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Date: Fri, 13 Nov 2015 16:20:39 -0800 From: Dan Williams <dan.j.williams@...el.com> To: Ross Zwisler <ross.zwisler@...ux.intel.com> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>, "J. Bruce Fields" <bfields@...ldses.org>, "Theodore Ts'o" <tytso@....edu>, Alexander Viro <viro@...iv.linux.org.uk>, Andreas Dilger <adilger.kernel@...ger.ca>, Dave Chinner <david@...morbit.com>, Ingo Molnar <mingo@...hat.com>, Jan Kara <jack@...e.com>, Jeff Layton <jlayton@...chiereds.net>, Matthew Wilcox <willy@...ux.intel.com>, Thomas Gleixner <tglx@...utronix.de>, linux-ext4@...r.kernel.org, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Linux MM <linux-mm@...ck.org>, "linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>, X86 ML <x86@...nel.org>, xfs@....sgi.com, Andrew Morton <akpm@...ux-foundation.org>, Matthew Wilcox <matthew.r.wilcox@...el.com>, Dave Hansen <dave.hansen@...ux.intel.com> Subject: Re: [PATCH v2 03/11] pmem: enable REQ_FUA/REQ_FLUSH handling On Fri, Nov 13, 2015 at 4:06 PM, Ross Zwisler <ross.zwisler@...ux.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@...ux.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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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