Re: [patch 03/22] fix deadlock in balance_dirty_pages

[Andrew Morton <akpm@linux-foundation.org>]

On Thu, 01 Mar 2007 09:37:06 +0100 Miklos Szeredi <miklos@szeredi.hu> wrote:

> > Sigh.  What's this about i_mutex?  That appears to be some critical
> > information which _still_ isn't being communicated.
> > 
> 
> This:
> 
> ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
> 		unsigned long nr_segs, loff_t pos)
> {
> 	struct file *file = iocb->ki_filp;
> 	struct address_space *mapping = file->f_mapping;
> 	struct inode *inode = mapping->host;
> 	ssize_t ret;
> 
> 	BUG_ON(iocb->ki_pos != pos);
> 
> 	mutex_lock(&inode->i_mutex);
> 	ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs,
> 			&iocb->ki_pos);
> 	mutex_unlock(&inode->i_mutex);
> 
> 
> It's in the stack trace.  I thought it was obvious.

No, it is not obvious.

I'm just not going to apply weird hacks to work around a bug which
I do not understand, and I have spent way too much time trying to understand
this one.

So let us persist.

Please fully describe the role of i_mutex in this hang.