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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/time.h> |
13 | #include <linux/sched.h> |
14 | #include <linux/slab.h> |
15 | #include <linux/vmalloc.h> |
16 | #include <linux/file.h> |
17 | #include <linux/fdtable.h> |
18 | #include <linux/bitops.h> |
19 | #include <linux/interrupt.h> |
20 | #include <linux/spinlock.h> |
21 | #include <linux/rcupdate.h> |
22 | #include <linux/workqueue.h> |
23 | |
24 | struct fdtable_defer { |
25 | spinlock_t lock; |
26 | struct work_struct wq; |
27 | struct fdtable *next; |
28 | }; |
29 | |
30 | int sysctl_nr_open __read_mostly = 1024*1024; |
31 | int sysctl_nr_open_min = BITS_PER_LONG; |
32 | int sysctl_nr_open_max = 1024 * 1024; /* raised later */ |
33 | |
34 | /* |
35 | * We use this list to defer free fdtables that have vmalloced |
36 | * sets/arrays. By keeping a per-cpu list, we avoid having to embed |
37 | * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in |
38 | * this per-task structure. |
39 | */ |
40 | static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list); |
41 | |
42 | static inline void *alloc_fdmem(unsigned int size) |
43 | { |
44 | void *data; |
45 | |
46 | data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN); |
47 | if (data != NULL) |
48 | return data; |
49 | |
50 | return vmalloc(size); |
51 | } |
52 | |
53 | static void free_fdmem(void *ptr) |
54 | { |
55 | is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr); |
56 | } |
57 | |
58 | static void __free_fdtable(struct fdtable *fdt) |
59 | { |
60 | free_fdmem(fdt->fd); |
61 | free_fdmem(fdt->open_fds); |
62 | kfree(fdt); |
63 | } |
64 | |
65 | static void free_fdtable_work(struct work_struct *work) |
66 | { |
67 | struct fdtable_defer *f = |
68 | container_of(work, struct fdtable_defer, wq); |
69 | struct fdtable *fdt; |
70 | |
71 | spin_lock_bh(&f->lock); |
72 | fdt = f->next; |
73 | f->next = NULL; |
74 | spin_unlock_bh(&f->lock); |
75 | while(fdt) { |
76 | struct fdtable *next = fdt->next; |
77 | |
78 | __free_fdtable(fdt); |
79 | fdt = next; |
80 | } |
81 | } |
82 | |
83 | void free_fdtable_rcu(struct rcu_head *rcu) |
84 | { |
85 | struct fdtable *fdt = container_of(rcu, struct fdtable, rcu); |
86 | struct fdtable_defer *fddef; |
87 | |
88 | BUG_ON(!fdt); |
89 | |
90 | if (fdt->max_fds <= NR_OPEN_DEFAULT) { |
91 | /* |
92 | * This fdtable is embedded in the files structure and that |
93 | * structure itself is getting destroyed. |
94 | */ |
95 | kmem_cache_free(files_cachep, |
96 | container_of(fdt, struct files_struct, fdtab)); |
97 | return; |
98 | } |
99 | if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) { |
100 | kfree(fdt->fd); |
101 | kfree(fdt->open_fds); |
102 | kfree(fdt); |
103 | } else { |
104 | fddef = &get_cpu_var(fdtable_defer_list); |
105 | spin_lock(&fddef->lock); |
106 | fdt->next = fddef->next; |
107 | fddef->next = fdt; |
108 | /* vmallocs are handled from the workqueue context */ |
109 | schedule_work(&fddef->wq); |
110 | spin_unlock(&fddef->lock); |
111 | put_cpu_var(fdtable_defer_list); |
112 | } |
113 | } |
114 | |
115 | /* |
116 | * Expand the fdset in the files_struct. Called with the files spinlock |
117 | * held for write. |
118 | */ |
119 | static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) |
120 | { |
121 | unsigned int cpy, set; |
122 | |
123 | BUG_ON(nfdt->max_fds < ofdt->max_fds); |
124 | |
125 | cpy = ofdt->max_fds * sizeof(struct file *); |
126 | set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); |
127 | memcpy(nfdt->fd, ofdt->fd, cpy); |
128 | memset((char *)(nfdt->fd) + cpy, 0, set); |
129 | |
130 | cpy = ofdt->max_fds / BITS_PER_BYTE; |
131 | set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE; |
132 | memcpy(nfdt->open_fds, ofdt->open_fds, cpy); |
