在 2021/1/6 下午12:28, Hugh Dickins 写道: > 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.shi@xxxxxxxxxxxxxxxxx> >> 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: abaci@xxxxxxxxxxxxxxxxx >> Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx> > > 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). > Right! The original line may want to be done whenever the BUG() enabled, I overlocked this points. Sorry! My fault! Please revert them. Thanks Alex > 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 <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: linux-mm@xxxxxxxxx >> Cc: linux-kernel@xxxxxxxxxxxxxxx >> --- >> 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
