File: /usr/src/linux/fs/file.c
1 /*
2 * linux/fs/open.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/fs.h>
10 #include <linux/mm.h>
11 #include <linux/sched.h>
12 #include <linux/slab.h>
13 #include <linux/vmalloc.h>
14
15 #include <asm/bitops.h>
16
17
18 /*
19 * Allocate an fd array, using kmalloc or vmalloc.
20 * Note: the array isn't cleared at allocation time.
21 */
22 struct file ** alloc_fd_array(int num)
23 {
24 struct file **new_fds;
25 int size = num * sizeof(struct file *);
26
27 if (size <= PAGE_SIZE)
28 new_fds = (struct file **) kmalloc(size, GFP_KERNEL);
29 else
30 new_fds = (struct file **) vmalloc(size);
31 return new_fds;
32 }
33
34 void free_fd_array(struct file **array, int num)
35 {
36 int size = num * sizeof(struct file *);
37
38 if (!array) {
39 printk (KERN_ERR __FUNCTION__ "array = 0 (num = %d)\n", num);
40 return;
41 }
42
43 if (num <= NR_OPEN_DEFAULT) /* Don't free the embedded fd array! */
44 return;
45 else if (size <= PAGE_SIZE)
46 kfree(array);
47 else
48 vfree(array);
49 }
50
51 /*
52 * Expand the fd array in the files_struct. Called with the files
53 * spinlock held for write.
54 */
55
56 int expand_fd_array(struct files_struct *files, int nr)
57 {
58 struct file **new_fds;
59 int error, nfds;
60
61
62 error = -EMFILE;
63 if (files->max_fds >= NR_OPEN || nr >= NR_OPEN)
64 goto out;
65
66 nfds = files->max_fds;
67 write_unlock(&files->file_lock);
68
69 /*
70 * Expand to the max in easy steps, and keep expanding it until
71 * we have enough for the requested fd array size.
72 */
73
74 do {
75 #if NR_OPEN_DEFAULT < 256
76 if (nfds < 256)
77 nfds = 256;
78 else
79 #endif
80 if (nfds < (PAGE_SIZE / sizeof(struct file *)))
81 nfds = PAGE_SIZE / sizeof(struct file *);
82 else {
83 nfds = nfds * 2;
84 if (nfds > NR_OPEN)
85 nfds = NR_OPEN;
86 }
87 } while (nfds <= nr);
88
89 error = -ENOMEM;
90 new_fds = alloc_fd_array(nfds);
91 write_lock(&files->file_lock);
92 if (!new_fds)
93 goto out;
94
95 /* Copy the existing array and install the new pointer */
96
97 if (nfds > files->max_fds) {
98 struct file **old_fds;
99 int i;
100
101 old_fds = xchg(&files->fd, new_fds);
102 i = xchg(&files->max_fds, nfds);
103
104 /* Don't copy/clear the array if we are creating a new
105 fd array for fork() */
106 if (i) {
107 memcpy(new_fds, old_fds, i * sizeof(struct file *));
108 /* clear the remainder of the array */
109 memset(&new_fds[i], 0,
110 (nfds-i) * sizeof(struct file *));
111
112 write_unlock(&files->file_lock);
113 free_fd_array(old_fds, i);
114 write_lock(&files->file_lock);
115 }
116 } else {
117 /* Somebody expanded the array while we slept ... */
118 write_unlock(&files->file_lock);
119 free_fd_array(new_fds, nfds);
120 write_lock(&files->file_lock);
121 }
122 error = 0;
123 out:
124 return error;
125 }
126
127 /*
128 * Allocate an fdset array, using kmalloc or vmalloc.
129 * Note: the array isn't cleared at allocation time.
130 */
131 fd_set * alloc_fdset(int num)
132 {
133 fd_set *new_fdset;
134 int size = num / 8;
135
136 if (size <= PAGE_SIZE)
137 new_fdset = (fd_set *) kmalloc(size, GFP_KERNEL);
138 else
139 new_fdset = (fd_set *) vmalloc(size);
140 return new_fdset;
141 }
142
143 void free_fdset(fd_set *array, int num)
144 {
145 int size = num / 8;
146
147 if (!array) {
148 printk (KERN_ERR __FUNCTION__ "array = 0 (num = %d)\n", num);
149 return;
150 }
151
152 if (num <= __FD_SETSIZE) /* Don't free an embedded fdset */
153 return;
154 else if (size <= PAGE_SIZE)
155 kfree(array);
156 else
157 vfree(array);
158 }
159
160 /*
161 * Expand the fdset in the files_struct. Called with the files spinlock
162 * held for write.
163 */
164 int expand_fdset(struct files_struct *files, int nr)
165 {
166 fd_set *new_openset = 0, *new_execset = 0;
167 int error, nfds = 0;
168
169 error = -EMFILE;
170 if (files->max_fdset >= NR_OPEN || nr >= NR_OPEN)
171 goto out;
172
173 nfds = files->max_fdset;
174 write_unlock(&files->file_lock);
175
176 /* Expand to the max in easy steps */
177 do {
178 if (nfds < (PAGE_SIZE * 8))
179 nfds = PAGE_SIZE * 8;
180 else {
181 nfds = nfds * 2;
182 if (nfds > NR_OPEN)
183 nfds = NR_OPEN;
184 }
185 } while (nfds <= nr);
186
187 error = -ENOMEM;
188 new_openset = alloc_fdset(nfds);
189 new_execset = alloc_fdset(nfds);
190 write_lock(&files->file_lock);
191 if (!new_openset || !new_execset)
192 goto out;
193
194 error = 0;
195
196 /* Copy the existing tables and install the new pointers */
197 if (nfds > files->max_fdset) {
198 int i = files->max_fdset / (sizeof(unsigned long) * 8);
199 int count = (nfds - files->max_fdset) / 8;
200
201 /*
202 * Don't copy the entire array if the current fdset is
203 * not yet initialised.
204 */
205 if (i) {
206 memcpy (new_openset, files->open_fds, files->max_fdset/8);
207 memcpy (new_execset, files->close_on_exec, files->max_fdset/8);
208 memset (&new_openset->fds_bits[i], 0, count);
209 memset (&new_execset->fds_bits[i], 0, count);
210 }
211
212 nfds = xchg(&files->max_fdset, nfds);
213 new_openset = xchg(&files->open_fds, new_openset);
214 new_execset = xchg(&files->close_on_exec, new_execset);
215 write_unlock(&files->file_lock);
216 free_fdset (new_openset, nfds);
217 free_fdset (new_execset, nfds);
218 write_lock(&files->file_lock);
219 return 0;
220 }
221 /* Somebody expanded the array while we slept ... */
222
223 out:
224 write_unlock(&files->file_lock);
225 if (new_openset)
226 free_fdset(new_openset, nfds);
227 if (new_execset)
228 free_fdset(new_execset, nfds);
229 write_lock(&files->file_lock);
230 return error;
231 }
232
233