On 2018/01/28 10:16, Tetsuo Handa wrote:
> Linus Torvalds wrote:
>> On Sat, Jan 27, 2018 at 2:24 PM, Dave Jones <davej@xxxxxxxxxxxxxxxxx> wrote:
>>> On Tue, Jan 23, 2018 at 08:36:51PM -0500, Dave Jones wrote:
>>> > Just triggered this on a server I was rsync'ing to.
>>>
>>> Actually, I can trigger this really easily, even with an rsync from one
>>> disk to another. Though that also smells a little like networking in
>>> the traces. Maybe netdev has ideas.
>>
>> Is this new to 4.15? Or is it just that you're testing something new?
>>
>> If it's new and easy to repro, can you just bisect it? And if it isn't
>> new, can you perhaps check whether it's new to 4.14 (ie 4.13 being
>> ok)?
>>
>> Because that fs_reclaim_acquire/release() debugging isn't new to 4.15,
>> but it was rewritten for 4.14.. I'm wondering if that remodeling ended
>> up triggering something.
>
> --- linux-4.13.16/mm/page_alloc.c
> +++ linux-4.14.15/mm/page_alloc.c
Oops. This output was inverted.
> @@ -3527,53 +3519,12 @@
> return true;
> }
> return false;
> }
> #endif /* CONFIG_COMPACTION */
>
> -#ifdef CONFIG_LOCKDEP
> -struct lockdep_map __fs_reclaim_map =
> - STATIC_LOCKDEP_MAP_INIT("fs_reclaim", &__fs_reclaim_map);
> -
> -static bool __need_fs_reclaim(gfp_t gfp_mask)
> -{
> - gfp_mask = current_gfp_context(gfp_mask);
> -
> - /* no reclaim without waiting on it */
> - if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
> - return false;
> -
> - /* this guy won't enter reclaim */
> - if ((current->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
> - return false;
Since __kmalloc_reserve() from __alloc_skb() adds __GFP_NOMEMALLOC | __GFP_NOWARN
to gfp_mask, __need_fs_reclaim() is failing to return false here.
But why checking __GFP_NOMEMALLOC here? __alloc_pages_slowpath() skips direct
reclaim if !(gfp_mask & __GFP_DIRECT_RECLAIM) or (current->flags & PF_MEMALLOC),
doesn't it?
----------
static inline struct page *
__alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
struct alloc_context *ac)
{
(...snipped...)
/* Caller is not willing to reclaim, we can't balance anything */
if (!can_direct_reclaim)
goto nopage;
/* Avoid recursion of direct reclaim */
if (current->flags & PF_MEMALLOC)
goto nopage;
/* Try direct reclaim and then allocating */
page = __alloc_pages_direct_reclaim(gfp_mask, order, alloc_flags, ac,
&did_some_progress);
if (page)
goto got_pg;
(...snipped...)
}
----------
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