133 | memset((char *)(nfdt->open_fds) + cpy, 0, set); |
134 | memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); |
135 | memset((char *)(nfdt->close_on_exec) + cpy, 0, set); |
136 | } |
137 | |
138 | static struct fdtable * alloc_fdtable(unsigned int nr) |
139 | { |
140 | struct fdtable *fdt; |
141 | char *data; |
142 | |
143 | /* |
144 | * Figure out how many fds we actually want to support in this fdtable. |
145 | * Allocation steps are keyed to the size of the fdarray, since it |
146 | * grows far faster than any of the other dynamic data. We try to fit |
147 | * the fdarray into comfortable page-tuned chunks: starting at 1024B |
148 | * and growing in powers of two from there on. |
149 | */ |
150 | nr /= (1024 / sizeof(struct file *)); |
151 | nr = roundup_pow_of_two(nr + 1); |
152 | nr *= (1024 / sizeof(struct file *)); |
153 | /* |
154 | * Note that this can drive nr *below* what we had passed if sysctl_nr_open |
155 | * had been set lower between the check in expand_files() and here. Deal |
156 | * with that in caller, it's cheaper that way. |
157 | * |
158 | * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise |
159 | * bitmaps handling below becomes unpleasant, to put it mildly... |
160 | */ |
161 | if (unlikely(nr > sysctl_nr_open)) |
162 | nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; |
163 | |
164 | fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL); |
165 | if (!fdt) |
166 | goto out; |
167 | fdt->max_fds = nr; |
168 | data = alloc_fdmem(nr * sizeof(struct file *)); |
169 | if (!data) |
170 | goto out_fdt; |
171 | fdt->fd = (struct file **)data; |
172 | data = alloc_fdmem(max_t(unsigned int, |
173 | 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); |
174 | if (!data) |
175 | goto out_arr; |
176 | fdt->open_fds = (fd_set *)data; |
177 | data += nr / BITS_PER_BYTE; |
178 | fdt->close_on_exec = (fd_set *)data; |
179 | fdt->next = NULL; |
180 | |
181 | return fdt; |
182 | |
183 | out_arr: |
184 | free_fdmem(fdt->fd); |
185 | out_fdt: |
186 | kfree(fdt); |
187 | out: |
188 | return NULL; |
189 | } |
190 | |
191 | /* |
192 | * Expand the file descriptor table. |
193 | * This function will allocate a new fdtable and both fd array and fdset, of |
194 | * the given size. |
195 | * Return <0 error code on error; 1 on successful completion. |
196 | * The files->file_lock should be held on entry, and will be held on exit. |
197 | */ |
198 | static int expand_fdtable(struct files_struct *files, int nr) |
199 | __releases(files->file_lock) |
200 | __acquires(files->file_lock) |
201 | { |
202 | struct fdtable *new_fdt, *cur_fdt; |
203 | |
204 | spin_unlock(&files->file_lock); |
205 | new_fdt = alloc_fdtable(nr); |
206 | spin_lock(&files->file_lock); |
207 | if (!new_fdt) |
208 | return -ENOMEM; |
209 | /* |
210 | * extremely unlikely race - sysctl_nr_open decreased between the check in |
211 | * caller and alloc_fdtable(). Cheaper to catch it here... |
212 | */ |
213 | if (unlikely(new_fdt->max_fds <= nr)) { |
214 | __free_fdtable(new_fdt); |
215 | return -EMFILE; |
216 | } |
217 | /* |
218 | * Check again since another task may have expanded the fd table while |
219 | * we dropped the lock |
220 | */ |
221 | cur_fdt = files_fdtable(files); |
222 | if (nr >= cur_fdt->max_fds) { |
223 | /* Continue as planned */ |
224 | copy_fdtable(new_fdt, cur_fdt); |
225 | rcu_assign_pointer(files->fdt, new_fdt); |
226 | if (cur_fdt->max_fds > NR_OPEN_DEFAULT) |
227 | free_fdtable(cur_fdt); |
228 | } else { |
229 | /* Somebody else expanded, so undo our attempt */ |
230 | __free_fdtable(new_fdt); |
231 | } |
232 | return 1; |
233 | } |
234 | |
235 | /* |
236 | * Expand files. |
237 | * This function will expand the file structures, if the requested size exceeds |
