On Tue, Feb 7, 2017 at 8:49 PM, Xiong Zhou <xzhou(a)redhat.com> wrote:
On Tue, Feb 07, 2017 at 08:10:14PM -0800, Dan Williams wrote:
> On Tue, Feb 7, 2017 at 7:51 PM, Xiong Zhou <xzhou(a)redhat.com> wrote:
> > On Fri, Jan 20, 2017 at 12:40:07PM +0800, Xiong Zhou wrote:
> >> Hi,
> >> At first, I am not sure whether this is an issue.
> >> mmap a file in a DAX mountpoint, open another file
> >> in a non-DAX mountpoint with O_DIRECT, write the
> >> mapped area to the other file.
> >> This write Success on pmem ramdisk(memmap=2G!20G like)
> >> This write Fail(Bad address) on nvdimm pmem devices.
> >> This write Fail(Bad address) on brd based ramdisk.
> >> If we skip the O_DIRECT flag, all tests pass.
> >> If we write from DAX to DAX, all tests pass.
> >> If we write from non-DAX to DAX, all tests pass.
> > snip..
> > To falloc instead of pwrite while initiating test files,
> > ( Thanks Ross! :)
> > the write call returned success, however the following
> > read back to mmaped area FAILED the same way:
> > return (Bad address) on raw-mode nvdimm device;
> > return (Success) on memory-mode nvdimm device;
> > return (Bad address) on brd based ramdisk.
> > Also, this only happends with O_DIRECT flag on.
> > This smells like an issue to me, still looking into why
> > read can't get that page..
> Why does it smell like an issue? Any path that calls get_user_pages()
Because the write call gets its page and succeeds, while read back fails.
__get_user_pages on the same address first pass, then fail.
Ok, I might have misread your description. Can you tell me the exact
reproduction steps so I can give it a try?