[PATCH] mm/hmm: hmm_range_fault handle pages swapped out

[Yang, Philip]

On 2019-08-15 8:54 p.m., Jason Gunthorpe wrote:
> On Thu, Aug 15, 2019 at 08:52:56PM +0000, Yang, Philip wrote:
>> hmm_range_fault may return NULL pages because some of pfns are equal to
>> HMM_PFN_NONE. This happens randomly under memory pressure. The reason is
>> for swapped out page pte path, hmm_vma_handle_pte doesn't update fault
>> variable from cpu_flags, so it failed to call hmm_vam_do_fault to swap
>> the page in.
>>
>> The fix is to call hmm_pte_need_fault to update fault variable.
> 
>> Change-Id: I2e8611485563d11d938881c18b7935fa1e7c91ee
> 
> I'll fix it for you but please be careful not to send Change-id's to
> the public lists.
> 
Thanks, the change-id was added by our Gerrit hook, I need generate 
patch files, remove change-id line and then send out modified patch 
files in future.

> Also what is the Fixes line for this?
> 
This fixes the issue found by the internal rocrtst, the 
rocrtstFunc.Memory_Max_Mem evicted some user buffers, and then following 
test restore those user buffers failed because the buffers are swapped 
out and application doesn't touch the buffers to swap it in.

>> Signed-off-by: Philip Yang <Philip.Yang at amd.com>
>>   mm/hmm.c | 3 +++
>>   1 file changed, 3 insertions(+)
> 
> Ralph has also been looking at this area also so I'll give him a bit
> to chime in, otherwise with Jerome's review this looks OK to go to
> linux-next
>
Ok, thanks for helping push this to hmm branch at 
https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git

> Thanks,
> Jason
>