On Tue 06-02-07 15:50:01, Andrew Morton wrote:
> On Tue, 6 Feb 2007 14:23:33 +0100
> Christoph Hellwig <hch@xxxxxx> wrote:
>
> > static void add_dquot_ref(struct super_block *sb, int type)
> > {
> > - struct list_head *p;
> > + struct inode *inode;
> >
> > restart:
> > - file_list_lock();
> > - list_for_each(p, &sb->s_files) {
> > - struct file *filp = list_entry(p, struct file, f_u.fu_list);
> > - struct inode *inode = filp->f_path.dentry->d_inode;
> > - if (filp->f_mode & FMODE_WRITE && dqinit_needed(inode, type)) {
> > - struct dentry *dentry = dget(filp->f_path.dentry);
> > - file_list_unlock();
> > - sb->dq_op->initialize(inode, type);
> > - dput(dentry);
> > - /* As we may have blocked we had better restart... */
> > - goto restart;
> > - }
> > + spin_lock(&inode_lock);
> > + list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
> > + if (!atomic_read(&inode->i_writecount))
> > + continue;
> > + if (!dqinit_needed(inode, type))
> > + continue;
> > + if (inode->i_state & (I_FREEING|I_WILL_FREE))
> > + continue;
> > +
> > + __iget(inode);
> > + spin_unlock(&inode_lock);
> > +
> > + sb->dq_op->initialize(inode, type);
> > + iput(inode);
> > + /* As we may have blocked we had better restart... */
> > + goto restart;
> > }
> > - file_list_unlock();
> > + spin_unlock(&inode_lock);
> > }
>
> That loop has (and had) up to O(n^n) operations. Is there something which
> prevents this from going insane?
Huh, I guess you meant O(n^2)... Yes, I know about this but as Christoph
pointed out, the loop runs only when quotaon is called on a filesystem and for
inodes somebody writes to. Usually, there are not so many such inodes. So
I'm not sure it's worth the trouble to fix this.
Honza
--
Jan Kara <jack@xxxxxxx>
SuSE CR Labs
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