Messages in this thread | | | Date | Tue, 23 Dec 2014 01:37:10 -0800 | From | Christoph Hellwig <> | Subject | Re: [PATCH 2/8] swap: lock i_mutex for swap_writepage direct_IO |
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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.
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