lkml.org 
[lkml]   [2019]   [Apr]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v12 23/31] mm: don't do swap readahead during speculative page fault
From
Date
Le 22/04/2019 à 23:36, Jerome Glisse a écrit :
> On Tue, Apr 16, 2019 at 03:45:14PM +0200, Laurent Dufour wrote:
>> Vinayak Menon faced a panic because one thread was page faulting a page in
>> swap, while another one was mprotecting a part of the VMA leading to a VMA
>> split.
>> This raise a panic in swap_vma_readahead() because the VMA's boundaries
>> were not more matching the faulting address.
>>
>> To avoid this, if the page is not found in the swap, the speculative page
>> fault is aborted to retry a regular page fault.
>>
>> Reported-by: Vinayak Menon <vinmenon@codeaurora.org>
>> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
>
> Reviewed-by: Jérôme Glisse <jglisse@redhat.com>
>
> Note that you should also skip non swap entry in do_swap_page() when doing
> speculative page fault at very least you need to is_device_private_entry()
> case.
>
> But this should either be part of patch 22 or another patch to fix swap
> case.

Thanks Jérôme,

Yes I missed that, I guess the best option would be to abort on non swap
entry. I'll add that in the patch 22.

>> ---
>> mm/memory.c | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 6e6bf61c0e5c..1991da97e2db 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -2900,6 +2900,17 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>> lru_cache_add_anon(page);
>> swap_readpage(page, true);
>> }
>> + } else if (vmf->flags & FAULT_FLAG_SPECULATIVE) {
>> + /*
>> + * Don't try readahead during a speculative page fault
>> + * as the VMA's boundaries may change in our back.
>> + * If the page is not in the swap cache and synchronous
>> + * read is disabled, fall back to the regular page
>> + * fault mechanism.
>> + */
>> + delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
>> + ret = VM_FAULT_RETRY;
>> + goto out;
>> } else {
>> page = swapin_readahead(entry, GFP_HIGHUSER_MOVABLE,
>> vmf);
>> --
>> 2.21.0
>>
>

\
 
 \ /
  Last update: 2019-04-24 16:58    [W:0.105 / U:0.376 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site