Messages in this thread | | | Date | Fri, 13 Nov 2015 16:20:39 -0800 | Subject | Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling | From | Dan Williams <> |
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On Fri, Nov 13, 2015 at 4:06 PM, Ross Zwisler <ross.zwisler@linux.intel.com> wrote: > Currently the PMEM driver doesn't accept REQ_FLUSH or REQ_FUA bios. These > are sent down via blkdev_issue_flush() in response to a fsync() or msync() > and are used by filesystems to order their metadata, among other things. > > When we get an msync() or fsync() it is the responsibility of the DAX code > to flush all dirty pages to media. The PMEM driver then just has issue a > wmb_pmem() in response to the REQ_FLUSH to ensure that before we return all > the flushed data has been durably stored on the media. > > Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Hmm, I'm not seeing why we need this patch. If the actual flushing of the cache is done by the core why does the driver need support REQ_FLUSH? Especially since it's just a couple instructions. REQ_FUA only makes sense if individual writes can bypass the "drive" cache, but no I/O submitted to the driver proper is ever cached we always flush it through to media.
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