238 | * the current capacity and there is room for expansion. |
239 | * Return <0 error code on error; 0 when nothing done; 1 when files were |
240 | * expanded and execution may have blocked. |
241 | * The files->file_lock should be held on entry, and will be held on exit. |
242 | */ |
243 | int expand_files(struct files_struct *files, int nr) |
244 | { |
245 | struct fdtable *fdt; |
246 | |
247 | fdt = files_fdtable(files); |
248 | |
249 | /* |
250 | * N.B. For clone tasks sharing a files structure, this test |
251 | * will limit the total number of files that can be opened. |
252 | */ |
253 | if (nr >= rlimit(RLIMIT_NOFILE)) |
254 | return -EMFILE; |
255 | |
256 | /* Do we need to expand? */ |
257 | if (nr < fdt->max_fds) |
258 | return 0; |
259 | |
260 | /* Can we expand? */ |
261 | if (nr >= sysctl_nr_open) |
262 | return -EMFILE; |
263 | |
264 | /* All good, so we try */ |
265 | return expand_fdtable(files, nr); |
266 | } |
267 | |
268 | static int count_open_files(struct fdtable *fdt) |
269 | { |
270 | int size = fdt->max_fds; |
271 | int i; |
272 | |
273 | /* Find the last open fd */ |
274 | for (i = size/(8*sizeof(long)); i > 0; ) { |
275 | if (fdt->open_fds->fds_bits[--i]) |
276 | break; |
277 | } |
278 | i = (i+1) * 8 * sizeof(long); |
279 | return i; |
280 | } |
281 | |
282 | /* |
283 | * Allocate a new files structure and copy contents from the |
284 | * passed in files structure. |
285 | * errorp will be valid only when the returned files_struct is NULL. |
286 | */ |
287 | struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) |
288 | { |
289 | struct files_struct *newf; |
290 | struct file **old_fds, **new_fds; |
291 | int open_files, size, i; |
292 | struct fdtable *old_fdt, *new_fdt; |
293 | |
294 | *errorp = -ENOMEM; |
295 | newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); |
296 | if (!newf) |
297 | goto out; |
298 | |
299 | atomic_set(&newf->count, 1); |
300 | |
301 | spin_lock_init(&newf->file_lock); |
302 | newf->next_fd = 0; |
303 | new_fdt = &newf->fdtab; |
304 | new_fdt->max_fds = NR_OPEN_DEFAULT; |
305 | new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init; |
306 | new_fdt->open_fds = (fd_set *)&newf->open_fds_init; |
307 | new_fdt->fd = &newf->fd_array[0]; |
308 | new_fdt->next = NULL; |
309 | |
310 | spin_lock(&oldf->file_lock); |
311 | old_fdt = files_fdtable(oldf); |
312 | open_files = count_open_files(old_fdt); |
313 | |
314 | /* |
315 | * Check whether we need to allocate a larger fd array and fd set. |
316 | */ |
317 | while (unlikely(open_files > new_fdt->max_fds)) { |
318 | spin_unlock(&oldf->file_lock); |
319 | |
320 | if (new_fdt != &newf->fdtab) |
321 | __free_fdtable(new_fdt); |
322 | |
323 | new_fdt = alloc_fdtable(open_files - 1); |
324 | if (!new_fdt) { |
325 | *errorp = -ENOMEM; |
326 | goto out_release; |
327 | } |
328 | |
329 | /* beyond sysctl_nr_open; nothing to do */ |
330 | if (unlikely(new_fdt->max_fds < open_files)) { |
331 | __free_fdtable(new_fdt); |
332 | *errorp = -EMFILE; |
333 | goto out_release; |
334 | } |
335 | |
336 | /* |
337 | * Reacquire the oldf lock and a pointer to its fd table |
338 | * who knows it may have a new bigger fd table. We need |
339 | * the latest pointer. |
340 | */ |
341 | spin_lock(&oldf->file_lock); |
342 | old_fdt = files_fdtable(oldf); |
343 | open_files = count_open_files(old_fdt); |
344 | } |
345 | |
346 | old_fds = old_fdt->fd; |
347 | new_fds = new_fdt->fd; |
348 | |
349 | memcpy(new_fdt->open_fds->fds_bits, |
350 | old_fdt->open_fds->fds_bits, open_files/8); |
351 | memcpy(new_fdt->close_on_exec->fds_bits, |
352 | old_fdt->close_on_exec->fds_bits, open_files/8); |
353 | |
354 | for (i = open_files; i != 0; i--) { |
355 | struct file *f = *old_fds++; |
356 | if (f) { |
