379 lines
8.6 KiB
C
379 lines
8.6 KiB
C
/*
|
|
* 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 <linux/bitops.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/spinlock.h>
|
|
#include <linux/rcupdate.h>
|
|
#include <linux/workqueue.h>
|
|
|
|
struct fdtable_defer {
|
|
spinlock_t lock;
|
|
struct work_struct wq;
|
|
struct timer_list timer;
|
|
struct fdtable *next;
|
|
};
|
|
|
|
/*
|
|
* We use this list to defer free fdtables that have vmalloced
|
|
* sets/arrays. By keeping a per-cpu list, we avoid having to embed
|
|
* the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
|
|
* this per-task structure.
|
|
*/
|
|
static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
|
|
|
|
|
|
/*
|
|
* 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);
|
|
}
|
|
|
|
static void __free_fdtable(struct fdtable *fdt)
|
|
{
|
|
free_fdset(fdt->open_fds, fdt->max_fdset);
|
|
free_fdset(fdt->close_on_exec, fdt->max_fdset);
|
|
free_fd_array(fdt->fd, fdt->max_fds);
|
|
kfree(fdt);
|
|
}
|
|
|
|
static void fdtable_timer(unsigned long data)
|
|
{
|
|
struct fdtable_defer *fddef = (struct fdtable_defer *)data;
|
|
|
|
spin_lock(&fddef->lock);
|
|
/*
|
|
* If someone already emptied the queue return.
|
|
*/
|
|
if (!fddef->next)
|
|
goto out;
|
|
if (!schedule_work(&fddef->wq))
|
|
mod_timer(&fddef->timer, 5);
|
|
out:
|
|
spin_unlock(&fddef->lock);
|
|
}
|
|
|
|
static void free_fdtable_work(struct fdtable_defer *f)
|
|
{
|
|
struct fdtable *fdt;
|
|
|
|
spin_lock_bh(&f->lock);
|
|
fdt = f->next;
|
|
f->next = NULL;
|
|
spin_unlock_bh(&f->lock);
|
|
while(fdt) {
|
|
struct fdtable *next = fdt->next;
|
|
__free_fdtable(fdt);
|
|
fdt = next;
|
|
}
|
|
}
|
|
|
|
static void free_fdtable_rcu(struct rcu_head *rcu)
|
|
{
|
|
struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
|
|
int fdset_size, fdarray_size;
|
|
struct fdtable_defer *fddef;
|
|
|
|
BUG_ON(!fdt);
|
|
fdset_size = fdt->max_fdset / 8;
|
|
fdarray_size = fdt->max_fds * sizeof(struct file *);
|
|
|
|
if (fdt->free_files) {
|
|
/*
|
|
* The this fdtable was embedded in the files structure
|
|
* and the files structure itself was getting destroyed.
|
|
* It is now safe to free the files structure.
|
|
*/
|
|
kmem_cache_free(files_cachep, fdt->free_files);
|
|
return;
|
|
}
|
|
if (fdt->max_fdset <= EMBEDDED_FD_SET_SIZE &&
|
|
fdt->max_fds <= NR_OPEN_DEFAULT) {
|
|
/*
|
|
* The fdtable was embedded
|
|
*/
|
|
return;
|
|
}
|
|
if (fdset_size <= PAGE_SIZE && fdarray_size <= PAGE_SIZE) {
|
|
kfree(fdt->open_fds);
|
|
kfree(fdt->close_on_exec);
|
|
kfree(fdt->fd);
|
|
kfree(fdt);
|
|
} else {
|
|
fddef = &get_cpu_var(fdtable_defer_list);
|
|
spin_lock(&fddef->lock);
|
|
fdt->next = fddef->next;
|
|
fddef->next = fdt;
|
|
/*
|
|
* vmallocs are handled from the workqueue context.
|
|
* If the per-cpu workqueue is running, then we
|
|
* defer work scheduling through a timer.
|
|
*/
|
|
if (!schedule_work(&fddef->wq))
|
|
mod_timer(&fddef->timer, 5);
|
|
spin_unlock(&fddef->lock);
|
|
put_cpu_var(fdtable_defer_list);
|
|
}
|
|
}
|
|
|
|
void free_fdtable(struct fdtable *fdt)
|
|
{
|
|
if (fdt->free_files ||
|
|
fdt->max_fdset > EMBEDDED_FD_SET_SIZE ||
|
|
fdt->max_fds > NR_OPEN_DEFAULT)
|
|
call_rcu(&fdt->rcu, free_fdtable_rcu);
|
|
}
|
|
|
|
/*
|
|
* Expand the fdset in the files_struct. Called with the files spinlock
|
|
* held for write.
|
|
*/
|
|
static void copy_fdtable(struct fdtable *nfdt, struct fdtable *fdt)
|
|
{
|
|
int i;
|
|
int count;
|
|
|
|
BUG_ON(nfdt->max_fdset < fdt->max_fdset);
|
|
BUG_ON(nfdt->max_fds < fdt->max_fds);
|
|
/* Copy the existing tables and install the new pointers */
|
|
|
|
i = fdt->max_fdset / (sizeof(unsigned long) * 8);
|
|
count = (nfdt->max_fdset - fdt->max_fdset) / 8;
|
|
|
|
/*
|
|
* Don't copy the entire array if the current fdset is
|
|
* not yet initialised.
