linux-kernel - Re: [RFC] nvfs: a filesystem for persistent memory

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Message-ID: <alpine.LRH.2.02.2009151332280.3851@file01.intranet.prod.int.rdu2.redhat.com>
Date:   Tue, 15 Sep 2020 13:38:09 -0400 (EDT)
From:   Mikulas Patocka <mpatocka@...hat.com>
To:     Dan Williams <dan.j.williams@...el.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
        Eric Sandeen <esandeen@...hat.com>,
        Dave Chinner <dchinner@...hat.com>,
        "Kani, Toshi" <toshi.kani@....com>,
        "Norton, Scott J" <scott.norton@....com>,
        "Tadakamadla, Rajesh (DCIG/CDI/HPS Perf)" 
        <rajesh.tadakamadla@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>
Subject: Re: [RFC] nvfs: a filesystem for persistent memory



On Tue, 15 Sep 2020, Mikulas Patocka wrote:

> > > - __copy_from_user_inatomic_nocache doesn't flush cache for leading and
> > > trailing bytes.
> > 
> > You want copy_user_flushcache(). See how fs/dax.c arranges for
> > dax_copy_from_iter() to route to pmem_copy_from_iter().
> 
> Is it something new for the kernel 5.10? I see only __copy_user_flushcache 
> that is implemented just for x86 and arm64.
> 
> There is __copy_from_user_flushcache implemented for x86, arm64 and power. 
> It is used in lib/iov_iter.c under
> #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE - so should I use this?
> 
> Mikulas

... and __copy_user_flushcache is not exported for modules. So, I am stuck 
with __copy_from_user_inatomic_nocache.

Mikulas