linux-kernel - Re: [PATCH V5 1/2] FS: Add generic data flush to fsync

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Message-Id: <20140514204304.94b0703f593626c2ea6f9465@skynet.be>
Date:	Wed, 14 May 2014 20:43:04 +0200
From:	Fabian Frederick <fabf@...net.be>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>, jack <jack@...e.cz>,
	hch <hch@...radead.org>, Viro <viro@...iv.linux.org.uk>,
	tytso <tytso@....edu>
Subject: Re: [PATCH V5 1/2] FS: Add generic data flush to fsync

On Mon, 12 May 2014 14:50:27 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Mon, 12 May 2014 07:20:27 +0200 Fabian Frederick <fabf@...net.be> wrote:
> 
> > This patch issues a flush in generic_file_fsync.
> > (Modern filesystems already do it)
> > 
> > Behaviour can be reversed using /sys/devices/.../cache_type
> > or by calling __generic_file_fsync
> 
> Well OK, but why?  What effect does the patch have?  Does it make the
> kernel better and if so, how?
> 
> >
> > +/**
> > + * generic_file_fsync - generic fsync implementation for simple filesystems
> > + *			with flush
> > + * @file:	file to synchronize
> > + * @start:	start offset in bytes
> > + * @end:	end offset in bytes (inclusive)
> > + * @datasync:	only synchronize essential metadata if true
> > + *
> > + */
> > +
> > +int generic_file_fsync(struct file *file, loff_t start, loff_t end,
> > +		       int datasync)
> > +{
> > +	struct inode *inode = file->f_mapping->host;
> > +	int err;
> > +
> > +	err = __generic_file_fsync(file, start, end, datasync);
> > +	if (err)
> > +		return err;
> > +
> > +	return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
> > +
> > +}
> 
> Documentation/SubmitChecklist, section 2b ;)

Hi Andrew,

   As Jan suggested, I can resubmit patches with #ifdef CONFIG_BLOCK around
blkdev_issue_flush and further description. Do you see something else ?

Thanks,
Fabian

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