4 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
6 * Manage the dynamic fd arrays in the process files_struct.
11 #include <linux/time.h>
12 #include <linux/slab.h>
13 #include <linux/vmalloc.h>
14 #include <linux/file.h>
15 #include <linux/bitops.h>
16 #include <linux/interrupt.h>
17 #include <linux/spinlock.h>
18 #include <linux/rcupdate.h>
19 #include <linux/workqueue.h>
21 struct fdtable_defer
{
23 struct work_struct wq
;
24 struct timer_list timer
;
29 * We use this list to defer free fdtables that have vmalloced
30 * sets/arrays. By keeping a per-cpu list, we avoid having to embed
31 * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
32 * this per-task structure.
34 static DEFINE_PER_CPU(struct fdtable_defer
, fdtable_defer_list
);
38 * Allocate an fd array, using kmalloc or vmalloc.
39 * Note: the array isn't cleared at allocation time.
41 struct file
** alloc_fd_array(int num
)
43 struct file
**new_fds
;
44 int size
= num
* sizeof(struct file
*);
46 if (size
<= PAGE_SIZE
)
47 new_fds
= (struct file
**) kmalloc(size
, GFP_KERNEL
);
49 new_fds
= (struct file
**) vmalloc(size
);
53 void free_fd_array(struct file
**array
, int num
)
55 int size
= num
* sizeof(struct file
*);
58 printk (KERN_ERR
"free_fd_array: array = 0 (num = %d)\n", num
);
62 if (num
<= NR_OPEN_DEFAULT
) /* Don't free the embedded fd array! */
64 else if (size
<= PAGE_SIZE
)
70 static void __free_fdtable(struct fdtable
*fdt
)
72 free_fdset(fdt
->open_fds
, fdt
->max_fdset
);
73 free_fdset(fdt
->close_on_exec
, fdt
->max_fdset
);
74 free_fd_array(fdt
->fd
, fdt
->max_fds
);
78 static void fdtable_timer(unsigned long data
)
80 struct fdtable_defer
*fddef
= (struct fdtable_defer
*)data
;
82 spin_lock(&fddef
->lock
);
84 * If someone already emptied the queue return.
88 if (!schedule_work(&fddef
->wq
))
89 mod_timer(&fddef
->timer
, 5);
91 spin_unlock(&fddef
->lock
);
94 static void free_fdtable_work(struct fdtable_defer
*f
)
98 spin_lock_bh(&f
->lock
);
101 spin_unlock_bh(&f
->lock
);
103 struct fdtable
*next
= fdt
->next
;
109 static void free_fdtable_rcu(struct rcu_head
*rcu
)
111 struct fdtable
*fdt
= container_of(rcu
, struct fdtable
, rcu
);
112 int fdset_size
, fdarray_size
;
113 struct fdtable_defer
*fddef
;
116 fdset_size
= fdt
->max_fdset
/ 8;
117 fdarray_size
= fdt
->max_fds
* sizeof(struct file
*);
119 if (fdt
->free_files
) {
121 * The this fdtable was embedded in the files structure
122 * and the files structure itself was getting destroyed.
123 * It is now safe to free the files structure.
125 kmem_cache_free(files_cachep
, fdt
->free_files
);
128 if (fdt
->max_fdset
<= EMBEDDED_FD_SET_SIZE
&&
129 fdt
->max_fds
<= NR_OPEN_DEFAULT
) {
131 * The fdtable was embedded
135 if (fdset_size
<= PAGE_SIZE
&& fdarray_size
<= PAGE_SIZE
) {
136 kfree(fdt
->open_fds
);
137 kfree(fdt
->close_on_exec
);
141 fddef
= &get_cpu_var(fdtable_defer_list
);
142 spin_lock(&fddef
->lock
);
143 fdt
->next
= fddef
->next
;
146 * vmallocs are handled from the workqueue context.
147 * If the per-cpu workqueue is running, then we
148 * defer work scheduling through a timer.
150 if (!schedule_work(&fddef
->wq
))
151 mod_timer(&fddef
->timer
, 5);
152 spin_unlock(&fddef
->lock
);
153 put_cpu_var(fdtable_defer_list
);
157 void free_fdtable(struct fdtable
*fdt
)
159 if (fdt
->free_files
||
160 fdt
->max_fdset
> EMBEDDED_FD_SET_SIZE
||
161 fdt
->max_fds
> NR_OPEN_DEFAULT
)
162 call_rcu(&fdt
->rcu
, free_fdtable_rcu
);
166 * Expand the fdset in the files_struct. Called with the files spinlock
169 static void copy_fdtable(struct fdtable
*nfdt
, struct fdtable
*fdt
)
174 BUG_ON(nfdt
->max_fdset
< fdt
->max_fdset
);
175 BUG_ON(nfdt
->max_fds
< fdt
->max_fds
);
176 /* Copy the existing tables and install the new pointers */
178 i
= fdt
->max_fdset
/ (sizeof(unsigned long) * 8);
179 count
= (nfdt
->max_fdset
- fdt
->max_fdset
) / 8;
182 * Don't copy the entire array if the current fdset is
183 * not yet initialised.
