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Date: Mon, 30 Dec 2013 11:18:15 -0800
From: Dave Hansen <dave.hansen@intel.com>
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To: Li Wang <liwang@ubuntukylin.com>, Alexander Viro <viro@zeniv.linux.org.uk>
CC: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Cong Wang <xiyou.wangcong@gmail.com>, Zefan Li <lizefan@huawei.com>,
        Matthew Wilcox <matthew@wil.cx>
Subject: Re: [PATCH 0/3] Fadvise: Directory level page cache cleaning support
References: <cover.1388409686.git.liwang@ubuntukylin.com>
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On 12/30/2013 05:45 AM, Li Wang wrote:
> This patch extends 'fadvise' to support directory level page cache
> cleaning. The call to posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED) 
> with 'fd' referring to a directory will recursively reclaim page cache 
> entries of files inside 'fd'. For secruity concern, those inodes
> which the caller does not own appropriate permissions will not 
> be manipulated.

Why is this necessary to do in the kernel?  Why not leave it to
userspace to walk the filesystem(s)?