inode.c

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static struct tq_struct unused_inodes_flush_task;

/**
 *	write_inode_now	-	write an inode to disk
 *	@inode: inode to write to disk
 *	@sync: whether the write should be synchronous or not
 *
 *	This function commits an inode to disk immediately if it is
 *	dirty. This is primarily needed by knfsd.
 */
 
void write_inode_now(struct inode *inode, int sync)
{
	struct super_block * sb = inode->i_sb;

	if (sb) {
		spin_lock(&inode_lock);
		while (inode->i_state & I_DIRTY)
			sync_one(inode, sync);
		spin_unlock(&inode_lock);
		if (sync)
			wait_on_inode(inode);
	}
	else
		printk(KERN_ERR "write_inode_now: no super block\n");
}

/**
 * generic_osync_inode - flush all dirty data for a given inode to disk
 * @inode: inode to write
 * @datasync: if set, don't bother flushing timestamps
 *
 * This can be called by file_write functions for files which have the
 * O_SYNC flag set, to flush dirty writes to disk.  
 */

int generic_osync_inode(struct inode *inode, int what)
{
	int err = 0, err2 = 0, need_write_inode_now = 0;
	
	/* 
	 * WARNING
	 *
	 * Currently, the filesystem write path does not pass the
	 * filp down to the low-level write functions.  Therefore it
	 * is impossible for (say) __block_commit_write to know if
	 * the operation is O_SYNC or not.
	 *
	 * Ideally, O_SYNC writes would have the filesystem call
	 * ll_rw_block as it went to kick-start the writes, and we
	 * could call osync_inode_buffers() here to wait only for
	 * those IOs which have already been submitted to the device
	 * driver layer.  As it stands, if we did this we'd not write
	 * anything to disk since our writes have not been queued by
	 * this point: they are still on the dirty LRU.
	 * 
	 * So, currently we will call fsync_inode_buffers() instead,
	 * to flush _all_ dirty buffers for this inode to disk on 
	 * every O_SYNC write, not just the synchronous I/Os.  --sct
	 */

	if (what & OSYNC_METADATA)
		err = fsync_inode_buffers(inode);
	if (what & OSYNC_DATA)
		err2 = fsync_inode_data_buffers(inode);
	if (!err)
		err = err2;

	spin_lock(&inode_lock);
	if ((inode->i_state & I_DIRTY) &&
	    ((what & OSYNC_INODE) || (inode->i_state & I_DIRTY_DATASYNC)))
		need_write_inode_now = 1;
	spin_unlock(&inode_lock);

	if (need_write_inode_now)
		write_inode_now(inode, 1);
	else
		wait_on_inode(inode);

	return err;
}

/**
 * clear_inode - clear an inode
 * @inode: inode to clear
 *
 * This is called by the filesystem to tell us
 * that the inode is no longer useful. We just
 * terminate it with extreme prejudice.
 */
 
void clear_inode(struct inode *inode)
{
	invalidate_inode_buffers(inode);
       
	if (inode->i_data.nrpages)
		BUG();
	if (!(inode->i_state & I_FREEING))
		BUG();
	if (inode->i_state & I_CLEAR)
		BUG();
	wait_on_inode(inode);
	DQUOT_DROP(inode);
	if (inode->i_sb && inode->i_sb->s_op && inode->i_sb->s_op->clear_inode)
		inode->i_sb->s_op->clear_inode(inode);
	if (inode->i_bdev)
		bd_forget(inode);
	else if (inode->i_cdev) {
		cdput(inode->i_cdev);
		inode->i_cdev = NULL;
	}
	inode->i_state = I_CLEAR;
}

/*
 * Dispose-list gets a local list with local inodes in it, so it doesn't
 * need to worry about list corruption and SMP locks.
 */
static void dispose_list(struct list_head * head)
{
	struct list_head * inode_entry;
	struct inode * inode;

	while ((inode_entry = head->next) != head)
	{
		list_del(inode_entry);

		inode = list_entry(inode_entry, struct inode, i_list);
		if (inode->i_data.nrpages)
			truncate_inode_pages(&inode->i_data, 0);
		clear_inode(inode);
		destroy_inode(inode);
		inodes_stat.nr_inodes--;
	}
}

