[net-next-2.6.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/module.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/time.h>
#include <linux/sched.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;
int sysctl_nr_open_min = BITS_PER_LONG;
int sysctl_nr_open_max = 1024 * 1024; /* raised later */

/*
 * 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);

	/*
	 * N.B. For clone tasks sharing a files structure, this test
	 * will limit the total number of files that can be opened.
	 */
	if (nr >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
		return -EMFILE;

	/* 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);
	sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
			     -BITS_PER_LONG;
}

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),
};

/*
 * allocate a file descriptor, mark it busy.
 */
int alloc_fd(unsigned start, unsigned flags)
{
	struct files_struct *files = current->files;
	unsigned int fd;
	int error;
	struct fdtable *fdt;

	spin_lock(&files->file_lock);
repeat:
	fdt = files_fdtable(files);
	fd = start;
	if (fd < files->next_fd)
		fd = files->next_fd;

	if (fd < fdt->max_fds)
		fd = find_next_zero_bit(fdt->open_fds->fds_bits,
					   fdt->max_fds, fd);

	error = expand_files(files, fd);
	if (error < 0)
		goto out;

	/*
	 * If we needed to expand the fs array we
	 * might have blocked - try again.
	 */
	if (error)
		goto repeat;

	if (start <= files->next_fd)
		files->next_fd = fd + 1;

	FD_SET(fd, fdt->open_fds);
	if (flags & O_CLOEXEC)
		FD_SET(fd, fdt->close_on_exec);
	else
		FD_CLR(fd, fdt->close_on_exec);
	error = fd;
#if 1
	/* Sanity check */
	if (rcu_dereference(fdt->fd[fd]) != NULL) {
		printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
		rcu_assign_pointer(fdt->fd[fd], NULL);
	}
#endif

