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Date: Fri, 13 Dec 2024 06:06:15 +0100
From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Carlos Maiolino <cem@kernel.org>,
	Hans Holmberg <hans.holmberg@wdc.com>, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 05/43] xfs: don't take m_sb_lock in xfs_fs_statfs
Message-ID: <20241213050615.GC5630@lst.de>
References: <20241211085636.1380516-1-hch@lst.de> <20241211085636.1380516-6-hch@lst.de> <20241212214206.GX6678@frogsfrogsfrogs>
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On Thu, Dec 12, 2024 at 01:42:06PM -0800, Darrick J. Wong wrote:
> On Wed, Dec 11, 2024 at 09:54:30AM +0100, Christoph Hellwig wrote:
> > The only non-constant value read under m_sb_lock in xfs_fs_statfs is
> > sb_dblocks, and it could become stale right after dropping the lock
> > anyway.  Remove the thus pointless lock section.
> 
> Is there a stronger reason later for removing the critical section?
> Do we lose much by leaving the protection in place?

It makes a completely mess of xfs_fs_statfs, and as stated in the
commit message about it's not actually useful at all.  I also don't
think taking a global lock from a non-privileged operation is an
old that good idea to start with if we can avoid it.