/*
 * Invalidate all inodes for a device.
 */
static int invalidate_list(struct list_head *head, struct super_block * sb, struct list_head * dispose)
{
	struct list_head *next;
	int busy = 0, count = 0;

	next = head->next;
	for (;;) {
		struct list_head * tmp = next;
		struct inode * inode;

		next = next->next;
		if (tmp == head)
			break;
		inode = list_entry(tmp, struct inode, i_list);
		if (inode->i_sb != sb)
			continue;
		invalidate_inode_buffers(inode);
		if (!atomic_read(&inode->i_count)) {
			list_del_init(&inode->i_hash);
			list_del(&inode->i_list);
			list_add(&inode->i_list, dispose);
			inode->i_state |= I_FREEING;
			count++;
			continue;
		}
		busy = 1;
	}
	/* only unused inodes may be cached with i_count zero */
	inodes_stat.nr_unused -= count;
	return busy;
}

/*
 * This is a two-stage process. First we collect all
 * offending inodes onto the throw-away list, and in
 * the second stage we actually dispose of them. This
 * is because we don't want to sleep while messing
 * with the global lists..
 */
 
/**
 *	invalidate_inodes	- discard the inodes on a device
 *	@sb: superblock
 *
 *	Discard all of the inodes for a given superblock. If the discard
 *	fails because there are busy inodes then a non zero value is returned.
 *	If the discard is successful all the inodes have been discarded.
 */
 
int invalidate_inodes(struct super_block * sb)
{
	int busy;
	LIST_HEAD(throw_away);

	spin_lock(&inode_lock);
	busy = invalidate_list(&inode_in_use, sb, &throw_away);
	busy |= invalidate_list(&inode_unused, sb, &throw_away);
	busy |= invalidate_list(&sb->s_dirty, sb, &throw_away);
	busy |= invalidate_list(&sb->s_locked_inodes, sb, &throw_away);
	spin_unlock(&inode_lock);

	dispose_list(&throw_away);

	return busy;
}
 
int invalidate_device(kdev_t dev, int do_sync)
{
	struct super_block *sb;
	int res;

	if (do_sync)
		fsync_dev(dev);

	res = 0;
	sb = get_super(dev);
	if (sb) {
		/*
		 * no need to lock the super, get_super holds the
		 * read semaphore so the filesystem cannot go away
		 * under us (->put_super runs with the write lock
		 * hold).
		 */
		shrink_dcache_sb(sb);
		res = invalidate_inodes(sb);
		drop_super(sb);
	}
	invalidate_buffers(dev);
	return res;
}


/*
 * This is called with the inode lock held. It searches
 * the in-use for freeable inodes, which are moved to a
 * temporary list and then placed on the unused list by
 * dispose_list. 
 *
 * We don't expect to have to call this very often.
 *
 * N.B. The spinlock is released during the call to
 *      dispose_list.
 */
#define CAN_UNUSE(inode) \
	((((inode)->i_state | (inode)->i_data.nrpages) == 0)  && \
	 !inode_has_buffers(inode))
#define INODE(entry)	(list_entry(entry, struct inode, i_list))

void prune_icache(int goal)
{
	LIST_HEAD(list);
	struct list_head *entry, *freeable = &list;
	int count;
	struct inode * inode;

	spin_lock(&inode_lock);

	count = 0;
	entry = inode_unused.prev;
	while (entry != &inode_unused)
	{
		struct list_head *tmp = entry;

		entry = entry->prev;
		inode = INODE(tmp);
		if (inode->i_state & (I_FREEING|I_CLEAR|I_LOCK))
			continue;
		if (!CAN_UNUSE(inode))
			continue;
		if (atomic_read(&inode->i_count))
			continue;
		list_del(tmp);
		list_del(&inode->i_hash);
		INIT_LIST_HEAD(&inode->i_hash);
		list_add(tmp, freeable);
		inode->i_state |= I_FREEING;
		count++;
		if (!--goal)
			break;
	}
	inodes_stat.nr_unused -= count;
	spin_unlock(&inode_lock);

	dispose_list(freeable);

