Viewing file:  file_table.c (4.36 KB) -rw-r--r--
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/*
* 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/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/iobuf.h>
/* sysctl tunables... */
struct files_stat_struct files_stat = {0, 0, NR_FILE};
/* Here the new files go */
static LIST_HEAD(anon_list);
/* And here the free ones sit */
static LIST_HEAD(free_list);
/* public *and* exported. Not pretty! */
spinlock_t files_lock = SPIN_LOCK_UNLOCKED;
/* 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.
*
* SMP-safe.
*/
struct file * get_empty_filp(void)
{
static int old_max = 0;
struct file * f;
file_list_lock();
if (files_stat.nr_free_files > NR_RESERVED_FILES) {
used_one:
f = list_entry(free_list.next, struct file, f_list);
list_del(&f->f_list);
files_stat.nr_free_files--;
new_one:
memset(f, 0, sizeof(*f));
atomic_set(&f->f_count,1);
f->f_version = ++event;
f->f_uid = current->fsuid;
f->f_gid = current->fsgid;
list_add(&f->f_list, &anon_list);
file_list_unlock();
return f;
}
/*
* Use a reserved one if we're the superuser
*/
if (files_stat.nr_free_files && !current->euid)
goto used_one;
/*
* Allocate a new one if we're below the limit.
*/
if (files_stat.nr_files < files_stat.max_files) {
file_list_unlock();
f = kmem_cache_alloc(filp_cachep, SLAB_KERNEL);
file_list_lock();
if (f) {
files_stat.nr_files++;
goto new_one;
}
/* Big problems... */
printk(KERN_WARNING "VFS: filp allocation failed\n");
} else if (files_stat.max_files > old_max) {
printk(KERN_INFO "VFS: file-max limit %d reached\n", files_stat.max_files);
old_max = files_stat.max_files;
}
file_list_unlock();
return NULL;
}
/*
* Clear and initialize a (private) struct file for the given dentry,
* and call the open function (if any). The caller must verify that
* inode->i_fop is not NULL.
*/
int init_private_file(struct file *filp, struct dentry *dentry, int mode)
{
memset(filp, 0, sizeof(*filp));
filp->f_mode = mode;
atomic_set(&filp->f_count, 1);
filp->f_dentry = dentry;
filp->f_uid = current->fsuid;
filp->f_gid = current->fsgid;
filp->f_op = dentry->d_inode->i_fop;
if (filp->f_op->open)
return filp->f_op->open(dentry->d_inode, filp);
else
return 0;
}
void fput(struct file * file)
{
struct dentry * dentry = file->f_dentry;
struct vfsmount * mnt = file->f_vfsmnt;
struct inode * inode = dentry->d_inode;
if (atomic_dec_and_test(&file->f_count)) {
locks_remove_flock(file);
if (file->f_iobuf)
free_kiovec(1, &file->f_iobuf);
if (file->f_op && file->f_op->release)
file->f_op->release(inode, file);
fops_put(file->f_op);
if (file->f_mode & FMODE_WRITE)
put_write_access(inode);
file_list_lock();
file->f_dentry = NULL;
file->f_vfsmnt = NULL;
list_del(&file->f_list);
list_add(&file->f_list, &free_list);
files_stat.nr_free_files++;
file_list_unlock();
dput(dentry);
mntput(mnt);
}
}
struct file * fget(unsigned int fd)
{
struct file * file;
struct files_struct *files = current->files;
read_lock(&files->file_lock);
file = fcheck(fd);
if (file)
get_file(file);
read_unlock(&files->file_lock);
return file;
}
/* Here. put_filp() is SMP-safe now. */
void put_filp(struct file *file)
{
if(atomic_dec_and_test(&file->f_count)) {
file_list_lock();
list_del(&file->f_list);
list_add(&file->f_list, &free_list);
files_stat.nr_free_files++;
file_list_unlock();
}
}
void file_move(struct file *file, struct list_head *list)
{
if (!list)
return;
file_list_lock();
list_del(&file->f_list);
list_add(&file->f_list, list);
file_list_unlock();
}
int fs_may_remount_ro(struct super_block *sb)
{
struct list_head *p;
/* Check that no files are currently opened for writing. */
file_list_lock();
for (p = sb->s_files.next; p != &sb->s_files; p = p->next) {
struct file *file = list_entry(p, struct file, f_list);
struct inode *inode = file->f_dentry->d_inode;
/* File with pending delete? */
if (inode->i_nlink == 0)
goto too_bad;
/* Writable file? */
if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
goto too_bad;
}
file_list_unlock();
return 1; /* Tis' cool bro. */
too_bad:
file_list_unlock();
return 0;
}
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