357 | get_file(f); |
358 | } else { |
359 | /* |
360 | * The fd may be claimed in the fd bitmap but not yet |
361 | * instantiated in the files array if a sibling thread |
362 | * is partway through open(). So make sure that this |
363 | * fd is available to the new process. |
364 | */ |
365 | FD_CLR(open_files - i, new_fdt->open_fds); |
366 | } |
367 | rcu_assign_pointer(*new_fds++, f); |
368 | } |
369 | spin_unlock(&oldf->file_lock); |
370 | |
371 | /* compute the remainder to be cleared */ |
372 | size = (new_fdt->max_fds - open_files) * sizeof(struct file *); |
373 | |
374 | /* This is long word aligned thus could use a optimized version */ |
375 | memset(new_fds, 0, size); |
376 | |
377 | if (new_fdt->max_fds > open_files) { |
378 | int left = (new_fdt->max_fds-open_files)/8; |
379 | int start = open_files / (8 * sizeof(unsigned long)); |
380 | |
381 | memset(&new_fdt->open_fds->fds_bits[start], 0, left); |
382 | memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); |
383 | } |
384 | |
385 | rcu_assign_pointer(newf->fdt, new_fdt); |
386 | |
387 | return newf; |
388 | |
389 | out_release: |
390 | kmem_cache_free(files_cachep, newf); |
391 | out: |
392 | return NULL; |
393 | } |
394 | |
395 | static void __devinit fdtable_defer_list_init(int cpu) |
396 | { |
397 | struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu); |
398 | spin_lock_init(&fddef->lock); |
399 | INIT_WORK(&fddef->wq, free_fdtable_work); |
400 | fddef->next = NULL; |
401 | } |
402 | |
403 | void __init files_defer_init(void) |
404 | { |
405 | int i; |
406 | for_each_possible_cpu(i) |
407 | fdtable_defer_list_init(i); |
408 | sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) & |
409 | -BITS_PER_LONG; |
410 | } |
411 | |
412 | struct files_struct init_files = { |
413 | .count = ATOMIC_INIT(1), |
414 | .fdt = &init_files.fdtab, |
415 | .fdtab = { |
416 | .max_fds = NR_OPEN_DEFAULT, |
417 | .fd = &init_files.fd_array[0], |
418 | .close_on_exec = (fd_set *)&init_files.close_on_exec_init, |
419 | .open_fds = (fd_set *)&init_files.open_fds_init, |
420 | }, |
421 | .file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock), |
422 | }; |
423 | |
424 | /* |
425 | * allocate a file descriptor, mark it busy. |
426 | */ |
427 | int alloc_fd(unsigned start, unsigned flags) |
428 | { |
429 | struct files_struct *files = current->files; |
430 | unsigned int fd; |
431 | int error; |
432 | struct fdtable *fdt; |
433 | |
434 | spin_lock(&files->file_lock); |
435 | repeat: |
436 | fdt = files_fdtable(files); |
437 | fd = start; |
438 | if (fd < files->next_fd) |
439 | fd = files->next_fd; |
440 | |
441 | if (fd < fdt->max_fds) |
442 | fd = find_next_zero_bit(fdt->open_fds->fds_bits, |
443 | fdt->max_fds, fd); |
444 | |
445 | error = expand_files(files, fd); |
446 | if (error < 0) |
447 | goto out; |
448 | |
449 | /* |
450 | * If we needed to expand the fs array we |
451 | * might have blocked - try again. |
452 | */ |
453 | if (error) |
454 | goto repeat; |
455 | |
456 | if (start <= files->next_fd) |
457 | files->next_fd = fd + 1; |
458 | |
459 | FD_SET(fd, fdt->open_fds); |
460 | if (flags & O_CLOEXEC) |
461 | FD_SET(fd, fdt->close_on_exec); |
462 | else |
463 | FD_CLR(fd, fdt->close_on_exec); |
464 | error = fd; |
465 | #if 1 |
466 | /* Sanity check */ |
467 | if (rcu_dereference_raw(fdt->fd[fd]) != NULL) { |
468 | printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); |
469 | rcu_assign_pointer(fdt->fd[fd], NULL); |
470 | } |
471 | #endif |
472 | |
473 | out: |
474 | spin_unlock(&files->file_lock); |
475 | return error; |
476 | } |
477 | |
478 | int get_unused_fd(void) |
479 | { |
480 | return alloc_fd(0, 0); |
481 | } |
482 | EXPORT_SYMBOL(get_unused_fd); |
483 |
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