.h>
 13#include <linux/time.h>
 14#include <linux/sched.h>
 15#include <linux/slab.h>
 16#include <linux/vmalloc.h>
 17#include <linux/file.h>
 18#include <linux/fdtable.h>
 19#include <linux/bitops.h>
 20#include <linux/interrupt.h>
 21#include <linux/spinlock.h>
 22#include <linux/rcupdate.h>
 23#include <linux/workqueue.h>
 24
 25struct fdtable_defer {
 26	spinlock_t lock;
 27	struct work_struct wq;
 28	struct fdtable *next;
 29};
 30
 31int sysctl_nr_open __read_mostly = 1024*1024;
 32int sysctl_nr_open_min = BITS_PER_LONG;
 33int sysctl_nr_open_max = 1024 * 1024; /* raised later */
 34
 35/*
 36 * We use this list to defer free fdtables that have vmalloced
 37 * sets/arrays. By keeping a per-cpu list, we avoid having to embed
 38 * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
 39 * this per-task structure.
 40 */
 41static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
 42
 43static void *alloc_fdmem(unsigned int size)
 44{
 45	/*
 46	 * Very large allocations can stress page reclaim, so fall back to
 47	 * vmalloc() if the allocation size will be considered "large" by the VM.
 48	 */
 49	if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {
 50		void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN);
 51		if (data != NULL)
 52			return data;
 53	}
 54	return vmalloc(size);
 55}
 56
 57static void free_fdmem(void *ptr)
 58{
 59	is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr);
 60}
 61
 62static void __free_fdtable(struct fdtable *fdt)
 63{
 64	free_fdmem(fdt->fd);
 65	free_fdmem(fdt->open_fds);
 66	kfree(fdt);
 67}
 68
 69static void free_fdtable_work(struct work_struct *work)
 70{
 71	struct fdtable_defer *f =
 72		container_of(work, struct fdtable_defer, wq);
 73	struct fdtable *fdt;
 74
 75	spin_lock_bh(&f->lock);
 76	fdt = f->next;
 77	f->next = NULL;
 78	spin_unlock_bh(&f->lock);
 79	while(fdt) {
 80		struct fdtable *next = fdt->next;
 81
 82		__free_fdtable(fdt);
 83		fdt = next;
 84	}
 85}
 86
 87void free_fdtable_rcu(struct rcu_head *rcu)
 
 
 
 
 
 
 
 
 
 88{
 89	struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
 90	struct fdtable_defer *fddef;
 91
 92	BUG_ON(!fdt);
 
 
 
 
 
 93
 94	if (fdt->max_fds <= NR_OPEN_DEFAULT) {
 95		/*
 96		 * This fdtable is embedded in the files structure and that
 97		 * structure itself is getting destroyed.
 98		 */
 99		kmem_cache_free(files_cachep,
100				container_of(fdt, struct files_struct, fdtab));
101		return;
102	}
103	if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) {
104		kfree(fdt->fd);
105		kfree(fdt->open_fds);
106		kfree(fdt);
107	} else {
108		fddef = &get_cpu_var(fdtable_defer_list);
109		spin_lock(&fddef->lock);
110		fdt->next = fddef->next;
111		fddef->next = fdt;
112		/* vmallocs are handled from the workqueue context */
113		schedule_work(&fddef->wq);
114		spin_unlock(&fddef->lock);
115		put_cpu_var(fdtable_defer_list);
116	}
117}
118
119/*
120 * Expand the fdset in the files_struct.  Called with the files spinlock
121 * held for write.
122 */
123static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
124{
125	unsigned int cpy, set;
126
127	BUG_ON(nfdt->max_fds < ofdt->max_fds);
128
129	cpy = ofdt->max_fds * sizeof(struct file *);
130	set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
131	memcpy(nfdt->fd, ofdt->fd, cpy);
132	memset((char *)(nfdt->fd) + cpy, 0, set);
133
134	cpy = ofdt->max_fds / BITS_PER_BYTE;
135	set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
136	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
137	memset((char *)(nfdt->open_fds) + cpy, 0, set);
138	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
139	memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
140}
141
142static struct fdtable * alloc_fdtable(unsigned int nr)
143{
144	struct fdtable *fdt;
145	char *data;
146
147	/*
148	 * Figure out how many fds we actually want to support in this fdtable.
149	 * Allocation steps are keyed to the size of the fdarray, since it
150	 * grows far faster than any of the other dynamic data. We try to fit
151	 * the fdarray into comfortable page-tuned chunks: starting at 1024B
152	 * and growing in powers of two from there on.
153	 */
154	nr /= (1024 / sizeof(struct file *));
155	nr = roundup_pow_of_two(nr + 1);
156	nr *= (1024 / sizeof(struct file *));
157	/*
158	 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
159	 * had been set lower between the check in expand_files() and here.  Deal
160	 * with that in caller, it's cheaper that way.
161	 *
162	 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
163	 * bitmaps handling below becomes unpleasant, to put it mildly...
164	 */
165	if (unlikely(nr > sysctl_nr_open))
166		nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
167
168	fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
169	if (!fdt)
170		goto out;
171	fdt->max_fds = nr;
172	data = alloc_fdmem(nr * sizeof(struct file *));
173	if (!data)
174		goto out_fdt;
175	fdt->fd = (struct file **)data;
176	data = alloc_fdmem(max_t(unsigned int,
177				 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
 
 
178	if (!data)
179		goto out_arr;
180	fdt->open_fds = (fd_set *)data;
 
 
181	data += nr / BITS_PER_BYTE;
182	fdt->close_on_exec = (fd_set *)data;
183	fdt->next = NULL;
184
185	return fdt;
186
187out_arr:
188	free_fdmem(fdt->fd);
189out_fdt:
190	kfree(fdt);
191out:
192	return NULL;
193}
194
195/*
196 * Expand the file descriptor table.
197 * This function will allocate a new fdtable and both fd array and fdset, of
198 * the given size.
199 * Return <0 error code on error; 1 on successful completion.
200 * The files->file_lock should be held on entry, and will be held on exit.
201 */
202static int expand_fdtable(struct files_struct *files, int nr)
203	__releases(files->file_lock)
204	__acquires(files->file_lock)
205{
206	struct fdtable *new_fdt, *cur_fdt;
207
208	spin_unlock(&files->file_lock);
209	new_fdt = alloc_fdtable(nr);
 
