390 lines
8.9 KiB
C
390 lines
8.9 KiB
C
/*
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* linux/fs/file.c
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*
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* Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
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*
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* Manage the dynamic fd arrays in the process files_struct.
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*/
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/time.h>
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#include <linux/slab.h>
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#include <linux/vmalloc.h>
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#include <linux/file.h>
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#include <linux/bitops.h>
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#include <linux/interrupt.h>
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#include <linux/spinlock.h>
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#include <linux/rcupdate.h>
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#include <linux/workqueue.h>
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struct fdtable_defer {
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spinlock_t lock;
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struct work_struct wq;
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struct timer_list timer;
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struct fdtable *next;
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};
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/*
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* We use this list to defer free fdtables that have vmalloced
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* sets/arrays. By keeping a per-cpu list, we avoid having to embed
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* the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
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* this per-task structure.
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*/
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static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
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/*
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* Allocate an fd array, using kmalloc or vmalloc.
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* Note: the array isn't cleared at allocation time.
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*/
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struct file ** alloc_fd_array(int num)
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{
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struct file **new_fds;
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int size = num * sizeof(struct file *);
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if (size <= PAGE_SIZE)
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new_fds = (struct file **) kmalloc(size, GFP_KERNEL);
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else
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new_fds = (struct file **) vmalloc(size);
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return new_fds;
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}
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void free_fd_array(struct file **array, int num)
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{
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int size = num * sizeof(struct file *);
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if (!array) {
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printk (KERN_ERR "free_fd_array: array = 0 (num = %d)\n", num);
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return;
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}
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if (num <= NR_OPEN_DEFAULT) /* Don't free the embedded fd array! */
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return;
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else if (size <= PAGE_SIZE)
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kfree(array);
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else
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vfree(array);
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}
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static void __free_fdtable(struct fdtable *fdt)
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{
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int fdset_size, fdarray_size;
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fdset_size = fdt->max_fdset / 8;
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fdarray_size = fdt->max_fds * sizeof(struct file *);
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free_fdset(fdt->open_fds, fdset_size);
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free_fdset(fdt->close_on_exec, fdset_size);
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free_fd_array(fdt->fd, fdarray_size);
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kfree(fdt);
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}
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static void fdtable_timer(unsigned long data)
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{
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struct fdtable_defer *fddef = (struct fdtable_defer *)data;
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spin_lock(&fddef->lock);
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/*
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* If someone already emptied the queue return.
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*/
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if (!fddef->next)
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goto out;
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if (!schedule_work(&fddef->wq))
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mod_timer(&fddef->timer, 5);
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out:
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spin_unlock(&fddef->lock);
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}
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static void free_fdtable_work(struct fdtable_defer *f)
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{
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struct fdtable *fdt;
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spin_lock_bh(&f->lock);
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fdt = f->next;
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f->next = NULL;
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spin_unlock_bh(&f->lock);
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while(fdt) {
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struct fdtable *next = fdt->next;
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__free_fdtable(fdt);
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fdt = next;
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}
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}
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static void free_fdtable_rcu(struct rcu_head *rcu)
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{
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struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
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int fdset_size, fdarray_size;
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struct fdtable_defer *fddef;
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BUG_ON(!fdt);
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fdset_size = fdt->max_fdset / 8;
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fdarray_size = fdt->max_fds * sizeof(struct file *);
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if (fdt->free_files) {
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/*
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* The this fdtable was embedded in the files structure
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* and the files structure itself was getting destroyed.
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* It is now safe to free the files structure.
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*/
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kmem_cache_free(files_cachep, fdt->free_files);
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return;
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}
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if (fdt->max_fdset <= __FD_SETSIZE && fdt->max_fds <= NR_OPEN_DEFAULT) {
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/*
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* The fdtable was embedded
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*/
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return;
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}
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if (fdset_size <= PAGE_SIZE && fdarray_size <= PAGE_SIZE) {
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kfree(fdt->open_fds);
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kfree(fdt->close_on_exec);
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kfree(fdt->fd);
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kfree(fdt);
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} else {
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fddef = &get_cpu_var(fdtable_defer_list);
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spin_lock(&fddef->lock);
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fdt->next = fddef->next;
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fddef->next = fdt;
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/*
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* vmallocs are handled from the workqueue context.
