[linux-2.6-block.git] / fs / file.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/fdtable.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;
};

int sysctl_nr_open __read_mostly = 1024*1024;

/*
 * 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);

	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 *));
	/*
	 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
	 * had been set lower between the check in expand_files() and here.  Deal
	 * with that in caller, it's cheaper that way.
	 *
	 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
	 * bitmaps handling below becomes unpleasant, to put it mildly...
	 */
	if (unlikely(nr > sysctl_nr_open))
		nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;

	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;
	/*
	 * extremely unlikely race - sysctl_nr_open decreased between the check in
	 * caller and alloc_fdtable().  Cheaper to catch it here...
	 */
	if (unlikely(new_fdt->max_fds <= nr)) {
		free_fdarr(new_fdt);
		free_fdset(new_fdt);
		kfree(new_fdt);
		return -EMFILE;
	}
	/*
	 * 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 >= sysctl_nr_open)
		return -EMFILE;

	/* All good, so we try */
	return expand_fdtable(files, nr);
}

static int count_open_files(struct fdtable *fdt)
{
	int size = fdt->max_fds;
	int i;

	/* Find the last open fd */
	for (i = size/(8*sizeof(long)); i > 0; ) {
		if (fdt->open_fds->fds_bits[--i])
			break;
	}
	i = (i+1) * 8 * sizeof(long);
	return i;
}

/*
 * Allocate a new files structure and copy contents from the
 * passed in files structure.
 * errorp will be valid only when the returned files_struct is NULL.
 */
struct files_struct *dup_fd(struct files_struct *oldf, int *errorp)
{
	struct files_struct *newf;
	struct file **old_fds, **new_fds;
	int open_files, size, i;
	struct fdtable *old_fdt, *new_fdt;

	*errorp = -ENOMEM;
	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
	if (!newf)
		goto out;

	atomic_set(&newf->count, 1);

	spin_lock_init(&newf->file_lock);
	newf->next_fd = 0;
	new_fdt = &newf->fdtab;
	new_fdt->max_fds = NR_OPEN_DEFAULT;
	new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
	new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
	new_fdt->fd = &newf->fd_array[0];
	INIT_RCU_HEAD(&new_fdt->rcu);
	new_fdt->next = NULL;

	spin_lock(&oldf->file_lock);
	old_fdt = files_fdtable(oldf);
	open_files = count_open_files(old_fdt);

	/*
	 * Check whether we need to allocate a larger fd array and fd set.
	 */
	while (unlikely(open_files > new_fdt->max_fds)) {
		spin_unlock(&oldf->file_lock);

		if (new_fdt != &newf->fdtab) {
			free_fdarr(new_fdt);
			free_fdset(new_fdt);
			kfree(new_fdt);
		}

		new_fdt = alloc_fdtable(open_files - 1);
		if (!new_fdt) {
			*errorp = -ENOMEM;
			goto out_release;
		}

		/* beyond sysctl_nr_open; nothing to do */
		if (unlikely(new_fdt->max_fds < open_files)) {
			free_fdarr(new_fdt);
			free_fdset(new_fdt);
			kfree(new_fdt);
			*errorp = -EMFILE;
			goto out_release;
		}

		/*
		 * Reacquire the oldf lock and a pointer to its fd table
		 * who knows it may have a new bigger fd table. We need
		 * the latest pointer.
		 */
		spin_lock(&oldf->file_lock);
		old_fdt = files_fdtable(oldf);
		open_files = count_open_files(old_fdt);
	}

	old_fds = old_fdt->fd;
	new_fds = new_fdt->fd;

	memcpy(new_fdt->open_fds->fds_bits,
		old_fdt->open_fds->fds_bits, open_files/8);
	memcpy(new_fdt->close_on_exec->fds_bits,
		old_fdt->close_on_exec->fds_bits, open_files/8);

	for (i = open_files; i != 0; i--) {
		struct file *f = *old_fds++;
		if (f) {
			get_file(f);
		} else {
			/*
			 * The fd may be claimed in the fd bitmap but not yet
			 * instantiated in the files array if a sibling thread
			 * is partway through open().  So make sure that this
			 * fd is available to the new process.
			 */
			FD_CLR(open_files - i, new_fdt->open_fds);
		}
		rcu_assign_pointer(*new_fds++, f);
	}
	spin_unlock(&oldf->file_lock);