 
 
 
 
 
 
210	spin_lock(&files->file_lock);
211	if (!new_fdt)
212		return -ENOMEM;
213	/*
214	 * extremely unlikely race - sysctl_nr_open decreased between the check in
215	 * caller and alloc_fdtable().  Cheaper to catch it here...
216	 */
217	if (unlikely(new_fdt->max_fds <= nr)) {
218		__free_fdtable(new_fdt);
219		return -EMFILE;
220	}
221	/*
222	 * Check again since another task may have expanded the fd table while
223	 * we dropped the lock
224	 */
225	cur_fdt = files_fdtable(files);
226	if (nr >= cur_fdt->max_fds) {
227		/* Continue as planned */
228		copy_fdtable(new_fdt, cur_fdt);
229		rcu_assign_pointer(files->fdt, new_fdt);
230		if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
231			free_fdtable(cur_fdt);
232	} else {
233		/* Somebody else expanded, so undo our attempt */
234		__free_fdtable(new_fdt);
235	}
236	return 1;
237}
238
239/*
240 * Expand files.
241 * This function will expand the file structures, if the requested size exceeds
242 * the current capacity and there is room for expansion.
243 * Return <0 error code on error; 0 when nothing done; 1 when files were
244 * expanded and execution may have blocked.
245 * The files->file_lock should be held on entry, and will be held on exit.
246 */
247int expand_files(struct files_struct *files, int nr)
 
 
248{
249	struct fdtable *fdt;
 
250
 
251	fdt = files_fdtable(files);
252
253	/*
254	 * N.B. For clone tasks sharing a files structure, this test
255	 * will limit the total number of files that can be opened.
256	 */
257	if (nr >= rlimit(RLIMIT_NOFILE))
258		return -EMFILE;
259
260	/* Do we need to expand? */
261	if (nr < fdt->max_fds)
262		return 0;
263
264	/* Can we expand? */
265	if (nr >= sysctl_nr_open)
266		return -EMFILE;
267
 
 
 
 
 
 
 
 
268	/* All good, so we try */
269	return expand_fdtable(files, nr);
 
 
 
 
 
270}
271
272static int count_open_files(struct fdtable *fdt)
273{
274	int size = fdt->max_fds;
275	int i;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
276
277	/* Find the last open fd */
278	for (i = size/(8*sizeof(long)); i > 0; ) {
279		if (fdt->open_fds->fds_bits[--i])
280			break;
281	}
282	i = (i+1) * 8 * sizeof(long);
283	return i;
284}
285
286/*
287 * Allocate a new files structure and copy contents from the
288 * passed in files structure.
289 * errorp will be valid only when the returned files_struct is NULL.
290 */
291struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
292{
293	struct files_struct *newf;
294	struct file **old_fds, **new_fds;
295	int open_files, size, i;
296	struct fdtable *old_fdt, *new_fdt;
297
298	*errorp = -ENOMEM;
299	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
300	if (!newf)
301		goto out;
302
303	atomic_set(&newf->count, 1);
304
305	spin_lock_init(&newf->file_lock);
 
 
306	newf->next_fd = 0;
307	new_fdt = &newf->fdtab;
308	new_fdt->max_fds = NR_OPEN_DEFAULT;
309	new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
310	new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
 
311	new_fdt->fd = &newf->fd_array[0];
312	new_fdt->next = NULL;
313
314	spin_lock(&oldf->file_lock);
315	old_fdt = files_fdtable(oldf);
316	open_files = count_open_files(old_fdt);
317
318	/*
319	 * Check whether we need to allocate a larger fd array and fd set.
320	 */
321	while (unlikely(open_files > new_fdt->max_fds)) {
322		spin_unlock(&oldf->file_lock);
323
324		if (new_fdt != &newf->fdtab)
325			__free_fdtable(new_fdt);
326
327		new_fdt = alloc_fdtable(open_files - 1);
328		if (!new_fdt) {
329			*errorp = -ENOMEM;
330			goto out_release;
331		}
332
333		/* beyond sysctl_nr_open; nothing to do */
334		if (unlikely(new_fdt->max_fds < open_files)) {
335			__free_fdtable(new_fdt);
336			*errorp = -EMFILE;
337			goto out_release;
338		}
339
340		/*
341		 * Reacquire the oldf lock and a pointer to its fd table
342		 * who knows it may have a new bigger fd table. We need
343		 * the latest pointer.
344		 */
345		spin_lock(&oldf->file_lock);
346		old_fdt = files_fdtable(oldf);
347		open_files = count_open_files(old_fdt);
348	}
349
 
 
350	old_fds = old_fdt->fd;
351	new_fds = new_fdt->fd;
352
353	memcpy(new_fdt->open_fds->fds_bits,
354		old_fdt->open_fds->fds_bits, open_files/8);
355	memcpy(new_fdt->close_on_exec->fds_bits,
356		old_fdt->close_on_exec->fds_bits, open_files/8);
357
358	for (i = open_files; i != 0; i--) {
359		struct file *f = *old_fds++;
360		if (f) {
361			get_file(f);
362		} else {
363			/*
364			 * The fd may be claimed in the fd bitmap but not yet
365			 * instantiated in the files array if a sibling thread
366			 * is partway through open().  So make sure that this
367			 * fd is available to the new process.
368			 */
369			FD_CLR(open_files - i, new_fdt->open_fds);
370		}
371		rcu_assign_pointer(*new_fds++, f);
372	}
373	spin_unlock(&oldf->file_lock);
374
375	/* compute the remainder to be cleared */
376	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
377
378	/* This is long word aligned thus could use a optimized version */
379	memset(new_fds, 0, size);
380
381	if (new_fdt->max_fds > open_files) {
382		int left = (new_fdt->max_fds-open_files)/8;
383		int start = open_files / (8 * sizeof(unsigned long));
384
385		memset(&new_fdt->open_fds->fds_bits[start], 0, left);
386		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
387	}
388
389	rcu_assign_pointer(newf->fdt, new_fdt);
390
391	return newf;
392
393out_release:
394	kmem_cache_free(files_cachep, newf);
395out:
396	return NULL;
397}
398
399static void __devinit fdtable_defer_list_init(int cpu)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
400{
401	struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
402	spin_lock_init(&fddef->lock);
403	INIT_WORK(&fddef->wq, free_fdtable_work);
404	fddef->next = NULL;
 
