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TOMOYO Linux Cross Reference
Linux/fs/file.c

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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/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 "%s array = 0 (num = %d)\n",
 40                                 __FUNCTION__, num);
 41                 return;
 42         }
 43 
 44         if (num <= NR_OPEN_DEFAULT) /* Don't free the embedded fd array! */
 45                 return;
 46         else if (size <= PAGE_SIZE)
 47                 kfree(array);
 48         else
 49                 vfree(array);
 50 }
 51 
 52 /*
 53  * Expand the fd array in the files_struct.  Called with the files
 54  * spinlock held for write.
 55  */
 56 
 57 int expand_fd_array(struct files_struct *files, int nr)
 58 {
 59         struct file **new_fds;
 60         int error, nfds;
 61 
 62         
 63         error = -EMFILE;
 64         if (files->max_fds >= NR_OPEN || nr >= NR_OPEN)
 65                 goto out;
 66 
 67         nfds = files->max_fds;
 68         write_unlock(&files->file_lock);
 69 
 70         /* 
 71          * Expand to the max in easy steps, and keep expanding it until
 72          * we have enough for the requested fd array size. 
 73          */
 74 
 75         do {
 76 #if NR_OPEN_DEFAULT < 256
 77                 if (nfds < 256)
 78                         nfds = 256;
 79                 else 
 80 #endif
 81                 if (nfds < (PAGE_SIZE / sizeof(struct file *)))
 82                         nfds = PAGE_SIZE / sizeof(struct file *);
 83                 else {
 84                         nfds = nfds * 2;
 85                         if (nfds > NR_OPEN)
 86                                 nfds = NR_OPEN;
 87                 }
 88         } while (nfds <= nr);
 89 
 90         error = -ENOMEM;
 91         new_fds = alloc_fd_array(nfds);
 92         write_lock(&files->file_lock);
 93         if (!new_fds)
 94                 goto out;
 95 
 96         /* Copy the existing array and install the new pointer */
 97 
 98         if (nfds > files->max_fds) {
 99                 struct file **old_fds;
100                 int i;
101                 
102                 old_fds = xchg(&files->fd, new_fds);
103                 i = xchg(&files->max_fds, nfds);
104 
105                 /* Don't copy/clear the array if we are creating a new
106                    fd array for fork() */
107                 if (i) {
108                         memcpy(new_fds, old_fds, i * sizeof(struct file *));
109                         /* clear the remainder of the array */
110                         memset(&new_fds[i], 0,
111                                (nfds-i) * sizeof(struct file *)); 
112 
113                         write_unlock(&files->file_lock);
114                         free_fd_array(old_fds, i);
115                         write_lock(&files->file_lock);
116                 }
117         } else {
118                 /* Somebody expanded the array while we slept ... */
119                 write_unlock(&files->file_lock);
120                 free_fd_array(new_fds, nfds);
121                 write_lock(&files->file_lock);
122         }
123         error = 0;
124 out:
125         return error;
126 }
127 
128 /*
129  * Allocate an fdset array, using kmalloc or vmalloc.
130  * Note: the array isn't cleared at allocation time.
131  */
132 fd_set * alloc_fdset(int num)
133 {
134         fd_set *new_fdset;
135         int size = num / 8;
136 
137         if (size <= PAGE_SIZE)
138                 new_fdset = (fd_set *) kmalloc(size, GFP_KERNEL);
139         else
140                 new_fdset = (fd_set *) vmalloc(size);
141         return new_fdset;
142 }
143 
144 void free_fdset(fd_set *array, int num)
145 {
146         int size = num / 8;
147 
148         if (!array) {
149                 printk(KERN_ERR "%s array = 0 (num = %d)\n",
150                                 __FUNCTION__, num);
151                 return;
152         }
153         
154         if (num <= __FD_SETSIZE) /* Don't free an embedded fdset */
155                 return;
156         else if (size <= PAGE_SIZE)
157                 kfree(array);
158         else
159                 vfree(array);
160 }
161 
162 /*
163  * Expand the fdset in the files_struct.  Called with the files spinlock
164  * held for write.
165  */
166 int expand_fdset(struct files_struct *files, int nr)
167 {
168         fd_set *new_openset = 0, *new_execset = 0;
169         int error, nfds = 0;
170 
171         error = -EMFILE;
172         if (files->max_fdset >= NR_OPEN || nr >= NR_OPEN)
173                 goto out;
174 
175         nfds = files->max_fdset;
176         write_unlock(&files->file_lock);
177 
178         /* Expand to the max in easy steps */
179         do {
180                 if (nfds < (PAGE_SIZE * 8))
181                         nfds = PAGE_SIZE * 8;
182                 else {
183                         nfds = nfds * 2;
184                         if (nfds > NR_OPEN)
185                                 nfds = NR_OPEN;
186                 }
187         } while (nfds <= nr);
188 
189         error = -ENOMEM;
190         new_openset = alloc_fdset(nfds);
191         new_execset = alloc_fdset(nfds);
192         write_lock(&files->file_lock);
193         if (!new_openset || !new_execset)
194                 goto out;
195 
196         error = 0;
197         
198         /* Copy the existing tables and install the new pointers */
199         if (nfds > files->max_fdset) {
200                 int i = files->max_fdset / (sizeof(unsigned long) * 8);
201                 int count = (nfds - files->max_fdset) / 8;
202                 
203                 /* 
204                  * Don't copy the entire array if the current fdset is
205                  * not yet initialised.  
206                  */
207                 if (i) {
208                         memcpy (new_openset, files->open_fds, files->max_fdset/8);
209                         memcpy (new_execset, files->close_on_exec, files->max_fdset/8);
210                         memset (&new_openset->fds_bits[i], 0, count);
211                         memset (&new_execset->fds_bits[i], 0, count);
212                 }
213                 
214                 nfds = xchg(&files->max_fdset, nfds);
215                 new_openset = xchg(&files->open_fds, new_openset);
216                 new_execset = xchg(&files->close_on_exec, new_execset);
217                 write_unlock(&files->file_lock);
218                 free_fdset (new_openset, nfds);
219                 free_fdset (new_execset, nfds);
220                 write_lock(&files->file_lock);
221                 return 0;
222         } 
223         /* Somebody expanded the array while we slept ... */
224 
225 out:
226         write_unlock(&files->file_lock);
227         if (new_openset)
228                 free_fdset(new_openset, nfds);
229         if (new_execset)
230                 free_fdset(new_execset, nfds);
231         write_lock(&files->file_lock);
232         return error;
233 }
234 
235 

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