out:
	spin_unlock(&files->file_lock);
	return error;
}

int get_unused_fd(void)
{
	return alloc_fd(0, 0);
}
EXPORT_SYMBOL(get_unused_fd);
Commit	Line	Data
1da177e4 LT	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
1027abe8	9	#include <linux/module.h>
1da177e4 LT	10	#include <linux/fs.h>
	11	#include <linux/mm.h>
	12	#include <linux/time.h>
d43c36dc	13	#include <linux/sched.h>
1da177e4 LT	14	#include <linux/slab.h>
	15	#include <linux/vmalloc.h>
	16	#include <linux/file.h>
9f3acc31	17	#include <linux/fdtable.h>
1da177e4	18	#include <linux/bitops.h>
ab2af1f5 DS	19	#include <linux/interrupt.h>
	20	#include <linux/spinlock.h>
	21	#include <linux/rcupdate.h>
	22	#include <linux/workqueue.h>
	23
	24	struct fdtable_defer {
	25	spinlock_t lock;
	26	struct work_struct wq;
ab2af1f5 DS	27	struct fdtable *next;
	28	};
	29
9cfe015a	30	int sysctl_nr_open __read_mostly = 1024*1024;
eceea0b3 AV	31	int sysctl_nr_open_min = BITS_PER_LONG;
eceea0b3 AV	32	int sysctl_nr_open_max = 1024 * 1024; /* raised later */
9cfe015a	33
ab2af1f5 DS	34	/*
	35	* We use this list to defer free fdtables that have vmalloced
	36	* sets/arrays. By keeping a per-cpu list, we avoid having to embed
	37	* the work_struct in fdtable itself which avoids a 64 byte (i386) increase in
	38	* this per-task structure.
	39	*/
	40	static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list);
1da177e4	41
5466b456	42	static inline void * alloc_fdmem(unsigned int size)
1da177e4	43	{
1da177e4	44	if (size <= PAGE_SIZE)
5466b456 VL	45	return kmalloc(size, GFP_KERNEL);
	46	else
	47	return vmalloc(size);
1da177e4 LT	48	}
1da177e4 LT	49
5466b456	50	static inline void free_fdarr(struct fdtable *fdt)
1da177e4	51	{
5466b456 VL	52	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *)))
5466b456 VL	53	kfree(fdt->fd);
1da177e4	54	else
5466b456	55	vfree(fdt->fd);
1da177e4 LT	56	}
1da177e4 LT	57
5466b456	58	static inline void free_fdset(struct fdtable *fdt)
1da177e4	59	{
5466b456 VL	60	if (fdt->max_fds <= (PAGE_SIZE * BITS_PER_BYTE / 2))
	61	kfree(fdt->open_fds);
	62	else
	63	vfree(fdt->open_fds);
ab2af1f5	64	}
1da177e4	65
65f27f38	66	static void free_fdtable_work(struct work_struct *work)
ab2af1f5	67	{
65f27f38 DH	68	struct fdtable_defer *f =
65f27f38 DH	69	container_of(work, struct fdtable_defer, wq);
ab2af1f5	70	struct fdtable *fdt;
1da177e4	71
ab2af1f5 DS	72	spin_lock_bh(&f->lock);
	73	fdt = f->next;
	74	f->next = NULL;
	75	spin_unlock_bh(&f->lock);
	76	while(fdt) {
	77	struct fdtable *next = fdt->next;
5466b456 VL	78	vfree(fdt->fd);
	79	free_fdset(fdt);
	80	kfree(fdt);
ab2af1f5 DS	81	fdt = next;
	82	}
	83	}
1da177e4	84
4fd45812	85	void free_fdtable_rcu(struct rcu_head *rcu)
ab2af1f5 DS	86	{
ab2af1f5 DS	87	struct fdtable *fdt = container_of(rcu, struct fdtable, rcu);
ab2af1f5	88	struct fdtable_defer *fddef;
1da177e4	89
ab2af1f5	90	BUG_ON(!fdt);
ab2af1f5	91
4fd45812	92	if (fdt->max_fds <= NR_OPEN_DEFAULT) {
ab2af1f5	93	/*
4fd45812 VL	94	* This fdtable is embedded in the files structure and that
4fd45812 VL	95	* structure itself is getting destroyed.
ab2af1f5	96	*/
4fd45812 VL	97	kmem_cache_free(files_cachep,
4fd45812 VL	98	container_of(fdt, struct files_struct, fdtab));
ab2af1f5 DS	99	return;
ab2af1f5 DS	100	}
5466b456	101	if (fdt->max_fds <= (PAGE_SIZE / sizeof(struct file *))) {
ab2af1f5	102	kfree(fdt->fd);
5466b456	103	kfree(fdt->open_fds);
ab2af1f5	104	kfree(fdt);
1da177e4	105	} else {
ab2af1f5 DS	106	fddef = &get_cpu_var(fdtable_defer_list);
	107	spin_lock(&fddef->lock);
	108	fdt->next = fddef->next;
	109	fddef->next = fdt;
593be07a TH	110	/* vmallocs are handled from the workqueue context */
593be07a TH	111	schedule_work(&fddef->wq);
ab2af1f5 DS	112	spin_unlock(&fddef->lock);
ab2af1f5 DS	113	put_cpu_var(fdtable_defer_list);
1da177e4	114	}
ab2af1f5 DS	115	}
ab2af1f5 DS	116
ab2af1f5 DS	117	/*
	118	* Expand the fdset in the files_struct. Called with the files spinlock
	119	* held for write.
	120	*/
5466b456	121	static void copy_fdtable(struct fdtable nfdt, struct fdtable ofdt)