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* If the per-cpu workqueue is running, then we
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* defer work scheduling through a timer.
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*/
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if (!schedule_work(&fddef->wq))
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mod_timer(&fddef->timer, 5);
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spin_unlock(&fddef->lock);
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put_cpu_var(fdtable_defer_list);
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}
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}
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void free_fdtable(struct fdtable *fdt)
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{
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if (fdt->free_files || fdt->max_fdset > __FD_SETSIZE ||
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fdt->max_fds > NR_OPEN_DEFAULT)
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call_rcu(&fdt->rcu, free_fdtable_rcu);
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}
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/*
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* Expand the fdset in the files_struct. Called with the files spinlock
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* held for write.
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*/
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static void copy_fdtable(struct fdtable *nfdt, struct fdtable *fdt)
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{
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int i;
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int count;
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BUG_ON(nfdt->max_fdset < fdt->max_fdset);
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BUG_ON(nfdt->max_fds < fdt->max_fds);
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/* Copy the existing tables and install the new pointers */
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i = fdt->max_fdset / (sizeof(unsigned long) * 8);
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count = (nfdt->max_fdset - fdt->max_fdset) / 8;
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/*
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* Don't copy the entire array if the current fdset is
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* not yet initialised.
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*/
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if (i) {
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memcpy (nfdt->open_fds, fdt->open_fds,
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fdt->max_fdset/8);
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memcpy (nfdt->close_on_exec, fdt->close_on_exec,
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fdt->max_fdset/8);
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memset (&nfdt->open_fds->fds_bits[i], 0, count);
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memset (&nfdt->close_on_exec->fds_bits[i], 0, count);
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}
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/* Don't copy/clear the array if we are creating a new
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fd array for fork() */
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if (fdt->max_fds) {
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memcpy(nfdt->fd, fdt->fd,
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fdt->max_fds * sizeof(struct file *));
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/* clear the remainder of the array */
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memset(&nfdt->fd[fdt->max_fds], 0,
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(nfdt->max_fds - fdt->max_fds) *
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sizeof(struct file *));
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}
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nfdt->next_fd = fdt->next_fd;
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}
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/*
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* Allocate an fdset array, using kmalloc or vmalloc.
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* Note: the array isn't cleared at allocation time.
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*/
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fd_set * alloc_fdset(int num)
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{
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fd_set *new_fdset;
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int size = num / 8;
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if (size <= PAGE_SIZE)
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new_fdset = (fd_set *) kmalloc(size, GFP_KERNEL);
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else
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new_fdset = (fd_set *) vmalloc(size);
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return new_fdset;
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}
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void free_fdset(fd_set *array, int num)
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{
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int size = num / 8;
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if (num <= __FD_SETSIZE) /* Don't free an embedded fdset */
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return;
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else if (size <= PAGE_SIZE)
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kfree(array);
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else
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vfree(array);
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}
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static struct fdtable *alloc_fdtable(int nr)
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{
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struct fdtable *fdt = NULL;
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int nfds = 0;
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fd_set *new_openset = NULL, *new_execset = NULL;
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struct file **new_fds;
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fdt = kmalloc(sizeof(*fdt), GFP_KERNEL);
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if (!fdt)
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goto out;
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memset(fdt, 0, sizeof(*fdt));
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nfds = __FD_SETSIZE;
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/* Expand to the max in easy steps */
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do {
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if (nfds < (PAGE_SIZE * 8))
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nfds = PAGE_SIZE * 8;
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else {
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nfds = nfds * 2;
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if (nfds > NR_OPEN)
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nfds = NR_OPEN;
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}
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} while (nfds <= nr);
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new_openset = alloc_fdset(nfds);
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new_execset = alloc_fdset(nfds);
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if (!new_openset || !new_execset)
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goto out;
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fdt->open_fds = new_openset;
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fdt->close_on_exec = new_execset;
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fdt->max_fdset = nfds;
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nfds = NR_OPEN_DEFAULT;
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/*
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* Expand to the max in easy steps, and keep expanding it until
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* we have enough for the requested fd array size.