	/* compute the remainder to be cleared */
	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);

	/* This is long word aligned thus could use a optimized version */
	memset(new_fds, 0, size);

	if (new_fdt->max_fds > open_files) {
		int left = (new_fdt->max_fds-open_files)/8;
		int start = open_files / (8 * sizeof(unsigned long));

		memset(&new_fdt->open_fds->fds_bits[start], 0, left);
		memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
	}

	rcu_assign_pointer(newf->fdt, new_fdt);

	return newf;

out_release:
	kmem_cache_free(files_cachep, newf);
out:
	return NULL;
}

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);
}

struct files_struct init_files = {
	.count		= ATOMIC_INIT(1),
	.fdt		= &init_files.fdtab,
	.fdtab		= {
		.max_fds	= NR_OPEN_DEFAULT,
		.fd		= &init_files.fd_array[0],
		.close_on_exec	= (fd_set *)&init_files.close_on_exec_init,
		.open_fds	= (fd_set *)&init_files.open_fds_init,
		.rcu		= RCU_HEAD_INIT,
	},
	.file_lock	= __SPIN_LOCK_UNLOCKED(init_task.file_lock),
};
Commit	Line	Data
	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/time.h>
	12	#include <linux/slab.h>
	13	#include <linux/vmalloc.h>
	14	#include <linux/file.h>
	15	#include <linux/fdtable.h>
	16	#include <linux/bitops.h>
	17	#include <linux/interrupt.h>
	18	#include <linux/spinlock.h>
	19	#include <linux/rcupdate.h>
	20	#include <linux/workqueue.h>
	21
	22	struct fdtable_defer {
	23	spinlock_t lock;
	24	struct work_struct wq;
	25	struct fdtable *next;
	26	};
	27
	28	int sysctl_nr_open __read_mostly = 1024*1024;
	29
	30	/*
	31	* We use this list to defer free fdtables that have vmalloced
	32	* sets/arrays. By keeping a per-cpu list, we avoid having to embed
	33	* the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
	34	* this per-task structure.
	35	*/
	36	static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
	37
	38	static inline void * alloc_fdmem(unsigned int size)
	39	{
	40	if (size <= PAGE_SIZE)
	41	return kmalloc(size, GFP_KERNEL);
	42	else
	43	return vmalloc(size);
	44	}
	45
	46	static inline void free_fdarr(struct fdtable *fdt)
	47	{
	48	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *)))
	49	kfree(fdt->fd);
	50	else
	51	vfree(fdt->fd);
	52	}
	53
	54	static inline void free_fdset(struct fdtable *fdt)
	55	{
	56	if (fdt->max_fds <= (PAGE_SIZE * BITS_PER_BYTE / 2))
	57	kfree(fdt->open_fds);
	58	else
	59	vfree(fdt->open_fds);
	60	}
	61
	62	static void free_fdtable_work(struct work_struct *work)
	63	{
	64	struct fdtable_defer *f =
	65	container_of(work, struct fdtable_defer, wq);
	66	struct fdtable *fdt;
	67
	68	spin_lock_bh(&f->lock);
	69	fdt = f->next;
	70	f->next = NULL;
	71	spin_unlock_bh(&f->lock);
	72	while(fdt) {
	73	struct fdtable *next = fdt->next;
	74	vfree(fdt->fd);
	75	free_fdset(fdt);
	76	kfree(fdt);
	77	fdt = next;
	78	}
	79	}
	80
	81	void free_fdtable_rcu(struct rcu_head *rcu)
	82	{
	83	struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
	84	struct fdtable_defer *fddef;
	85
	86	BUG_ON(!fdt);
	87
	88	if (fdt->max_fds <= NR_OPEN_DEFAULT) {
	89	/*
	90	* This fdtable is embedded in the files structure and that
	91	* structure itself is getting destroyed.
	92	*/
	93	kmem_cache_free(files_cachep,
	94	container_of(fdt, struct files_struct, fdtab));
	95	return;
	96	}
