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From: Dan Williams <dan.j.williams@intel.com>
To: Mikulas Patocka <mpatocka@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
	Eric Sandeen <esandeen@redhat.com>,
	Dave Chinner <dchinner@redhat.com>,
	"Kani, Toshi" <toshi.kani@hpe.com>,
	"Norton, Scott J" <scott.norton@hpe.com>,
	"Tadakamadla,
	Rajesh (DCIG/CDI/HPS Perf)"  <rajesh.tadakamadla@hpe.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: [PATCH] pmem: fix __copy_user_flushcache
Date: Thu, 17 Sep 2020 18:53:41 -0700	[thread overview]
Message-ID: <CAPcyv4gFz6vBVVp_aiX4i2rL+8fps3gTQGj5cYw8QESCf7=DfQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.LRH.2.02.2009161451140.21915@file01.intranet.prod.int.rdu2.redhat.com>

On Wed, Sep 16, 2020 at 11:57 AM Mikulas Patocka <mpatocka@redhat.com> wrote:
>
>
>
> On Wed, 16 Sep 2020, Dan Williams wrote:
>
> > On Wed, Sep 16, 2020 at 10:24 AM Mikulas Patocka <mpatocka@redhat.com> wrote:
> > >
> > >
> > >
> > > On Wed, 16 Sep 2020, Dan Williams wrote:
> > >
> > > > On Wed, Sep 16, 2020 at 3:57 AM Mikulas Patocka <mpatocka@redhat.com> wrote:
> > > > >
> > > > >
> > > > >
> > > > > I'm submitting this patch that adds the required exports (so that we could
> > > > > use __copy_from_user_flushcache on x86, arm64 and powerpc). Please, queue
> > > > > it for the next merge window.
> > > >
> > > > Why? This should go with the first user, and it's not clear that it
> > > > needs to be relative to the current dax_operations export scheme.
> > >
> > > Before nvfs gets included in the kernel, I need to distribute it as a
> > > module. So, it would make my maintenance easier. But if you don't want to
> > > export it now, no problem, I can just copy __copy_user_flushcache from the
> > > kernel to the module.
> >
> > That sounds a better plan than exporting symbols with no in-kernel consumer.
>
> BTW, this function is buggy. Here I'm submitting the patch.
>
>
>
> From: Mikulas Patocka <mpatocka@redhat.com>
>
> If we copy less than 8 bytes and if the destination crosses a cache line,
> __copy_user_flushcache would invalidate only the first cache line. This
> patch makes it invalidate the second cache line as well.

Good catch.

> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
> Cc: stable@vger.kernel.org
>
> ---
>  arch/x86/lib/usercopy_64.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6/arch/x86/lib/usercopy_64.c
> ===================================================================
> --- linux-2.6.orig/arch/x86/lib/usercopy_64.c   2020-09-05 10:01:27.000000000 +0200
> +++ linux-2.6/arch/x86/lib/usercopy_64.c        2020-09-16 20:48:31.000000000 +0200
> @@ -120,7 +120,7 @@ long __copy_user_flushcache(void *dst, c
>          */
>         if (size < 8) {
>                 if (!IS_ALIGNED(dest, 4) || size != 4)
> -                       clean_cache_range(dst, 1);
> +                       clean_cache_range(dst, size);
>         } else {
>                 if (!IS_ALIGNED(dest, 8)) {
>                         dest = ALIGN(dest, boot_cpu_data.x86_clflush_size);
>

You can add:

Fixes: 0aed55af8834 ("x86, uaccess: introduce
copy_from_iter_flushcache for pmem / cache-bypass operations")
Reviewed-by: Dan Williams <dan.j.wiilliams@intel.com>

  reply	other threads:[~2020-09-18  1:53 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-15 12:34 [RFC] nvfs: a filesystem for persistent memory Mikulas Patocka
2020-09-15 13:00 ` Matthew Wilcox
2020-09-15 13:24   ` Mikulas Patocka
2020-09-22 10:04   ` Ritesh Harjani
2020-09-15 15:16 ` Dan Williams
2020-09-15 16:58   ` Mikulas Patocka
2020-09-15 17:38     ` Mikulas Patocka
2020-09-16 10:57       ` [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache Mikulas Patocka
2020-09-16 16:21         ` Dan Williams
2020-09-16 17:24           ` Mikulas Patocka
2020-09-16 17:40             ` Dan Williams
2020-09-16 18:06               ` Mikulas Patocka
2020-09-21 16:20                 ` NVFS XFS metadata (was: [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache) Mikulas Patocka
2020-09-22  5:03                   ` Dave Chinner
2020-09-22 16:46                     ` Mikulas Patocka
2020-09-22 17:25                       ` Matthew Wilcox
2020-09-24 15:00                         ` Mikulas Patocka
2020-09-28 15:22                           ` Mikulas Patocka
2020-09-23  2:45                       ` Dave Chinner
2020-09-23  9:20                         ` A bug in ext4 with big directories (was: NVFS XFS metadata) Mikulas Patocka
2020-09-23  9:44                           ` Jan Kara
2020-09-23 12:46                             ` Mikulas Patocka
2020-09-23 20:20                             ` Andreas Dilger
2020-09-23 17:19                         ` NVFS XFS metadata (was: [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache) Mikulas Patocka
2020-09-23  9:57                       ` Jan Kara
2020-09-23 13:11                         ` Mikulas Patocka
2020-09-23 15:04                           ` Matthew Wilcox
2020-09-22 12:28                   ` Matthew Wilcox
2020-09-22 12:39                     ` Mikulas Patocka
2020-09-16 18:56               ` [PATCH] pmem: fix __copy_user_flushcache Mikulas Patocka
2020-09-18  1:53                 ` Dan Williams [this message]
2020-09-18 12:25                   ` the "read" syscall sees partial effects of the "write" syscall Mikulas Patocka
2020-09-18 13:13                     ` Jan Kara
2020-09-18 18:02                       ` Linus Torvalds
2020-09-20 23:41                       ` Dave Chinner
2020-09-17  6:50               ` [PATCH] pmem: export the symbols __copy_user_flushcache and __copy_from_user_flushcache Christoph Hellwig
2020-09-21 16:19   ` [RFC] nvfs: a filesystem for persistent memory Mikulas Patocka
2020-09-21 16:29     ` Dan Williams
2020-09-22 15:43     ` Ira Weiny

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