ab2af1f5	122	{
5466b456	123	unsigned int cpy, set;
ab2af1f5	124
5466b456	125	BUG_ON(nfdt->max_fds < ofdt->max_fds);
5466b456 VL	126
	127	cpy = ofdt->max_fds * sizeof(struct file *);
	128	set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
	129	memcpy(nfdt->fd, ofdt->fd, cpy);
	130	memset((char *)(nfdt->fd) + cpy, 0, set);
	131
	132	cpy = ofdt->max_fds / BITS_PER_BYTE;
	133	set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE;
	134	memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
	135	memset((char *)(nfdt->open_fds) + cpy, 0, set);
	136	memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
	137	memset((char *)(nfdt->close_on_exec) + cpy, 0, set);
1da177e4 LT	138	}
1da177e4 LT	139
5466b456	140	static struct fdtable * alloc_fdtable(unsigned int nr)
1da177e4	141	{
5466b456 VL	142	struct fdtable *fdt;
5466b456 VL	143	char *data;
1da177e4	144
ab2af1f5	145	/*
5466b456 VL	146	* Figure out how many fds we actually want to support in this fdtable.
	147	* Allocation steps are keyed to the size of the fdarray, since it
	148	* grows far faster than any of the other dynamic data. We try to fit
	149	* the fdarray into comfortable page-tuned chunks: starting at 1024B
	150	* and growing in powers of two from there on.
ab2af1f5	151	*/
5466b456 VL	152	nr /= (1024 / sizeof(struct file *));
	153	nr = roundup_pow_of_two(nr + 1);
	154	nr = (1024 / sizeof(struct file ));
5c598b34 AV	155	/*
	156	* Note that this can drive nr below what we had passed if sysctl_nr_open
	157	* had been set lower between the check in expand_files() and here. Deal
	158	* with that in caller, it's cheaper that way.
	159	*
	160	* We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
	161	* bitmaps handling below becomes unpleasant, to put it mildly...
	162	*/
	163	if (unlikely(nr > sysctl_nr_open))
	164	nr = ((sysctl_nr_open - 1) \| (BITS_PER_LONG - 1)) + 1;
bbea9f69	165
5466b456 VL	166	fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL);
5466b456 VL	167	if (!fdt)
bbea9f69	168	goto out;
5466b456 VL	169	fdt->max_fds = nr;
	170	data = alloc_fdmem(nr * sizeof(struct file *));
	171	if (!data)
	172	goto out_fdt;
	173	fdt->fd = (struct file **)data;
	174	data = alloc_fdmem(max_t(unsigned int,
	175	2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES));
	176	if (!data)
	177	goto out_arr;
	178	fdt->open_fds = (fd_set *)data;
	179	data += nr / BITS_PER_BYTE;
	180	fdt->close_on_exec = (fd_set *)data;
	181	INIT_RCU_HEAD(&fdt->rcu);
	182	fdt->next = NULL;
	183
ab2af1f5	184	return fdt;
5466b456 VL	185
	186	out_arr:
	187	free_fdarr(fdt);
	188	out_fdt:
ab2af1f5	189	kfree(fdt);
5466b456	190	out:
ab2af1f5 DS	191	return NULL;
ab2af1f5 DS	192	}
1da177e4	193
ab2af1f5	194	/*
74d392aa VL	195	* Expand the file descriptor table.
	196	* This function will allocate a new fdtable and both fd array and fdset, of
	197	* the given size.
	198	* Return <0 error code on error; 1 on successful completion.
	199	* The files->file_lock should be held on entry, and will be held on exit.
ab2af1f5 DS	200	*/
	201	static int expand_fdtable(struct files_struct *files, int nr)
	202	__releases(files->file_lock)
	203	__acquires(files->file_lock)
	204	{
74d392aa	205	struct fdtable new_fdt, cur_fdt;
ab2af1f5 DS	206
ab2af1f5 DS	207	spin_unlock(&files->file_lock);
74d392aa	208	new_fdt = alloc_fdtable(nr);
ab2af1f5	209	spin_lock(&files->file_lock);
74d392aa VL	210	if (!new_fdt)
74d392aa VL	211	return -ENOMEM;
5c598b34 AV	212	/*
	213	* extremely unlikely race - sysctl_nr_open decreased between the check in
	214	* caller and alloc_fdtable(). Cheaper to catch it here...
	215	*/
	216	if (unlikely(new_fdt->max_fds <= nr)) {
	217	free_fdarr(new_fdt);
	218	free_fdset(new_fdt);
	219	kfree(new_fdt);
	220	return -EMFILE;
	221	}
ab2af1f5	222	/*
74d392aa VL	223	* Check again since another task may have expanded the fd table while
74d392aa VL	224	* we dropped the lock
ab2af1f5	225	*/
74d392aa	226	cur_fdt = files_fdtable(files);
