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

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Date:	Thu, 9 Feb 2012 13:06:35 -0500
From:	Christoph Hellwig <hch@...radead.org>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Dave Chinner <david@...morbit.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Jens Axboe <axboe@...nel.dk>, Li Shaohua <shaohua.li@...el.com>
Subject: Re: [PATCH] block: remove plugging at buffered write time

On Thu, Feb 09, 2012 at 04:02:24PM +0800, Wu Fengguang wrote:
> On Thu, Feb 09, 2012 at 10:27:19AM +1100, Dave Chinner wrote:
> > On Wed, Feb 08, 2012 at 07:01:44PM +0800, Wu Fengguang wrote:
> > > Buffered write(2) is not directly tied to IO, so it's not suitable to
> > > handle plug in generic_file_aio_write().
> > 
> > But generic_sync_write() does issue IO for O_SYNC writes, so unless
> > there is plugging at a lower layer in the writeback code then it
> > appears to me that plugging is still necessary (at least inside the
> > sync branch)....
> 
> Good catch! It looks that generic_write_sync() eventually calls into
> vfs_fsync_range() which further calls ->fsync(). We may add plugging
> around it:


NAK, please keep the plugging down in the fs, or the libraries used but
not common VFS code.

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