 
 
 
405}
406
407void __init files_defer_init(void)
408{
409	int i;
410	for_each_possible_cpu(i)
411		fdtable_defer_list_init(i);
412	sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
413			     -BITS_PER_LONG;
 
 
 
414}
415
416struct files_struct init_files = {
417	.count		= ATOMIC_INIT(1),
418	.fdt		= &init_files.fdtab,
419	.fdtab		= {
420		.max_fds	= NR_OPEN_DEFAULT,
421		.fd		= &init_files.fd_array[0],
422		.close_on_exec	= (fd_set *)&init_files.close_on_exec_init,
423		.open_fds	= (fd_set *)&init_files.open_fds_init,
 
424	},
425	.file_lock	= __SPIN_LOCK_UNLOCKED(init_task.file_lock),
 
426};
427
 
 
 
 
 
 
 
 
 
 
 
 
 
 
428/*
429 * allocate a file descriptor, mark it busy.
430 */
431int alloc_fd(unsigned start, unsigned flags)
 
432{
433	struct files_struct *files = current->files;
434	unsigned int fd;
435	int error;
436	struct fdtable *fdt;
437
438	spin_lock(&files->file_lock);
439repeat:
440	fdt = files_fdtable(files);
441	fd = start;
442	if (fd < files->next_fd)
443		fd = files->next_fd;
444
445	if (fd < fdt->max_fds)
446		fd = find_next_zero_bit(fdt->open_fds->fds_bits,
447					   fdt->max_fds, fd);
 
 
 
 
 
 
 
448
449	error = expand_files(files, fd);
450	if (error < 0)
451		goto out;
452
453	/*
454	 * If we needed to expand the fs array we
455	 * might have blocked - try again.
456	 */
457	if (error)
458		goto repeat;
459
460	if (start <= files->next_fd)
461		files->next_fd = fd + 1;
462
463	FD_SET(fd, fdt->open_fds);
464	if (flags & O_CLOEXEC)
465		FD_SET(fd, fdt->close_on_exec);
466	else
467		FD_CLR(fd, fdt->close_on_exec);
468	error = fd;
469#if 1
470	/* Sanity check */
471	if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
472		printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
473		rcu_assign_pointer(fdt->fd[fd], NULL);
474	}
475#endif
476
477out:
478	spin_unlock(&files->file_lock);
479	return error;
480}
481
482int get_unused_fd(void)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
483{
484	return alloc_fd(0, 0);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
485}
486EXPORT_SYMBOL(get_unused_fd);
v5.4
   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 *  linux/fs/file.c
   4 *
   5 *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
   6 *
   7 *  Manage the dynamic fd arrays in the process files_struct.
   8 */
   9
  10#include <linux/syscalls.h>
  11#include <linux/export.h>
  12#include <linux/fs.h>
  13#include <linux/mm.h>
  14#include <linux/sched/signal.h>
 
 
  15#include <linux/slab.h>
 
  16#include <linux/file.h>
  17#include <linux/fdtable.h>
  18#include <linux/bitops.h>
 
  19#include <linux/spinlock.h>
  20#include <linux/rcupdate.h>
 
  21
  22unsigned int sysctl_nr_open __read_mostly = 1024*1024;
  23unsigned int sysctl_nr_open_min = BITS_PER_LONG;
  24/* our min() is unusable in constant expressions ;-/ */
  25#define __const_min(x, y) ((x) < (y) ? (x) : (y))
  26unsigned int sysctl_nr_open_max =
  27	__const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  28
  29static void __free_fdtable(struct fdtable *fdt)
  30{
  31	kvfree(fdt->fd);
  32	kvfree(fdt->open_fds);
  33	kfree(fdt);
  34}
  35
  36static void free_fdtable_rcu(struct rcu_head *rcu)
  37{
  38	__free_fdtable(container_of(rcu, struct fdtable, rcu));
 
 
 
 
 
 
 
 
 
 
 
 
 
  39}
  40
  41#define BITBIT_NR(nr)	BITS_TO_LONGS(BITS_TO_LONGS(nr))
  42#define BITBIT_SIZE(nr)	(BITBIT_NR(nr) * sizeof(long))
  43
  44/*
  45 * Copy 'count' fd bits from the old table to the new table and clear the extra
  46 * space if any.  This does not copy the file pointers.  Called with the files
  47 * spinlock held for write.
  48 */
  49static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
  50			    unsigned int count)
  51{
  52	unsigned int cpy, set;
 
  53
  54	cpy = count / BITS_PER_BYTE;
  55	set = (nfdt->max_fds - count) / BITS_PER_BYTE;
  56	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
  57	memset((char *)nfdt->open_fds + cpy, 0, set);
  58	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
  59	memset((char *)nfdt->close_on_exec + cpy, 0, set);
  60
  61	cpy = BITBIT_SIZE(count);
  62	set = BITBIT_SIZE(nfdt->max_fds) - cpy;
  63	memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
  64	memset((char *)nfdt->full_fds_bits + cpy, 0, set);
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  65}
  66
  67/*
  68 * Copy all file descriptors from the old table to the new, expanded table and
  69 * clear the extra space.  Called with the files spinlock held for write.
  70 */
  71static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
  72{
  73	unsigned int cpy, set;
  74
  75	BUG_ON(nfdt->max_fds < ofdt->max_fds);
  76
  77	cpy = ofdt->max_fds * sizeof(struct file *);
  78	set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
  79	memcpy(nfdt->fd, ofdt->fd, cpy);
  80	memset((char *)nfdt->fd + cpy, 0, set);
  81
  82	copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
 