bbea9f69	227	if (nr >= cur_fdt->max_fds) {
74d392aa VL	228	/* Continue as planned */
	229	copy_fdtable(new_fdt, cur_fdt);
	230	rcu_assign_pointer(files->fdt, new_fdt);
4fd45812	231	if (cur_fdt->max_fds > NR_OPEN_DEFAULT)
01b2d93c	232	free_fdtable(cur_fdt);
ab2af1f5	233	} else {
74d392aa	234	/* Somebody else expanded, so undo our attempt */
5466b456 VL	235	free_fdarr(new_fdt);
	236	free_fdset(new_fdt);
	237	kfree(new_fdt);
ab2af1f5	238	}
74d392aa	239	return 1;
1da177e4 LT	240	}
	241
	242	/*
	243	* Expand files.
74d392aa VL	244	* This function will expand the file structures, if the requested size exceeds
	245	* the current capacity and there is room for expansion.
	246	* Return <0 error code on error; 0 when nothing done; 1 when files were
	247	* expanded and execution may have blocked.
	248	* The files->file_lock should be held on entry, and will be held on exit.
1da177e4 LT	249	*/
	250	int expand_files(struct files_struct *files, int nr)
	251	{
badf1662	252	struct fdtable *fdt;
1da177e4	253
badf1662	254	fdt = files_fdtable(files);
4e1e018e AV	255
	256	/*
	257	* N.B. For clone tasks sharing a files structure, this test
	258	* will limit the total number of files that can be opened.
	259	*/
	260	if (nr >= current->signal->rlim[RLIMIT_NOFILE].rlim_cur)
	261	return -EMFILE;
	262
74d392aa	263	/* Do we need to expand? */
bbea9f69	264	if (nr < fdt->max_fds)
74d392aa	265	return 0;
4e1e018e	266
74d392aa	267	/* Can we expand? */
9cfe015a	268	if (nr >= sysctl_nr_open)
74d392aa VL	269	return -EMFILE;
	270
	271	/* All good, so we try */
	272	return expand_fdtable(files, nr);
1da177e4	273	}
ab2af1f5	274
02afc626 AV	275	static int count_open_files(struct fdtable *fdt)
	276	{
	277	int size = fdt->max_fds;
	278	int i;
	279
	280	/* Find the last open fd */
	281	for (i = size/(8*sizeof(long)); i > 0; ) {
	282	if (fdt->open_fds->fds_bits[--i])
	283	break;
	284	}
	285	i = (i+1) * 8 * sizeof(long);
	286	return i;
	287	}
	288
02afc626 AV	289	/*
	290	* Allocate a new files structure and copy contents from the
	291	* passed in files structure.
	292	* errorp will be valid only when the returned files_struct is NULL.
	293	*/
	294	struct files_struct dup_fd(struct files_struct oldf, int *errorp)
	295	{
	296	struct files_struct *newf;
	297	struct file old_fds, new_fds;
	298	int open_files, size, i;
	299	struct fdtable old_fdt, new_fdt;
	300
	301	*errorp = -ENOMEM;
afbec7ff	302	newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
02afc626 AV	303	if (!newf)
	304	goto out;
	305
afbec7ff AV	306	atomic_set(&newf->count, 1);
	307
	308	spin_lock_init(&newf->file_lock);
	309	newf->next_fd = 0;
	310	new_fdt = &newf->fdtab;
	311	new_fdt->max_fds = NR_OPEN_DEFAULT;
	312	new_fdt->close_on_exec = (fd_set *)&newf->close_on_exec_init;
	313	new_fdt->open_fds = (fd_set *)&newf->open_fds_init;
	314	new_fdt->fd = &newf->fd_array[0];
	315	INIT_RCU_HEAD(&new_fdt->rcu);
	316	new_fdt->next = NULL;
	317
02afc626 AV	318	spin_lock(&oldf->file_lock);
02afc626 AV	319	old_fdt = files_fdtable(oldf);
02afc626 AV	320	open_files = count_open_files(old_fdt);
	321
	322	/*
	323	* Check whether we need to allocate a larger fd array and fd set.
02afc626	324	*/
adbecb12	325	while (unlikely(open_files > new_fdt->max_fds)) {
02afc626	326	spin_unlock(&oldf->file_lock);
9dec3c4d	327
adbecb12 AV	328	if (new_fdt != &newf->fdtab) {
	329	free_fdarr(new_fdt);
	330	free_fdset(new_fdt);
	331	kfree(new_fdt);
	332	}
	333
9dec3c4d AV	334	new_fdt = alloc_fdtable(open_files - 1);
	335	if (!new_fdt) {
	336	*errorp = -ENOMEM;
	337	goto out_release;
	338	}
	339
	340	/* beyond sysctl_nr_open; nothing to do */
	341	if (unlikely(new_fdt->max_fds < open_files)) {
	342	free_fdarr(new_fdt);
	343	free_fdset(new_fdt);
	344	kfree(new_fdt);
	345	*errorp = -EMFILE;
02afc626	346	goto out_release;
9dec3c4d	347	}
9dec3c4d	348
02afc626 AV	349	/*
	350	* Reacquire the oldf lock and a pointer to its fd table
	351	* who knows it may have a new bigger fd table. We need
	352	* the latest pointer.
	353	*/
