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Re: Re: Re: Delivered state of DMAPI Event

To: xfs@xxxxxxxxxxx
Subject: Re: Re: Re: Delivered state of DMAPI Event
From: Dean Roehrich <dean.roehrich@xxxxxxx>
Date: Fri, 14 Jul 2006 11:04:49 -0500
In-reply-to: <bc5727090607132007w7e884c3cr3339eaf745ea5207@mail.gmail.com>
References: <bc5727090607132007w7e884c3cr3339eaf745ea5207@mail.gmail.com>
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On Fri, Jul 14, 2006 at 11:07:40AM +0800, Michael Li (Gmail) wrote:

> Or: No matther the event is outstanding or not, if it is read event and
> DMAPI enabled, it will cause a read process hang although the event will not
> be in delivered state(outstanding state)?

The state (new or delivered) doesn't matter.  The file had a dmapi event set
for that action so the filesystem deferred the thread to dmapi.  That thread
is now in the DMAPI module and, ultimately, the only mechanism to release it
from DMAPI and allow it to return to the filesystem is a call to
dm_respond_event.

You don't have a usable filesystem if there's no DM app responding to events.
You need to think in terms of making that app robust and keeping it running.
The people writing that DM app also need to be aware that through DMAPI their
app becomes a part of the filesystem's I/O path and they need to think
appropriately, given that context.

Dean


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