	/* 
	 * If we didn't freed enough clean inodes schedule
	 * a sync of the dirty inodes, we cannot do it
	 * from here or we're either synchronously dogslow
	 * or we deadlock with oom.
	 */
	if (goal)
		schedule_task(&unused_inodes_flush_task);
}

int shrink_icache_memory(int priority, int gfp_mask)
{
	int count = 0;

	/*
	 * Nasty deadlock avoidance..
	 *
	 * We may hold various FS locks, and we don't
	 * want to recurse into the FS that called us
	 * in clear_inode() and friends..
	 */
	if (!(gfp_mask & __GFP_FS))
		return 0;

	count = inodes_stat.nr_unused / priority;

	prune_icache(count);
	kmem_cache_shrink(inode_cachep);
	return 0;
}

/*
 * Called with the inode lock held.
 * NOTE: we are not increasing the inode-refcount, you must call __iget()
 * by hand after calling find_inode now! This simplifies iunique and won't
 * add any additional branch in the common code.
 */
static struct inode * find_inode(struct super_block * sb, unsigned long ino, struct list_head *head, find_inode_t find_actor, void *opaque)
{
	struct list_head *tmp;
	struct inode * inode;

	tmp = head;
	for (;;) {
		tmp = tmp->next;
		inode = NULL;
		if (tmp == head)
			break;
		inode = list_entry(tmp, struct inode, i_hash);
		if (inode->i_ino != ino)
			continue;
		if (inode->i_sb != sb)
			continue;
		if (find_actor && !find_actor(inode, ino, opaque))
			continue;
		break;
	}
	return inode;
}

/*
 * This just initializes the inode fields
 * to known values before returning the inode..
 *
 * i_sb, i_ino, i_count, i_state and the lists have
 * been initialized elsewhere..
 */
static void clean_inode(struct inode *inode)
{
	static struct address_space_operations empty_aops;
	static struct inode_operations empty_iops;
	static struct file_operations empty_fops;
	memset(&inode->u, 0, sizeof(inode->u));
	inode->i_sock = 0;
	inode->i_op = &empty_iops;
	inode->i_fop = &empty_fops;
	inode->i_nlink = 1;
	atomic_set(&inode->i_writecount, 0);
	inode->i_size = 0;
	inode->i_blocks = 0;
	inode->i_generation = 0;
	memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
	inode->i_pipe = NULL;
	inode->i_bdev = NULL;
	inode->i_cdev = NULL;
	inode->i_data.a_ops = &empty_aops;
	inode->i_data.host = inode;
	inode->i_data.gfp_mask = GFP_HIGHUSER;
	inode->i_mapping = &inode->i_data;
}

/**
 * get_empty_inode 	- obtain an inode
 *
 * This is called by things like the networking layer
 * etc that want to get an inode without any inode
 * number, or filesystems that allocate new inodes with
 * no pre-existing information.
 *
 * On a successful return the inode pointer is returned. On a failure
 * a %NULL pointer is returned. The returned inode is not on any superblock
 * lists.
 */
 
struct inode * get_empty_inode(void)
{
	static unsigned long last_ino;
	struct inode * inode;

	spin_lock_prefetch(&inode_lock);
	
	inode = alloc_inode();
	if (inode)
	{
		spin_lock(&inode_lock);
		inodes_stat.nr_inodes++;
		list_add(&inode->i_list, &inode_in_use);
		inode->i_sb = NULL;
		inode->i_dev = 0;
		inode->i_blkbits = 0;
		inode->i_ino = ++last_ino;
		inode->i_flags = 0;
		atomic_set(&inode->i_count, 1);
		inode->i_state = 0;
		spin_unlock(&inode_lock);
		clean_inode(inode);
	}
	return inode;
}

/*
 * This is called without the inode lock held.. Be careful.