/* *  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 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); static inline void * alloc_fdmem(unsigned int size){	if (size <= PAGE_SIZE)		return kmalloc(size, GFP_KERNEL);	else		return vmalloc(size);} static inline void free_fdarr(struct fdtable *fdt){	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *)))		kfree(fdt->fd);	else		vfree(fdt->fd);} static inline void free_fdset(struct fdtable *fdt){	if (fdt->max_fds <= (PAGE_SIZE * BITS_PER_BYTE / 2))		kfree(fdt->open_fds);	else		vfree(fdt->open_fds);} static void free_fdtable_work(struct work_struct *work){	struct fdtable_defer *f =		container_of(work, struct fdtable_defer, wq);	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;		vfree(fdt->fd);		free_fdset(fdt);		kfree(fdt);		fdt = next;	}} void free_fdtable_rcu(struct rcu_head *rcu){	struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);	struct fdtable_defer *fddef; 	BUG_ON(!fdt); 	if (fdt->max_fds <= NR_OPEN_DEFAULT) {		/*		 * This fdtable is embedded in the files structure and that		 * structure itself is getting destroyed.		 */		kmem_cache_free(files_cachep,				container_of(fdt, struct files_struct, fdtab));		return;	}	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *))) {		kfree(fdt->fd);		kfree(fdt->open_fds);		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 */		schedule_work(&fddef->wq);		spin_unlock(&fddef->lock);		put_cpu_var(fdtable_defer_list);	}} /* * Expand the fdset in the files_struct.  Called with the files spinlock * held for write. */static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt){	unsigned int cpy, set; 	BUG_ON(nfdt->max_fds < ofdt->max_fds);	if (ofdt->max_fds == 0)		return; 	cpy = ofdt->max_fds * sizeof(struct file *);	set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);	memcpy(nfdt->fd, ofdt->fd, cpy);	memset((char *)(nfdt->fd) + cpy, 0, set); 	cpy = ofdt->max_fds / BITS_PER_BYTE;	set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);	memset((char *)(nfdt->open_fds) + cpy, 0, set);	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);	memset((char *)(nfdt->close_on_exec) + cpy, 0, set);} static struct fdtable * alloc_fdtable(unsigned int nr){	struct fdtable *fdt;	char *data; 	/*	 * Figure out how many fds we actually want to support in this fdtable.	 * Allocation steps are keyed to the size of the fdarray, since it	 * grows far faster than any of the other dynamic data. We try to fit	 * the fdarray into comfortable page-tuned chunks: starting at 1024B	 * and growing in powers of two from there on.	 */	nr /= (1024 / sizeof(struct file *));	nr = roundup_pow_of_two(nr + 1);	nr *= (1024 / sizeof(struct file *));	if (nr > NR_OPEN)		nr = NR_OPEN; 	fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);	if (!fdt)		goto out;	fdt->max_fds = nr;	data = alloc_fdmem(nr * sizeof(struct file *));	if (!data)		goto out_fdt;	fdt->fd = (struct file **)data;	data = alloc_fdmem(max_t(unsigned int,				 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));	if (!data)		goto out_arr;	fdt->open_fds = (fd_set *)data;	data += nr / BITS_PER_BYTE;	fdt->close_on_exec = (fd_set *)data;	INIT_RCU_HEAD(&fdt->rcu);	fdt->next = NULL; 	return fdt; out_arr:	free_fdarr(fdt);out_fdt:	kfree(fdt);out:	return NULL;} /* * Expand the file descriptor table. * This function will allocate a new fdtable and both fd array and fdset, of * the given size. * Return <0 error code on error; 1 on successful completion. * The files->file_lock should be held on entry, and will be held on exit. */static int expand_fdtable(struct files_struct *files, int nr)	__releases(files->file_lock)	__acquires(files->file_lock){	struct fdtable *new_fdt, *cur_fdt; 	spin_unlock(&files->file_lock);	new_fdt = alloc_fdtable(nr);	spin_lock(&files->file_lock);	if (!new_fdt)		return -ENOMEM;	/*	 * Check again since another task may have expanded the fd table while	 * we dropped the lock	 */	cur_fdt = files_fdtable(files);	if (nr >= cur_fdt->max_fds) {		/* Continue as planned */		copy_fdtable(new_fdt, cur_fdt);		rcu_assign_pointer(files->fdt, new_fdt);		if (cur_fdt->max_fds > NR_OPEN_DEFAULT)			free_fdtable(cur_fdt);	} else {		/* Somebody else expanded, so undo our attempt */		free_fdarr(new_fdt);		free_fdset(new_fdt);		kfree(new_fdt);	}	return 1;} /* * Expand files. * This function will expand the file structures, if the requested size exceeds * the current capacity and there is room for expansion. * Return <0 error code on error; 0 when nothing done; 1 when files were * expanded and execution may have blocked. * The files->file_lock should be held on entry, and will be held on exit. */int expand_files(struct files_struct *files, int nr){	struct fdtable *fdt; 	fdt = files_fdtable(files);	/* Do we need to expand? */	if (nr < fdt->max_fds)		return 0;	/* Can we expand? */	if (nr >= NR_OPEN)		return -EMFILE; 	/* All good, so we try */	return expand_fdtable(files, nr);} 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, free_fdtable_work);	fddef->next = NULL;} void __init files_defer_init(void){	int i;	for_each_possible_cpu(i)		fdtable_defer_list_init(i);}