 
 
 
 
  83}
  84
  85static struct fdtable * alloc_fdtable(unsigned int nr)
  86{
  87	struct fdtable *fdt;
  88	void *data;
  89
  90	/*
  91	 * Figure out how many fds we actually want to support in this fdtable.
  92	 * Allocation steps are keyed to the size of the fdarray, since it
  93	 * grows far faster than any of the other dynamic data. We try to fit
  94	 * the fdarray into comfortable page-tuned chunks: starting at 1024B
  95	 * and growing in powers of two from there on.
  96	 */
  97	nr /= (1024 / sizeof(struct file *));
  98	nr = roundup_pow_of_two(nr + 1);
  99	nr *= (1024 / sizeof(struct file *));
 100	/*
 101	 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
 102	 * had been set lower between the check in expand_files() and here.  Deal
 103	 * with that in caller, it's cheaper that way.
 104	 *
 105	 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
 106	 * bitmaps handling below becomes unpleasant, to put it mildly...
 107	 */
 108	if (unlikely(nr > sysctl_nr_open))
 109		nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
 110
 111	fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
 112	if (!fdt)
 113		goto out;
 114	fdt->max_fds = nr;
 115	data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
 116	if (!data)
 117		goto out_fdt;
 118	fdt->fd = data;
 119
 120	data = kvmalloc(max_t(size_t,
 121				 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
 122				 GFP_KERNEL_ACCOUNT);
 123	if (!data)
 124		goto out_arr;
 125	fdt->open_fds = data;
 126	data += nr / BITS_PER_BYTE;
 127	fdt->close_on_exec = data;
 128	data += nr / BITS_PER_BYTE;
 129	fdt->full_fds_bits = data;
 
 130
 131	return fdt;
 132
 133out_arr:
 134	kvfree(fdt->fd);
 135out_fdt:
 136	kfree(fdt);
 137out:
 138	return NULL;
 139}
 140
 141/*
 142 * Expand the file descriptor table.
 143 * This function will allocate a new fdtable and both fd array and fdset, of
 144 * the given size.
 145 * Return <0 error code on error; 1 on successful completion.
 146 * The files->file_lock should be held on entry, and will be held on exit.
 147 */
 148static int expand_fdtable(struct files_struct *files, unsigned int nr)
 149	__releases(files->file_lock)
 150	__acquires(files->file_lock)
 151{
 152	struct fdtable *new_fdt, *cur_fdt;
 153
 154	spin_unlock(&files->file_lock);
 155	new_fdt = alloc_fdtable(nr);
 156
 157	/* make sure all __fd_install() have seen resize_in_progress
 158	 * or have finished their rcu_read_lock_sched() section.
 159	 */
 160	if (atomic_read(&files->count) > 1)
 161		synchronize_rcu();
 162
 163	spin_lock(&files->file_lock);
 164	if (!new_fdt)
 165		return -ENOMEM;
 166	/*
 167	 * extremely unlikely race - sysctl_nr_open decreased between the check in
 168	 * caller and alloc_fdtable().  Cheaper to catch it here...
 169	 */
 170	if (unlikely(new_fdt->max_fds <= nr)) {
 171		__free_fdtable(new_fdt);
 172		return -EMFILE;
 173	}
 
 
 
 
 174	cur_fdt = files_fdtable(files);
 175	BUG_ON(nr < cur_fdt->max_fds);
 176	copy_fdtable(new_fdt, cur_fdt);
 177	rcu_assign_pointer(files->fdt, new_fdt);
 178	if (cur_fdt != &files->fdtab)
 179		call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
 180	/* coupled with smp_rmb() in __fd_install() */
 181	smp_wmb();
 
 
 
 182	return 1;
 183}
 184
 185/*
 186 * Expand files.
 187 * This function will expand the file structures, if the requested size exceeds
 188 * the current capacity and there is room for expansion.
 189 * Return <0 error code on error; 0 when nothing done; 1 when files were
 190 * expanded and execution may have blocked.
 191 * The files->file_lock should be held on entry, and will be held on exit.
 192 */
 193static int expand_files(struct files_struct *files, unsigned int nr)
 194	__releases(files->file_lock)
 195	__acquires(files->file_lock)
 196{
 197	struct fdtable *fdt;
 198	int expanded = 0;
 199
 200repeat:
 201	fdt = files_fdtable(files);
 202
 
 
 
 
 
 
 
 203	/* Do we need to expand? */
 204	if (nr < fdt->max_fds)
 205		return expanded;
 206
 207	/* Can we expand? */
 208	if (nr >= sysctl_nr_open)
 209		return -EMFILE;
 210
 211	if (unlikely(files->resize_in_progress)) {
 212		spin_unlock(&files->file_lock);
 213		expanded = 1;
 214		wait_event(files->resize_wait, !files->resize_in_progress);
 215		spin_lock(&files->file_lock);
 216		goto repeat;
 217	}
 218
 219	/* All good, so we try */
 220	files->resize_in_progress = true;
 221	expanded = expand_fdtable(files, nr);
 222	files->resize_in_progress = false;
 223
 224	wake_up_all(&files->resize_wait);
 225	return expanded;
 226}
 227
 228static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
 229{
 230	__set_bit(fd, fdt->close_on_exec);
 231}
 232
 233static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
 234{
 235	if (test_bit(fd, fdt->close_on_exec))
 236		__clear_bit(fd, fdt->close_on_exec);
 237}
 238
 239static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
 240{
 241	__set_bit(fd, fdt->open_fds);
 242	fd /= BITS_PER_LONG;
 243	if (!~fdt->open_fds[fd])
 244		__set_bit(fd, fdt->full_fds_bits);
 245}
 246
 247static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
 248{
 249	__clear_bit(fd, fdt->open_fds);
 250	__clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
 251}
 252
 253static unsigned int count_open_files(struct fdtable *fdt)
 254{
 255	unsigned int size = fdt->max_fds;
 256	unsigned int i;
 257
 258	/* Find the last open fd */
 259	for (i = size / BITS_PER_LONG; i > 0; ) {
 260		if (fdt->open_fds[--i])
 261			break;
 262	}
 263	i = (i + 1) * BITS_PER_LONG;
 264	return i;
 265}
 266
 267/*
 268 * Allocate a new files structure and copy contents from the
 269 * passed in files structure.
 270 * errorp will be valid only when the returned files_struct is NULL.
 271 */
 272struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
 273{
 274	struct files_struct *newf;
 275	struct file **old_fds, **new_fds;
 276	unsigned int open_files, i;
 277	struct fdtable *old_fdt, *new_fdt;
 278
 279	*errorp = -ENOMEM;
 280	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
 281	if (!newf)
 282		goto out;
 283
 284	atomic_set(&newf->count, 1);
 285
 286	spin_lock_init(&newf->file_lock);
 287	newf->resize_in_progress = false;
 288	init_waitqueue_head(&newf->resize_wait);
 289	newf->next_fd = 0;
 290	new_fdt = &newf->fdtab;
 291	new_fdt->max_fds = NR_OPEN_DEFAULT;
 292	new_fdt->close_on_exec = newf->close_on_exec_init;
 293	new_fdt->open_fds = newf->open_fds_init;
 294	new_fdt->full_fds_bits = newf->full_fds_bits_init;
 295	new_fdt->fd = &newf->fd_array[0];
 
