linux-kernel - Re: [RESEND][PATCH v2] block: remove plugging at buffered write time

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Message-ID: <x494nst7z3v.fsf@segfault.boston.devel.redhat.com>
Date:	Mon, 09 Apr 2012 10:34:44 -0400
From:	Jeff Moyer <jmoyer@...hat.com>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Chinner <david@...morbit.com>,
	Christoph Hellwig <hch@...radead.org>, Jan Kara <jack@...e.cz>,
	Chris Mason <chris.mason@...cle.com>,
	Shaohua Li <shli@...ionio.com>
Subject: Re: [RESEND][PATCH v2] block: remove plugging at buffered write time

Wu Fengguang <fengguang.wu@...el.com> writes:

> Buffered write(2) is not directly tied to IO, so it's not suitable to
> handle plug in generic_file_aio_write().
[snip, moved]
> Note that plugging for O_SYNC writes is also removed. The user may pass
> arbitrary @size arguments, which may be much larger than the preferable
> I/O size, or may cross extent/device boundaries. Let the lower layers
> handle the plugging. Otherwise the plugging code here will turn the
> low level plugging into no-ops.

I assume you have some numbers to back this up, right?  Care to share
those?

> Also moves unplugging for direct I/O from around ->direct_IO() down to
> do_blockdev_direct_IO().

This could be handled in a separate patch.  Acked-by: Jeff Moyer
<jmoyer@...hat.com> for this part.

Cheers,
Jeff
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