Re: [Lsf] IO less throttling and cgroup aware writeback (Was: Re: Preliminary Agenda and Activities for LSF)

Jan Kara
2011-04-20T19:16:53Z

On Wed 20-04-11 14:44:33, Vivek Goyal wrote:
> Ok, will look into it. That will probably take care of READS. What
> about WRITES and meta data. Is it safe to assume that any meta data
> write will come in some jounalling thread context and not in user
> process context?
For ext3/4 it is a journal thread context or flusher thread context
because after metadata is written to journal by journal thread, they are
left as dirty buffers in page cache of the block device. So flusher thread
can come and write them - and these writes will hold buffer lock and thus
also block any manipulation with the metadata.

I don't know about other filesystems.

Honza
--
Jan Kara <jack@suse.cz>
SUSE Labs, CR