Re: [4.15-rc9] fs_reclaim lockdep trace
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: 2018-01-28 04:26:26
Also in:
linux-mm, lkml
On 2018/01/28 10:16, Tetsuo Handa wrote:
quoted hunk ↗ jump to hunk
Linus Torvalds wrote:quoted
On Sat, Jan 27, 2018 at 2:24 PM, Dave Jones [off-list ref] wrote:quoted
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.
quoted hunk ↗ jump to hunk
@@ -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...)
}
----------
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