 296
 297	spin_lock(&oldf->file_lock);
 298	old_fdt = files_fdtable(oldf);
 299	open_files = count_open_files(old_fdt);
 300
 301	/*
 302	 * Check whether we need to allocate a larger fd array and fd set.
 303	 */
 304	while (unlikely(open_files > new_fdt->max_fds)) {
 305		spin_unlock(&oldf->file_lock);
 306
 307		if (new_fdt != &newf->fdtab)
 308			__free_fdtable(new_fdt);
 309
 310		new_fdt = alloc_fdtable(open_files - 1);
 311		if (!new_fdt) {
 312			*errorp = -ENOMEM;
 313			goto out_release;
 314		}
 315
 316		/* beyond sysctl_nr_open; nothing to do */
 317		if (unlikely(new_fdt->max_fds < open_files)) {
 318			__free_fdtable(new_fdt);
 319			*errorp = -EMFILE;
 320			goto out_release;
 321		}
 322
 323		/*
 324		 * Reacquire the oldf lock and a pointer to its fd table
 325		 * who knows it may have a new bigger fd table. We need
 326		 * the latest pointer.
 327		 */
 328		spin_lock(&oldf->file_lock);
 329		old_fdt = files_fdtable(oldf);
 330		open_files = count_open_files(old_fdt);
 331	}
 332
 333	copy_fd_bitmaps(new_fdt, old_fdt, open_files);
 334
 335	old_fds = old_fdt->fd;
 336	new_fds = new_fdt->fd;
 337
 
 
 
 
 
 338	for (i = open_files; i != 0; i--) {
 339		struct file *f = *old_fds++;
 340		if (f) {
 341			get_file(f);
 342		} else {
 343			/*
 344			 * The fd may be claimed in the fd bitmap but not yet
 345			 * instantiated in the files array if a sibling thread
 346			 * is partway through open().  So make sure that this
 347			 * fd is available to the new process.
 348			 */
 349			__clear_open_fd(open_files - i, new_fdt);
 350		}
 351		rcu_assign_pointer(*new_fds++, f);
 352	}
 353	spin_unlock(&oldf->file_lock);
 354
 355	/* clear the remainder */
 356	memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
 
 
 
 
 
 
 
 
 
 
 
 357
 358	rcu_assign_pointer(newf->fdt, new_fdt);
 359
 360	return newf;
 361
 362out_release:
 363	kmem_cache_free(files_cachep, newf);
 364out:
 365	return NULL;
 366}
 367
 368static struct fdtable *close_files(struct files_struct * files)
 369{
 370	/*
 371	 * It is safe to dereference the fd table without RCU or
 372	 * ->file_lock because this is the last reference to the
 373	 * files structure.
 374	 */
 375	struct fdtable *fdt = rcu_dereference_raw(files->fdt);
 376	unsigned int i, j = 0;
 377
 378	for (;;) {
 379		unsigned long set;
 380		i = j * BITS_PER_LONG;
 381		if (i >= fdt->max_fds)
 382			break;
 383		set = fdt->open_fds[j++];
 384		while (set) {
 385			if (set & 1) {
 386				struct file * file = xchg(&fdt->fd[i], NULL);
 387				if (file) {
 388					filp_close(file, files);
 389					cond_resched();
 390				}
 391			}
 392			i++;
 393			set >>= 1;
 394		}
 395	}
 396
 397	return fdt;
 398}
 399
 400struct files_struct *get_files_struct(struct task_struct *task)
 401{
 402	struct files_struct *files;
 403
 404	task_lock(task);
 405	files = task->files;
 406	if (files)
 407		atomic_inc(&files->count);
 408	task_unlock(task);
 409
 410	return files;
 411}
 412
 413void put_files_struct(struct files_struct *files)
 414{
 415	if (atomic_dec_and_test(&files->count)) {
 416		struct fdtable *fdt = close_files(files);
 417
 418		/* free the arrays if they are not embedded */
 419		if (fdt != &files->fdtab)
 420			__free_fdtable(fdt);
 421		kmem_cache_free(files_cachep, files);
 422	}
 423}
 424
 425void reset_files_struct(struct files_struct *files)
 426{
 427	struct task_struct *tsk = current;
 428	struct files_struct *old;
 429
 430	old = tsk->files;
 431	task_lock(tsk);
 432	tsk->files = files;
 433	task_unlock(tsk);
 434	put_files_struct(old);
 435}
 436
 437void exit_files(struct task_struct *tsk)
 438{
 439	struct files_struct * files = tsk->files;
 440
 441	if (files) {
 442		task_lock(tsk);
 443		tsk->files = NULL;
 444		task_unlock(tsk);
 445		put_files_struct(files);
 446	}
 447}
 448
 449struct files_struct init_files = {
 450	.count		= ATOMIC_INIT(1),
 451	.fdt		= &init_files.fdtab,
 452	.fdtab		= {
 453		.max_fds	= NR_OPEN_DEFAULT,
 454		.fd		= &init_files.fd_array[0],
 455		.close_on_exec	= init_files.close_on_exec_init,
 456		.open_fds	= init_files.open_fds_init,
 457		.full_fds_bits	= init_files.full_fds_bits_init,
 458	},
 459	.file_lock	= __SPIN_LOCK_UNLOCKED(init_files.file_lock),
 460	.resize_wait	= __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
 461};
 462
 463static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
 464{
 465	unsigned int maxfd = fdt->max_fds;
 466	unsigned int maxbit = maxfd / BITS_PER_LONG;
 467	unsigned int bitbit = start / BITS_PER_LONG;
 468
 469	bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
 470	if (bitbit > maxfd)
 471		return maxfd;
 472	if (bitbit > start)
 473		start = bitbit;
 474	return find_next_zero_bit(fdt->open_fds, maxfd, start);
 475}
 476
 477/*
 478 * allocate a file descriptor, mark it busy.
 479 */
 480int __alloc_fd(struct files_struct *files,
 481	       unsigned start, unsigned end, unsigned flags)
 482{
 