	97	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *))) {
	98	kfree(fdt->fd);
	99	kfree(fdt->open_fds);
	100	kfree(fdt);
	101	} else {
	102	fddef = &get_cpu_var(fdtable_defer_list);
	103	spin_lock(&fddef->lock);
	104	fdt->next = fddef->next;
	105	fddef->next = fdt;
	106	/* vmallocs are handled from the workqueue context */
	107	schedule_work(&fddef->wq);
	108	spin_unlock(&fddef->lock);
	109	put_cpu_var(fdtable_defer_list);
	110	}
	111	}
	112
	113	/*
	114	* Expand the fdset in the files_struct. Called with the files spinlock
	115	* held for write.
	116	*/
	117	static void copy_fdtable(struct fdtable nfdt, struct fdtable ofdt)
	118	{
	119	unsigned int cpy, set;
	120
	121	BUG_ON(nfdt->max_fds < ofdt->max_fds);
	122
	123	cpy = ofdt->max_fds * sizeof(struct file *);
	124	set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
	125	memcpy(nfdt->fd, ofdt->fd, cpy);
	126	memset((char *)(nfdt->fd) + cpy, 0, set);
	127
	128	cpy = ofdt->max_fds / BITS_PER_BYTE;
	129	set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
	130	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
	131	memset((char *)(nfdt->open_fds) + cpy, 0, set);
	132	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
	133	memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
	134	}
	135
	136	static struct fdtable * alloc_fdtable(unsigned int nr)
	137	{
	138	struct fdtable *fdt;
	139	char *data;
	140
	141	/*
	142	* Figure out how many fds we actually want to support in this fdtable.
	143	* Allocation steps are keyed to the size of the fdarray, since it
	144	* grows far faster than any of the other dynamic data. We try to fit
	145	* the fdarray into comfortable page-tuned chunks: starting at 1024B
	146	* and growing in powers of two from there on.
	147	*/
	148	nr /= (1024 / sizeof(struct file *));
	149	nr = roundup_pow_of_two(nr + 1);
	150	nr = (1024 / sizeof(struct file ));
	151	/*
	152	* Note that this can drive nr below what we had passed if sysctl_nr_open
	153	* had been set lower between the check in expand_files() and here. Deal
	154	* with that in caller, it's cheaper that way.
	155	*
	156	* We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
	157	* bitmaps handling below becomes unpleasant, to put it mildly...
	158	*/
	159	if (unlikely(nr > sysctl_nr_open))
	160	nr = ((sysctl_nr_open - 1) \| (BITS_PER_LONG - 1)) + 1;
	161
	162	fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
	163	if (!fdt)
	164	goto out;
	165	fdt->max_fds = nr;
	166	data = alloc_fdmem(nr * sizeof(struct file *));
	167	if (!data)
	168	goto out_fdt;
	169	fdt->fd = (struct file **)data;
	170	data = alloc_fdmem(max_t(unsigned int,
	171	2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
	172	if (!data)
	173	goto out_arr;
	174	fdt->open_fds = (fd_set *)data;
	175	data += nr / BITS_PER_BYTE;
	176	fdt->close_on_exec = (fd_set *)data;
	177	INIT_RCU_HEAD(&fdt->rcu);
	178	fdt->next = NULL;
	179
	180	return fdt;
	181
	182	out_arr:
	183	free_fdarr(fdt);
	184	out_fdt:
	185	kfree(fdt);
	186	out:
	187	return NULL;
	188	}
	189
	190	/*
	191	* Expand the file descriptor table.
	192	* This function will allocate a new fdtable and both fd array and fdset, of
	193	* the given size.
	194	* Return <0 error code on error; 1 on successful completion.
	195	* The files->file_lock should be held on entry, and will be held on exit.
