From: Christoph Hellwig <hch@infradead.org>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Jan Kara <jack@suse.cz>, Omar Sandoval <osandov@osandov.com>,
Andrew Morton <akpm@linux-foundation.org>,
Trond Myklebust <trond.myklebust@primarydata.com>,
David Sterba <dsterba@suse.cz>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/8] swap: lock i_mutex for swap_writepage direct_IO
Date: Tue, 23 Dec 2014 01:37:10 -0800 [thread overview]
Message-ID: <20141223093710.GA29096@infradead.org> (raw)
In-Reply-To: <20141220065133.GC22149@ZenIV.linux.org.uk>
On Sat, Dec 20, 2014 at 06:51:33AM +0000, Al Viro wrote:
> > The problem is that the use of ->direct_IO by the swap code is a gross
> > layering violation. ->direct_IO is a callback for the filesystem, and
> > the swap code need to call ->read_iter instead of ->readpage and
> > ->write_tier instead of ->direct_IO, and leave the locking to the
> > filesystem.
>
> The thing is, ->read_iter() and ->write_iter() might decide to fall back to
> buffered IO path. XFS is unusual in that respect - there O_DIRECT ends up
> with short write in such case. Other filesystems, OTOH...
We'll just need a ->swap_activate method that makes sure we really do
direct I/O. For all filesystems currently suporting swap just checking
that all blocks are allocated (as the ->bmap path already does) should
be enough.
next prev parent reply other threads:[~2014-12-23 9:37 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-15 5:26 [PATCH 0/8] clean up and generalize swap-over-NFS Omar Sandoval
2014-12-15 5:26 ` [PATCH 1/8] nfs: follow direct I/O write locking convention Omar Sandoval
2014-12-15 12:49 ` Trond Myklebust
2014-12-15 15:42 ` Omar Sandoval
2014-12-15 5:26 ` [PATCH 2/8] swap: lock i_mutex for swap_writepage direct_IO Omar Sandoval
2014-12-15 16:27 ` Jan Kara
2014-12-15 16:56 ` Christoph Hellwig
2014-12-15 22:11 ` Omar Sandoval
2014-12-16 8:35 ` Christoph Hellwig
2014-12-16 8:56 ` Omar Sandoval
2014-12-17 8:06 ` Christoph Hellwig
2014-12-17 8:20 ` Al Viro
2014-12-17 8:24 ` Christoph Hellwig
2014-12-17 14:58 ` Omar Sandoval
2014-12-17 18:52 ` Christoph Hellwig
2014-12-17 22:03 ` Al Viro
2014-12-19 6:24 ` Omar Sandoval
2014-12-19 6:28 ` Al Viro
2014-12-20 6:51 ` Al Viro
2014-12-22 7:26 ` Omar Sandoval
2014-12-23 9:37 ` Christoph Hellwig [this message]
2014-12-15 5:26 ` [PATCH 3/8] swap: don't add ITER_BVEC flag to direct_IO rw Omar Sandoval
2014-12-15 6:16 ` Al Viro
2014-12-15 15:57 ` Omar Sandoval
2014-12-15 5:26 ` [PATCH 4/8] iov_iter: add iov_iter_bvec and convert callers Omar Sandoval
2014-12-15 5:26 ` [PATCH 5/8] direct-io: don't dirty ITER_BVEC pages on read Omar Sandoval
2014-12-15 5:27 ` [PATCH 6/8] nfs: don't dirty ITER_BVEC pages read through direct I/O Omar Sandoval
2014-12-15 6:17 ` Al Viro
2014-12-15 5:27 ` [PATCH 7/8] swap: use direct I/O for SWP_FILE swap_readpage Omar Sandoval
2014-12-15 5:27 ` [PATCH 8/8] vfs: update swap_{,de}activate documentation Omar Sandoval
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