Re: 2.6.33.3-rt16 Oops caused by umount

[Xianghua Xiao]

On Wed, Apr 28, 2010 at 4:46 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> On Wed, 28 Apr 2010, Xianghua Xiao wrote:
>> On Wed, Apr 28, 2010 at 3:22 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>> >
>> > Can you please decode the code lines with
>> >
>> > # addr2line -e vmlinux 0xc009ca1c 0xc009c9cc
>> >
>> > You need to enable CONFIG_DEBUG_INFO to get real line numbers.
>>
>> # reboot
>> # Oops: Kernel access of bad area, sig: 11 [#1]
>> PREEMPT 834x SYS
>> Modules linked in:
>> NIP: c009ded8 LR: c009de88 CTR: 00000000
>
> Again. Can you please decode the code lines with
>
> # addr2line -e vmlinux 0xc009ded8 0xc009de88
>
> Please run the above shell command in the directory where your kernel
> compile output resides. If you compiled with O=BUILD_DIR then cd to
> $BUILD_DIR otherwise you will find vmlinux in the root of your kernel
> source tree. Please provide the output.
>
> Thanks,
>
> Â Â Â Âtglx
>

here it is, just in case I also attached the source file related:
addr2line -e vmlinux c009ded8   c009de88
/home/xxiao/xxiao/linux-2.6.33.3/fs/file_table.c:436
/home/xxiao/xxiao/linux-2.6.33.3/fs/file_table.c:440

thanks,
/*
 *  linux/fs/file_table.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Copyright (C) 1997 David S. Miller (davem@xxxxxxxxxxxxxxxx)
 */

#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 <linux/ima.h>
#include <linux/percpu.h>

#include <asm/atomic.h>

#include "internal.h"

/* sysctl tunables... */
struct files_stat_struct files_stat = {
	.max_files = NR_FILE
};

static DEFINE_PER_CPU(spinlock_t, files_cpulock);

/* 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 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,
                     void __user *buffer, size_t *lenp, loff_t *ppos)
{
	files_stat.nr_files = get_nr_files();
	return proc_dointvec(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 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;

	INIT_LIST_HEAD(&f->f_u.fu_list);
	atomic_long_set(&f->f_count, 1);
	rwlock_init(&f->f_owner.lock);
	f->f_cred = get_cred(cred);
	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) {
		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;
}

/**
 * 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));
	}
	ima_counts_get(file);
	return file;
}
EXPORT_SYMBOL(alloc_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);
	ima_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_sb_list_del(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_sb_list_del(file);
		file_free(file);
	}
}

void file_sb_list_add(struct file *file, struct super_block *sb)
{
	spinlock_t *lock;
	struct list_head *list;
#ifdef CONFIG_SMP
	int cpu;
#endif

	lock = &get_cpu_var(files_cpulock);
#ifdef CONFIG_SMP
	cpu = smp_processor_id();
	list = per_cpu_ptr(sb->s_files, cpu);
	file->f_sb_list_cpu = cpu;
#else
	list = &sb->s_files;
#endif
	put_cpu_var(files_cpulock);
	spin_lock(lock);
	BUG_ON(!list_empty(&file->f_u.fu_list));
	list_add(&file->f_u.fu_list, list);
	spin_unlock(lock);
}

void file_sb_list_del(struct file *file)
{
	if (!list_empty(&file->f_u.fu_list)) {
		spinlock_t *lock;

#ifdef CONFIG_SMP
		lock = &per_cpu(files_cpulock, file->f_sb_list_cpu);
#else
		lock = &__get_cpu_var(files_cpulock);
#endif
		spin_lock(lock);
		list_del_init(&file->f_u.fu_list);
		spin_unlock(lock);
	}
}

static void file_list_lock_all(void)
{
	int i;
	int nr = 0;

	for_each_possible_cpu(i) {
		spinlock_t *lock;

		lock = &per_cpu(files_cpulock, i);
		spin_lock_nested(lock, nr);
		nr++;
	}
}

static void file_list_unlock_all(void)
{
	int i;

	for_each_possible_cpu(i) {
		spinlock_t *lock;

		lock = &per_cpu(files_cpulock, i);
		spin_unlock(lock);
	}
}

int fs_may_remount_ro(struct super_block *sb)
{
	int i;

	/* Check that no files are currently opened for writing. */
	file_list_lock_all();
	for_each_possible_cpu(i) {
		struct file *file;
		struct list_head *list;

#ifdef CONFIG_SMP
		list = per_cpu_ptr(sb->s_files, i);
#else
		list = &sb->s_files;
#endif
		list_for_each_entry(file, list, f_u.fu_list) {
                       struct inode *inode;

                       if (!(&(file->f_path))) {
                               printk(KERN_ERR "file %p fpath == NULL\n",
                                      file);
                               continue;
                       }

                       if (!file->f_path.dentry) {
                               printk(KERN_ERR "file %p dentry == NULL\n",
                                      file);
                               continue;
                       }

                       if (!file->f_path.dentry->d_inode) {
                              printk(KERN_ERR "file %p d_inode == NULL\n",
                                      file);
                               continue;
                       }

                       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_all();
	return 1; /* Tis' cool bro. */
too_bad:
	file_list_unlock_all();
	return 0;
}

/**
 *	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)
{
	int i;

retry:
	file_list_lock_all();
	for_each_possible_cpu(i) {
		struct file *f;
		struct list_head *list;

#ifdef CONFIG_SMP
		list = per_cpu_ptr(sb->s_files, i);
#else
		list = &sb->s_files;
#endif
		list_for_each_entry(f, list, f_u.fu_list) {
			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. */
			file_list_unlock_all();
			mnt_drop_write(mnt);
			mntput(mnt);
			goto retry;
		}
	}
	file_list_unlock_all();
}

void __init files_init(unsigned long mempages)
{ 
	int n; 
	int i;

	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 = n; 
	if (files_stat.max_files < NR_FILE)
		files_stat.max_files = NR_FILE;
	files_defer_init();
	for_each_possible_cpu(i)
		spin_lock_init(&per_cpu(files_cpulock, i));
	percpu_counter_init(&nr_files, 0);
}