 483	unsigned int fd;
 484	int error;
 485	struct fdtable *fdt;
 486
 487	spin_lock(&files->file_lock);
 488repeat:
 489	fdt = files_fdtable(files);
 490	fd = start;
 491	if (fd < files->next_fd)
 492		fd = files->next_fd;
 493
 494	if (fd < fdt->max_fds)
 495		fd = find_next_fd(fdt, fd);
 496
 497	/*
 498	 * N.B. For clone tasks sharing a files structure, this test
 499	 * will limit the total number of files that can be opened.
 500	 */
 501	error = -EMFILE;
 502	if (fd >= end)
 503		goto out;
 504
 505	error = expand_files(files, fd);
 506	if (error < 0)
 507		goto out;
 508
 509	/*
 510	 * If we needed to expand the fs array we
 511	 * might have blocked - try again.
 512	 */
 513	if (error)
 514		goto repeat;
 515
 516	if (start <= files->next_fd)
 517		files->next_fd = fd + 1;
 518
 519	__set_open_fd(fd, fdt);
 520	if (flags & O_CLOEXEC)
 521		__set_close_on_exec(fd, fdt);
 522	else
 523		__clear_close_on_exec(fd, fdt);
 524	error = fd;
 525#if 1
 526	/* Sanity check */
 527	if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
 528		printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
 529		rcu_assign_pointer(fdt->fd[fd], NULL);
 530	}
 531#endif
 532
 533out:
 534	spin_unlock(&files->file_lock);
 535	return error;
 536}
 537
 538static int alloc_fd(unsigned start, unsigned flags)
 539{
 540	return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
 541}
 542
 543int get_unused_fd_flags(unsigned flags)
 544{
 545	return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
 546}
 547EXPORT_SYMBOL(get_unused_fd_flags);
 548
 549static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 550{
 551	struct fdtable *fdt = files_fdtable(files);
 552	__clear_open_fd(fd, fdt);
 553	if (fd < files->next_fd)
 554		files->next_fd = fd;
 555}
 556
 557void put_unused_fd(unsigned int fd)
 558{
 559	struct files_struct *files = current->files;
 560	spin_lock(&files->file_lock);
 561	__put_unused_fd(files, fd);
 562	spin_unlock(&files->file_lock);
 563}
 564
 565EXPORT_SYMBOL(put_unused_fd);
 566
 567/*
 568 * Install a file pointer in the fd array.
 569 *
 570 * The VFS is full of places where we drop the files lock between
 571 * setting the open_fds bitmap and installing the file in the file
 572 * array.  At any such point, we are vulnerable to a dup2() race
 573 * installing a file in the array before us.  We need to detect this and
 574 * fput() the struct file we are about to overwrite in this case.
 575 *
 576 * It should never happen - if we allow dup2() do it, _really_ bad things
 577 * will follow.
 578 *
 579 * NOTE: __fd_install() variant is really, really low-level; don't
 580 * use it unless you are forced to by truly lousy API shoved down
 581 * your throat.  'files' *MUST* be either current->files or obtained
 582 * by get_files_struct(current) done by whoever had given it to you,
 583 * or really bad things will happen.  Normally you want to use
 584 * fd_install() instead.
 585 */
 586
 587void __fd_install(struct files_struct *files, unsigned int fd,
 588		struct file *file)
 589{
 590	struct fdtable *fdt;
 591
 592	rcu_read_lock_sched();
 593
 594	if (unlikely(files->resize_in_progress)) {
 595		rcu_read_unlock_sched();
 596		spin_lock(&files->file_lock);
 597		fdt = files_fdtable(files);
 598		BUG_ON(fdt->fd[fd] != NULL);
 599		rcu_assign_pointer(fdt->fd[fd], file);
 600		spin_unlock(&files->file_lock);
 601		return;
 602	}
 603	/* coupled with smp_wmb() in expand_fdtable() */
 604	smp_rmb();
 605	fdt = rcu_dereference_sched(files->fdt);
 606	BUG_ON(fdt->fd[fd] != NULL);
 607	rcu_assign_pointer(fdt->fd[fd], file);
 608	rcu_read_unlock_sched();
 609}
 610
 611void fd_install(unsigned int fd, struct file *file)
 612{
 613	__fd_install(current->files, fd, file);
 614}
 615
 616EXPORT_SYMBOL(fd_install);
 617
 618/*
 619 * The same warnings as for __alloc_fd()/__fd_install() apply here...
 620 */
 621int __close_fd(struct files_struct *files, unsigned fd)
 622{
 623	struct file *file;
 624	struct fdtable *fdt;
 625
 626	spin_lock(&files->file_lock);
 627	fdt = files_fdtable(files);
 628	if (fd >= fdt->max_fds)
 629		goto out_unlock;
 630	file = fdt->fd[fd];
 631	if (!file)
 632		goto out_unlock;
 633	rcu_assign_pointer(fdt->fd[fd], NULL);
 634	__put_unused_fd(files, fd);
 635	spin_unlock(&files->file_lock);
 636	return filp_close(file, files);
 637
 638out_unlock:
 639	spin_unlock(&files->file_lock);
 640	return -EBADF;
 641}
 642EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
 643
 644/*
 645 * variant of __close_fd that gets a ref on the file for later fput
 646 */
 647int __close_fd_get_file(unsigned int fd, struct file **res)
 648{
 649	struct files_struct *files = current->files;
 650	struct file *file;
 651	struct fdtable *fdt;
 652
 653	spin_lock(&files->file_lock);
 654	fdt = files_fdtable(files);
