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Date: Fri, 8 Sep 2023 13:27:54 +0200
From: Christian Brauner <brauner@kernel.org>
To: Christoph Hellwig <hch@lst.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, Jan Kara <jack@suse.cz>,
	Guenter Roeck <linux@roeck-us.net>,
	Konstantin Komarov <almaz.alexandrovich@paragon-software.com>,
	linux-fsdevel@vger.kernel.org, ntfs3@lists.linux.dev
Subject: Re: [PATCH] ntfs3: drop inode references in ntfs_put_super()
Message-ID: <20230908-grundlos-morgig-e055946fde44@brauner>
References: <20230907-vfs-ntfs3-kill_sb-v1-1-ef4397dd941d@kernel.org>
 <20230908081213.GA8240@lst.de>
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In-Reply-To: <20230908081213.GA8240@lst.de>

On Fri, Sep 08, 2023 at 10:12:13AM +0200, Christoph Hellwig wrote:
> On Thu, Sep 07, 2023 at 06:03:40PM +0200, Christian Brauner wrote:
> > Recently we moved most cleanup from ntfs_put_super() into
> > ntfs3_kill_sb() as part of a bigger cleanup. This accidently also moved
> > dropping inode references stashed in ntfs3's sb->s_fs_info from
> > @sb->put_super() to @sb->kill_sb(). But generic_shutdown_super()
> > verifies that there are no busy inodes past sb->put_super(). Fix this
> > and disentangle dropping inode references from freeing @sb->s_fs_info.
> 
> Sorry for the delay, I've been travelling.  Wouldn't it make more
> sense to just free it in ->kill_sb before calling kill_block_super?

ntfs3 has ntfs_evict_inodes() which might depend on the info in
sbi->s_fs_info to be valid. So calling it before kill_block_super()
risks putting resources that ntfs_evict_inodes() might depend on. Doing
it in ntfs_put_super() will prevent this from becoming an issue without
having to wade through all callchains. And since we can't get rid of
ntfs_put_super() anyway why bother risking that.