/*

* 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/mmzone.h>

#include <linux/time.h>

#include <linux/sched.h>

#include <linux/slab.h>

#include <linux/vmalloc.h>

#include <linux/file.h>

#include <linux/security.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 {

};

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 void *alloc_fdmem(unsigned int size)

{

/*

* Very large allocations can stress page reclaim, so fall back to

* vmalloc() if the allocation size will be considered "large" by the VM.

*/

if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) {

void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN);

if (data != NULL)

return data;

}

return vmalloc(size);

}

static void free_fdmem(void *ptr)

{

is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr);

}

static void __free_fdtable(struct fdtable *fdt)

{

free_fdmem(fdt->fd);

free_fdmem(fdt->open_fds);

kfree(fdt);

}

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;

__free_fdtable(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 (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) {

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;

fdt->next = NULL;

return fdt;

out_arr:

free_fdmem(fdt->fd);

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_fdtable(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_fdtable(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.

*/

gr_learn_resource(current, RLIMIT_NOFILE, nr, 0);

if (nr >= rlimit(RLIMIT_NOFILE))

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];

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_fdtable(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_fdtable(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,

},

.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_raw(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);