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file.c
228 lines (192 loc) · 4.91 KB
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file.c
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/*
* linux/fs/file.c
*
* Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
*
* Manage the dynamic fd arrays in the process files_struct.
*/
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/time.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/file.h>
#include <asm/bitops.h>
/*
* Allocate an fd array, using kmalloc or vmalloc.
* Note: the array isn't cleared at allocation time.
*/
struct file ** alloc_fd_array(int num)
{
struct file **new_fds;
int size = num * sizeof(struct file *);
if (size <= PAGE_SIZE)
new_fds = (struct file **) kmalloc(size, GFP_KERNEL);
else
new_fds = (struct file **) vmalloc(size);
return new_fds;
}
void free_fd_array(struct file **array, int num)
{
int size = num * sizeof(struct file *);
if (!array) {
printk (KERN_ERR "free_fd_array: array = 0 (num = %d)\n", num);
return;
}
if (num <= NR_OPEN_DEFAULT) /* Don't free the embedded fd array! */
return;
else if (size <= PAGE_SIZE)
kfree(array);
else
vfree(array);
}
/*
* Expand the fd array in the files_struct. Called with the files
* spinlock held for write.
*/
int expand_fd_array(struct files_struct *files, int nr)
{
struct file **new_fds;
int error, nfds;
error = -EMFILE;
if (files->max_fds >= NR_OPEN || nr >= NR_OPEN)
goto out;
nfds = files->max_fds;
spin_unlock(&files->file_lock);
/*
* Expand to the max in easy steps, and keep expanding it until
* we have enough for the requested fd array size.
*/
do {
#if NR_OPEN_DEFAULT < 256
if (nfds < 256)
nfds = 256;
else
#endif
if (nfds < (PAGE_SIZE / sizeof(struct file *)))
nfds = PAGE_SIZE / sizeof(struct file *);
else {
nfds = nfds * 2;
if (nfds > NR_OPEN)
nfds = NR_OPEN;
}
} while (nfds <= nr);
error = -ENOMEM;
new_fds = alloc_fd_array(nfds);
spin_lock(&files->file_lock);
if (!new_fds)
goto out;
/* Copy the existing array and install the new pointer */
if (nfds > files->max_fds) {
struct file **old_fds;
int i;
old_fds = xchg(&files->fd, new_fds);
i = xchg(&files->max_fds, nfds);
/* Don't copy/clear the array if we are creating a new
fd array for fork() */
if (i) {
memcpy(new_fds, old_fds, i * sizeof(struct file *));
/* clear the remainder of the array */
memset(&new_fds[i], 0,
(nfds-i) * sizeof(struct file *));
spin_unlock(&files->file_lock);
free_fd_array(old_fds, i);
spin_lock(&files->file_lock);
}
} else {
/* Somebody expanded the array while we slept ... */
spin_unlock(&files->file_lock);
free_fd_array(new_fds, nfds);
spin_lock(&files->file_lock);
}
error = 0;
out:
return error;
}
/*
* Allocate an fdset array, using kmalloc or vmalloc.
* Note: the array isn't cleared at allocation time.
*/
fd_set * alloc_fdset(int num)
{
fd_set *new_fdset;
int size = num / 8;
if (size <= PAGE_SIZE)
new_fdset = (fd_set *) kmalloc(size, GFP_KERNEL);
else
new_fdset = (fd_set *) vmalloc(size);
return new_fdset;
}
void free_fdset(fd_set *array, int num)
{
int size = num / 8;
if (num <= __FD_SETSIZE) /* Don't free an embedded fdset */
return;
else if (size <= PAGE_SIZE)
kfree(array);
else
vfree(array);
}
/*
* Expand the fdset in the files_struct. Called with the files spinlock
* held for write.
*/
int expand_fdset(struct files_struct *files, int nr)
{
fd_set *new_openset = 0, *new_execset = 0;
int error, nfds = 0;
error = -EMFILE;
if (files->max_fdset >= NR_OPEN || nr >= NR_OPEN)
goto out;
nfds = files->max_fdset;
spin_unlock(&files->file_lock);
/* Expand to the max in easy steps */
do {
if (nfds < (PAGE_SIZE * 8))
nfds = PAGE_SIZE * 8;
else {
nfds = nfds * 2;
if (nfds > NR_OPEN)
nfds = NR_OPEN;
}
} while (nfds <= nr);
error = -ENOMEM;
new_openset = alloc_fdset(nfds);
new_execset = alloc_fdset(nfds);
spin_lock(&files->file_lock);
if (!new_openset || !new_execset)
goto out;
error = 0;
/* Copy the existing tables and install the new pointers */
if (nfds > files->max_fdset) {
int i = files->max_fdset / (sizeof(unsigned long) * 8);
int count = (nfds - files->max_fdset) / 8;
/*
* Don't copy the entire array if the current fdset is
* not yet initialised.
*/
if (i) {
memcpy (new_openset, files->open_fds, files->max_fdset/8);
memcpy (new_execset, files->close_on_exec, files->max_fdset/8);
memset (&new_openset->fds_bits[i], 0, count);
memset (&new_execset->fds_bits[i], 0, count);
}
nfds = xchg(&files->max_fdset, nfds);
new_openset = xchg(&files->open_fds, new_openset);
new_execset = xchg(&files->close_on_exec, new_execset);
spin_unlock(&files->file_lock);
free_fdset (new_openset, nfds);
free_fdset (new_execset, nfds);
spin_lock(&files->file_lock);
return 0;
}
/* Somebody expanded the array while we slept ... */
out:
spin_unlock(&files->file_lock);
if (new_openset)
free_fdset(new_openset, nfds);
if (new_execset)
free_fdset(new_execset, nfds);
spin_lock(&files->file_lock);
return error;
}