 655	if (fd >= fdt->max_fds)
 656		goto out_unlock;
 657	file = fdt->fd[fd];
 658	if (!file)
 659		goto out_unlock;
 660	rcu_assign_pointer(fdt->fd[fd], NULL);
 661	__put_unused_fd(files, fd);
 662	spin_unlock(&files->file_lock);
 663	get_file(file);
 664	*res = file;
 665	return filp_close(file, files);
 666
 667out_unlock:
 668	spin_unlock(&files->file_lock);
 669	*res = NULL;
 670	return -ENOENT;
 671}
 672
 673void do_close_on_exec(struct files_struct *files)
 674{
 675	unsigned i;
 676	struct fdtable *fdt;
 677
 678	/* exec unshares first */
 679	spin_lock(&files->file_lock);
 680	for (i = 0; ; i++) {
 681		unsigned long set;
 682		unsigned fd = i * BITS_PER_LONG;
 683		fdt = files_fdtable(files);
 684		if (fd >= fdt->max_fds)
 685			break;
 686		set = fdt->close_on_exec[i];
 687		if (!set)
 688			continue;
 689		fdt->close_on_exec[i] = 0;
 690		for ( ; set ; fd++, set >>= 1) {
 691			struct file *file;
 692			if (!(set & 1))
 693				continue;
 694			file = fdt->fd[fd];
 695			if (!file)
 696				continue;
 697			rcu_assign_pointer(fdt->fd[fd], NULL);
 698			__put_unused_fd(files, fd);
 699			spin_unlock(&files->file_lock);
 700			filp_close(file, files);
 701			cond_resched();
 702			spin_lock(&files->file_lock);
 703		}
 704
 705	}
 706	spin_unlock(&files->file_lock);
 707}
 708
 709static struct file *__fget(unsigned int fd, fmode_t mask, unsigned int refs)
 710{
 711	struct files_struct *files = current->files;
 712	struct file *file;
 713
 714	rcu_read_lock();
 715loop:
 716	file = fcheck_files(files, fd);
 717	if (file) {
 718		/* File object ref couldn't be taken.
 719		 * dup2() atomicity guarantee is the reason
 720		 * we loop to catch the new file (or NULL pointer)
 721		 */
 722		if (file->f_mode & mask)
 723			file = NULL;
 724		else if (!get_file_rcu_many(file, refs))
 725			goto loop;
 726	}
 727	rcu_read_unlock();
 728
 729	return file;
 730}
 731
 732struct file *fget_many(unsigned int fd, unsigned int refs)
 733{
 734	return __fget(fd, FMODE_PATH, refs);
 735}
 736
 737struct file *fget(unsigned int fd)
 738{
 739	return __fget(fd, FMODE_PATH, 1);
 740}
 741EXPORT_SYMBOL(fget);
 742
 743struct file *fget_raw(unsigned int fd)
 744{
 745	return __fget(fd, 0, 1);
 746}
 747EXPORT_SYMBOL(fget_raw);
 748
 749/*
 750 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
 751 *
 752 * You can use this instead of fget if you satisfy all of the following
 753 * conditions:
 754 * 1) You must call fput_light before exiting the syscall and returning control
 755 *    to userspace (i.e. you cannot remember the returned struct file * after
 756 *    returning to userspace).
 757 * 2) You must not call filp_close on the returned struct file * in between
 758 *    calls to fget_light and fput_light.
 759 * 3) You must not clone the current task in between the calls to fget_light
 760 *    and fput_light.
 761 *
 762 * The fput_needed flag returned by fget_light should be passed to the
 763 * corresponding fput_light.
 764 */
 765static unsigned long __fget_light(unsigned int fd, fmode_t mask)
 766{
 767	struct files_struct *files = current->files;
 768	struct file *file;
 769
 770	if (atomic_read(&files->count) == 1) {
 771		file = __fcheck_files(files, fd);
 772		if (!file || unlikely(file->f_mode & mask))
 773			return 0;
 774		return (unsigned long)file;
 775	} else {
 776		file = __fget(fd, mask, 1);
 777		if (!file)
 778			return 0;
 779		return FDPUT_FPUT | (unsigned long)file;
 780	}
 781}
 782unsigned long __fdget(unsigned int fd)
 783{
 784	return __fget_light(fd, FMODE_PATH);
 785}
 786EXPORT_SYMBOL(__fdget);
 787
 788unsigned long __fdget_raw(unsigned int fd)
 789{
 790	return __fget_light(fd, 0);
 791}
 792
 793unsigned long __fdget_pos(unsigned int fd)
 794{
 795	unsigned long v = __fdget(fd);
 796	struct file *file = (struct file *)(v & ~3);
 797
 798	if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
 799		if (file_count(file) > 1) {
 800			v |= FDPUT_POS_UNLOCK;
 801			mutex_lock(&file->f_pos_lock);
 802		}
 803	}
 804	return v;
 805}
 806
 807void __f_unlock_pos(struct file *f)
 808{
 809	mutex_unlock(&f->f_pos_lock);
 810}
 811
 812/*
 813 * We only lock f_pos if we have threads or if the file might be
 814 * shared with another process. In both cases we'll have an elevated
 815 * file count (done either by fdget() or by fork()).
 816 */
 817
 818void set_close_on_exec(unsigned int fd, int flag)
 819{
 820	struct files_struct *files = current->files;
 821	struct fdtable *fdt;
 822	spin_lock(&files->file_lock);
 823	fdt = files_fdtable(files);
 824	if (flag)
 825		__set_close_on_exec(fd, fdt);
 826	else
 827		__clear_close_on_exec(fd, fdt);
 828	spin_unlock(&files->file_lock);
 829}
 830
 831bool get_close_on_exec(unsigned int fd)
 832{
 833	struct files_struct *files = current->files;
