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From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [Lsf] IO less throttling and cgroup aware writeback
Date: Thu, 7 Apr 2011 16:33:03 -0400
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Cc: Dave Chinner <david@fromorbit.com>,
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To: Vivek Goyal <vgoyal@redhat.com>
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On Thu, Apr 07, 2011 at 03:24:24PM -0400, Vivek Goyal wrote:
> IIUC, so first we need to fix existing code where we seem to be moving
> any inode on bdi writeback list based on I_DIRTY flag.

I_DIRTY is a set of flags.  Inodes are on the dirty list if any of
the flags is set.

> BTW, what's the difference between I_DIRTY_DATASYNC and I_DIRTY_PAGES? To
> me both seem to mean that data needs to be written back and not the
> inode itself.

I_DIRTY_PAGES means dirty data (pages)
I_DIRTY_DATASYNC means dirty metadata which needs to be written for fdatasync
I_DIRTY_SYNC means dirty metadata which only needs to be written for fsync