root/fs/file_table.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/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/eventpoll.h>
#include <linux/mount.h>
#include <linux/cdev.h>

#include <asm/callgate.h>
/* sysctl tunables... */
struct files_stat_struct files_stat = {
        .max_files = NR_FILE
};

EXPORT_SYMBOL(files_stat); /* Needed by unix.o */

/* public *and* exported. Not pretty! */
spinlock_t __cacheline_aligned_in_smp files_lock = SPIN_LOCK_UNLOCKED;

EXPORT_SYMBOL(files_lock);

static spinlock_t filp_count_lock = SPIN_LOCK_UNLOCKED;

/* slab constructors and destructors are called from arbitrary
 * context and must be fully threaded - use a local spinlock
 * to protect files_stat.nr_files
 */
void filp_ctor(void * objp, struct kmem_cache_s *cachep, unsigned long cflags)
{
        if ((cflags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
            SLAB_CTOR_CONSTRUCTOR) {
                unsigned long flags;
                spin_lock_irqsave(&filp_count_lock, flags);
                files_stat.nr_files++;
                spin_unlock_irqrestore(&filp_count_lock, flags);
        }
}

void filp_dtor(void * objp, struct kmem_cache_s *cachep, unsigned long dflags)
{
        unsigned long flags;
        spin_lock_irqsave(&filp_count_lock, flags);
        files_stat.nr_files--;
        spin_unlock_irqrestore(&filp_count_lock, flags);
}

static inline void file_free(struct file *f)
{
        kmem_cache_free(filp_cachep, f);
}

/* 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.
 */
struct file *get_empty_filp(void)
{
static int old_max;
        struct file * f;

        /*
         * Privileged users can go above max_files
         */
        if (files_stat.nr_files < files_stat.max_files ||
                                capable(CAP_SYS_ADMIN)) {
                f = kmem_cache_alloc(filp_cachep, GFP_KERNEL);
                if (f) {
                        memset(f, 0, sizeof(*f));
                        if (security_file_alloc(f)) {
                                file_free(f);
                                goto fail;
                        }
                        eventpoll_init_file(f);
                        atomic_set(&f->f_count, 1);
                        f->f_uid = current->fsuid;
                        f->f_gid = current->fsgid;
                        f->f_owner.lock = RW_LOCK_UNLOCKED;
                        /* f->f_version: 0 */
                        INIT_LIST_HEAD(&f->f_list);
                        return f;
                }
        }

        /* Ran out of filps - report that */
        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;
        } else {
                /* Big problems... */
                printk(KERN_WARNING "VFS: filp allocation failed\n");
        }
fail:
        return NULL;
}

EXPORT_SYMBOL(get_empty_filp);

/*
 * Clear and initialize a (private) struct file for the given dentry,
 * allocate the security structure, and call the open function (if any).  
 * The file should be released using close_private_file.
 */
int open_private_file(struct file *filp, struct dentry *dentry, int flags)
{
        int error;
        memset(filp, 0, sizeof(*filp));
        eventpoll_init_file(filp);
        filp->f_flags  = flags;
        filp->f_mode   = (flags+1) & O_ACCMODE;
        atomic_set(&filp->f_count, 1);
        filp->f_dentry = dentry;
        filp->f_mapping = dentry->d_inode->i_mapping;
        filp->f_uid    = current->fsuid;
        filp->f_gid    = current->fsgid;
        filp->f_op     = dentry->d_inode->i_fop;
        INIT_LIST_HEAD(&filp->f_list);
        error = security_file_alloc(filp);
        if (!error)
                if (filp->f_op && filp->f_op->open) {
                        error = filp->f_op->open(dentry->d_inode, filp);
                        if (error)
                                security_file_free(filp);
                }
        return error;
}

EXPORT_SYMBOL(open_private_file);

