On 1.03.2017 11:46, Peter Zijlstra wrote: > 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.
static inline gfp_t memalloc_noio_flags(gfp_t flags) { if (unlikely(current->flags & PF_MEMALLOC_NOIO)) flags &= ~(__GFP_IO | __GFP_FS); return flags; } > > 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 <nbori...@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 >> >