|
|
*/
|
|
if (i) {
|
|
memcpy (nfdt->open_fds, fdt->open_fds,
|
|
fdt->max_fdset/8);
|
|
memcpy (nfdt->close_on_exec, fdt->close_on_exec,
|
|
fdt->max_fdset/8);
|
|
memset (&nfdt->open_fds->fds_bits[i], 0, count);
|
|
memset (&nfdt->close_on_exec->fds_bits[i], 0, count);
|
|
}
|
|
|
|
/* Don't copy/clear the array if we are creating a new
|
|
fd array for fork() */
|
|
if (fdt->max_fds) {
|
|
memcpy(nfdt->fd, fdt->fd,
|
|
fdt->max_fds * sizeof(struct file *));
|
|
/* clear the remainder of the array */
|
|
memset(&nfdt->fd[fdt->max_fds], 0,
|
|
(nfdt->max_fds - fdt->max_fds) *
|
|
sizeof(struct file *));
|
|
}
|
|
}
|
|
|
|
/*
|
|
* 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)
|
|
{
|
|
if (num <= EMBEDDED_FD_SET_SIZE) /* Don't free an embedded fdset */
|
|
return;
|
|
else if (num <= 8 * PAGE_SIZE)
|
|
kfree(array);
|
|
else
|
|
vfree(array);
|
|
}
|
|
|
|
static struct fdtable *alloc_fdtable(int nr)
|
|
{
|
|
struct fdtable *fdt = NULL;
|
|
int nfds = 0;
|
|
fd_set *new_openset = NULL, *new_execset = NULL;
|
|
struct file **new_fds;
|
|
|
|
fdt = kzalloc(sizeof(*fdt), GFP_KERNEL);
|
|
if (!fdt)
|
|
goto out;
|
|
|
|
nfds = 8 * L1_CACHE_BYTES;
|
|
/* Expand to the max in easy steps */
|
|
while (nfds <= nr) {
|
|
nfds = nfds * 2;
|
|
if (nfds > NR_OPEN)
|
|
nfds = NR_OPEN;
|
|
}
|
|
|
|
new_openset = alloc_fdset(nfds);
|
|
new_execset = alloc_fdset(nfds);
|
|
if (!new_openset || !new_execset)
|
|
goto out;
|
|
fdt->open_fds = new_openset;
|
|
fdt->close_on_exec = new_execset;
|
|
fdt->max_fdset = nfds;
|
|
|
|
nfds = NR_OPEN_DEFAULT;
|
|
/*
|
|
* 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);
|
|
new_fds = alloc_fd_array(nfds);
|
|
if (!new_fds)
|
|
goto out;
|
|
fdt->fd = new_fds;
|
|
fdt->max_fds = nfds;
|
|
fdt->free_files = NULL;
|
|
return fdt;
|
|
out:
|
|
if (new_openset)
|
|
free_fdset(new_openset, nfds);
|
|
if (new_execset)
|
|
free_fdset(new_execset, nfds);
|
|
kfree(fdt);
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Expands the file descriptor table - it will allocate a new fdtable and
|
|
* both fd array and fdset. It is expected to be called with the
|
|
* files_lock held.
|
|
*/
|
|
static int expand_fdtable(struct files_struct *files, int nr)
|
|
__releases(files->file_lock)
|
|
__acquires(files->file_lock)
|
|
{
|
|
int error = 0;
|
|
struct fdtable *fdt;
|
|
struct fdtable *nfdt = NULL;
|
|
|
|
spin_unlock(&files->file_lock);
|
|
nfdt = alloc_fdtable(nr);
|
|
if (!nfdt) {
|
|
error = -ENOMEM;
|
|
spin_lock(&files->file_lock);
|
|
goto out;
|
|
}
|
|
|
|
spin_lock(&files->file_lock);
|
|
fdt = files_fdtable(files);
|
|
/*
|
|
* Check again since another task may have expanded the
|
|
* fd table while we dropped the lock
|
|
*/
|
|
if (nr >= fdt->max_fds || nr >= fdt->max_fdset) {
|
|
copy_fdtable(nfdt, fdt);
|
|
} else {
|
|
/* Somebody expanded while we dropped file_lock */
|
|
spin_unlock(&files->file_lock);
|
|
__free_fdtable(nfdt);
|
|
spin_lock(&files->file_lock);
|
|
goto out;
|
|
}
|
|
rcu_assign_pointer(files->fdt, nfdt);
|
|
free_fdtable(fdt);
|
|
out:
|
|
return error;
|
|
}
|
|
|
|
/*
|
|
* Expand files.
|
|
* Return <0 on error; 0 nothing done; 1 files expanded, we may have blocked.
|
|
* Should be called with the files->file_lock spinlock held for write.
|
|
*/
|
|
int expand_files(struct files_struct *files, int nr)
|
|
{
|
|
int err, expand = 0;
|
|
struct fdtable *fdt;
|
|
|
|
fdt = files_fdtable(files);
|
|
if (nr >= fdt->max_fdset || nr >= fdt->max_fds) {
|
|
if (fdt->max_fdset >= NR_OPEN ||
|
|
fdt->max_fds >= NR_OPEN || nr >= NR_OPEN) {
|
|
err = -EMFILE;
|
|
goto out;
|
|
}
|
|
expand = 1;
|
|
if ((err = expand_fdtable(files, nr)))
|
|
goto out;
|
|
}
|
|
err = expand;
|
|
out:
|
|
return err;
|
|
}
|
|
|
|
static void __devinit fdtable_defer_list_init(int cpu)
|
|
{
|
|
struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
|
|
spin_lock_init(&fddef->lock);
|
|
INIT_WORK(&fddef->wq, (void (*)(void *))free_fdtable_work, fddef);
|
|
init_timer(&fddef->timer);
|
|
fddef->timer.data = (unsigned long)fddef;
|
|
fddef->timer.function = fdtable_timer;
|
|
fddef->next = NULL;
|
|
}
|
|
|
|
void __init files_defer_init(void)
|
|
{
|
|
int i;
|
|
for_each_cpu(i)
|
|
fdtable_defer_list_init(i);
|
|
}
|