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Date:   Thu, 15 Oct 2020 12:38:26 +0100
From:   Matthew Wilcox <willy@infradead.org>
To:     "Darrick J. Wong" <darrick.wong@oracle.com>
Cc:     akpm@linux-foundation.org, viro@zeniv.linux.org.uk,
        torvalds@linux-foundation.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH 1/2] vfs: move generic_remap_checks out of mm
Message-ID: <20201015113826.GX20115@casper.infradead.org>
References: <160272187483.913987.4254237066433242737.stgit@magnolia>
 <160272188127.913987.8729718777463390497.stgit@magnolia>
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On Wed, Oct 14, 2020 at 05:31:21PM -0700, Darrick J. Wong wrote:
> I would like to move all the generic helpers for the vfs remap range
> functionality (aka clonerange and dedupe) into a separate file so that
> they won't be scattered across the vfs and the mm subsystems.  The
> eventual goal is to be able to deselect remap_range.c if none of the
> filesystems need that code, but the tricky part here is picking a
> stable(ish) part of the merge window to rearrange code.

This makes sense to me.  There's nothing page-cache about this function.

> diff --git a/mm/filemap.c b/mm/filemap.c
> index 99c49eeae71b..cf20e5aeb11b 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3098,8 +3098,7 @@ EXPORT_SYMBOL(read_cache_page_gfp);
>   * LFS limits.  If pos is under the limit it becomes a short access.  If it
>   * exceeds the limit we return -EFBIG.
>   */
> -static int generic_write_check_limits(struct file *file, loff_t pos,
> -				      loff_t *count)
> +int generic_write_check_limits(struct file *file, loff_t pos, loff_t *count)
>  {
>  	struct inode *inode = file->f_mapping->host;
>  	loff_t max_size = inode->i_sb->s_maxbytes;

I wonder if generic_write_check_limits should be in fs/read_write.c --
it has nothing to do with the pagecache either.