linux-kernel - Re: [RFC 2/2] writeback: Fix false warning in inode_to

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Message-ID: <Z_eGvBHssVtGKpty@infradead.org>
Date: Thu, 10 Apr 2025 01:52:12 -0700
From: Christoph Hellwig <hch@...radead.org>
To: Andreas Gruenbacher <agruenba@...hat.com>
Cc: cgroups@...r.kernel.org, Jan Kara <jack@...e.cz>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Rafael Aquini <aquini@...hat.com>, gfs2@...ts.linux.dev,
	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/2] writeback: Fix false warning in inode_to_wb()

On Mon, Apr 07, 2025 at 08:21:02PM +0200, Andreas Gruenbacher wrote:
> -static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
> +static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
>  {
>  #ifdef CONFIG_LOCKDEP
>  	WARN_ON_ONCE(debug_locks &&
> +		     inode_cgwb_enabled(inode) &&
>  		     (!lockdep_is_held(&inode->i_lock) &&
>  		      !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) &&
>  		      !lockdep_is_held(&inode->i_wb->list_lock)));
> -- 

This means that even on cgroup aware file systems we now only get
the locking validation if cgroups are actually enabled for the file
system instance and thus hugely reducing coverage, which is rather
unfortunate.