	196	*/
	197	static int expand_fdtable(struct files_struct *files, int nr)
	198	__releases(files->file_lock)
	199	__acquires(files->file_lock)
	200	{
	201	struct fdtable new_fdt, cur_fdt;
	202
	203	spin_unlock(&files->file_lock);
	204	new_fdt = alloc_fdtable(nr);
	205	spin_lock(&files->file_lock);
	206	if (!new_fdt)
	207	return -ENOMEM;
	208	/*
	209	* extremely unlikely race - sysctl_nr_open decreased between the check in
	210	* caller and alloc_fdtable(). Cheaper to catch it here...
	211	*/
	212	if (unlikely(new_fdt->max_fds <= nr)) {
	213	free_fdarr(new_fdt);
	214	free_fdset(new_fdt);
	215	kfree(new_fdt);
	216	return -EMFILE;
	217	}
	218	/*
	219	* Check again since another task may have expanded the fd table while
	220	* we dropped the lock
	221	*/
	222	cur_fdt = files_fdtable(files);
	223	if (nr >= cur_fdt->max_fds) {
	224	/* Continue as planned */
	225	copy_fdtable(new_fdt, cur_fdt);
	226	rcu_assign_pointer(files->fdt, new_fdt);
	227	if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
	228	free_fdtable(cur_fdt);
	229	} else {
	230	/* Somebody else expanded, so undo our attempt */
	231	free_fdarr(new_fdt);
	232	free_fdset(new_fdt);
	233	kfree(new_fdt);
	234	}
	235	return 1;
	236	}
	237
	238	/*
	239	* Expand files.
	240	* This function will expand the file structures, if the requested size exceeds
	241	* the current capacity and there is room for expansion.
	242	* Return <0 error code on error; 0 when nothing done; 1 when files were
	243	* expanded and execution may have blocked.
	244	* The files->file_lock should be held on entry, and will be held on exit.
	245	*/
	246	int expand_files(struct files_struct *files, int nr)
	247	{
	248	struct fdtable *fdt;
	249
	250	fdt = files_fdtable(files);
	251	/* Do we need to expand? */
	252	if (nr < fdt->max_fds)
	253	return 0;
	254	/* Can we expand? */
	255	if (nr >= sysctl_nr_open)
	256	return -EMFILE;
	257
	258	/* All good, so we try */
	259	return expand_fdtable(files, nr);
	260	}
	261
	262	static int count_open_files(struct fdtable *fdt)
	263	{
	264	int size = fdt->max_fds;
	265	int i;
	266
	267	/* Find the last open fd */
	268	for (i = size/(8*sizeof(long)); i > 0; ) {
	269	if (fdt->open_fds->fds_bits[--i])
	270	break;
	271	}
	272	i = (i+1) * 8 * sizeof(long);
	273	return i;
	274	}
	275
	276	/*
	277	* Allocate a new files structure and copy contents from the
	278	* passed in files structure.
	279	* errorp will be valid only when the returned files_struct is NULL.
	280	*/
	281	struct files_struct dup_fd(struct files_struct oldf, int *errorp)
	282	{
	283	struct files_struct *newf;
	284	struct file old_fds, new_fds;
	285	int open_files, size, i;
	286	struct fdtable old_fdt, new_fdt;
	287
	288	*errorp = -ENOMEM;
	289	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
	290	if (!newf)
	291	goto out;
	292
	293	atomic_set(&newf->count, 1);
	294
	295	spin_lock_init(&newf->file_lock);
	296	newf->next_fd = 0;
	297	new_fdt = &newf->fdtab;
	298	new_fdt->max_fds = NR_OPEN_DEFAULT;
	299	new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
	300	new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
	301	new_fdt->fd = &newf->fd_array[0];
	302	INIT_RCU_HEAD(&new_fdt->rcu);
	303	new_fdt->next = NULL;
	304
	305	spin_lock(&oldf->file_lock);
