linux-kernel - RE: [PATCH RFC] introduce ioctl to completely invalidate page cache

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Date:	Fri, 3 Oct 2014 09:25:34 +0000
From:	Thanos Makatos <thanos.makatos@...rix.com>
To:	'Jens Axboe' <axboe@...nel.dk>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
	"jlayton@...chiereds.net" <jlayton@...chiereds.net>,
	"bfields@...ldses.org" <bfields@...ldses.org>,
	"jack@...e.cz" <jack@...e.cz>
Subject: RE: [PATCH RFC] introduce ioctl to completely invalidate page cache

> > -		fsync_bdev(bdev);
> > -		invalidate_bdev(bdev);
> > +		flush_buffer_cache(bdev);
> > +		if (BLKFLSBUF2 == cmd)
> > +			return invalidate_inode_pages2(
> > +					bdev->bd_inode->i_mapping);
> >  		return 0;
> 
> We're currently ignoring the buffer cache sync and invalidation (which is odd),
> but at least being consistent would be good.
> 
> Might also need a filemap_write_and_wait() to sync before invalidation.

(I've got zero knowledge in this area, so excuse my ignorance!)

Does filemap_write_and_wait() writes back modified, memory-mapped pages? If so, isn't there a race condition? Or have I got it completely wrong?
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