Date: Mon, 21 Mar 2016 08:38:27 -0700
From: Christoph Hellwig <hch@infradead.org>
To: "Darrick J. Wong" <darrick.wong@oracle.com>
Cc: axboe@kernel.dk, torvalds@linux-foundation.org, bfields@fieldses.org,
        tytso@mit.edu, martin.petersen@oracle.com, linux-api@vger.kernel.org,
        david@fromorbit.com, linux-kernel@vger.kernel.org,
        shane.seymour@hpe.com, hch@infradead.org,
        linux-fsdevel@vger.kernel.org, jlayton@poochiereds.net,
        akpm@linux-foundation.org
Subject: Re: [PATCH 3/3] block: implement (some of) fallocate for block
 devices
Message-ID: <20160321153827.GA27230@infradead.org>
References: <20160315194221.30093.70506.stgit@birch.djwong.org>
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On Tue, Mar 15, 2016 at 12:42:44PM -0700, Darrick J. Wong wrote:
>  #include <linux/cleancache.h>
>  #include <linux/dax.h>
>  #include <asm/uaccess.h>
> +#include <linux/falloc.h>

Maybe keep this before asm/uaccess.h

> +long blkdev_fallocate(struct file *file, int mode, loff_t start, loff_t len)

should be marked static.

> +	/* We haven't a primitive for "ensure space exists" right now. */
> +	if (!(mode & ~FALLOC_FL_KEEP_SIZE))
> +		return -EOPNOTSUPP;

I don't really understand the comment.  But I think you'd be much
better off with having blkdev_fallocate as just a tiny wrapper that has
a switch for the supported modes, e.g.

	switch (mode) {
	case FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE:
		return blkdev_punch_hole();
	case FALLOC_FL_ZERO_RANGE | FALLOC_FL_KEEP_SIZE::
		return blkdev_zero_range();
	default:
		return -EOPNOTSUPP;
	}

> +EXPORT_SYMBOL_GPL(blkdev_fallocate);

and no need to export it either..