/*
 * Release a private file by calling the release function (if any) and
 * freeing the security structure.
 */
void close_private_file(struct file *file)
{
        struct inode * inode = file->f_dentry->d_inode;

        if (file->f_op && file->f_op->release) {
      if ((unsigned long) file->f_op->release > PAGE_OFFSET)
          file->f_op->release(inode, file);
      else {
          CALLDRIVER_PREP2(rel, inode, file)
          calldriver((unsigned long) file->f_op->release, rel_args, rel_sizes, 2, current->mm, 3, 0);
      }
  }
        security_file_free(file);
}

EXPORT_SYMBOL(close_private_file);

void fastcall fput(struct file *file)
{
        if (atomic_dec_and_test(&file->f_count))
                __fput(file);
}

EXPORT_SYMBOL(fput);

/* __fput is called from task context when aio completion releases the last
 * last use of a struct file *.  Do not use otherwise.
 */
void fastcall __fput(struct file *file)
{
        struct dentry *dentry = file->f_dentry;
        struct vfsmount *mnt = file->f_vfsmnt;
        struct inode *inode = dentry->d_inode;

        /*
         * The function eventpoll_release() should be the first called
         * in the file cleanup chain.
         */
        eventpoll_release(file);
        locks_remove_flock(file);

        if (file->f_op && file->f_op->release) {
      if ((unsigned long) file->f_op->release > PAGE_OFFSET) 
          file->f_op->release(inode, file);
      else {
          CALLDRIVER_PREP2(rel, inode, file)
          calldriver((unsigned long) file->f_op->release, rel_args, rel_sizes, 2, current->mm, 3, 0);
      }
  }
        security_file_free(file);
        if (unlikely(inode->i_cdev != NULL))
                cdev_put(inode->i_cdev);
        fops_put(file->f_op);
        if (file->f_mode & FMODE_WRITE)
                put_write_access(inode);
        file_kill(file);
        file->f_dentry = NULL;
        file->f_vfsmnt = NULL;
        file_free(file);
        dput(dentry);
        mntput(mnt);
}

struct file fastcall *fget(unsigned int fd)
{
        struct file *file;
        struct files_struct *files = current->files;

        spin_lock(&files->file_lock);
        file = fcheck_files(files, fd);
        if (file)
                get_file(file);
        spin_unlock(&files->file_lock);
        return file;
}

EXPORT_SYMBOL(fget);

/*
 * Lightweight file lookup - no refcnt increment if fd table isn't shared. 
 * You can use this only if it is guranteed that the current task already 
 * holds a refcnt to that file. That check has to be done at fget() only
 * and a flag is returned to be passed to the corresponding fput_light().
 * There must not be a cloning between an fget_light/fput_light pair.
 */
struct file fastcall *fget_light(unsigned int fd, int *fput_needed)
{
        struct file *file;
        struct files_struct *files = current->files;

        *fput_needed = 0;
        if (likely((atomic_read(&files->count) == 1))) {
                file = fcheck_files(files, fd);
        } else {
                spin_lock(&files->file_lock);
                file = fcheck_files(files, fd);
                if (file) {
                        get_file(file);
                        *fput_needed = 1;
                }
                spin_unlock(&files->file_lock);
        }
        return file;
}


void put_filp(struct file *file)
{
        if (atomic_dec_and_test(&file->f_count)) {
                security_file_free(file);
                file_kill(file);
                file_free(file);
        }
}

EXPORT_SYMBOL(put_filp);

void file_move(struct file *file, struct list_head *list)
{
        if (!list)
                return;
        file_list_lock();
        list_move(&file->f_list, list);
        file_list_unlock();
}

void file_kill(struct file *file)
{
        if (!list_empty(&file->f_list)) {
                file_list_lock();
                list_del_init(&file->f_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();
        list_for_each(p, &sb->s_files) {
                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;

                /* Writeable 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;
}

void __init files_init(unsigned long mempages)
{ 
        int n; 
        /* 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 = n; 
        if (files_stat.max_files < NR_FILE)
                files_stat.max_files = NR_FILE;
}