On Mon, Dec 15, 2014 at 02:51:11PM -0800, Andrew Morton wrote:
> From: Weiwei Wang <wangww...@huawei.com>
> Subject: ocfs2: eliminate the static flag of some functions
>
> Currently in case of append O_DIRECT write (block not allocated yet),
> ocfs2 will fall back to buffered I/O. This has some disadvantages.
> Firstly, it is not the behavior as expected.
>
> Secondly, it will consume huge page cache, e.g. in mass backup scenario.
> Thirdly, modern filesystems such as ext4 support this feature.
>
> In this patch set, the direct I/O write doesn't fallback to buffer I/O
> write any more because the allocate blocks are enabled in direct I/O now.
Thanks for taking this task on Weiwei - it's not an easy one!
I have one comment right off the bat - since we're changing how things work
on disk (in particular, the orphan handling), we'll have to gate this on a
feature flag. Otherwise, we risk corrupting if an older FS loads the newer
format. I would suggest adding a readonly feature flag and moving as much of
the fallback code into it's own set of functions to be used when the flag is
not set.
--Mark
--
Mark Fasheh
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