linux/fs/file_table.c
Andi Kleen eea62f831b brlocks/lglocks: turn into functions
lglocks and brlocks are currently generated with some complicated macros
in lglock.h.  But there's no reason to not just use common utility
functions and put all the data into a common data structure.

Since there are at least two users it makes sense to share this code in a
library.  This is also easier maintainable than a macro forest.

This will also make it later possible to dynamically allocate lglocks and
also use them in modules (this would both still need some additional, but
now straightforward, code)

[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2012-05-29 23:28:41 -04:00

530 lines
13 KiB
C

/*
* linux/fs/file_table.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
* Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
*/
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/eventpoll.h>
#include <linux/rcupdate.h>
#include <linux/mount.h>
#include <linux/capability.h>
#include <linux/cdev.h>
#include <linux/fsnotify.h>
#include <linux/sysctl.h>
#include <linux/lglock.h>
#include <linux/percpu_counter.h>
#include <linux/percpu.h>
#include <linux/ima.h>
#include <linux/atomic.h>
#include "internal.h"
/* sysctl tunables... */
struct files_stat_struct files_stat = {
.max_files = NR_FILE
};
DEFINE_LGLOCK(files_lglock);
/* SLAB cache for file structures */
static struct kmem_cache *filp_cachep __read_mostly;
static struct percpu_counter nr_files __cacheline_aligned_in_smp;
static inline void file_free_rcu(struct rcu_head *head)
{
struct file *f = container_of(head, struct file, f_u.fu_rcuhead);
put_cred(f->f_cred);
kmem_cache_free(filp_cachep, f);
}
static inline void file_free(struct file *f)
{
percpu_counter_dec(&nr_files);
file_check_state(f);
call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
}
/*
* Return the total number of open files in the system
*/
static long get_nr_files(void)
{
return percpu_counter_read_positive(&nr_files);
}
/*
* Return the maximum number of open files in the system
*/
unsigned long get_max_files(void)
{
return files_stat.max_files;
}
EXPORT_SYMBOL_GPL(get_max_files);
/*
* Handle nr_files sysctl
*/
#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
int proc_nr_files(ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
files_stat.nr_files = get_nr_files();
return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
}
#else
int proc_nr_files(ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
return -ENOSYS;
}
#endif
/* Find an unused file structure and return a pointer to it.
* Returns NULL, if there are no more free file structures or
* we run out of memory.
*
* Be very careful using this. You are responsible for
* getting write access to any mount that you might assign
* to this filp, if it is opened for write. If this is not
* done, you will imbalance int the mount's writer count
* and a warning at __fput() time.
*/
struct file *get_empty_filp(void)
{
const struct cred *cred = current_cred();
static long old_max;
struct file * f;
/*
* Privileged users can go above max_files
*/
if (get_nr_files() >= files_stat.max_files && !capable(CAP_SYS_ADMIN)) {
/*
* percpu_counters are inaccurate. Do an expensive check before
* we go and fail.
*/
if (percpu_counter_sum_positive(&nr_files) >= files_stat.max_files)
goto over;
}
f = kmem_cache_zalloc(filp_cachep, GFP_KERNEL);
if (f == NULL)
goto fail;
percpu_counter_inc(&nr_files);
f->f_cred = get_cred(cred);
if (security_file_alloc(f))
goto fail_sec;
INIT_LIST_HEAD(&f->f_u.fu_list);
atomic_long_set(&f->f_count, 1);
rwlock_init(&f->f_owner.lock);
spin_lock_init(&f->f_lock);
eventpoll_init_file(f);
/* f->f_version: 0 */
return f;
over:
/* Ran out of filps - report that */
if (get_nr_files() > old_max) {
pr_info("VFS: file-max limit %lu reached\n", get_max_files());
old_max = get_nr_files();
}
goto fail;
fail_sec:
file_free(f);
fail:
return NULL;
}
/**
* alloc_file - allocate and initialize a 'struct file'
* @mnt: the vfsmount on which the file will reside
* @dentry: the dentry representing the new file
* @mode: the mode with which the new file will be opened
* @fop: the 'struct file_operations' for the new file
*
* Use this instead of get_empty_filp() to get a new
