Re: [f2fs-dev] [PATCH v2 1/1] f2fs: fix lockdep WARN of sbi->cp_global_sem and q->q_usage_counter

[Shinichiro Kawasaki via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On Mar 05, 2026 / 09:38, Chao Yu wrote:
> On 2026/3/4 16:55, Chao Yu wrote:
> > On 2026/3/4 12:57, Shinichiro Kawasaki wrote:
[...]
> > > I will seek out other ways to avoid the lockdep. I have no idea how to do that
> > > at this moment, though.
> > 
> > Shinichiro,
> > 
> > IMO, this looks like a false alarm of lockdep, what do you think of this fix?
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git/commit/?h=bugfix/syzbot&id=3b19564b95e9ba9803ef30e90eace0977b9d140d
> > 
> > ---
> >   fs/f2fs/f2fs.h  | 3 +++
> >   fs/f2fs/super.c | 3 +++
> >   2 files changed, 6 insertions(+)
> > 
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index bb34e864d0ef..5b400e99f332 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -2042,6 +2042,9 @@ struct f2fs_sb_info {
> >          spinlock_t iostat_lat_lock;
> >          struct iostat_lat_info *iostat_io_lat;
> >   #endif
> > +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> > +       struct lock_class_key cp_global_sem_key;
> > +#endif
> >   };
> > 
> >   /* Definitions to access f2fs_sb_info */
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 8774c60b4be4..9e85f31fa828 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -4948,6 +4948,9 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc)
> >          init_f2fs_rwsem_trace(&sbi->gc_lock, sbi, LOCK_NAME_GC_LOCK);
> >          mutex_init(&sbi->writepages);
> >          init_f2fs_rwsem_trace(&sbi->cp_global_sem, sbi, LOCK_NAME_CP_GLOBAL);
> > +#ifdef CONFIG_DEBUG_LOCK_ALLOC
> > +       lockdep_set_class(&sbi->cp_global_sem, &sbi->cp_global_sem_key);
> 
> Sorry, should be:
> 
> +	lockdep_set_class(&sbi->cp_global_sem.internal_rwsem,
> +					&sbi->cp_global_sem_key);
> 
> Thanks,

Chao, thank you very much for the idea and the trial patch! I will try it out.
Let me have a day or two.

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