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Message-ID: <20110427184756.GB16716@parisc-linux.org>
Date: Wed, 27 Apr 2011 12:47:56 -0600
From: Matthew Wilcox <matthew@....cx>
To: Mike Frysinger <vapier@...too.org>
Cc: Andrea Righi <andrea@...terlinux.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dave Chinner <david@...morbit.com>,
Al Viro <viro@...iv.linux.org.uk>,
Arnd Bergmann <arnd@...db.de>, linux-fsdevel@...r.kernel.org,
linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] fadvise: introduce POSIX_FADV_DONTNEED_FS
On Wed, Apr 27, 2011 at 02:39:53PM -0400, Mike Frysinger wrote:
> > Mmm ... what if I open /dev/sdxyz and call fadvise() on it? ??I think
> > you end up flushing /dev's page cache entries, instead of the filesystem
> > which is on /dev/sdxyz.
>
> i was thinking of that, but was trying to come up with situations
> where there might not have a node to work on. fs's in a file go
> through loop devs, dm/lvm have ones created, and flash fs's still have
> a mtd block. how about network based fs's ? how you going to signal
> dropping of pages for nfs or cifs or fuse ones ?
For a regular file, mapping->host->i_sb points to the superblock this
file is on. For a device, mapping->host->i_sb points to the superblock
corresponding to this device. So it's always what we want.
(hm, what about block devices not currently mounted? do we need to check
whether mapping->host is NULL?)
--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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