Initial import of modified Linux 2.6.28 tree

Original upstream URL:
git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git | branch linux-2.6.28.y

1 files changed, 410 insertions, 0 deletions

diff --git a/fs/file_table.c b/fs/file_table.c
new file mode 100644
index 0000000..5ad0eca
--- /dev/null
+++ b/fs/file_table.c
@@ -0,0 +1,410 @@
+/*
+ *  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/percpu_counter.h>
+
+#include <asm/atomic.h>
+
+/* sysctl tunables... */
+struct files_stat_struct files_stat = {
+	.max_files = NR_FILE
+};
+
+/* public. Not pretty! */
+__cacheline_aligned_in_smp DEFINE_SPINLOCK(files_lock);
+
+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);
+	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 int get_nr_files(void)
+{
+	return percpu_counter_read_positive(&nr_files);
+}
+
+/*
+ * Return the maximum number of open files in the system
+ */
+int 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, struct file *filp,
+                     void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	files_stat.nr_files = get_nr_files();
+	return proc_dointvec(table, write, filp, buffer, lenp, ppos);
+}
+#else
+int proc_nr_files(ctl_table *table, int write, struct file *filp,
+                     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)
+{
+	struct task_struct *tsk;
+	static int 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);
+	if (security_file_alloc(f))
+		goto fail_sec;
+
+	tsk = current;
+	INIT_LIST_HEAD(&f->f_u.fu_list);
+	atomic_long_set(&f->f_count, 1);
+	rwlock_init(&f->f_owner.lock);
+	f->f_uid = tsk->fsuid;
+	f->f_gid = tsk->fsgid;
+	eventpoll_init_file(f);
+	/* f->f_version: 0 */
+	return f;
+
+over:
+	/* Ran out of filps - report that */
+	if (get_nr_files() > old_max) {
+		printk(KERN_INFO "VFS: file-max limit %d reached\n",
+					get_max_files());
+		old_max = get_nr_files();
+	}
+	goto fail;
+
+fail_sec:
+	file_free(f);
+fail:
+	return NULL;
+}
+
+EXPORT_SYMBOL(get_empty_filp);
+
+/**
+ * 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 vfsmount *mnt, struct dentry *dentry,
+		fmode_t mode, const struct file_operations *fop)
+{
+	struct file *file;
+	struct path;
+
+	file = get_empty_filp();
+	if (!file)
+		return NULL;
+
+	init_file(file, mnt, dentry, mode, fop);
+	return file;
+}
+EXPORT_SYMBOL(alloc_file);
+
+/**
+ * init_file - initialize a 'struct file'
+ * @file: the already allocated 'struct file' to initialized
+ * @mnt: the vfsmount on which the file resides
+ * @dentry: the dentry representing this file
+ * @mode: the mode the file is opened with
+ * @fop: the 'struct file_operations' for this file
+ *
+ * Use this instead of setting the members directly.  Doing so
+ * avoids making mistakes like forgetting the mntget() or
+ * forgetting to take a write on the mnt.
+ *
+ * Note: This is a crappy interface.  It is here to make
+ * merging with the existing users of get_empty_filp()
+ * who have complex failure logic easier.  All users
+ * of this should be moving to alloc_file().
+ */
+int init_file(struct file *file, struct vfsmount *mnt, struct dentry *dentry,
+	   fmode_t mode, const struct file_operations *fop)
+{
+	int error = 0;
+	file->f_path.dentry = dentry;
+	file->f_path.mnt = mntget(mnt);
+	file->f_mapping = 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(dentry->d_inode->i_mode)) {
+		file_take_write(file);
+		error = mnt_want_write(mnt);
+		WARN_ON(error);
+	}
+	return error;
+}
+EXPORT_SYMBOL(init_file);
+
+void fput(struct file *file)
+{
+	if (atomic_long_dec_and_test(&file->f_count))
+		__fput(file);
+}
+
+EXPORT_SYMBOL(fput);
+
+/**
+ * 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.
+ */
+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);
+}
+EXPORT_SYMBOL_GPL(drop_file_write_access);
+
+/* __fput is called from task context when aio completion releases the last
+ * last use of a struct file *.  Do not use otherwise.
+ */
+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);
+	if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL))
+		cdev_put(inode->i_cdev);
+	fops_put(file->f_op);
+	put_pid(file->f_owner.pid);
+	file_kill(file);
+	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);
+}
+
+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) {
+		if (!atomic_long_inc_not_zero(&file->f_count)) {
+			/* File object ref couldn't be taken */
+			rcu_read_unlock();
+			return NULL;
+		}
+	}
+	rcu_read_unlock();
+
+	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 *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 {
+		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_kill(file);
+		file_free(file);
+	}
+}
+
+void file_move(struct file *file, struct list_head *list)
+{
+	if (!list)
+		return;
+	file_list_lock();
+	list_move(&file->f_u.fu_list, list);
+	file_list_unlock();
+}
+
+void file_kill(struct file *file)
+{
+	if (!list_empty(&file->f_u.fu_list)) {
+		file_list_lock();
+		list_del_init(&file->f_u.fu_list);
+		file_list_unlock();
+	}
+}
+
+int fs_may_remount_ro(struct super_block *sb)
+{
+	struct file *file;
+
+	/* Check that no files are currently opened for writing. */
+	file_list_lock();
+	list_for_each_entry(file, &sb->s_files, f_u.fu_list) {
+		struct inode *inode = file->f_path.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;
+	files_defer_init();
+	percpu_counter_init(&nr_files, 0);
+}