* 'struct file'. Do so because of the same initialization
* pitfalls reasons listed for init_file(). This is a
* preferred interface to using init_file().
*
* If all the callers of init_file() are eliminated, its
* code should be moved into this function.
*/
struct file *alloc_file(struct path *path, fmode_t mode,
const struct file_operations *fop)
{
struct file *file;
file = get_empty_filp();
if (!file)
return NULL;
file->f_path = *path;
file->f_mapping = path->dentry->d_inode->i_mapping;
file->f_mode = mode;
file->f_op = fop;
/*
* These mounts don't really matter in practice
* for r/o bind mounts. They aren't userspace-
* visible. We do this for consistency, and so
* that we can do debugging checks at __fput()
*/
if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
file_take_write(file);
WARN_ON(mnt_clone_write(path->mnt));
}
if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
i_readcount_inc(path->dentry->d_inode);
return file;
}
EXPORT_SYMBOL(alloc_file);
/**
* drop_file_write_access - give up ability to write to a file
* @file: the file to which we will stop writing
*
* This is a central place which will give up the ability
* to write to @file, along with access to write through
* its vfsmount.
*/
static void drop_file_write_access(struct file *file)
{
struct vfsmount *mnt = file->f_path.mnt;
struct dentry *dentry = file->f_path.dentry;
struct inode *inode = dentry->d_inode;
put_write_access(inode);
if (special_file(inode->i_mode))
return;
if (file_check_writeable(file) != 0)
return;
mnt_drop_write(mnt);
file_release_write(file);
}
/* the real guts of fput() - releasing the last reference to file
*/
static void __fput(struct file *file)
{
struct dentry *dentry = file->f_path.dentry;
struct vfsmount *mnt = file->f_path.mnt;
struct inode *inode = dentry->d_inode;
might_sleep();
fsnotify_close(file);
/*
* The function eventpoll_release() should be the first called
* in the file cleanup chain.
*/
eventpoll_release(file);
locks_remove_flock(file);
if (unlikely(file->f_flags & FASYNC)) {
if (file->f_op && file->f_op->fasync)
file->f_op->fasync(-1, file, 0);
}
if (file->f_op && file->f_op->release)
file->f_op->release(inode, file);
security_file_free(file);
ima_file_free(file);
if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
!(file->f_mode & FMODE_PATH))) {
cdev_put(inode->i_cdev);
}
fops_put(file->f_op);
put_pid(file->f_owner.pid);
file_sb_list_del(file);
if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
i_readcount_dec(inode);
if (file->f_mode & FMODE_WRITE)
drop_file_write_access(file);
file->f_path.dentry = NULL;
file->f_path.mnt = NULL;
file_free(file);
dput(dentry);
mntput(mnt);
}
void fput(struct file *file)
{
if (atomic_long_dec_and_test(&file->f_count))
__fput(file);
}
EXPORT_SYMBOL(fput);
struct file *fget(unsigned int fd)
{
struct file *file;
struct files_struct *files = current->files;
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
/* File object ref couldn't be taken */
if (file->f_mode & FMODE_PATH ||
!atomic_long_inc_not_zero(&file->f_count))
file = NULL;
}
rcu_read_unlock();
return file;
}
EXPORT_SYMBOL(fget);
struct file *fget_raw(unsigned int fd)
{
struct file *file;
struct files_struct *files = current->files;
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
/* File object ref couldn't be taken */
if (!atomic_long_inc_not_zero(&file->f_count))
file = NULL;
}
rcu_read_unlock();
return file;
}
EXPORT_SYMBOL(fget_raw);
/*
* Lightweight file lookup - no refcnt increment if fd table isn't shared.
*
* You can use this instead of fget if you satisfy all of the following
* conditions:
* 1) You must call fput_light before exiting the syscall and returning control
* to userspace (i.e. you cannot remember the returned struct file * after
* returning to userspace).
* 2) You must not call filp_close on the returned struct file * in between
* calls to fget_light and fput_light.
* 3) You must not clone the current task in between the calls to fget_light
* and fput_light.
*
* The fput_needed flag returned by fget_light should be passed to the
* corresponding fput_light.
*/
struct file *fget_light(unsigned int fd, int *fput_needed)
{
struct file *file;
struct files_struct *files = current->files;
