On Sat, 12 Dec 2020, Alex Shi wrote: > > I'm very sorry, a typo here. the patch should be updated: > > From ed4fa1c6d5bed5766c5f0c35af0c597855d7be06 Mon Sep 17 00:00:00 2001 > From: Alex Shi <alex....@linux.alibaba.com> > Date: Fri, 11 Dec 2020 21:26:46 +0800 > Subject: [PATCH] mm/mmap: replace if (cond) BUG() with BUG_ON() > > coccinelle reports some warnings: > WARNING: Use BUG_ON instead of if condition followed by BUG. > > It could be fixed by BUG_ON(). > > Reported-by: ab...@linux.alibaba.com > Signed-off-by: Alex Shi <alex....@linux.alibaba.com>
When diffing mmotm just now, I was sorry to find this: NAK. Alex, please consider why the authors of these lines (whom you did not Cc) chose to write them without BUG_ON(): it has always been preferred practice to use BUG_ON() on predicates, but not on functionally effective statements (sorry, I've forgotten the proper term: I'd say statements with side-effects, but here they are not just side-effects: they are their main purpose). We prefer not to hide those away inside BUG macros: please fix your "abaci" to respect kernel style here - unless it turns out that the kernel has moved away from that, and it's me who's behind the times. Andrew, if you agree, please drop mm-mmap-replace-if-cond-bug-with-bug_on.patch from your stack. (And did Minchan really Ack it? I see an Ack from Minchan to a similar mm/zsmalloc patch: which surprises me, but is Minchan's business not mine; but that patch is not in mmotm.) On the whole, I think there are far too many patches submitted, where Developer B chooses to rewrite a line to their own preference, without respecting that Author A chose to write it in another way. That's great when it really does improve readability, but often not. Thanks, Hugh > Cc: Andrew Morton <a...@linux-foundation.org> > Cc: linux...@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/mmap.c | 22 ++++++++-------------- > 1 file changed, 8 insertions(+), 14 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 8144fc3c5a78..107fa91bb59f 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -712,9 +712,8 @@ static void __insert_vm_struct(struct mm_struct *mm, > struct vm_area_struct *vma) > struct vm_area_struct *prev; > struct rb_node **rb_link, *rb_parent; > > - if (find_vma_links(mm, vma->vm_start, vma->vm_end, > - &prev, &rb_link, &rb_parent)) > - BUG(); > + BUG_ON(find_vma_links(mm, vma->vm_start, vma->vm_end, > + &prev, &rb_link, &rb_parent)); > __vma_link(mm, vma, prev, rb_link, rb_parent); > mm->map_count++; > } > @@ -3585,9 +3584,8 @@ static void vm_lock_anon_vma(struct mm_struct *mm, > struct anon_vma *anon_vma) > * can't change from under us thanks to the > * anon_vma->root->rwsem. > */ > - if (__test_and_set_bit(0, (unsigned long *) > - > &anon_vma->root->rb_root.rb_root.rb_node)) > - BUG(); > + BUG_ON(__test_and_set_bit(0, (unsigned long *) > + &anon_vma->root->rb_root.rb_root.rb_node)); > } > } > > @@ -3603,8 +3601,7 @@ static void vm_lock_mapping(struct mm_struct *mm, > struct address_space *mapping) > * mm_all_locks_mutex, there may be other cpus > * changing other bitflags in parallel to us. > */ > - if (test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags)) > - BUG(); > + BUG_ON(test_and_set_bit(AS_MM_ALL_LOCKS, &mapping->flags)); > down_write_nest_lock(&mapping->i_mmap_rwsem, &mm->mmap_lock); > } > } > @@ -3701,9 +3698,8 @@ static void vm_unlock_anon_vma(struct anon_vma > *anon_vma) > * can't change from under us until we release the > * anon_vma->root->rwsem. > */ > - if (!__test_and_clear_bit(0, (unsigned long *) > - > &anon_vma->root->rb_root.rb_root.rb_node)) > - BUG(); > + BUG_ON(!__test_and_clear_bit(0, (unsigned long *) > + &anon_vma->root->rb_root.rb_root.rb_node)); > anon_vma_unlock_write(anon_vma); > } > } > @@ -3716,9 +3712,7 @@ static void vm_unlock_mapping(struct address_space > *mapping) > * because we hold the mm_all_locks_mutex. > */ > i_mmap_unlock_write(mapping); > - if (!test_and_clear_bit(AS_MM_ALL_LOCKS, > - &mapping->flags)) > - BUG(); > + BUG_ON(!test_and_clear_bit(AS_MM_ALL_LOCKS, &mapping->flags)); > } > } > > -- > 2.29.GIT
