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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);
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/export.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(size_t 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 void *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 = data;
176
177 data = alloc_fdmem(max_t(size_t,
178 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
179 if (!data)
180 goto out_arr;
181 fdt->open_fds = data;
182 data += nr / BITS_PER_BYTE;
183 fdt->close_on_exec = data;
184 fdt->next = NULL;
185
186 return fdt;
187
188out_arr:
189 free_fdmem(fdt->fd);
190out_fdt:
191 kfree(fdt);
192out:
193 return NULL;
194}
195
196/*
197 * Expand the file descriptor table.
198 * This function will allocate a new fdtable and both fd array and fdset, of
199 * the given size.
200 * Return <0 error code on error; 1 on successful completion.
201 * The files->file_lock should be held on entry, and will be held on exit.
202 */
203static int expand_fdtable(struct files_struct *files, int nr)
204 __releases(files->file_lock)
205 __acquires(files->file_lock)
206{
207 struct fdtable *new_fdt, *cur_fdt;
208
209 spin_unlock(&files->file_lock);
210 new_fdt = alloc_fdtable(nr);
211 spin_lock(&files->file_lock);
212 if (!new_fdt)
213 return -ENOMEM;
214 /*
215 * extremely unlikely race - sysctl_nr_open decreased between the check in
216 * caller and alloc_fdtable(). Cheaper to catch it here...
217 */
218 if (unlikely(new_fdt->max_fds <= nr)) {
219 __free_fdtable(new_fdt);
220 return -EMFILE;
221 }
222 /*
223 * Check again since another task may have expanded the fd table while
224 * we dropped the lock
225 */
226 cur_fdt = files_fdtable(files);
227 if (nr >= cur_fdt->max_fds) {
228 /* Continue as planned */
229 copy_fdtable(new_fdt, cur_fdt);
230 rcu_assign_pointer(files->fdt, new_fdt);
231 if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
232 free_fdtable(cur_fdt);
233 } else {
234 /* Somebody else expanded, so undo our attempt */
235 __free_fdtable(new_fdt);
236 }
237 return 1;
238}
239
240/*
241 * Expand files.
242 * This function will expand the file structures, if the requested size exceeds
243 * the current capacity and there is room for expansion.
244 * Return <0 error code on error; 0 when nothing done; 1 when files were
245 * expanded and execution may have blocked.
246 * The files->file_lock should be held on entry, and will be held on exit.
247 */
248int expand_files(struct files_struct *files, int nr)
249{
250 struct fdtable *fdt;
251
252 fdt = files_fdtable(files);
253
254 /*
255 * N.B. For clone tasks sharing a files structure, this test
256 * will limit the total number of files that can be opened.
257 */
258 if (nr >= rlimit(RLIMIT_NOFILE))
259 return -EMFILE;
260
261 /* Do we need to expand? */
262 if (nr < fdt->max_fds)
263 return 0;
264
265 /* Can we expand? */
266 if (nr >= sysctl_nr_open)
267 return -EMFILE;
268
269 /* All good, so we try */
270 return expand_fdtable(files, nr);
271}
272
273static int count_open_files(struct fdtable *fdt)
274{
275 int size = fdt->max_fds;
276 int i;
277
278 /* Find the last open fd */
279 for (i = size / BITS_PER_LONG; i > 0; ) {
280 if (fdt->open_fds[--i])
281 break;
282 }
283 i = (i + 1) * BITS_PER_LONG;
284 return i;
285}
286
287/*
288 * Allocate a new files structure and copy contents from the
289 * passed in files structure.
290 * errorp will be valid only when the returned files_struct is NULL.
291 */
292struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
293{
294 struct files_struct *newf;
295 struct file **old_fds, **new_fds;
296 int open_files, size, i;
297 struct fdtable *old_fdt, *new_fdt;
298
299 *errorp = -ENOMEM;
300 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
301 if (!newf)
302 goto out;
303
304 atomic_set(&newf->count, 1);
305
306 spin_lock_init(&newf->file_lock);
307 newf->next_fd = 0;
308 new_fdt = &newf->fdtab;
309 new_fdt->max_fds = NR_OPEN_DEFAULT;
310 new_fdt->close_on_exec = newf->close_on_exec_init;
311 new_fdt->open_fds = newf->open_fds_init;
312 new_fdt->fd = &newf->fd_array[0];
313 new_fdt->next = NULL;
314
315 spin_lock(&oldf->file_lock);
316 old_fdt = files_fdtable(oldf);
317 open_files = count_open_files(old_fdt);
318
319 /*
320 * Check whether we need to allocate a larger fd array and fd set.