186 memcpy (nfdt
->open_fds
, fdt
->open_fds
,
188 memcpy (nfdt
->close_on_exec
, fdt
->close_on_exec
,
190 memset (&nfdt
->open_fds
->fds_bits
[i
], 0, count
);
191 memset (&nfdt
->close_on_exec
->fds_bits
[i
], 0, count
);
194 /* Don't copy/clear the array if we are creating a new
195 fd array for fork() */
197 memcpy(nfdt
->fd
, fdt
->fd
,
198 fdt
->max_fds
* sizeof(struct file
*));
199 /* clear the remainder of the array */
200 memset(&nfdt
->fd
[fdt
->max_fds
], 0,
201 (nfdt
->max_fds
- fdt
->max_fds
) *
202 sizeof(struct file
*));
207 * Allocate an fdset array, using kmalloc or vmalloc.
208 * Note: the array isn't cleared at allocation time.
210 fd_set
* alloc_fdset(int num
)
215 if (size
<= PAGE_SIZE
)
216 new_fdset
= (fd_set
*) kmalloc(size
, GFP_KERNEL
);
218 new_fdset
= (fd_set
*) vmalloc(size
);
222 void free_fdset(fd_set
*array
, int num
)
224 if (num
<= EMBEDDED_FD_SET_SIZE
) /* Don't free an embedded fdset */
226 else if (num
<= 8 * PAGE_SIZE
)
232 static struct fdtable
*alloc_fdtable(int nr
)
234 struct fdtable
*fdt
= NULL
;
236 fd_set
*new_openset
= NULL
, *new_execset
= NULL
;
237 struct file
**new_fds
;
239 fdt
= kzalloc(sizeof(*fdt
), GFP_KERNEL
);
243 nfds
= max_t(int, 8 * L1_CACHE_BYTES
, roundup_pow_of_two(nr
+ 1));
247 new_openset
= alloc_fdset(nfds
);
248 new_execset
= alloc_fdset(nfds
);
249 if (!new_openset
|| !new_execset
)
251 fdt
->open_fds
= new_openset
;
252 fdt
->close_on_exec
= new_execset
;
253 fdt
->max_fdset
= nfds
;
255 nfds
= NR_OPEN_DEFAULT
;
257 * Expand to the max in easy steps, and keep expanding it until
258 * we have enough for the requested fd array size.
261 #if NR_OPEN_DEFAULT < 256
266 if (nfds
< (PAGE_SIZE
/ sizeof(struct file
*)))
267 nfds
= PAGE_SIZE
/ sizeof(struct file
*);
273 } while (nfds
<= nr
);
274 new_fds
= alloc_fd_array(nfds
);
279 fdt
->free_files
= NULL
;
282 nfds
= fdt
->max_fdset
;
284 free_fdset(new_openset
, nfds
);
285 free_fdset(new_execset
, nfds
);
291 * Expand the file descriptor table.
292 * This function will allocate a new fdtable and both fd array and fdset, of
294 * Return <0 error code on error; 1 on successful completion.
295 * The files->file_lock should be held on entry, and will be held on exit.
297 static int expand_fdtable(struct files_struct
*files
, int nr
)
298 __releases(files
->file_lock
)
299 __acquires(files
->file_lock
)
301 struct fdtable
*new_fdt
, *cur_fdt
;
303 spin_unlock(&files
->file_lock
);
304 new_fdt
= alloc_fdtable(nr
);
305 spin_lock(&files
->file_lock
);
309 * Check again since another task may have expanded the fd table while
310 * we dropped the lock
312 cur_fdt
= files_fdtable(files
);
313 if (nr
>= cur_fdt
->max_fds
|| nr
>= cur_fdt
->max_fdset
) {
314 /* Continue as planned */
315 copy_fdtable(new_fdt
, cur_fdt
);
316 rcu_assign_pointer(files
->fdt
, new_fdt
);
317 free_fdtable(cur_fdt
);
319 /* Somebody else expanded, so undo our attempt */
320 __free_fdtable(new_fdt
);
327 * This function will expand the file structures, if the requested size exceeds
328 * the current capacity and there is room for expansion.
329 * Return <0 error code on error; 0 when nothing done; 1 when files were
330 * expanded and execution may have blocked.
331 * The files->file_lock should be held on entry, and will be held on exit.
333 int expand_files(struct files_struct
*files
, int nr
)
337 fdt
= files_fdtable(files
);
338 /* Do we need to expand? */
339 if (nr
< fdt
->max_fdset
&& nr
< fdt
->max_fds
)
342 if (fdt
->max_fdset
>= NR_OPEN
|| fdt
->max_fds
>= NR_OPEN
||
346 /* All good, so we try */
347 return expand_fdtable(files
, nr
);
350 static void __devinit
fdtable_defer_list_init(int cpu
)
352 struct fdtable_defer
*fddef
= &per_cpu(fdtable_defer_list
, cpu
);
353 spin_lock_init(&fddef
->lock
);
354 INIT_WORK(&fddef
->wq
, (void (*)(void *))free_fdtable_work
, fddef
);
355 init_timer(&fddef
->timer
);
356 fddef
->timer
.data
= (unsigned long)fddef
;
357 fddef
->timer
.function
= fdtable_timer
;
361 void __init
files_defer_init(void)
364 for_each_possible_cpu(i
)
365 fdtable_defer_list_init(i
);
This page took 0.038203 seconds and 5 git commands to generate.