 834	struct fdtable *fdt;
 835	bool res;
 836	rcu_read_lock();
 837	fdt = files_fdtable(files);
 838	res = close_on_exec(fd, fdt);
 839	rcu_read_unlock();
 840	return res;
 841}
 842
 843static int do_dup2(struct files_struct *files,
 844	struct file *file, unsigned fd, unsigned flags)
 845__releases(&files->file_lock)
 846{
 847	struct file *tofree;
 848	struct fdtable *fdt;
 849
 850	/*
 851	 * We need to detect attempts to do dup2() over allocated but still
 852	 * not finished descriptor.  NB: OpenBSD avoids that at the price of
 853	 * extra work in their equivalent of fget() - they insert struct
 854	 * file immediately after grabbing descriptor, mark it larval if
 855	 * more work (e.g. actual opening) is needed and make sure that
 856	 * fget() treats larval files as absent.  Potentially interesting,
 857	 * but while extra work in fget() is trivial, locking implications
 858	 * and amount of surgery on open()-related paths in VFS are not.
 859	 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
 860	 * deadlocks in rather amusing ways, AFAICS.  All of that is out of
 861	 * scope of POSIX or SUS, since neither considers shared descriptor
 862	 * tables and this condition does not arise without those.
 863	 */
 864	fdt = files_fdtable(files);
 865	tofree = fdt->fd[fd];
 866	if (!tofree && fd_is_open(fd, fdt))
 867		goto Ebusy;
 868	get_file(file);
 869	rcu_assign_pointer(fdt->fd[fd], file);
 870	__set_open_fd(fd, fdt);
 871	if (flags & O_CLOEXEC)
 872		__set_close_on_exec(fd, fdt);
 873	else
 874		__clear_close_on_exec(fd, fdt);
 875	spin_unlock(&files->file_lock);
 876
 877	if (tofree)
 878		filp_close(tofree, files);
 879
 880	return fd;
 881
 882Ebusy:
 883	spin_unlock(&files->file_lock);
 884	return -EBUSY;
 885}
 886
 887int replace_fd(unsigned fd, struct file *file, unsigned flags)
 888{
 889	int err;
 890	struct files_struct *files = current->files;
 891
 892	if (!file)
 893		return __close_fd(files, fd);
 894
 895	if (fd >= rlimit(RLIMIT_NOFILE))
 896		return -EBADF;
 897
 898	spin_lock(&files->file_lock);
 899	err = expand_files(files, fd);
 900	if (unlikely(err < 0))
 901		goto out_unlock;
 902	return do_dup2(files, file, fd, flags);
 903
 904out_unlock:
 905	spin_unlock(&files->file_lock);
 906	return err;
 907}
 908
 909static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 910{
 911	int err = -EBADF;
 912	struct file *file;
 913	struct files_struct *files = current->files;
 914
 915	if ((flags & ~O_CLOEXEC) != 0)
 916		return -EINVAL;
 917
 918	if (unlikely(oldfd == newfd))
 919		return -EINVAL;
 920
 921	if (newfd >= rlimit(RLIMIT_NOFILE))
 922		return -EBADF;
 923
 924	spin_lock(&files->file_lock);
 925	err = expand_files(files, newfd);
 926	file = fcheck(oldfd);
 927	if (unlikely(!file))
 928		goto Ebadf;
 929	if (unlikely(err < 0)) {
 930		if (err == -EMFILE)
 931			goto Ebadf;
 932		goto out_unlock;
 933	}
 934	return do_dup2(files, file, newfd, flags);
 935
 936Ebadf:
 937	err = -EBADF;
 938out_unlock:
 939	spin_unlock(&files->file_lock);
 940	return err;
 941}
 942
 943SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
 944{
 945	return ksys_dup3(oldfd, newfd, flags);
 946}
 947
 948SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 949{
 950	if (unlikely(newfd == oldfd)) { /* corner case */
 951		struct files_struct *files = current->files;
 952		int retval = oldfd;
 953
 954		rcu_read_lock();
 955		if (!fcheck_files(files, oldfd))
 956			retval = -EBADF;
 957		rcu_read_unlock();
 958		return retval;
 959	}
 960	return ksys_dup3(oldfd, newfd, 0);
 961}
 962
 963int ksys_dup(unsigned int fildes)
 964{
 965	int ret = -EBADF;
 966	struct file *file = fget_raw(fildes);
 967
 968	if (file) {
 969		ret = get_unused_fd_flags(0);
 970		if (ret >= 0)
 971			fd_install(ret, file);
 972		else
 973			fput(file);
 974	}
 975	return ret;
 976}
 977
 978SYSCALL_DEFINE1(dup, unsigned int, fildes)
 979{
 980	return ksys_dup(fildes);
 981}
 982
 983int f_dupfd(unsigned int from, struct file *file, unsigned flags)
 984{
 985	int err;
 986	if (from >= rlimit(RLIMIT_NOFILE))
 987		return -EINVAL;
 988	err = alloc_fd(from, flags);
 989	if (err >= 0) {
 990		get_file(file);
 991		fd_install(err, file);
 992	}
 993	return err;
 994}
 995
 996int iterate_fd(struct files_struct *files, unsigned n,
 997		int (*f)(const void *, struct file *, unsigned),
 998		const void *p)
 999{
1000	struct fdtable *fdt;
1001	int res = 0;
1002	if (!files)
1003		return 0;
1004	spin_lock(&files->file_lock);
1005	for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1006		struct file *file;
1007		file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1008		if (!file)
1009			continue;
1010		res = f(p, file, n);
1011		if (res)
1012			break;
1013	}
1014	spin_unlock(&files->file_lock);
1015	return res;
1016}
1017EXPORT_SYMBOL(iterate_fd);