*fput_needed = 0;
if (atomic_read(&files->count) == 1) {
file = fcheck_files(files, fd);
if (file && (file->f_mode & FMODE_PATH))
file = NULL;
} else {
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
if (!(file->f_mode & FMODE_PATH) &&
atomic_long_inc_not_zero(&file->f_count))
*fput_needed = 1;
else
/* Didn't get the reference, someone's freed */
file = NULL;
}
rcu_read_unlock();
}
return file;
}
struct file *fget_raw_light(unsigned int fd, int *fput_needed)
{
struct file *file;
struct files_struct *files = current->files;
*fput_needed = 0;
if (atomic_read(&files->count) == 1) {
file = fcheck_files(files, fd);
} else {
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
if (atomic_long_inc_not_zero(&file->f_count))
*fput_needed = 1;
else
/* Didn't get the reference, someone's freed */
file = NULL;
}
rcu_read_unlock();
}
return file;
}
void put_filp(struct file *file)
{
if (atomic_long_dec_and_test(&file->f_count)) {
security_file_free(file);
file_sb_list_del(file);
file_free(file);
}
}
static inline int file_list_cpu(struct file *file)
{
#ifdef CONFIG_SMP
return file->f_sb_list_cpu;
#else
return smp_processor_id();
#endif
}
/* helper for file_sb_list_add to reduce ifdefs */
static inline void __file_sb_list_add(struct file *file, struct super_block *sb)
{
struct list_head *list;
#ifdef CONFIG_SMP
int cpu;
cpu = smp_processor_id();
file->f_sb_list_cpu = cpu;
list = per_cpu_ptr(sb->s_files, cpu);
#else
list = &sb->s_files;
#endif
list_add(&file->f_u.fu_list, list);
}
/**
* file_sb_list_add - add a file to the sb's file list
* @file: file to add
* @sb: sb to add it to
*
* Use this function to associate a file with the superblock of the inode it
* refers to.
*/
void file_sb_list_add(struct file *file, struct super_block *sb)
{
lg_local_lock(files_lglock);
__file_sb_list_add(file, sb);
lg_local_unlock(files_lglock);
}
/**
* file_sb_list_del - remove a file from the sb's file list
* @file: file to remove
* @sb: sb to remove it from
*
* Use this function to remove a file from its superblock.
*/
void file_sb_list_del(struct file *file)
{
if (!list_empty(&file->f_u.fu_list)) {
lg_local_lock_cpu(files_lglock, file_list_cpu(file));
list_del_init(&file->f_u.fu_list);
lg_local_unlock_cpu(files_lglock, file_list_cpu(file));
}
}
#ifdef CONFIG_SMP
/*
* These macros iterate all files on all CPUs for a given superblock.
* files_lglock must be held globally.
*/
#define do_file_list_for_each_entry(__sb, __file) \
{ \
int i; \
for_each_possible_cpu(i) { \
struct list_head *list; \
list = per_cpu_ptr((__sb)->s_files, i); \
list_for_each_entry((__file), list, f_u.fu_list)
#define while_file_list_for_each_entry \
} \
}
#else
#define do_file_list_for_each_entry(__sb, __file) \
{ \
struct list_head *list; \
list = &(sb)->s_files; \
list_for_each_entry((__file), list, f_u.fu_list)
#define while_file_list_for_each_entry \
}
#endif
/**
* mark_files_ro - mark all files read-only
* @sb: superblock in question
*
* All files are marked read-only. We don't care about pending
* delete files so this should be used in 'force' mode only.
*/
void mark_files_ro(struct super_block *sb)
{
struct file *f;
retry:
lg_global_lock(files_lglock);
do_file_list_for_each_entry(sb, f) {
struct vfsmount *mnt;
if (!S_ISREG(f->f_path.dentry->d_inode->i_mode))
continue;
if (!file_count(f))
continue;
if (!(f->f_mode & FMODE_WRITE))
continue;
spin_lock(&f->f_lock);
f->f_mode &= ~FMODE_WRITE;
spin_unlock(&f->f_lock);
if (file_check_writeable(f) != 0)
continue;
file_release_write(f);
mnt = mntget(f->f_path.mnt);
/* This can sleep, so we can't hold the spinlock. */
lg_global_unlock(files_lglock);
mnt_drop_write(mnt);
mntput(mnt);
goto retry;
} while_file_list_for_each_entry;
lg_global_unlock(files_lglock);
}
void __init files_init(unsigned long mempages)
{
unsigned long n;
filp_cachep = kmem_cache_create("filp", sizeof(struct file), 0,
SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
/*
* One file with associated inode and dcache is very roughly 1K.
* Per default don't use more than 10% of our memory for files.
*/
n = (mempages * (PAGE_SIZE / 1024)) / 10;
files_stat.max_files = max_t(unsigned long, n, NR_FILE);
files_defer_init();
lg_lock_init(files_lglock);
percpu_counter_init(&nr_files, 0);
}