	306	old_fdt = files_fdtable(oldf);
	307	open_files = count_open_files(old_fdt);
	308
	309	/*
	310	* Check whether we need to allocate a larger fd array and fd set.
	311	*/
	312	while (unlikely(open_files > new_fdt->max_fds)) {
	313	spin_unlock(&oldf->file_lock);
	314
	315	if (new_fdt != &newf->fdtab) {
	316	free_fdarr(new_fdt);
	317	free_fdset(new_fdt);
	318	kfree(new_fdt);
	319	}
	320
	321	new_fdt = alloc_fdtable(open_files - 1);
	322	if (!new_fdt) {
	323	*errorp = -ENOMEM;
	324	goto out_release;
	325	}
	326
	327	/* beyond sysctl_nr_open; nothing to do */
	328	if (unlikely(new_fdt->max_fds < open_files)) {
	329	free_fdarr(new_fdt);
	330	free_fdset(new_fdt);
	331	kfree(new_fdt);
	332	*errorp = -EMFILE;
	333	goto out_release;
	334	}
	335
	336	/*
	337	* Reacquire the oldf lock and a pointer to its fd table
	338	* who knows it may have a new bigger fd table. We need
	339	* the latest pointer.
	340	*/
	341	spin_lock(&oldf->file_lock);
	342	old_fdt = files_fdtable(oldf);
	343	open_files = count_open_files(old_fdt);
	344	}
	345
	346	old_fds = old_fdt->fd;
	347	new_fds = new_fdt->fd;
	348
	349	memcpy(new_fdt->open_fds->fds_bits,
	350	old_fdt->open_fds->fds_bits, open_files/8);
	351	memcpy(new_fdt->close_on_exec->fds_bits,
	352	old_fdt->close_on_exec->fds_bits, open_files/8);
	353
	354	for (i = open_files; i != 0; i--) {
	355	struct file f = old_fds++;
	356	if (f) {
	357	get_file(f);
	358	} else {
	359	/*
	360	* The fd may be claimed in the fd bitmap but not yet
	361	* instantiated in the files array if a sibling thread
	362	* is partway through open(). So make sure that this
	363	* fd is available to the new process.
	364	*/
	365	FD_CLR(open_files - i, new_fdt->open_fds);
	366	}
	367	rcu_assign_pointer(*new_fds++, f);
	368	}
	369	spin_unlock(&oldf->file_lock);
	370
	371	/* compute the remainder to be cleared */
	372	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
	373
	374	/* This is long word aligned thus could use a optimized version */
	375	memset(new_fds, 0, size);
	376
	377	if (new_fdt->max_fds > open_files) {
	378	int left = (new_fdt->max_fds-open_files)/8;
	379	int start = open_files / (8 * sizeof(unsigned long));
	380
	381	memset(&new_fdt->open_fds->fds_bits[start], 0, left);
	382	memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
	383	}
	384
	385	rcu_assign_pointer(newf->fdt, new_fdt);
	386
	387	return newf;
	388
	389	out_release:
	390	kmem_cache_free(files_cachep, newf);
	391	out:
	392	return NULL;
	393	}
	394
	395	static void __devinit fdtable_defer_list_init(int cpu)
	396	{
	397	struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
	398	spin_lock_init(&fddef->lock);
	399	INIT_WORK(&fddef->wq, free_fdtable_work);
	400	fddef->next = NULL;
	401	}
	402
	403	void __init files_defer_init(void)
	404	{
	405	int i;
	406	for_each_possible_cpu(i)
	407	fdtable_defer_list_init(i);
	408	}
	409
	410	struct files_struct init_files = {
	411	.count = ATOMIC_INIT(1),
	412	.fdt = &init_files.fdtab,
	413	.fdtab = {
	414	.max_fds = NR_OPEN_DEFAULT,
	415	.fd = &init_files.fd_array[0],
	416	.close_on_exec = (fd_set *)&init_files.close_on_exec_init,
	417	.open_fds = (fd_set *)&init_files.open_fds_init,
	418	.rcu = RCU_HEAD_INIT,
	419	},
	420	.file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
	421	};