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*/
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do {
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#if NR_OPEN_DEFAULT < 256
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if (nfds < 256)
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nfds = 256;
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else
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#endif
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if (nfds < (PAGE_SIZE / sizeof(struct file *)))
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nfds = PAGE_SIZE / sizeof(struct file *);
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else {
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nfds = nfds * 2;
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if (nfds > NR_OPEN)
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nfds = NR_OPEN;
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}
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} while (nfds <= nr);
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new_fds = alloc_fd_array(nfds);
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if (!new_fds)
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goto out;
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fdt->fd = new_fds;
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fdt->max_fds = nfds;
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fdt->free_files = NULL;
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return fdt;
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out:
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if (new_openset)
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free_fdset(new_openset, nfds);
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if (new_execset)
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free_fdset(new_execset, nfds);
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kfree(fdt);
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return NULL;
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}
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/*
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* Expands the file descriptor table - it will allocate a new fdtable and
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* both fd array and fdset. It is expected to be called with the
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* files_lock held.
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*/
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static int expand_fdtable(struct files_struct *files, int nr)
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__releases(files->file_lock)
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__acquires(files->file_lock)
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{
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int error = 0;
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struct fdtable *fdt;
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struct fdtable *nfdt = NULL;
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spin_unlock(&files->file_lock);
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nfdt = alloc_fdtable(nr);
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if (!nfdt) {
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error = -ENOMEM;
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spin_lock(&files->file_lock);
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goto out;
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}
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spin_lock(&files->file_lock);
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fdt = files_fdtable(files);
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/*
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* Check again since another task may have expanded the
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* fd table while we dropped the lock
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*/
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if (nr >= fdt->max_fds || nr >= fdt->max_fdset) {
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copy_fdtable(nfdt, fdt);
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} else {
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/* Somebody expanded while we dropped file_lock */
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spin_unlock(&files->file_lock);
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__free_fdtable(nfdt);
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spin_lock(&files->file_lock);
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goto out;
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}
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rcu_assign_pointer(files->fdt, nfdt);
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free_fdtable(fdt);
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out:
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return error;
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}
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/*
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* Expand files.
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* Return <0 on error; 0 nothing done; 1 files expanded, we may have blocked.
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* Should be called with the files->file_lock spinlock held for write.
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*/
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int expand_files(struct files_struct *files, int nr)
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{
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int err, expand = 0;
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struct fdtable *fdt;
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fdt = files_fdtable(files);
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if (nr >= fdt->max_fdset || nr >= fdt->max_fds) {
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if (fdt->max_fdset >= NR_OPEN ||
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fdt->max_fds >= NR_OPEN || nr >= NR_OPEN) {
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err = -EMFILE;
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goto out;
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}
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expand = 1;
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if ((err = expand_fdtable(files, nr)))
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goto out;
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}
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err = expand;
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out:
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return err;
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}
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static void __devinit fdtable_defer_list_init(int cpu)
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{
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struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
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spin_lock_init(&fddef->lock);
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INIT_WORK(&fddef->wq, (void (*)(void *))free_fdtable_work, fddef);
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init_timer(&fddef->timer);
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fddef->timer.data = (unsigned long)fddef;
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fddef->timer.function = fdtable_timer;
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fddef->next = NULL;
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}
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void __init files_defer_init(void)
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{
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int i;
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/* Really early - can't use for_each_cpu */
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for (i = 0; i < NR_CPUS; i++)
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fdtable_defer_list_init(i);
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}
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