Re: [PATCH v3] lockdep: Teach lockdep about memalloc_noio_save

Michal Hocko
2017-03-02T00:44:47Z

On Wed 01-03-17 16:46:59, Peter Zijlstra wrote:
> On Wed, Mar 01, 2017 at 01:29:57PM +0200, Nikolay Borisov wrote:
> > Commit 21caf2fc1931 ("mm: teach mm by current context info to not do I/O
> > during memory allocation") added the memalloc_noio_(save|restore) functions
> > to enable people to modify the MM behavior by disbaling I/O during memory
> > allocation. This was further extended in Fixes: 934f3072c17c ("mm: clear
> > __GFP_FS when PF_MEMALLOC_NOIO is set"). memalloc_noio_* functions prevent
> > allocation paths recursing back into the filesystem without explicitly
> > changing the flags for every allocation site. However, lockdep hasn't been
> > keeping up with the changes and it entirely misses handling the memalloc_noio
> > adjustments. Instead, it is left to the callers of __lockdep_trace_alloc to
> > call the functino after they have shaven the respective GFP flags.
> >
> > Let's fix this by making lockdep explicitly do the shaving of respective
> > GFP flags.
>
> I edited that to look like the below, then my compiler said:
>
> ../kernel/locking/lockdep.c: In function ‘lockdep_set_current_reclaim_state’:
> ../kernel/locking/lockdep.c:3866:33: error: implicit declaration of function ‘memalloc_noio_flags’ [-Werror=implicit-function-declaration]
> current->lockdep_reclaim_gfp = memalloc_noio_flags(gfp_mask);
> ^~~~~~~~~~~~~~~~~~~
> cc1: some warnings being treated as errors
> ../scripts/Makefile.build:294: recipe for target 'kernel/locking/lockdep.o' failed

It did compile for me
$ grep CONFIG_LOCKDEP .config
CONFIG_LOCKDEP_SUPPORT=y
CONFIG_LOCKDEP=y

Anyway, does the following help?
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 47e4f82380e4..d5386ad7ed3f 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -47,6 +47,7 @@
#include <linux/kmemcheck.h>
#include <linux/random.h>
#include <linux/jhash.h>
+#include <linux/sched.h>

#include <asm/sections.h>

--
Michal Hocko
SUSE Labs