linux-kernel - Re: [PATCH v3 01/14] x86, uaccess: introduce copy_from_iter_flushcache for pmem / cache-bypass operations

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Date:   Sun, 18 Jun 2017 10:28:41 +0200
From:   Christoph Hellwig <hch@....de>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     linux-nvdimm@...ts.01.org, Jan Kara <jack@...e.cz>,
        dm-devel@...hat.com, Toshi Kani <toshi.kani@....com>,
        Matthew Wilcox <mawilcox@...rosoft.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, hch@....de,
        Jeff Moyer <jmoyer@...hat.com>, Ingo Molnar <mingo@...hat.com>,
        viro@...iv.linux.org.uk, "H. Peter Anvin" <hpa@...or.com>,
        linux-fsdevel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH v3 01/14] x86, uaccess: introduce
        copy_from_iter_flushcache for pmem / cache-bypass operations

On Fri, Jun 09, 2017 at 01:23:51PM -0700, Dan Williams wrote:
> Implement a __copy_from_user_inatomic_flushcache, memcpy_page_flushcache, and
> memcpy_flushcache, that guarantee that the destination buffer is not dirty in
> the cpu cache on completion. The new copy_from_iter_flushcache and sub-routines

Wouldn't writethrough be a better name?

> will be used to replace the "pmem api" (include/linux/pmem.h +
> arch/x86/include/asm/pmem.h). The availability of copy_from_iter_flushcache()
> and memcpy_flushcache() are gated by the CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
> config symbol, and fallback to copy_from_iter_nocache() and plain memcpy()
> otherwise.

What is UACCESS about memcpy_flushcache?