linux-kernel - Re: [PATCH v2 2/4] mm: add file_fdatawait_range and file_write_and

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Message-ID: <20170727084914.GC21100@quack2.suse.cz>
Date:   Thu, 27 Jul 2017 10:49:14 +0200
From:   Jan Kara <jack@...e.cz>
To:     Jeff Layton <jlayton@...nel.org>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Matthew Wilcox <willy@...radead.org>,
        Bob Peterson <rpeterso@...hat.com>,
        Steven Whitehouse <swhiteho@...hat.com>,
        cluster-devel@...hat.com
Subject: Re: [PATCH v2 2/4] mm: add file_fdatawait_range and
 file_write_and_wait

On Wed 26-07-17 13:55:36, Jeff Layton wrote:
> +int file_write_and_wait(struct file *file)
> +{
> +	int err = 0, err2;
> +	struct address_space *mapping = file->f_mapping;
> +
> +	if ((!dax_mapping(mapping) && mapping->nrpages) ||
> +	    (dax_mapping(mapping) && mapping->nrexceptional)) {
> +		err = filemap_fdatawrite(mapping);
> +		/* See comment of filemap_write_and_wait() */
> +		if (err != -EIO) {
> +			loff_t i_size = i_size_read(mapping->host);
> +
> +			if (i_size != 0)
> +				__filemap_fdatawait_range(mapping, 0,
> +							  i_size - 1);
> +		}
> +	}

Err, what's the i_size check doing here? I'd just pass ~0 as the end of the
range and ignore i_size. It is much easier than trying to wrap your head
around possible races with file operations modifying i_size.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR