linux-kernel - Re: O_NONBLOCK with Ext3

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Date:	Fri, 11 Jun 2010 14:56:30 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	"Yedire\, Sandeep" <syedire@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: O_NONBLOCK with Ext3

"Yedire, Sandeep" <syedire@...il.com> writes:

> Hi ALL,
> I am currently using o_nonblock flag for writing a file of 64MB over a
> flash device. Flash is formatted with ext3 filesystem with default
> options.
> When instrumented the driver code for collecting the erase/write count
> at sector level. I noticed that o_nonblock has no effect on this
> count. There is no difference in erase/write count with o_nonblock
> flag or without this flag.
> When selected Ext2 as filesystem I noticed a significant difference in
> the erase/write count.
> There were more updates with o_nonblock and test application was
> faster. I could confirm this by checking the Dirty page limit in the
> background. It was updating faster in case of Ext2 not incase of Ext3.
>
> Can any one explain on o_nonblock flag in case of  Ext3 filesystem?

The O_NONBLOCK flag should be ignored when opening files on a file
system.  I'm not sure how to explain your observations.

What exactly were you trying to accomplish?

Cheers,
Jeff
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