Messages in this thread | | | Date | Wed, 1 Mar 2017 10:46:57 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] lockdep: Teach lockdep about memalloc_noio_save |
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On Wed, Mar 01, 2017 at 09:59:00AM +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 prevents allocation paths recursing back into the filesystem > without explicitly changing the flags for every allocation site. Yet, lockdep > not being aware of that is prone to showing false positives. Fix this > by teaching it that the presence of PF_MEMALLOC_NOIO flag mean we are not > going to issue any I/O
I'm not up to date on the specific, but GFP_IO is separate from GFP_FS.
And MEMALLOC_NOIO only clears GFP_IO but leaves GFP_FS set.
Therefore I think your change is wrong, but I might have overlooked a detail. Added original authors to Cc to clarify.
> Signed-off-by: Nikolay Borisov <nborisov@suse.com> > --- > kernel/locking/lockdep.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > > Turned out there was another place where RELCAIM_FS was being set, fix it > by using the memalloc_noio_flags when setting ->lockdep_reclaim_gfp flags. > > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c > index 9812e5dd409e..87cf9910e66f 100644 > --- a/kernel/locking/lockdep.c > +++ b/kernel/locking/lockdep.c > @@ -2866,7 +2866,8 @@ static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags) > return; > > /* this guy won't enter reclaim */ > - if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC)) > + if (((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC)) || > + curr->flags & PF_MEMALLOC_NOIO) > return; > > /* We're only interested __GFP_FS allocations for now */ > @@ -3852,7 +3853,7 @@ EXPORT_SYMBOL_GPL(lock_unpin_lock); > > void lockdep_set_current_reclaim_state(gfp_t gfp_mask) > { > - current->lockdep_reclaim_gfp = gfp_mask; > + current->lockdep_reclaim_gfp = memalloc_noio_flags(gfp_mask); > } > > void lockdep_clear_current_reclaim_state(void) > -- > 2.7.4 >
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