From: Christoph Hellwig <hch@lst.de>
To: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Christoph Hellwig <hch@lst.de>,
linux-xfs@vger.kernel.org, axboe@fb.com,
linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org
Subject: Re: [PATCH 5/6] iomap: implement direct I/O
Date: Wed, 26 Oct 2016 09:44:43 +0200 [thread overview]
Message-ID: <20161026074443.GA28408@lst.de> (raw)
In-Reply-To: <20161025171329.2txmbsgdnvn5vinn@kmo-pixel>
On Tue, Oct 25, 2016 at 09:13:29AM -0800, Kent Overstreet wrote:
> Also - what are you doing about the race between shooting down the range in the
> pagecache and dirty pages being readded? The existing direct IO code falls back
> to buffered IO for that, but your code doesn't appear to - I seem to recall that
> XFS has its own locking for this, are you just relying on that for now? It'd be
> really nice to get some generic locking for this, anything that relies on
> pagecache invalidation is sketchy as hell in other filesystems.
Yes, XFS always had a shared/exclusive lock for I/O operations,
which is taken exclusive for buffered writes and those corner cases
of direct writes that needs exclusіon (e.g. sub-fs block size I/O).
This prevents new dirty pages from being added while direct I/O is
in progress. There is nothing to prevent direct reads, though - that's
why both the old common code, the old XFS code and this new code do
a second invalidation after the write is done.
Now that the VFS i_mutex has been replaced with i_rwsem we can apply
this scheme to common code as well by taking i_rwsem shared for
direct I/O reads.
next prev parent reply other threads:[~2016-10-26 7:44 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-25 15:08 Christoph Hellwig
2016-10-25 15:08 ` [PATCH 1/6] locking/lockdep: Provide a type check for lock_is_held Christoph Hellwig
2016-10-25 15:08 ` [PATCH 2/6] xfs: remove i_iolock and use i_rwsem in the VFS inode instead Christoph Hellwig
2016-10-25 15:08 ` [PATCH 3/6] block: add bio_iov_iter_get_pages() Christoph Hellwig
2016-10-25 15:08 ` [PATCH 4/6] fs: make sb_init_dio_done_wq available outside of direct-io.c Christoph Hellwig
2016-10-25 15:08 ` [PATCH 5/6] iomap: implement direct I/O Christoph Hellwig
2016-10-25 15:31 ` Kent Overstreet
2016-10-25 16:34 ` Christoph Hellwig
2016-10-25 17:13 ` Kent Overstreet
2016-10-26 7:44 ` Christoph Hellwig [this message]
2016-10-25 19:51 ` Kent Overstreet
2016-10-26 7:57 ` Christoph Hellwig
2016-10-26 13:53 ` Bob Peterson
2016-10-26 14:02 ` Christoph Hellwig
2016-10-25 15:08 ` [PATCH 6/6] xfs: use iomap_dio_rw Christoph Hellwig
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