Ocfs2 devel - Apr 2016 - OCFS2 cache coherent quesiton

Hi OCFS2 experts,

According to OCFS2 user guide, OCFS2 supports cache consistency, which means one
node writes to shared disk while another node can get the newest data just
written.

I am working hard on OCFS2 kernel code. I am confused that OCFS2 also adopts
page cache provided by Linux Kernel, however, page cache does not know anything
about other nodes in cluster.

Well, my question is that if data is cached by page cache in one node, how could
another node read the newest data from it? At this scenario, the page cache is
dirty and the disk data is old. How OCFS2 can support cache consistency?

Thanks,

Best regards.


Gechangwei
H3C Technologies Co., Limited


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Hello Changwei,

You can take a look at dlm_lock related code, dlm_lock callback functions will
handle how to make other nodes' certain inode page cache invalidate. Or,
force the writing page cache to disk before read the data from other nodes.


Thanks
Gang

>>> 
> Hi OCFS2 experts,
> 
> According to OCFS2 user guide, OCFS2 supports cache consistency, which
means
> one node writes to shared disk while another node can get the newest data 
> just written.
> 
> I am working hard on OCFS2 kernel code. I am confused that OCFS2 also
adopts
> page cache provided by Linux Kernel, however, page cache does not know 
> anything about other nodes in cluster.
> 
> Well, my question is that if data is cached by page cache in one node, how 
> could another node read the newest data from it? At this scenario, the page
> cache is dirty and the disk data is old. How OCFS2 can support cache 
> consistency?
> 
> Thanks,
> 
> Best regards.
> 
> 
> Gechangwei
> H3C Technologies Co., Limited
> 
> 
>
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> ---------------------------------------------------------
> ????????????????????????????????????????
> ????????????????????????????????????????
> ????????????????????????????????????????
> ???
> This e-mail and its attachments contain confidential information from H3C, 
> which is
> intended only for the person or entity whose address is listed above. Any 
> use of the
> information contained herein in any way (including, but not limited to, 
> total or partial
> disclosure, reproduction, or dissemination) by persons other than the 
> intended
> recipient(s) is prohibited. If you receive this e-mail in error, please 
> notify the sender
> by phone or email immediately and delete it!