321 */
322 while (unlikely(open_files > new_fdt->max_fds)) {
323 spin_unlock(&oldf->file_lock);
324
325 if (new_fdt != &newf->fdtab)
326 __free_fdtable(new_fdt);
327
328 new_fdt = alloc_fdtable(open_files - 1);
329 if (!new_fdt) {
330 *errorp = -ENOMEM;
331 goto out_release;
332 }
333
334 /* beyond sysctl_nr_open; nothing to do */
335 if (unlikely(new_fdt->max_fds < open_files)) {
336 __free_fdtable(new_fdt);
337 *errorp = -EMFILE;
338 goto out_release;
339 }
340
341 /*
342 * Reacquire the oldf lock and a pointer to its fd table
343 * who knows it may have a new bigger fd table. We need
344 * the latest pointer.
345 */
346 spin_lock(&oldf->file_lock);
347 old_fdt = files_fdtable(oldf);
348 open_files = count_open_files(old_fdt);
349 }
350
351 old_fds = old_fdt->fd;
352 new_fds = new_fdt->fd;
353
354 memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8);
355 memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8);
356
357 for (i = open_files; i != 0; i--) {
358 struct file *f = *old_fds++;
359 if (f) {
360 get_file(f);
361 } else {
362 /*
363 * The fd may be claimed in the fd bitmap but not yet
364 * instantiated in the files array if a sibling thread
365 * is partway through open(). So make sure that this
366 * fd is available to the new process.
367 */
368 __clear_open_fd(open_files - i, new_fdt);
369 }
370 rcu_assign_pointer(*new_fds++, f);
371 }
372 spin_unlock(&oldf->file_lock);
373
374 /* compute the remainder to be cleared */
375 size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
376
377 /* This is long word aligned thus could use a optimized version */
378 memset(new_fds, 0, size);
379
380 if (new_fdt->max_fds > open_files) {
381 int left = (new_fdt->max_fds - open_files) / 8;
382 int start = open_files / BITS_PER_LONG;
383
384 memset(&new_fdt->open_fds[start], 0, left);
385 memset(&new_fdt->close_on_exec[start], 0, left);
386 }
387
388 rcu_assign_pointer(newf->fdt, new_fdt);
389
390 return newf;
391
392out_release:
393 kmem_cache_free(files_cachep, newf);
394out:
395 return NULL;
396}
397
398static void __devinit fdtable_defer_list_init(int cpu)
399{
400 struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
401 spin_lock_init(&fddef->lock);
402 INIT_WORK(&fddef->wq, free_fdtable_work);
403 fddef->next = NULL;
404}
405
406void __init files_defer_init(void)
407{
408 int i;
409 for_each_possible_cpu(i)
410 fdtable_defer_list_init(i);
411 sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
412 -BITS_PER_LONG;
413}
414
415struct files_struct init_files = {
416 .count = ATOMIC_INIT(1),
417 .fdt = &init_files.fdtab,
418 .fdtab = {
419 .max_fds = NR_OPEN_DEFAULT,
420 .fd = &init_files.fd_array[0],
421 .close_on_exec = init_files.close_on_exec_init,
422 .open_fds = init_files.open_fds_init,
423 },
424 .file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
425};
426
427/*
428 * allocate a file descriptor, mark it busy.
429 */
430int alloc_fd(unsigned start, unsigned flags)
431{
432 struct files_struct *files = current->files;
433 unsigned int fd;
434 int error;
435 struct fdtable *fdt;
436
437 spin_lock(&files->file_lock);
438repeat:
439 fdt = files_fdtable(files);
440 fd = start;
441 if (fd < files->next_fd)
442 fd = files->next_fd;
443
444 if (fd < fdt->max_fds)
445 fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd);
446
447 error = expand_files(files, fd);
448 if (error < 0)
449 goto out;
450
451 /*
452 * If we needed to expand the fs array we
453 * might have blocked - try again.
454 */
455 if (error)
456 goto repeat;
457
458 if (start <= files->next_fd)
459 files->next_fd = fd + 1;
460
461 __set_open_fd(fd, fdt);
462 if (flags & O_CLOEXEC)
463 __set_close_on_exec(fd, fdt);
464 else
465 __clear_close_on_exec(fd, fdt);
466 error = fd;
467#if 1
468 /* Sanity check */
469 if (rcu_dereference_raw(fdt->fd[fd]) != NULL) {
470 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
471 rcu_assign_pointer(fdt->fd[fd], NULL);
472 }
473#endif
474
475out:
476 spin_unlock(&files->file_lock);
477 return error;
478}
479
480int get_unused_fd(void)
481{
482 return alloc_fd(0, 0);
483}
484EXPORT_SYMBOL(get_unused_fd);