	354	spin_lock(&oldf->file_lock);
	355	old_fdt = files_fdtable(oldf);
adbecb12	356	open_files = count_open_files(old_fdt);
02afc626 AV	357	}
	358
	359	old_fds = old_fdt->fd;
	360	new_fds = new_fdt->fd;
	361
	362	memcpy(new_fdt->open_fds->fds_bits,
	363	old_fdt->open_fds->fds_bits, open_files/8);
	364	memcpy(new_fdt->close_on_exec->fds_bits,
	365	old_fdt->close_on_exec->fds_bits, open_files/8);
	366
	367	for (i = open_files; i != 0; i--) {
	368	struct file f = old_fds++;
	369	if (f) {
	370	get_file(f);
	371	} else {
	372	/*
	373	* The fd may be claimed in the fd bitmap but not yet
	374	* instantiated in the files array if a sibling thread
	375	* is partway through open(). So make sure that this
	376	* fd is available to the new process.
	377	*/
	378	FD_CLR(open_files - i, new_fdt->open_fds);
	379	}
	380	rcu_assign_pointer(*new_fds++, f);
	381	}
	382	spin_unlock(&oldf->file_lock);
	383
	384	/* compute the remainder to be cleared */
	385	size = (new_fdt->max_fds - open_files) * sizeof(struct file *);
	386
	387	/* This is long word aligned thus could use a optimized version */
	388	memset(new_fds, 0, size);
	389
	390	if (new_fdt->max_fds > open_files) {
	391	int left = (new_fdt->max_fds-open_files)/8;
	392	int start = open_files / (8 * sizeof(unsigned long));
	393
	394	memset(&new_fdt->open_fds->fds_bits[start], 0, left);
	395	memset(&new_fdt->close_on_exec->fds_bits[start], 0, left);
	396	}
	397
afbec7ff AV	398	rcu_assign_pointer(newf->fdt, new_fdt);
afbec7ff AV	399
02afc626 AV	400	return newf;
	401
	402	out_release:
	403	kmem_cache_free(files_cachep, newf);
	404	out:
	405	return NULL;
	406	}
	407
ab2af1f5 DS	408	static void __devinit fdtable_defer_list_init(int cpu)
	409	{
	410	struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu);
	411	spin_lock_init(&fddef->lock);
65f27f38	412	INIT_WORK(&fddef->wq, free_fdtable_work);
ab2af1f5 DS	413	fddef->next = NULL;
	414	}
	415
	416	void __init files_defer_init(void)
	417	{
	418	int i;
0a945022	419	for_each_possible_cpu(i)
ab2af1f5	420	fdtable_defer_list_init(i);
eceea0b3 AV	421	sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) &
eceea0b3 AV	422	-BITS_PER_LONG;
ab2af1f5	423	}
f52111b1 AV	424
	425	struct files_struct init_files = {
	426	.count = ATOMIC_INIT(1),
	427	.fdt = &init_files.fdtab,
	428	.fdtab = {
	429	.max_fds = NR_OPEN_DEFAULT,
	430	.fd = &init_files.fd_array[0],
	431	.close_on_exec = (fd_set *)&init_files.close_on_exec_init,
	432	.open_fds = (fd_set *)&init_files.open_fds_init,
	433	.rcu = RCU_HEAD_INIT,
	434	},
	435	.file_lock = __SPIN_LOCK_UNLOCKED(init_task.file_lock),
	436	};
1027abe8 AV	437
	438	/*
	439	* allocate a file descriptor, mark it busy.
	440	*/
	441	int alloc_fd(unsigned start, unsigned flags)
	442	{
	443	struct files_struct *files = current->files;
	444	unsigned int fd;
	445	int error;
	446	struct fdtable *fdt;
	447
	448	spin_lock(&files->file_lock);
	449	repeat:
	450	fdt = files_fdtable(files);
	451	fd = start;
	452	if (fd < files->next_fd)
	453	fd = files->next_fd;
	454
	455	if (fd < fdt->max_fds)
	456	fd = find_next_zero_bit(fdt->open_fds->fds_bits,
	457	fdt->max_fds, fd);
	458
	459	error = expand_files(files, fd);
	460	if (error < 0)
	461	goto out;
	462
	463	/*
	464	* If we needed to expand the fs array we
	465	* might have blocked - try again.
	466	*/
	467	if (error)
	468	goto repeat;
	469
	470	if (start <= files->next_fd)
	471	files->next_fd = fd + 1;
	472
	473	FD_SET(fd, fdt->open_fds);
	474	if (flags & O_CLOEXEC)
	475	FD_SET(fd, fdt->close_on_exec);
	476	else
	477	FD_CLR(fd, fdt->close_on_exec);
	478	error = fd;
	479	#if 1
	480	/* Sanity check */
	481	if (rcu_dereference(fdt->fd[fd]) != NULL) {
	482	printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
	483	rcu_assign_pointer(fdt->fd[fd], NULL);
	484	}
	485	#endif
	486
	487	out:
	488	spin_unlock(&files->file_lock);
	489	return error;
	490	}
	491
	492	int get_unused_fd(void)
	493	{
	494	return alloc_fd(0, 0);
	495	}
	496	EXPORT_SYMBOL(get_unused_fd);